mirror of
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git
synced 2024-09-12 05:48:40 +00:00
![Arianna Avanzini](/assets/img/avatar_default.png)
A set of processes may happen to perform interleaved reads, i.e., read requests whose union would give rise to a sequential read pattern. There are two typical cases: first, processes reading fixed-size chunks of data at a fixed distance from each other; second, processes reading variable-size chunks at variable distances. The latter case occurs for example with QEMU, which splits the I/O generated by a guest into multiple chunks, and lets these chunks be served by a pool of I/O threads, iteratively assigning the next chunk of I/O to the first available thread. CFQ denotes as 'cooperating' a set of processes that are doing interleaved I/O, and when it detects cooperating processes, it merges their queues to obtain a sequential I/O pattern from the union of their I/O requests, and hence boost the throughput. Unfortunately, in the following frequent case, the mechanism implemented in CFQ for detecting cooperating processes and merging their queues is not responsive enough to handle also the fluctuating I/O pattern of the second type of processes. Suppose that one process of the second type issues a request close to the next request to serve of another process of the same type. At that time the two processes would be considered as cooperating. But, if the request issued by the first process is to be merged with some other already-queued request, then, from the moment at which this request arrives, to the moment when CFQ controls whether the two processes are cooperating, the two processes are likely to be already doing I/O in distant zones of the disk surface or device memory. CFQ uses however preemption to get a sequential read pattern out of the read requests performed by the second type of processes too. As a consequence, CFQ uses two different mechanisms to achieve the same goal: boosting the throughput with interleaved I/O. This patch introduces Early Queue Merge (EQM), a unified mechanism to get a sequential read pattern with both types of processes. The main idea is to immediately check whether a newly-arrived request lets some pair of processes become cooperating, both in the case of actual request insertion and, to be responsive with the second type of processes, in the case of request merge. Both types of processes are then handled by just merging their queues. Signed-off-by: Arianna Avanzini <avanzini.arianna@gmail.com> Signed-off-by: Mauro Andreolini <mauro.andreolini@unimore.it> Signed-off-by: Paolo Valente <paolo.valente@linaro.org> Signed-off-by: Jens Axboe <axboe@fb.com>
8028 lines
243 KiB
C
8028 lines
243 KiB
C
/*
|
|
* Budget Fair Queueing (BFQ) I/O scheduler.
|
|
*
|
|
* Based on ideas and code from CFQ:
|
|
* Copyright (C) 2003 Jens Axboe <axboe@kernel.dk>
|
|
*
|
|
* Copyright (C) 2008 Fabio Checconi <fabio@gandalf.sssup.it>
|
|
* Paolo Valente <paolo.valente@unimore.it>
|
|
*
|
|
* Copyright (C) 2010 Paolo Valente <paolo.valente@unimore.it>
|
|
* Arianna Avanzini <avanzini@google.com>
|
|
*
|
|
* Copyright (C) 2017 Paolo Valente <paolo.valente@linaro.org>
|
|
*
|
|
* This program is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU General Public License as
|
|
* published by the Free Software Foundation; either version 2 of the
|
|
* License, or (at your option) any later version.
|
|
*
|
|
* This program is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* General Public License for more details.
|
|
*
|
|
* BFQ is a proportional-share I/O scheduler, with some extra
|
|
* low-latency capabilities. BFQ also supports full hierarchical
|
|
* scheduling through cgroups. Next paragraphs provide an introduction
|
|
* on BFQ inner workings. Details on BFQ benefits, usage and
|
|
* limitations can be found in Documentation/block/bfq-iosched.txt.
|
|
*
|
|
* BFQ is a proportional-share storage-I/O scheduling algorithm based
|
|
* on the slice-by-slice service scheme of CFQ. But BFQ assigns
|
|
* budgets, measured in number of sectors, to processes instead of
|
|
* time slices. The device is not granted to the in-service process
|
|
* for a given time slice, but until it has exhausted its assigned
|
|
* budget. This change from the time to the service domain enables BFQ
|
|
* to distribute the device throughput among processes as desired,
|
|
* without any distortion due to throughput fluctuations, or to device
|
|
* internal queueing. BFQ uses an ad hoc internal scheduler, called
|
|
* B-WF2Q+, to schedule processes according to their budgets. More
|
|
* precisely, BFQ schedules queues associated with processes. Each
|
|
* process/queue is assigned a user-configurable weight, and B-WF2Q+
|
|
* guarantees that each queue receives a fraction of the throughput
|
|
* proportional to its weight. Thanks to the accurate policy of
|
|
* B-WF2Q+, BFQ can afford to assign high budgets to I/O-bound
|
|
* processes issuing sequential requests (to boost the throughput),
|
|
* and yet guarantee a low latency to interactive and soft real-time
|
|
* applications.
|
|
*
|
|
* In particular, to provide these low-latency guarantees, BFQ
|
|
* explicitly privileges the I/O of two classes of time-sensitive
|
|
* applications: interactive and soft real-time. This feature enables
|
|
* BFQ to provide applications in these classes with a very low
|
|
* latency. Finally, BFQ also features additional heuristics for
|
|
* preserving both a low latency and a high throughput on NCQ-capable,
|
|
* rotational or flash-based devices, and to get the job done quickly
|
|
* for applications consisting in many I/O-bound processes.
|
|
*
|
|
* BFQ is described in [1], where also a reference to the initial, more
|
|
* theoretical paper on BFQ can be found. The interested reader can find
|
|
* in the latter paper full details on the main algorithm, as well as
|
|
* formulas of the guarantees and formal proofs of all the properties.
|
|
* With respect to the version of BFQ presented in these papers, this
|
|
* implementation adds a few more heuristics, such as the one that
|
|
* guarantees a low latency to soft real-time applications, and a
|
|
* hierarchical extension based on H-WF2Q+.
|
|
*
|
|
* B-WF2Q+ is based on WF2Q+, which is described in [2], together with
|
|
* H-WF2Q+, while the augmented tree used here to implement B-WF2Q+
|
|
* with O(log N) complexity derives from the one introduced with EEVDF
|
|
* in [3].
|
|
*
|
|
* [1] P. Valente, A. Avanzini, "Evolution of the BFQ Storage I/O
|
|
* Scheduler", Proceedings of the First Workshop on Mobile System
|
|
* Technologies (MST-2015), May 2015.
|
|
* http://algogroup.unimore.it/people/paolo/disk_sched/mst-2015.pdf
|
|
*
|
|
* [2] Jon C.R. Bennett and H. Zhang, "Hierarchical Packet Fair Queueing
|
|
* Algorithms", IEEE/ACM Transactions on Networking, 5(5):675-689,
|
|
* Oct 1997.
|
|
*
|
|
* http://www.cs.cmu.edu/~hzhang/papers/TON-97-Oct.ps.gz
|
|
*
|
|
* [3] I. Stoica and H. Abdel-Wahab, "Earliest Eligible Virtual Deadline
|
|
* First: A Flexible and Accurate Mechanism for Proportional Share
|
|
* Resource Allocation", technical report.
|
|
*
|
|
* http://www.cs.berkeley.edu/~istoica/papers/eevdf-tr-95.pdf
|
|
*/
|
|
#include <linux/module.h>
|
|
#include <linux/slab.h>
|
|
#include <linux/blkdev.h>
|
|
#include <linux/cgroup.h>
|
|
#include <linux/elevator.h>
|
|
#include <linux/ktime.h>
|
|
#include <linux/rbtree.h>
|
|
#include <linux/ioprio.h>
|
|
#include <linux/sbitmap.h>
|
|
#include <linux/delay.h>
|
|
|
|
#include "blk.h"
|
|
#include "blk-mq.h"
|
|
#include "blk-mq-tag.h"
|
|
#include "blk-mq-sched.h"
|
|
#include <linux/blktrace_api.h>
|
|
#include <linux/hrtimer.h>
|
|
#include <linux/blk-cgroup.h>
|
|
|
|
#define BFQ_IOPRIO_CLASSES 3
|
|
#define BFQ_CL_IDLE_TIMEOUT (HZ/5)
|
|
|
|
#define BFQ_MIN_WEIGHT 1
|
|
#define BFQ_MAX_WEIGHT 1000
|
|
#define BFQ_WEIGHT_CONVERSION_COEFF 10
|
|
|
|
#define BFQ_DEFAULT_QUEUE_IOPRIO 4
|
|
|
|
#define BFQ_WEIGHT_LEGACY_DFL 100
|
|
#define BFQ_DEFAULT_GRP_IOPRIO 0
|
|
#define BFQ_DEFAULT_GRP_CLASS IOPRIO_CLASS_BE
|
|
|
|
/*
|
|
* Soft real-time applications are extremely more latency sensitive
|
|
* than interactive ones. Over-raise the weight of the former to
|
|
* privilege them against the latter.
|
|
*/
|
|
#define BFQ_SOFTRT_WEIGHT_FACTOR 100
|
|
|
|
struct bfq_entity;
|
|
|
|
/**
|
|
* struct bfq_service_tree - per ioprio_class service tree.
|
|
*
|
|
* Each service tree represents a B-WF2Q+ scheduler on its own. Each
|
|
* ioprio_class has its own independent scheduler, and so its own
|
|
* bfq_service_tree. All the fields are protected by the queue lock
|
|
* of the containing bfqd.
|
|
*/
|
|
struct bfq_service_tree {
|
|
/* tree for active entities (i.e., those backlogged) */
|
|
struct rb_root active;
|
|
/* tree for idle entities (i.e., not backlogged, with V <= F_i)*/
|
|
struct rb_root idle;
|
|
|
|
/* idle entity with minimum F_i */
|
|
struct bfq_entity *first_idle;
|
|
/* idle entity with maximum F_i */
|
|
struct bfq_entity *last_idle;
|
|
|
|
/* scheduler virtual time */
|
|
u64 vtime;
|
|
/* scheduler weight sum; active and idle entities contribute to it */
|
|
unsigned long wsum;
|
|
};
|
|
|
|
/**
|
|
* struct bfq_sched_data - multi-class scheduler.
|
|
*
|
|
* bfq_sched_data is the basic scheduler queue. It supports three
|
|
* ioprio_classes, and can be used either as a toplevel queue or as an
|
|
* intermediate queue on a hierarchical setup. @next_in_service
|
|
* points to the active entity of the sched_data service trees that
|
|
* will be scheduled next. It is used to reduce the number of steps
|
|
* needed for each hierarchical-schedule update.
|
|
*
|
|
* The supported ioprio_classes are the same as in CFQ, in descending
|
|
* priority order, IOPRIO_CLASS_RT, IOPRIO_CLASS_BE, IOPRIO_CLASS_IDLE.
|
|
* Requests from higher priority queues are served before all the
|
|
* requests from lower priority queues; among requests of the same
|
|
* queue requests are served according to B-WF2Q+.
|
|
* All the fields are protected by the queue lock of the containing bfqd.
|
|
*/
|
|
struct bfq_sched_data {
|
|
/* entity in service */
|
|
struct bfq_entity *in_service_entity;
|
|
/* head-of-line entity (see comments above) */
|
|
struct bfq_entity *next_in_service;
|
|
/* array of service trees, one per ioprio_class */
|
|
struct bfq_service_tree service_tree[BFQ_IOPRIO_CLASSES];
|
|
/* last time CLASS_IDLE was served */
|
|
unsigned long bfq_class_idle_last_service;
|
|
|
|
};
|
|
|
|
/**
|
|
* struct bfq_entity - schedulable entity.
|
|
*
|
|
* A bfq_entity is used to represent either a bfq_queue (leaf node in the
|
|
* cgroup hierarchy) or a bfq_group into the upper level scheduler. Each
|
|
* entity belongs to the sched_data of the parent group in the cgroup
|
|
* hierarchy. Non-leaf entities have also their own sched_data, stored
|
|
* in @my_sched_data.
|
|
*
|
|
* Each entity stores independently its priority values; this would
|
|
* allow different weights on different devices, but this
|
|
* functionality is not exported to userspace by now. Priorities and
|
|
* weights are updated lazily, first storing the new values into the
|
|
* new_* fields, then setting the @prio_changed flag. As soon as
|
|
* there is a transition in the entity state that allows the priority
|
|
* update to take place the effective and the requested priority
|
|
* values are synchronized.
|
|
*
|
|
* Unless cgroups are used, the weight value is calculated from the
|
|
* ioprio to export the same interface as CFQ. When dealing with
|
|
* ``well-behaved'' queues (i.e., queues that do not spend too much
|
|
* time to consume their budget and have true sequential behavior, and
|
|
* when there are no external factors breaking anticipation) the
|
|
* relative weights at each level of the cgroups hierarchy should be
|
|
* guaranteed. All the fields are protected by the queue lock of the
|
|
* containing bfqd.
|
|
*/
|
|
struct bfq_entity {
|
|
/* service_tree member */
|
|
struct rb_node rb_node;
|
|
|
|
/*
|
|
* Flag, true if the entity is on a tree (either the active or
|
|
* the idle one of its service_tree) or is in service.
|
|
*/
|
|
bool on_st;
|
|
|
|
/* B-WF2Q+ start and finish timestamps [sectors/weight] */
|
|
u64 start, finish;
|
|
|
|
/* tree the entity is enqueued into; %NULL if not on a tree */
|
|
struct rb_root *tree;
|
|
|
|
/*
|
|
* minimum start time of the (active) subtree rooted at this
|
|
* entity; used for O(log N) lookups into active trees
|
|
*/
|
|
u64 min_start;
|
|
|
|
/* amount of service received during the last service slot */
|
|
int service;
|
|
|
|
/* budget, used also to calculate F_i: F_i = S_i + @budget / @weight */
|
|
int budget;
|
|
|
|
/* weight of the queue */
|
|
int weight;
|
|
/* next weight if a change is in progress */
|
|
int new_weight;
|
|
|
|
/* original weight, used to implement weight boosting */
|
|
int orig_weight;
|
|
|
|
/* parent entity, for hierarchical scheduling */
|
|
struct bfq_entity *parent;
|
|
|
|
/*
|
|
* For non-leaf nodes in the hierarchy, the associated
|
|
* scheduler queue, %NULL on leaf nodes.
|
|
*/
|
|
struct bfq_sched_data *my_sched_data;
|
|
/* the scheduler queue this entity belongs to */
|
|
struct bfq_sched_data *sched_data;
|
|
|
|
/* flag, set to request a weight, ioprio or ioprio_class change */
|
|
int prio_changed;
|
|
};
|
|
|
|
struct bfq_group;
|
|
|
|
/**
|
|
* struct bfq_ttime - per process thinktime stats.
|
|
*/
|
|
struct bfq_ttime {
|
|
/* completion time of the last request */
|
|
u64 last_end_request;
|
|
|
|
/* total process thinktime */
|
|
u64 ttime_total;
|
|
/* number of thinktime samples */
|
|
unsigned long ttime_samples;
|
|
/* average process thinktime */
|
|
u64 ttime_mean;
|
|
};
|
|
|
|
/**
|
|
* struct bfq_queue - leaf schedulable entity.
|
|
*
|
|
* A bfq_queue is a leaf request queue; it can be associated with an
|
|
* io_context or more, if it is async or shared between cooperating
|
|
* processes. @cgroup holds a reference to the cgroup, to be sure that it
|
|
* does not disappear while a bfqq still references it (mostly to avoid
|
|
* races between request issuing and task migration followed by cgroup
|
|
* destruction).
|
|
* All the fields are protected by the queue lock of the containing bfqd.
|
|
*/
|
|
struct bfq_queue {
|
|
/* reference counter */
|
|
int ref;
|
|
/* parent bfq_data */
|
|
struct bfq_data *bfqd;
|
|
|
|
/* current ioprio and ioprio class */
|
|
unsigned short ioprio, ioprio_class;
|
|
/* next ioprio and ioprio class if a change is in progress */
|
|
unsigned short new_ioprio, new_ioprio_class;
|
|
|
|
/*
|
|
* Shared bfq_queue if queue is cooperating with one or more
|
|
* other queues.
|
|
*/
|
|
struct bfq_queue *new_bfqq;
|
|
/* request-position tree member (see bfq_group's @rq_pos_tree) */
|
|
struct rb_node pos_node;
|
|
/* request-position tree root (see bfq_group's @rq_pos_tree) */
|
|
struct rb_root *pos_root;
|
|
|
|
/* sorted list of pending requests */
|
|
struct rb_root sort_list;
|
|
/* if fifo isn't expired, next request to serve */
|
|
struct request *next_rq;
|
|
/* number of sync and async requests queued */
|
|
int queued[2];
|
|
/* number of requests currently allocated */
|
|
int allocated;
|
|
/* number of pending metadata requests */
|
|
int meta_pending;
|
|
/* fifo list of requests in sort_list */
|
|
struct list_head fifo;
|
|
|
|
/* entity representing this queue in the scheduler */
|
|
struct bfq_entity entity;
|
|
|
|
/* maximum budget allowed from the feedback mechanism */
|
|
int max_budget;
|
|
/* budget expiration (in jiffies) */
|
|
unsigned long budget_timeout;
|
|
|
|
/* number of requests on the dispatch list or inside driver */
|
|
int dispatched;
|
|
|
|
/* status flags */
|
|
unsigned long flags;
|
|
|
|
/* node for active/idle bfqq list inside parent bfqd */
|
|
struct list_head bfqq_list;
|
|
|
|
/* associated @bfq_ttime struct */
|
|
struct bfq_ttime ttime;
|
|
|
|
/* bit vector: a 1 for each seeky requests in history */
|
|
u32 seek_history;
|
|
/* position of the last request enqueued */
|
|
sector_t last_request_pos;
|
|
|
|
/* Number of consecutive pairs of request completion and
|
|
* arrival, such that the queue becomes idle after the
|
|
* completion, but the next request arrives within an idle
|
|
* time slice; used only if the queue's IO_bound flag has been
|
|
* cleared.
|
|
*/
|
|
unsigned int requests_within_timer;
|
|
|
|
/* pid of the process owning the queue, used for logging purposes */
|
|
pid_t pid;
|
|
|
|
/*
|
|
* Pointer to the bfq_io_cq owning the bfq_queue, set to %NULL
|
|
* if the queue is shared.
|
|
*/
|
|
struct bfq_io_cq *bic;
|
|
|
|
/* current maximum weight-raising time for this queue */
|
|
unsigned long wr_cur_max_time;
|
|
/*
|
|
* Minimum time instant such that, only if a new request is
|
|
* enqueued after this time instant in an idle @bfq_queue with
|
|
* no outstanding requests, then the task associated with the
|
|
* queue it is deemed as soft real-time (see the comments on
|
|
* the function bfq_bfqq_softrt_next_start())
|
|
*/
|
|
unsigned long soft_rt_next_start;
|
|
/*
|
|
* Start time of the current weight-raising period if
|
|
* the @bfq-queue is being weight-raised, otherwise
|
|
* finish time of the last weight-raising period.
|
|
*/
|
|
unsigned long last_wr_start_finish;
|
|
/* factor by which the weight of this queue is multiplied */
|
|
unsigned int wr_coeff;
|
|
/*
|
|
* Time of the last transition of the @bfq_queue from idle to
|
|
* backlogged.
|
|
*/
|
|
unsigned long last_idle_bklogged;
|
|
/*
|
|
* Cumulative service received from the @bfq_queue since the
|
|
* last transition from idle to backlogged.
|
|
*/
|
|
unsigned long service_from_backlogged;
|
|
|
|
/*
|
|
* Value of wr start time when switching to soft rt
|
|
*/
|
|
unsigned long wr_start_at_switch_to_srt;
|
|
|
|
unsigned long split_time; /* time of last split */
|
|
};
|
|
|
|
/**
|
|
* struct bfq_io_cq - per (request_queue, io_context) structure.
|
|
*/
|
|
struct bfq_io_cq {
|
|
/* associated io_cq structure */
|
|
struct io_cq icq; /* must be the first member */
|
|
/* array of two process queues, the sync and the async */
|
|
struct bfq_queue *bfqq[2];
|
|
/* per (request_queue, blkcg) ioprio */
|
|
int ioprio;
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
uint64_t blkcg_serial_nr; /* the current blkcg serial */
|
|
#endif
|
|
/*
|
|
* Snapshot of the idle window before merging; taken to
|
|
* remember this value while the queue is merged, so as to be
|
|
* able to restore it in case of split.
|
|
*/
|
|
bool saved_idle_window;
|
|
/*
|
|
* Same purpose as the previous two fields for the I/O bound
|
|
* classification of a queue.
|
|
*/
|
|
bool saved_IO_bound;
|
|
|
|
/*
|
|
* Similar to previous fields: save wr information.
|
|
*/
|
|
unsigned long saved_wr_coeff;
|
|
unsigned long saved_last_wr_start_finish;
|
|
unsigned long saved_wr_start_at_switch_to_srt;
|
|
unsigned int saved_wr_cur_max_time;
|
|
struct bfq_ttime saved_ttime;
|
|
};
|
|
|
|
enum bfq_device_speed {
|
|
BFQ_BFQD_FAST,
|
|
BFQ_BFQD_SLOW,
|
|
};
|
|
|
|
/**
|
|
* struct bfq_data - per-device data structure.
|
|
*
|
|
* All the fields are protected by @lock.
|
|
*/
|
|
struct bfq_data {
|
|
/* device request queue */
|
|
struct request_queue *queue;
|
|
/* dispatch queue */
|
|
struct list_head dispatch;
|
|
|
|
/* root bfq_group for the device */
|
|
struct bfq_group *root_group;
|
|
|
|
/*
|
|
* Number of bfq_queues containing requests (including the
|
|
* queue in service, even if it is idling).
|
|
*/
|
|
int busy_queues;
|
|
/* number of weight-raised busy @bfq_queues */
|
|
int wr_busy_queues;
|
|
/* number of queued requests */
|
|
int queued;
|
|
/* number of requests dispatched and waiting for completion */
|
|
int rq_in_driver;
|
|
|
|
/*
|
|
* Maximum number of requests in driver in the last
|
|
* @hw_tag_samples completed requests.
|
|
*/
|
|
int max_rq_in_driver;
|
|
/* number of samples used to calculate hw_tag */
|
|
int hw_tag_samples;
|
|
/* flag set to one if the driver is showing a queueing behavior */
|
|
int hw_tag;
|
|
|
|
/* number of budgets assigned */
|
|
int budgets_assigned;
|
|
|
|
/*
|
|
* Timer set when idling (waiting) for the next request from
|
|
* the queue in service.
|
|
*/
|
|
struct hrtimer idle_slice_timer;
|
|
|
|
/* bfq_queue in service */
|
|
struct bfq_queue *in_service_queue;
|
|
/* bfq_io_cq (bic) associated with the @in_service_queue */
|
|
struct bfq_io_cq *in_service_bic;
|
|
|
|
/* on-disk position of the last served request */
|
|
sector_t last_position;
|
|
|
|
/* time of last request completion (ns) */
|
|
u64 last_completion;
|
|
|
|
/* time of first rq dispatch in current observation interval (ns) */
|
|
u64 first_dispatch;
|
|
/* time of last rq dispatch in current observation interval (ns) */
|
|
u64 last_dispatch;
|
|
|
|
/* beginning of the last budget */
|
|
ktime_t last_budget_start;
|
|
/* beginning of the last idle slice */
|
|
ktime_t last_idling_start;
|
|
|
|
/* number of samples in current observation interval */
|
|
int peak_rate_samples;
|
|
/* num of samples of seq dispatches in current observation interval */
|
|
u32 sequential_samples;
|
|
/* total num of sectors transferred in current observation interval */
|
|
u64 tot_sectors_dispatched;
|
|
/* max rq size seen during current observation interval (sectors) */
|
|
u32 last_rq_max_size;
|
|
/* time elapsed from first dispatch in current observ. interval (us) */
|
|
u64 delta_from_first;
|
|
/*
|
|
* Current estimate of the device peak rate, measured in
|
|
* [BFQ_RATE_SHIFT * sectors/usec]. The left-shift by
|
|
* BFQ_RATE_SHIFT is performed to increase precision in
|
|
* fixed-point calculations.
|
|
*/
|
|
u32 peak_rate;
|
|
|
|
/* maximum budget allotted to a bfq_queue before rescheduling */
|
|
int bfq_max_budget;
|
|
|
|
/* list of all the bfq_queues active on the device */
|
|
struct list_head active_list;
|
|
/* list of all the bfq_queues idle on the device */
|
|
struct list_head idle_list;
|
|
|
|
/*
|
|
* Timeout for async/sync requests; when it fires, requests
|
|
* are served in fifo order.
|
|
*/
|
|
u64 bfq_fifo_expire[2];
|
|
/* weight of backward seeks wrt forward ones */
|
|
unsigned int bfq_back_penalty;
|
|
/* maximum allowed backward seek */
|
|
unsigned int bfq_back_max;
|
|
/* maximum idling time */
|
|
u32 bfq_slice_idle;
|
|
|
|
/* user-configured max budget value (0 for auto-tuning) */
|
|
int bfq_user_max_budget;
|
|
/*
|
|
* Timeout for bfq_queues to consume their budget; used to
|
|
* prevent seeky queues from imposing long latencies to
|
|
* sequential or quasi-sequential ones (this also implies that
|
|
* seeky queues cannot receive guarantees in the service
|
|
* domain; after a timeout they are charged for the time they
|
|
* have been in service, to preserve fairness among them, but
|
|
* without service-domain guarantees).
|
|
*/
|
|
unsigned int bfq_timeout;
|
|
|
|
/*
|
|
* Number of consecutive requests that must be issued within
|
|
* the idle time slice to set again idling to a queue which
|
|
* was marked as non-I/O-bound (see the definition of the
|
|
* IO_bound flag for further details).
|
|
*/
|
|
unsigned int bfq_requests_within_timer;
|
|
|
|
/*
|
|
* Force device idling whenever needed to provide accurate
|
|
* service guarantees, without caring about throughput
|
|
* issues. CAVEAT: this may even increase latencies, in case
|
|
* of useless idling for processes that did stop doing I/O.
|
|
*/
|
|
bool strict_guarantees;
|
|
|
|
/* if set to true, low-latency heuristics are enabled */
|
|
bool low_latency;
|
|
/*
|
|
* Maximum factor by which the weight of a weight-raised queue
|
|
* is multiplied.
|
|
*/
|
|
unsigned int bfq_wr_coeff;
|
|
/* maximum duration of a weight-raising period (jiffies) */
|
|
unsigned int bfq_wr_max_time;
|
|
|
|
/* Maximum weight-raising duration for soft real-time processes */
|
|
unsigned int bfq_wr_rt_max_time;
|
|
/*
|
|
* Minimum idle period after which weight-raising may be
|
|
* reactivated for a queue (in jiffies).
|
|
*/
|
|
unsigned int bfq_wr_min_idle_time;
|
|
/*
|
|
* Minimum period between request arrivals after which
|
|
* weight-raising may be reactivated for an already busy async
|
|
* queue (in jiffies).
|
|
*/
|
|
unsigned long bfq_wr_min_inter_arr_async;
|
|
|
|
/* Max service-rate for a soft real-time queue, in sectors/sec */
|
|
unsigned int bfq_wr_max_softrt_rate;
|
|
/*
|
|
* Cached value of the product R*T, used for computing the
|
|
* maximum duration of weight raising automatically.
|
|
*/
|
|
u64 RT_prod;
|
|
/* device-speed class for the low-latency heuristic */
|
|
enum bfq_device_speed device_speed;
|
|
|
|
/* fallback dummy bfqq for extreme OOM conditions */
|
|
struct bfq_queue oom_bfqq;
|
|
|
|
spinlock_t lock;
|
|
|
|
/*
|
|
* bic associated with the task issuing current bio for
|
|
* merging. This and the next field are used as a support to
|
|
* be able to perform the bic lookup, needed by bio-merge
|
|
* functions, before the scheduler lock is taken, and thus
|
|
* avoid taking the request-queue lock while the scheduler
|
|
* lock is being held.
|
|
*/
|
|
struct bfq_io_cq *bio_bic;
|
|
/* bfqq associated with the task issuing current bio for merging */
|
|
struct bfq_queue *bio_bfqq;
|
|
|
|
/*
|
|
* io context to put right after bfqd->lock is released. This
|
|
* filed is used to perform put_io_context, when needed, to
|
|
* after the scheduler lock has been released, and thus
|
|
* prevent an ioc->lock from being possibly taken while the
|
|
* scheduler lock is being held.
|
|
*/
|
|
struct io_context *ioc_to_put;
|
|
};
|
|
|
|
enum bfqq_state_flags {
|
|
BFQQF_busy = 0, /* has requests or is in service */
|
|
BFQQF_wait_request, /* waiting for a request */
|
|
BFQQF_non_blocking_wait_rq, /*
|
|
* waiting for a request
|
|
* without idling the device
|
|
*/
|
|
BFQQF_fifo_expire, /* FIFO checked in this slice */
|
|
BFQQF_idle_window, /* slice idling enabled */
|
|
BFQQF_sync, /* synchronous queue */
|
|
BFQQF_IO_bound, /*
|
|
* bfqq has timed-out at least once
|
|
* having consumed at most 2/10 of
|
|
* its budget
|
|
*/
|
|
BFQQF_softrt_update, /*
|
|
* may need softrt-next-start
|
|
* update
|
|
*/
|
|
BFQQF_coop, /* bfqq is shared */
|
|
BFQQF_split_coop /* shared bfqq will be split */
|
|
};
|
|
|
|
#define BFQ_BFQQ_FNS(name) \
|
|
static void bfq_mark_bfqq_##name(struct bfq_queue *bfqq) \
|
|
{ \
|
|
__set_bit(BFQQF_##name, &(bfqq)->flags); \
|
|
} \
|
|
static void bfq_clear_bfqq_##name(struct bfq_queue *bfqq) \
|
|
{ \
|
|
__clear_bit(BFQQF_##name, &(bfqq)->flags); \
|
|
} \
|
|
static int bfq_bfqq_##name(const struct bfq_queue *bfqq) \
|
|
{ \
|
|
return test_bit(BFQQF_##name, &(bfqq)->flags); \
|
|
}
|
|
|
|
BFQ_BFQQ_FNS(busy);
|
|
BFQ_BFQQ_FNS(wait_request);
|
|
BFQ_BFQQ_FNS(non_blocking_wait_rq);
|
|
BFQ_BFQQ_FNS(fifo_expire);
|
|
BFQ_BFQQ_FNS(idle_window);
|
|
BFQ_BFQQ_FNS(sync);
|
|
BFQ_BFQQ_FNS(IO_bound);
|
|
BFQ_BFQQ_FNS(coop);
|
|
BFQ_BFQQ_FNS(split_coop);
|
|
BFQ_BFQQ_FNS(softrt_update);
|
|
#undef BFQ_BFQQ_FNS
|
|
|
|
/* Logging facilities. */
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
|
|
static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg);
|
|
|
|
#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) do { \
|
|
char __pbuf[128]; \
|
|
\
|
|
blkg_path(bfqg_to_blkg(bfqq_group(bfqq)), __pbuf, sizeof(__pbuf)); \
|
|
blk_add_trace_msg((bfqd)->queue, "bfq%d%c %s " fmt, (bfqq)->pid, \
|
|
bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \
|
|
__pbuf, ##args); \
|
|
} while (0)
|
|
|
|
#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do { \
|
|
char __pbuf[128]; \
|
|
\
|
|
blkg_path(bfqg_to_blkg(bfqg), __pbuf, sizeof(__pbuf)); \
|
|
blk_add_trace_msg((bfqd)->queue, "%s " fmt, __pbuf, ##args); \
|
|
} while (0)
|
|
|
|
#else /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
|
|
#define bfq_log_bfqq(bfqd, bfqq, fmt, args...) \
|
|
blk_add_trace_msg((bfqd)->queue, "bfq%d%c " fmt, (bfqq)->pid, \
|
|
bfq_bfqq_sync((bfqq)) ? 'S' : 'A', \
|
|
##args)
|
|
#define bfq_log_bfqg(bfqd, bfqg, fmt, args...) do {} while (0)
|
|
|
|
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
|
|
#define bfq_log(bfqd, fmt, args...) \
|
|
blk_add_trace_msg((bfqd)->queue, "bfq " fmt, ##args)
|
|
|
|
/* Expiration reasons. */
|
|
enum bfqq_expiration {
|
|
BFQQE_TOO_IDLE = 0, /*
|
|
* queue has been idling for
|
|
* too long
|
|
*/
|
|
BFQQE_BUDGET_TIMEOUT, /* budget took too long to be used */
|
|
BFQQE_BUDGET_EXHAUSTED, /* budget consumed */
|
|
BFQQE_NO_MORE_REQUESTS, /* the queue has no more requests */
|
|
BFQQE_PREEMPTED /* preemption in progress */
|
|
};
|
|
|
|
struct bfqg_stats {
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
/* number of ios merged */
|
|
struct blkg_rwstat merged;
|
|
/* total time spent on device in ns, may not be accurate w/ queueing */
|
|
struct blkg_rwstat service_time;
|
|
/* total time spent waiting in scheduler queue in ns */
|
|
struct blkg_rwstat wait_time;
|
|
/* number of IOs queued up */
|
|
struct blkg_rwstat queued;
|
|
/* total disk time and nr sectors dispatched by this group */
|
|
struct blkg_stat time;
|
|
/* sum of number of ios queued across all samples */
|
|
struct blkg_stat avg_queue_size_sum;
|
|
/* count of samples taken for average */
|
|
struct blkg_stat avg_queue_size_samples;
|
|
/* how many times this group has been removed from service tree */
|
|
struct blkg_stat dequeue;
|
|
/* total time spent waiting for it to be assigned a timeslice. */
|
|
struct blkg_stat group_wait_time;
|
|
/* time spent idling for this blkcg_gq */
|
|
struct blkg_stat idle_time;
|
|
/* total time with empty current active q with other requests queued */
|
|
struct blkg_stat empty_time;
|
|
/* fields after this shouldn't be cleared on stat reset */
|
|
uint64_t start_group_wait_time;
|
|
uint64_t start_idle_time;
|
|
uint64_t start_empty_time;
|
|
uint16_t flags;
|
|
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
};
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
|
|
/*
|
|
* struct bfq_group_data - per-blkcg storage for the blkio subsystem.
|
|
*
|
|
* @ps: @blkcg_policy_storage that this structure inherits
|
|
* @weight: weight of the bfq_group
|
|
*/
|
|
struct bfq_group_data {
|
|
/* must be the first member */
|
|
struct blkcg_policy_data pd;
|
|
|
|
unsigned int weight;
|
|
};
|
|
|
|
/**
|
|
* struct bfq_group - per (device, cgroup) data structure.
|
|
* @entity: schedulable entity to insert into the parent group sched_data.
|
|
* @sched_data: own sched_data, to contain child entities (they may be
|
|
* both bfq_queues and bfq_groups).
|
|
* @bfqd: the bfq_data for the device this group acts upon.
|
|
* @async_bfqq: array of async queues for all the tasks belonging to
|
|
* the group, one queue per ioprio value per ioprio_class,
|
|
* except for the idle class that has only one queue.
|
|
* @async_idle_bfqq: async queue for the idle class (ioprio is ignored).
|
|
* @my_entity: pointer to @entity, %NULL for the toplevel group; used
|
|
* to avoid too many special cases during group creation/
|
|
* migration.
|
|
* @stats: stats for this bfqg.
|
|
* @rq_pos_tree: rbtree sorted by next_request position, used when
|
|
* determining if two or more queues have interleaving
|
|
* requests (see bfq_find_close_cooperator()).
|
|
*
|
|
* Each (device, cgroup) pair has its own bfq_group, i.e., for each cgroup
|
|
* there is a set of bfq_groups, each one collecting the lower-level
|
|
* entities belonging to the group that are acting on the same device.
|
|
*
|
|
* Locking works as follows:
|
|
* o @bfqd is protected by the queue lock, RCU is used to access it
|
|
* from the readers.
|
|
* o All the other fields are protected by the @bfqd queue lock.
|
|
*/
|
|
struct bfq_group {
|
|
/* must be the first member */
|
|
struct blkg_policy_data pd;
|
|
|
|
struct bfq_entity entity;
|
|
struct bfq_sched_data sched_data;
|
|
|
|
void *bfqd;
|
|
|
|
struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
|
|
struct bfq_queue *async_idle_bfqq;
|
|
|
|
struct bfq_entity *my_entity;
|
|
|
|
struct rb_root rq_pos_tree;
|
|
|
|
struct bfqg_stats stats;
|
|
};
|
|
|
|
#else
|
|
struct bfq_group {
|
|
struct bfq_sched_data sched_data;
|
|
|
|
struct bfq_queue *async_bfqq[2][IOPRIO_BE_NR];
|
|
struct bfq_queue *async_idle_bfqq;
|
|
|
|
struct rb_root rq_pos_tree;
|
|
};
|
|
#endif
|
|
|
|
static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity);
|
|
|
|
static unsigned int bfq_class_idx(struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
return bfqq ? bfqq->ioprio_class - 1 :
|
|
BFQ_DEFAULT_GRP_CLASS - 1;
|
|
}
|
|
|
|
static struct bfq_service_tree *
|
|
bfq_entity_service_tree(struct bfq_entity *entity)
|
|
{
|
|
struct bfq_sched_data *sched_data = entity->sched_data;
|
|
unsigned int idx = bfq_class_idx(entity);
|
|
|
|
return sched_data->service_tree + idx;
|
|
}
|
|
|
|
static struct bfq_queue *bic_to_bfqq(struct bfq_io_cq *bic, bool is_sync)
|
|
{
|
|
return bic->bfqq[is_sync];
|
|
}
|
|
|
|
static void bic_set_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq,
|
|
bool is_sync)
|
|
{
|
|
bic->bfqq[is_sync] = bfqq;
|
|
}
|
|
|
|
static struct bfq_data *bic_to_bfqd(struct bfq_io_cq *bic)
|
|
{
|
|
return bic->icq.q->elevator->elevator_data;
|
|
}
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
|
|
static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *group_entity = bfqq->entity.parent;
|
|
|
|
if (!group_entity)
|
|
group_entity = &bfqq->bfqd->root_group->entity;
|
|
|
|
return container_of(group_entity, struct bfq_group, entity);
|
|
}
|
|
|
|
#else
|
|
|
|
static struct bfq_group *bfq_bfqq_to_bfqg(struct bfq_queue *bfqq)
|
|
{
|
|
return bfqq->bfqd->root_group;
|
|
}
|
|
|
|
#endif
|
|
|
|
static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio);
|
|
static void bfq_put_queue(struct bfq_queue *bfqq);
|
|
static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
|
|
struct bio *bio, bool is_sync,
|
|
struct bfq_io_cq *bic);
|
|
static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
|
|
struct bfq_group *bfqg);
|
|
static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg);
|
|
static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq);
|
|
|
|
/* Expiration time of sync (0) and async (1) requests, in ns. */
|
|
static const u64 bfq_fifo_expire[2] = { NSEC_PER_SEC / 4, NSEC_PER_SEC / 8 };
|
|
|
|
/* Maximum backwards seek (magic number lifted from CFQ), in KiB. */
|
|
static const int bfq_back_max = 16 * 1024;
|
|
|
|
/* Penalty of a backwards seek, in number of sectors. */
|
|
static const int bfq_back_penalty = 2;
|
|
|
|
/* Idling period duration, in ns. */
|
|
static u64 bfq_slice_idle = NSEC_PER_SEC / 125;
|
|
|
|
/* Minimum number of assigned budgets for which stats are safe to compute. */
|
|
static const int bfq_stats_min_budgets = 194;
|
|
|
|
/* Default maximum budget values, in sectors and number of requests. */
|
|
static const int bfq_default_max_budget = 16 * 1024;
|
|
|
|
/*
|
|
* Async to sync throughput distribution is controlled as follows:
|
|
* when an async request is served, the entity is charged the number
|
|
* of sectors of the request, multiplied by the factor below
|
|
*/
|
|
static const int bfq_async_charge_factor = 10;
|
|
|
|
/* Default timeout values, in jiffies, approximating CFQ defaults. */
|
|
static const int bfq_timeout = HZ / 8;
|
|
|
|
static struct kmem_cache *bfq_pool;
|
|
|
|
/* Below this threshold (in ns), we consider thinktime immediate. */
|
|
#define BFQ_MIN_TT (2 * NSEC_PER_MSEC)
|
|
|
|
/* hw_tag detection: parallel requests threshold and min samples needed. */
|
|
#define BFQ_HW_QUEUE_THRESHOLD 4
|
|
#define BFQ_HW_QUEUE_SAMPLES 32
|
|
|
|
#define BFQQ_SEEK_THR (sector_t)(8 * 100)
|
|
#define BFQQ_SECT_THR_NONROT (sector_t)(2 * 32)
|
|
#define BFQQ_CLOSE_THR (sector_t)(8 * 1024)
|
|
#define BFQQ_SEEKY(bfqq) (hweight32(bfqq->seek_history) > 32/8)
|
|
|
|
/* Min number of samples required to perform peak-rate update */
|
|
#define BFQ_RATE_MIN_SAMPLES 32
|
|
/* Min observation time interval required to perform a peak-rate update (ns) */
|
|
#define BFQ_RATE_MIN_INTERVAL (300*NSEC_PER_MSEC)
|
|
/* Target observation time interval for a peak-rate update (ns) */
|
|
#define BFQ_RATE_REF_INTERVAL NSEC_PER_SEC
|
|
|
|
/* Shift used for peak rate fixed precision calculations. */
|
|
#define BFQ_RATE_SHIFT 16
|
|
|
|
/*
|
|
* By default, BFQ computes the duration of the weight raising for
|
|
* interactive applications automatically, using the following formula:
|
|
* duration = (R / r) * T, where r is the peak rate of the device, and
|
|
* R and T are two reference parameters.
|
|
* In particular, R is the peak rate of the reference device (see below),
|
|
* and T is a reference time: given the systems that are likely to be
|
|
* installed on the reference device according to its speed class, T is
|
|
* about the maximum time needed, under BFQ and while reading two files in
|
|
* parallel, to load typical large applications on these systems.
|
|
* In practice, the slower/faster the device at hand is, the more/less it
|
|
* takes to load applications with respect to the reference device.
|
|
* Accordingly, the longer/shorter BFQ grants weight raising to interactive
|
|
* applications.
|
|
*
|
|
* BFQ uses four different reference pairs (R, T), depending on:
|
|
* . whether the device is rotational or non-rotational;
|
|
* . whether the device is slow, such as old or portable HDDs, as well as
|
|
* SD cards, or fast, such as newer HDDs and SSDs.
|
|
*
|
|
* The device's speed class is dynamically (re)detected in
|
|
* bfq_update_peak_rate() every time the estimated peak rate is updated.
|
|
*
|
|
* In the following definitions, R_slow[0]/R_fast[0] and
|
|
* T_slow[0]/T_fast[0] are the reference values for a slow/fast
|
|
* rotational device, whereas R_slow[1]/R_fast[1] and
|
|
* T_slow[1]/T_fast[1] are the reference values for a slow/fast
|
|
* non-rotational device. Finally, device_speed_thresh are the
|
|
* thresholds used to switch between speed classes. The reference
|
|
* rates are not the actual peak rates of the devices used as a
|
|
* reference, but slightly lower values. The reason for using these
|
|
* slightly lower values is that the peak-rate estimator tends to
|
|
* yield slightly lower values than the actual peak rate (it can yield
|
|
* the actual peak rate only if there is only one process doing I/O,
|
|
* and the process does sequential I/O).
|
|
*
|
|
* Both the reference peak rates and the thresholds are measured in
|
|
* sectors/usec, left-shifted by BFQ_RATE_SHIFT.
|
|
*/
|
|
static int R_slow[2] = {1000, 10700};
|
|
static int R_fast[2] = {14000, 33000};
|
|
/*
|
|
* To improve readability, a conversion function is used to initialize the
|
|
* following arrays, which entails that they can be initialized only in a
|
|
* function.
|
|
*/
|
|
static int T_slow[2];
|
|
static int T_fast[2];
|
|
static int device_speed_thresh[2];
|
|
|
|
#define BFQ_SERVICE_TREE_INIT ((struct bfq_service_tree) \
|
|
{ RB_ROOT, RB_ROOT, NULL, NULL, 0, 0 })
|
|
|
|
#define RQ_BIC(rq) ((struct bfq_io_cq *) (rq)->elv.priv[0])
|
|
#define RQ_BFQQ(rq) ((rq)->elv.priv[1])
|
|
|
|
/**
|
|
* icq_to_bic - convert iocontext queue structure to bfq_io_cq.
|
|
* @icq: the iocontext queue.
|
|
*/
|
|
static struct bfq_io_cq *icq_to_bic(struct io_cq *icq)
|
|
{
|
|
/* bic->icq is the first member, %NULL will convert to %NULL */
|
|
return container_of(icq, struct bfq_io_cq, icq);
|
|
}
|
|
|
|
/**
|
|
* bfq_bic_lookup - search into @ioc a bic associated to @bfqd.
|
|
* @bfqd: the lookup key.
|
|
* @ioc: the io_context of the process doing I/O.
|
|
* @q: the request queue.
|
|
*/
|
|
static struct bfq_io_cq *bfq_bic_lookup(struct bfq_data *bfqd,
|
|
struct io_context *ioc,
|
|
struct request_queue *q)
|
|
{
|
|
if (ioc) {
|
|
unsigned long flags;
|
|
struct bfq_io_cq *icq;
|
|
|
|
spin_lock_irqsave(q->queue_lock, flags);
|
|
icq = icq_to_bic(ioc_lookup_icq(ioc, q));
|
|
spin_unlock_irqrestore(q->queue_lock, flags);
|
|
|
|
return icq;
|
|
}
|
|
|
|
return NULL;
|
|
}
|
|
|
|
/*
|
|
* Scheduler run of queue, if there are requests pending and no one in the
|
|
* driver that will restart queueing.
|
|
*/
|
|
static void bfq_schedule_dispatch(struct bfq_data *bfqd)
|
|
{
|
|
if (bfqd->queued != 0) {
|
|
bfq_log(bfqd, "schedule dispatch");
|
|
blk_mq_run_hw_queues(bfqd->queue, true);
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Next two functions release bfqd->lock and put the io context
|
|
* pointed by bfqd->ioc_to_put. This delayed put is used to not risk
|
|
* to take an ioc->lock while the scheduler lock is being held.
|
|
*/
|
|
static void bfq_unlock_put_ioc(struct bfq_data *bfqd)
|
|
{
|
|
struct io_context *ioc_to_put = bfqd->ioc_to_put;
|
|
|
|
bfqd->ioc_to_put = NULL;
|
|
spin_unlock_irq(&bfqd->lock);
|
|
|
|
if (ioc_to_put)
|
|
put_io_context(ioc_to_put);
|
|
}
|
|
|
|
static void bfq_unlock_put_ioc_restore(struct bfq_data *bfqd,
|
|
unsigned long flags)
|
|
{
|
|
struct io_context *ioc_to_put = bfqd->ioc_to_put;
|
|
|
|
bfqd->ioc_to_put = NULL;
|
|
spin_unlock_irqrestore(&bfqd->lock, flags);
|
|
|
|
if (ioc_to_put)
|
|
put_io_context(ioc_to_put);
|
|
}
|
|
|
|
/**
|
|
* bfq_gt - compare two timestamps.
|
|
* @a: first ts.
|
|
* @b: second ts.
|
|
*
|
|
* Return @a > @b, dealing with wrapping correctly.
|
|
*/
|
|
static int bfq_gt(u64 a, u64 b)
|
|
{
|
|
return (s64)(a - b) > 0;
|
|
}
|
|
|
|
static struct bfq_entity *bfq_root_active_entity(struct rb_root *tree)
|
|
{
|
|
struct rb_node *node = tree->rb_node;
|
|
|
|
return rb_entry(node, struct bfq_entity, rb_node);
|
|
}
|
|
|
|
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd);
|
|
|
|
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service);
|
|
|
|
/**
|
|
* bfq_update_next_in_service - update sd->next_in_service
|
|
* @sd: sched_data for which to perform the update.
|
|
* @new_entity: if not NULL, pointer to the entity whose activation,
|
|
* requeueing or repositionig triggered the invocation of
|
|
* this function.
|
|
*
|
|
* This function is called to update sd->next_in_service, which, in
|
|
* its turn, may change as a consequence of the insertion or
|
|
* extraction of an entity into/from one of the active trees of
|
|
* sd. These insertions/extractions occur as a consequence of
|
|
* activations/deactivations of entities, with some activations being
|
|
* 'true' activations, and other activations being requeueings (i.e.,
|
|
* implementing the second, requeueing phase of the mechanism used to
|
|
* reposition an entity in its active tree; see comments on
|
|
* __bfq_activate_entity and __bfq_requeue_entity for details). In
|
|
* both the last two activation sub-cases, new_entity points to the
|
|
* just activated or requeued entity.
|
|
*
|
|
* Returns true if sd->next_in_service changes in such a way that
|
|
* entity->parent may become the next_in_service for its parent
|
|
* entity.
|
|
*/
|
|
static bool bfq_update_next_in_service(struct bfq_sched_data *sd,
|
|
struct bfq_entity *new_entity)
|
|
{
|
|
struct bfq_entity *next_in_service = sd->next_in_service;
|
|
bool parent_sched_may_change = false;
|
|
|
|
/*
|
|
* If this update is triggered by the activation, requeueing
|
|
* or repositiong of an entity that does not coincide with
|
|
* sd->next_in_service, then a full lookup in the active tree
|
|
* can be avoided. In fact, it is enough to check whether the
|
|
* just-modified entity has a higher priority than
|
|
* sd->next_in_service, or, even if it has the same priority
|
|
* as sd->next_in_service, is eligible and has a lower virtual
|
|
* finish time than sd->next_in_service. If this compound
|
|
* condition holds, then the new entity becomes the new
|
|
* next_in_service. Otherwise no change is needed.
|
|
*/
|
|
if (new_entity && new_entity != sd->next_in_service) {
|
|
/*
|
|
* Flag used to decide whether to replace
|
|
* sd->next_in_service with new_entity. Tentatively
|
|
* set to true, and left as true if
|
|
* sd->next_in_service is NULL.
|
|
*/
|
|
bool replace_next = true;
|
|
|
|
/*
|
|
* If there is already a next_in_service candidate
|
|
* entity, then compare class priorities or timestamps
|
|
* to decide whether to replace sd->service_tree with
|
|
* new_entity.
|
|
*/
|
|
if (next_in_service) {
|
|
unsigned int new_entity_class_idx =
|
|
bfq_class_idx(new_entity);
|
|
struct bfq_service_tree *st =
|
|
sd->service_tree + new_entity_class_idx;
|
|
|
|
/*
|
|
* For efficiency, evaluate the most likely
|
|
* sub-condition first.
|
|
*/
|
|
replace_next =
|
|
(new_entity_class_idx ==
|
|
bfq_class_idx(next_in_service)
|
|
&&
|
|
!bfq_gt(new_entity->start, st->vtime)
|
|
&&
|
|
bfq_gt(next_in_service->finish,
|
|
new_entity->finish))
|
|
||
|
|
new_entity_class_idx <
|
|
bfq_class_idx(next_in_service);
|
|
}
|
|
|
|
if (replace_next)
|
|
next_in_service = new_entity;
|
|
} else /* invoked because of a deactivation: lookup needed */
|
|
next_in_service = bfq_lookup_next_entity(sd);
|
|
|
|
if (next_in_service) {
|
|
parent_sched_may_change = !sd->next_in_service ||
|
|
bfq_update_parent_budget(next_in_service);
|
|
}
|
|
|
|
sd->next_in_service = next_in_service;
|
|
|
|
if (!next_in_service)
|
|
return parent_sched_may_change;
|
|
|
|
return parent_sched_may_change;
|
|
}
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
/* both next loops stop at one of the child entities of the root group */
|
|
#define for_each_entity(entity) \
|
|
for (; entity ; entity = entity->parent)
|
|
|
|
/*
|
|
* For each iteration, compute parent in advance, so as to be safe if
|
|
* entity is deallocated during the iteration. Such a deallocation may
|
|
* happen as a consequence of a bfq_put_queue that frees the bfq_queue
|
|
* containing entity.
|
|
*/
|
|
#define for_each_entity_safe(entity, parent) \
|
|
for (; entity && ({ parent = entity->parent; 1; }); entity = parent)
|
|
|
|
/*
|
|
* Returns true if this budget changes may let next_in_service->parent
|
|
* become the next_in_service entity for its parent entity.
|
|
*/
|
|
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
|
|
{
|
|
struct bfq_entity *bfqg_entity;
|
|
struct bfq_group *bfqg;
|
|
struct bfq_sched_data *group_sd;
|
|
bool ret = false;
|
|
|
|
group_sd = next_in_service->sched_data;
|
|
|
|
bfqg = container_of(group_sd, struct bfq_group, sched_data);
|
|
/*
|
|
* bfq_group's my_entity field is not NULL only if the group
|
|
* is not the root group. We must not touch the root entity
|
|
* as it must never become an in-service entity.
|
|
*/
|
|
bfqg_entity = bfqg->my_entity;
|
|
if (bfqg_entity) {
|
|
if (bfqg_entity->budget > next_in_service->budget)
|
|
ret = true;
|
|
bfqg_entity->budget = next_in_service->budget;
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* This function tells whether entity stops being a candidate for next
|
|
* service, according to the following logic.
|
|
*
|
|
* This function is invoked for an entity that is about to be set in
|
|
* service. If such an entity is a queue, then the entity is no longer
|
|
* a candidate for next service (i.e, a candidate entity to serve
|
|
* after the in-service entity is expired). The function then returns
|
|
* true.
|
|
*/
|
|
static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
|
|
{
|
|
if (bfq_entity_to_bfqq(entity))
|
|
return true;
|
|
|
|
return false;
|
|
}
|
|
|
|
#else /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
/*
|
|
* Next two macros are fake loops when cgroups support is not
|
|
* enabled. I fact, in such a case, there is only one level to go up
|
|
* (to reach the root group).
|
|
*/
|
|
#define for_each_entity(entity) \
|
|
for (; entity ; entity = NULL)
|
|
|
|
#define for_each_entity_safe(entity, parent) \
|
|
for (parent = NULL; entity ; entity = parent)
|
|
|
|
static bool bfq_update_parent_budget(struct bfq_entity *next_in_service)
|
|
{
|
|
return false;
|
|
}
|
|
|
|
static bool bfq_no_longer_next_in_service(struct bfq_entity *entity)
|
|
{
|
|
return true;
|
|
}
|
|
|
|
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
|
|
/*
|
|
* Shift for timestamp calculations. This actually limits the maximum
|
|
* service allowed in one timestamp delta (small shift values increase it),
|
|
* the maximum total weight that can be used for the queues in the system
|
|
* (big shift values increase it), and the period of virtual time
|
|
* wraparounds.
|
|
*/
|
|
#define WFQ_SERVICE_SHIFT 22
|
|
|
|
static struct bfq_queue *bfq_entity_to_bfqq(struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = NULL;
|
|
|
|
if (!entity->my_sched_data)
|
|
bfqq = container_of(entity, struct bfq_queue, entity);
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
|
|
/**
|
|
* bfq_delta - map service into the virtual time domain.
|
|
* @service: amount of service.
|
|
* @weight: scale factor (weight of an entity or weight sum).
|
|
*/
|
|
static u64 bfq_delta(unsigned long service, unsigned long weight)
|
|
{
|
|
u64 d = (u64)service << WFQ_SERVICE_SHIFT;
|
|
|
|
do_div(d, weight);
|
|
return d;
|
|
}
|
|
|
|
/**
|
|
* bfq_calc_finish - assign the finish time to an entity.
|
|
* @entity: the entity to act upon.
|
|
* @service: the service to be charged to the entity.
|
|
*/
|
|
static void bfq_calc_finish(struct bfq_entity *entity, unsigned long service)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
entity->finish = entity->start +
|
|
bfq_delta(service, entity->weight);
|
|
|
|
if (bfqq) {
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq,
|
|
"calc_finish: serv %lu, w %d",
|
|
service, entity->weight);
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq,
|
|
"calc_finish: start %llu, finish %llu, delta %llu",
|
|
entity->start, entity->finish,
|
|
bfq_delta(service, entity->weight));
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bfq_entity_of - get an entity from a node.
|
|
* @node: the node field of the entity.
|
|
*
|
|
* Convert a node pointer to the relative entity. This is used only
|
|
* to simplify the logic of some functions and not as the generic
|
|
* conversion mechanism because, e.g., in the tree walking functions,
|
|
* the check for a %NULL value would be redundant.
|
|
*/
|
|
static struct bfq_entity *bfq_entity_of(struct rb_node *node)
|
|
{
|
|
struct bfq_entity *entity = NULL;
|
|
|
|
if (node)
|
|
entity = rb_entry(node, struct bfq_entity, rb_node);
|
|
|
|
return entity;
|
|
}
|
|
|
|
/**
|
|
* bfq_extract - remove an entity from a tree.
|
|
* @root: the tree root.
|
|
* @entity: the entity to remove.
|
|
*/
|
|
static void bfq_extract(struct rb_root *root, struct bfq_entity *entity)
|
|
{
|
|
entity->tree = NULL;
|
|
rb_erase(&entity->rb_node, root);
|
|
}
|
|
|
|
/**
|
|
* bfq_idle_extract - extract an entity from the idle tree.
|
|
* @st: the service tree of the owning @entity.
|
|
* @entity: the entity being removed.
|
|
*/
|
|
static void bfq_idle_extract(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
struct rb_node *next;
|
|
|
|
if (entity == st->first_idle) {
|
|
next = rb_next(&entity->rb_node);
|
|
st->first_idle = bfq_entity_of(next);
|
|
}
|
|
|
|
if (entity == st->last_idle) {
|
|
next = rb_prev(&entity->rb_node);
|
|
st->last_idle = bfq_entity_of(next);
|
|
}
|
|
|
|
bfq_extract(&st->idle, entity);
|
|
|
|
if (bfqq)
|
|
list_del(&bfqq->bfqq_list);
|
|
}
|
|
|
|
/**
|
|
* bfq_insert - generic tree insertion.
|
|
* @root: tree root.
|
|
* @entity: entity to insert.
|
|
*
|
|
* This is used for the idle and the active tree, since they are both
|
|
* ordered by finish time.
|
|
*/
|
|
static void bfq_insert(struct rb_root *root, struct bfq_entity *entity)
|
|
{
|
|
struct bfq_entity *entry;
|
|
struct rb_node **node = &root->rb_node;
|
|
struct rb_node *parent = NULL;
|
|
|
|
while (*node) {
|
|
parent = *node;
|
|
entry = rb_entry(parent, struct bfq_entity, rb_node);
|
|
|
|
if (bfq_gt(entry->finish, entity->finish))
|
|
node = &parent->rb_left;
|
|
else
|
|
node = &parent->rb_right;
|
|
}
|
|
|
|
rb_link_node(&entity->rb_node, parent, node);
|
|
rb_insert_color(&entity->rb_node, root);
|
|
|
|
entity->tree = root;
|
|
}
|
|
|
|
/**
|
|
* bfq_update_min - update the min_start field of a entity.
|
|
* @entity: the entity to update.
|
|
* @node: one of its children.
|
|
*
|
|
* This function is called when @entity may store an invalid value for
|
|
* min_start due to updates to the active tree. The function assumes
|
|
* that the subtree rooted at @node (which may be its left or its right
|
|
* child) has a valid min_start value.
|
|
*/
|
|
static void bfq_update_min(struct bfq_entity *entity, struct rb_node *node)
|
|
{
|
|
struct bfq_entity *child;
|
|
|
|
if (node) {
|
|
child = rb_entry(node, struct bfq_entity, rb_node);
|
|
if (bfq_gt(entity->min_start, child->min_start))
|
|
entity->min_start = child->min_start;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bfq_update_active_node - recalculate min_start.
|
|
* @node: the node to update.
|
|
*
|
|
* @node may have changed position or one of its children may have moved,
|
|
* this function updates its min_start value. The left and right subtrees
|
|
* are assumed to hold a correct min_start value.
|
|
*/
|
|
static void bfq_update_active_node(struct rb_node *node)
|
|
{
|
|
struct bfq_entity *entity = rb_entry(node, struct bfq_entity, rb_node);
|
|
|
|
entity->min_start = entity->start;
|
|
bfq_update_min(entity, node->rb_right);
|
|
bfq_update_min(entity, node->rb_left);
|
|
}
|
|
|
|
/**
|
|
* bfq_update_active_tree - update min_start for the whole active tree.
|
|
* @node: the starting node.
|
|
*
|
|
* @node must be the deepest modified node after an update. This function
|
|
* updates its min_start using the values held by its children, assuming
|
|
* that they did not change, and then updates all the nodes that may have
|
|
* changed in the path to the root. The only nodes that may have changed
|
|
* are the ones in the path or their siblings.
|
|
*/
|
|
static void bfq_update_active_tree(struct rb_node *node)
|
|
{
|
|
struct rb_node *parent;
|
|
|
|
up:
|
|
bfq_update_active_node(node);
|
|
|
|
parent = rb_parent(node);
|
|
if (!parent)
|
|
return;
|
|
|
|
if (node == parent->rb_left && parent->rb_right)
|
|
bfq_update_active_node(parent->rb_right);
|
|
else if (parent->rb_left)
|
|
bfq_update_active_node(parent->rb_left);
|
|
|
|
node = parent;
|
|
goto up;
|
|
}
|
|
|
|
/**
|
|
* bfq_active_insert - insert an entity in the active tree of its
|
|
* group/device.
|
|
* @st: the service tree of the entity.
|
|
* @entity: the entity being inserted.
|
|
*
|
|
* The active tree is ordered by finish time, but an extra key is kept
|
|
* per each node, containing the minimum value for the start times of
|
|
* its children (and the node itself), so it's possible to search for
|
|
* the eligible node with the lowest finish time in logarithmic time.
|
|
*/
|
|
static void bfq_active_insert(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
struct rb_node *node = &entity->rb_node;
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
struct bfq_sched_data *sd = NULL;
|
|
struct bfq_group *bfqg = NULL;
|
|
struct bfq_data *bfqd = NULL;
|
|
#endif
|
|
|
|
bfq_insert(&st->active, entity);
|
|
|
|
if (node->rb_left)
|
|
node = node->rb_left;
|
|
else if (node->rb_right)
|
|
node = node->rb_right;
|
|
|
|
bfq_update_active_tree(node);
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
sd = entity->sched_data;
|
|
bfqg = container_of(sd, struct bfq_group, sched_data);
|
|
bfqd = (struct bfq_data *)bfqg->bfqd;
|
|
#endif
|
|
if (bfqq)
|
|
list_add(&bfqq->bfqq_list, &bfqq->bfqd->active_list);
|
|
}
|
|
|
|
/**
|
|
* bfq_ioprio_to_weight - calc a weight from an ioprio.
|
|
* @ioprio: the ioprio value to convert.
|
|
*/
|
|
static unsigned short bfq_ioprio_to_weight(int ioprio)
|
|
{
|
|
return (IOPRIO_BE_NR - ioprio) * BFQ_WEIGHT_CONVERSION_COEFF;
|
|
}
|
|
|
|
/**
|
|
* bfq_weight_to_ioprio - calc an ioprio from a weight.
|
|
* @weight: the weight value to convert.
|
|
*
|
|
* To preserve as much as possible the old only-ioprio user interface,
|
|
* 0 is used as an escape ioprio value for weights (numerically) equal or
|
|
* larger than IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF.
|
|
*/
|
|
static unsigned short bfq_weight_to_ioprio(int weight)
|
|
{
|
|
return max_t(int, 0,
|
|
IOPRIO_BE_NR * BFQ_WEIGHT_CONVERSION_COEFF - weight);
|
|
}
|
|
|
|
static void bfq_get_entity(struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
if (bfqq) {
|
|
bfqq->ref++;
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "get_entity: %p %d",
|
|
bfqq, bfqq->ref);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bfq_find_deepest - find the deepest node that an extraction can modify.
|
|
* @node: the node being removed.
|
|
*
|
|
* Do the first step of an extraction in an rb tree, looking for the
|
|
* node that will replace @node, and returning the deepest node that
|
|
* the following modifications to the tree can touch. If @node is the
|
|
* last node in the tree return %NULL.
|
|
*/
|
|
static struct rb_node *bfq_find_deepest(struct rb_node *node)
|
|
{
|
|
struct rb_node *deepest;
|
|
|
|
if (!node->rb_right && !node->rb_left)
|
|
deepest = rb_parent(node);
|
|
else if (!node->rb_right)
|
|
deepest = node->rb_left;
|
|
else if (!node->rb_left)
|
|
deepest = node->rb_right;
|
|
else {
|
|
deepest = rb_next(node);
|
|
if (deepest->rb_right)
|
|
deepest = deepest->rb_right;
|
|
else if (rb_parent(deepest) != node)
|
|
deepest = rb_parent(deepest);
|
|
}
|
|
|
|
return deepest;
|
|
}
|
|
|
|
/**
|
|
* bfq_active_extract - remove an entity from the active tree.
|
|
* @st: the service_tree containing the tree.
|
|
* @entity: the entity being removed.
|
|
*/
|
|
static void bfq_active_extract(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
struct rb_node *node;
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
struct bfq_sched_data *sd = NULL;
|
|
struct bfq_group *bfqg = NULL;
|
|
struct bfq_data *bfqd = NULL;
|
|
#endif
|
|
|
|
node = bfq_find_deepest(&entity->rb_node);
|
|
bfq_extract(&st->active, entity);
|
|
|
|
if (node)
|
|
bfq_update_active_tree(node);
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
sd = entity->sched_data;
|
|
bfqg = container_of(sd, struct bfq_group, sched_data);
|
|
bfqd = (struct bfq_data *)bfqg->bfqd;
|
|
#endif
|
|
if (bfqq)
|
|
list_del(&bfqq->bfqq_list);
|
|
}
|
|
|
|
/**
|
|
* bfq_idle_insert - insert an entity into the idle tree.
|
|
* @st: the service tree containing the tree.
|
|
* @entity: the entity to insert.
|
|
*/
|
|
static void bfq_idle_insert(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
struct bfq_entity *first_idle = st->first_idle;
|
|
struct bfq_entity *last_idle = st->last_idle;
|
|
|
|
if (!first_idle || bfq_gt(first_idle->finish, entity->finish))
|
|
st->first_idle = entity;
|
|
if (!last_idle || bfq_gt(entity->finish, last_idle->finish))
|
|
st->last_idle = entity;
|
|
|
|
bfq_insert(&st->idle, entity);
|
|
|
|
if (bfqq)
|
|
list_add(&bfqq->bfqq_list, &bfqq->bfqd->idle_list);
|
|
}
|
|
|
|
/**
|
|
* bfq_forget_entity - do not consider entity any longer for scheduling
|
|
* @st: the service tree.
|
|
* @entity: the entity being removed.
|
|
* @is_in_service: true if entity is currently the in-service entity.
|
|
*
|
|
* Forget everything about @entity. In addition, if entity represents
|
|
* a queue, and the latter is not in service, then release the service
|
|
* reference to the queue (the one taken through bfq_get_entity). In
|
|
* fact, in this case, there is really no more service reference to
|
|
* the queue, as the latter is also outside any service tree. If,
|
|
* instead, the queue is in service, then __bfq_bfqd_reset_in_service
|
|
* will take care of putting the reference when the queue finally
|
|
* stops being served.
|
|
*/
|
|
static void bfq_forget_entity(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity,
|
|
bool is_in_service)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
entity->on_st = false;
|
|
st->wsum -= entity->weight;
|
|
if (bfqq && !is_in_service)
|
|
bfq_put_queue(bfqq);
|
|
}
|
|
|
|
/**
|
|
* bfq_put_idle_entity - release the idle tree ref of an entity.
|
|
* @st: service tree for the entity.
|
|
* @entity: the entity being released.
|
|
*/
|
|
static void bfq_put_idle_entity(struct bfq_service_tree *st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
bfq_idle_extract(st, entity);
|
|
bfq_forget_entity(st, entity,
|
|
entity == entity->sched_data->in_service_entity);
|
|
}
|
|
|
|
/**
|
|
* bfq_forget_idle - update the idle tree if necessary.
|
|
* @st: the service tree to act upon.
|
|
*
|
|
* To preserve the global O(log N) complexity we only remove one entry here;
|
|
* as the idle tree will not grow indefinitely this can be done safely.
|
|
*/
|
|
static void bfq_forget_idle(struct bfq_service_tree *st)
|
|
{
|
|
struct bfq_entity *first_idle = st->first_idle;
|
|
struct bfq_entity *last_idle = st->last_idle;
|
|
|
|
if (RB_EMPTY_ROOT(&st->active) && last_idle &&
|
|
!bfq_gt(last_idle->finish, st->vtime)) {
|
|
/*
|
|
* Forget the whole idle tree, increasing the vtime past
|
|
* the last finish time of idle entities.
|
|
*/
|
|
st->vtime = last_idle->finish;
|
|
}
|
|
|
|
if (first_idle && !bfq_gt(first_idle->finish, st->vtime))
|
|
bfq_put_idle_entity(st, first_idle);
|
|
}
|
|
|
|
static struct bfq_service_tree *
|
|
__bfq_entity_update_weight_prio(struct bfq_service_tree *old_st,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_service_tree *new_st = old_st;
|
|
|
|
if (entity->prio_changed) {
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
unsigned int prev_weight, new_weight;
|
|
struct bfq_data *bfqd = NULL;
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
struct bfq_sched_data *sd;
|
|
struct bfq_group *bfqg;
|
|
#endif
|
|
|
|
if (bfqq)
|
|
bfqd = bfqq->bfqd;
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
else {
|
|
sd = entity->my_sched_data;
|
|
bfqg = container_of(sd, struct bfq_group, sched_data);
|
|
bfqd = (struct bfq_data *)bfqg->bfqd;
|
|
}
|
|
#endif
|
|
|
|
old_st->wsum -= entity->weight;
|
|
|
|
if (entity->new_weight != entity->orig_weight) {
|
|
if (entity->new_weight < BFQ_MIN_WEIGHT ||
|
|
entity->new_weight > BFQ_MAX_WEIGHT) {
|
|
pr_crit("update_weight_prio: new_weight %d\n",
|
|
entity->new_weight);
|
|
if (entity->new_weight < BFQ_MIN_WEIGHT)
|
|
entity->new_weight = BFQ_MIN_WEIGHT;
|
|
else
|
|
entity->new_weight = BFQ_MAX_WEIGHT;
|
|
}
|
|
entity->orig_weight = entity->new_weight;
|
|
if (bfqq)
|
|
bfqq->ioprio =
|
|
bfq_weight_to_ioprio(entity->orig_weight);
|
|
}
|
|
|
|
if (bfqq)
|
|
bfqq->ioprio_class = bfqq->new_ioprio_class;
|
|
entity->prio_changed = 0;
|
|
|
|
/*
|
|
* NOTE: here we may be changing the weight too early,
|
|
* this will cause unfairness. The correct approach
|
|
* would have required additional complexity to defer
|
|
* weight changes to the proper time instants (i.e.,
|
|
* when entity->finish <= old_st->vtime).
|
|
*/
|
|
new_st = bfq_entity_service_tree(entity);
|
|
|
|
prev_weight = entity->weight;
|
|
new_weight = entity->orig_weight *
|
|
(bfqq ? bfqq->wr_coeff : 1);
|
|
entity->weight = new_weight;
|
|
|
|
new_st->wsum += entity->weight;
|
|
|
|
if (new_st != old_st)
|
|
entity->start = new_st->vtime;
|
|
}
|
|
|
|
return new_st;
|
|
}
|
|
|
|
static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg);
|
|
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq);
|
|
|
|
/**
|
|
* bfq_bfqq_served - update the scheduler status after selection for
|
|
* service.
|
|
* @bfqq: the queue being served.
|
|
* @served: bytes to transfer.
|
|
*
|
|
* NOTE: this can be optimized, as the timestamps of upper level entities
|
|
* are synchronized every time a new bfqq is selected for service. By now,
|
|
* we keep it to better check consistency.
|
|
*/
|
|
static void bfq_bfqq_served(struct bfq_queue *bfqq, int served)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
struct bfq_service_tree *st;
|
|
|
|
for_each_entity(entity) {
|
|
st = bfq_entity_service_tree(entity);
|
|
|
|
entity->service += served;
|
|
|
|
st->vtime += bfq_delta(served, st->wsum);
|
|
bfq_forget_idle(st);
|
|
}
|
|
bfqg_stats_set_start_empty_time(bfqq_group(bfqq));
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "bfqq_served %d secs", served);
|
|
}
|
|
|
|
/**
|
|
* bfq_bfqq_charge_time - charge an amount of service equivalent to the length
|
|
* of the time interval during which bfqq has been in
|
|
* service.
|
|
* @bfqd: the device
|
|
* @bfqq: the queue that needs a service update.
|
|
* @time_ms: the amount of time during which the queue has received service
|
|
*
|
|
* If a queue does not consume its budget fast enough, then providing
|
|
* the queue with service fairness may impair throughput, more or less
|
|
* severely. For this reason, queues that consume their budget slowly
|
|
* are provided with time fairness instead of service fairness. This
|
|
* goal is achieved through the BFQ scheduling engine, even if such an
|
|
* engine works in the service, and not in the time domain. The trick
|
|
* is charging these queues with an inflated amount of service, equal
|
|
* to the amount of service that they would have received during their
|
|
* service slot if they had been fast, i.e., if their requests had
|
|
* been dispatched at a rate equal to the estimated peak rate.
|
|
*
|
|
* It is worth noting that time fairness can cause important
|
|
* distortions in terms of bandwidth distribution, on devices with
|
|
* internal queueing. The reason is that I/O requests dispatched
|
|
* during the service slot of a queue may be served after that service
|
|
* slot is finished, and may have a total processing time loosely
|
|
* correlated with the duration of the service slot. This is
|
|
* especially true for short service slots.
|
|
*/
|
|
static void bfq_bfqq_charge_time(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
unsigned long time_ms)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
int tot_serv_to_charge = entity->service;
|
|
unsigned int timeout_ms = jiffies_to_msecs(bfq_timeout);
|
|
|
|
if (time_ms > 0 && time_ms < timeout_ms)
|
|
tot_serv_to_charge =
|
|
(bfqd->bfq_max_budget * time_ms) / timeout_ms;
|
|
|
|
if (tot_serv_to_charge < entity->service)
|
|
tot_serv_to_charge = entity->service;
|
|
|
|
/* Increase budget to avoid inconsistencies */
|
|
if (tot_serv_to_charge > entity->budget)
|
|
entity->budget = tot_serv_to_charge;
|
|
|
|
bfq_bfqq_served(bfqq,
|
|
max_t(int, 0, tot_serv_to_charge - entity->service));
|
|
}
|
|
|
|
static void bfq_update_fin_time_enqueue(struct bfq_entity *entity,
|
|
struct bfq_service_tree *st,
|
|
bool backshifted)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
st = __bfq_entity_update_weight_prio(st, entity);
|
|
bfq_calc_finish(entity, entity->budget);
|
|
|
|
/*
|
|
* If some queues enjoy backshifting for a while, then their
|
|
* (virtual) finish timestamps may happen to become lower and
|
|
* lower than the system virtual time. In particular, if
|
|
* these queues often happen to be idle for short time
|
|
* periods, and during such time periods other queues with
|
|
* higher timestamps happen to be busy, then the backshifted
|
|
* timestamps of the former queues can become much lower than
|
|
* the system virtual time. In fact, to serve the queues with
|
|
* higher timestamps while the ones with lower timestamps are
|
|
* idle, the system virtual time may be pushed-up to much
|
|
* higher values than the finish timestamps of the idle
|
|
* queues. As a consequence, the finish timestamps of all new
|
|
* or newly activated queues may end up being much larger than
|
|
* those of lucky queues with backshifted timestamps. The
|
|
* latter queues may then monopolize the device for a lot of
|
|
* time. This would simply break service guarantees.
|
|
*
|
|
* To reduce this problem, push up a little bit the
|
|
* backshifted timestamps of the queue associated with this
|
|
* entity (only a queue can happen to have the backshifted
|
|
* flag set): just enough to let the finish timestamp of the
|
|
* queue be equal to the current value of the system virtual
|
|
* time. This may introduce a little unfairness among queues
|
|
* with backshifted timestamps, but it does not break
|
|
* worst-case fairness guarantees.
|
|
*
|
|
* As a special case, if bfqq is weight-raised, push up
|
|
* timestamps much less, to keep very low the probability that
|
|
* this push up causes the backshifted finish timestamps of
|
|
* weight-raised queues to become higher than the backshifted
|
|
* finish timestamps of non weight-raised queues.
|
|
*/
|
|
if (backshifted && bfq_gt(st->vtime, entity->finish)) {
|
|
unsigned long delta = st->vtime - entity->finish;
|
|
|
|
if (bfqq)
|
|
delta /= bfqq->wr_coeff;
|
|
|
|
entity->start += delta;
|
|
entity->finish += delta;
|
|
}
|
|
|
|
bfq_active_insert(st, entity);
|
|
}
|
|
|
|
/**
|
|
* __bfq_activate_entity - handle activation of entity.
|
|
* @entity: the entity being activated.
|
|
* @non_blocking_wait_rq: true if entity was waiting for a request
|
|
*
|
|
* Called for a 'true' activation, i.e., if entity is not active and
|
|
* one of its children receives a new request.
|
|
*
|
|
* Basically, this function updates the timestamps of entity and
|
|
* inserts entity into its active tree, ater possible extracting it
|
|
* from its idle tree.
|
|
*/
|
|
static void __bfq_activate_entity(struct bfq_entity *entity,
|
|
bool non_blocking_wait_rq)
|
|
{
|
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
|
|
bool backshifted = false;
|
|
unsigned long long min_vstart;
|
|
|
|
/* See comments on bfq_fqq_update_budg_for_activation */
|
|
if (non_blocking_wait_rq && bfq_gt(st->vtime, entity->finish)) {
|
|
backshifted = true;
|
|
min_vstart = entity->finish;
|
|
} else
|
|
min_vstart = st->vtime;
|
|
|
|
if (entity->tree == &st->idle) {
|
|
/*
|
|
* Must be on the idle tree, bfq_idle_extract() will
|
|
* check for that.
|
|
*/
|
|
bfq_idle_extract(st, entity);
|
|
entity->start = bfq_gt(min_vstart, entity->finish) ?
|
|
min_vstart : entity->finish;
|
|
} else {
|
|
/*
|
|
* The finish time of the entity may be invalid, and
|
|
* it is in the past for sure, otherwise the queue
|
|
* would have been on the idle tree.
|
|
*/
|
|
entity->start = min_vstart;
|
|
st->wsum += entity->weight;
|
|
/*
|
|
* entity is about to be inserted into a service tree,
|
|
* and then set in service: get a reference to make
|
|
* sure entity does not disappear until it is no
|
|
* longer in service or scheduled for service.
|
|
*/
|
|
bfq_get_entity(entity);
|
|
|
|
entity->on_st = true;
|
|
}
|
|
|
|
bfq_update_fin_time_enqueue(entity, st, backshifted);
|
|
}
|
|
|
|
/**
|
|
* __bfq_requeue_entity - handle requeueing or repositioning of an entity.
|
|
* @entity: the entity being requeued or repositioned.
|
|
*
|
|
* Requeueing is needed if this entity stops being served, which
|
|
* happens if a leaf descendant entity has expired. On the other hand,
|
|
* repositioning is needed if the next_inservice_entity for the child
|
|
* entity has changed. See the comments inside the function for
|
|
* details.
|
|
*
|
|
* Basically, this function: 1) removes entity from its active tree if
|
|
* present there, 2) updates the timestamps of entity and 3) inserts
|
|
* entity back into its active tree (in the new, right position for
|
|
* the new values of the timestamps).
|
|
*/
|
|
static void __bfq_requeue_entity(struct bfq_entity *entity)
|
|
{
|
|
struct bfq_sched_data *sd = entity->sched_data;
|
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
|
|
|
|
if (entity == sd->in_service_entity) {
|
|
/*
|
|
* We are requeueing the current in-service entity,
|
|
* which may have to be done for one of the following
|
|
* reasons:
|
|
* - entity represents the in-service queue, and the
|
|
* in-service queue is being requeued after an
|
|
* expiration;
|
|
* - entity represents a group, and its budget has
|
|
* changed because one of its child entities has
|
|
* just been either activated or requeued for some
|
|
* reason; the timestamps of the entity need then to
|
|
* be updated, and the entity needs to be enqueued
|
|
* or repositioned accordingly.
|
|
*
|
|
* In particular, before requeueing, the start time of
|
|
* the entity must be moved forward to account for the
|
|
* service that the entity has received while in
|
|
* service. This is done by the next instructions. The
|
|
* finish time will then be updated according to this
|
|
* new value of the start time, and to the budget of
|
|
* the entity.
|
|
*/
|
|
bfq_calc_finish(entity, entity->service);
|
|
entity->start = entity->finish;
|
|
/*
|
|
* In addition, if the entity had more than one child
|
|
* when set in service, then was not extracted from
|
|
* the active tree. This implies that the position of
|
|
* the entity in the active tree may need to be
|
|
* changed now, because we have just updated the start
|
|
* time of the entity, and we will update its finish
|
|
* time in a moment (the requeueing is then, more
|
|
* precisely, a repositioning in this case). To
|
|
* implement this repositioning, we: 1) dequeue the
|
|
* entity here, 2) update the finish time and
|
|
* requeue the entity according to the new
|
|
* timestamps below.
|
|
*/
|
|
if (entity->tree)
|
|
bfq_active_extract(st, entity);
|
|
} else { /* The entity is already active, and not in service */
|
|
/*
|
|
* In this case, this function gets called only if the
|
|
* next_in_service entity below this entity has
|
|
* changed, and this change has caused the budget of
|
|
* this entity to change, which, finally implies that
|
|
* the finish time of this entity must be
|
|
* updated. Such an update may cause the scheduling,
|
|
* i.e., the position in the active tree, of this
|
|
* entity to change. We handle this change by: 1)
|
|
* dequeueing the entity here, 2) updating the finish
|
|
* time and requeueing the entity according to the new
|
|
* timestamps below. This is the same approach as the
|
|
* non-extracted-entity sub-case above.
|
|
*/
|
|
bfq_active_extract(st, entity);
|
|
}
|
|
|
|
bfq_update_fin_time_enqueue(entity, st, false);
|
|
}
|
|
|
|
static void __bfq_activate_requeue_entity(struct bfq_entity *entity,
|
|
struct bfq_sched_data *sd,
|
|
bool non_blocking_wait_rq)
|
|
{
|
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
|
|
|
|
if (sd->in_service_entity == entity || entity->tree == &st->active)
|
|
/*
|
|
* in service or already queued on the active tree,
|
|
* requeue or reposition
|
|
*/
|
|
__bfq_requeue_entity(entity);
|
|
else
|
|
/*
|
|
* Not in service and not queued on its active tree:
|
|
* the activity is idle and this is a true activation.
|
|
*/
|
|
__bfq_activate_entity(entity, non_blocking_wait_rq);
|
|
}
|
|
|
|
|
|
/**
|
|
* bfq_activate_entity - activate or requeue an entity representing a bfq_queue,
|
|
* and activate, requeue or reposition all ancestors
|
|
* for which such an update becomes necessary.
|
|
* @entity: the entity to activate.
|
|
* @non_blocking_wait_rq: true if this entity was waiting for a request
|
|
* @requeue: true if this is a requeue, which implies that bfqq is
|
|
* being expired; thus ALL its ancestors stop being served and must
|
|
* therefore be requeued
|
|
*/
|
|
static void bfq_activate_requeue_entity(struct bfq_entity *entity,
|
|
bool non_blocking_wait_rq,
|
|
bool requeue)
|
|
{
|
|
struct bfq_sched_data *sd;
|
|
|
|
for_each_entity(entity) {
|
|
sd = entity->sched_data;
|
|
__bfq_activate_requeue_entity(entity, sd, non_blocking_wait_rq);
|
|
|
|
if (!bfq_update_next_in_service(sd, entity) && !requeue)
|
|
break;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* __bfq_deactivate_entity - deactivate an entity from its service tree.
|
|
* @entity: the entity to deactivate.
|
|
* @ins_into_idle_tree: if false, the entity will not be put into the
|
|
* idle tree.
|
|
*
|
|
* Deactivates an entity, independently from its previous state. Must
|
|
* be invoked only if entity is on a service tree. Extracts the entity
|
|
* from that tree, and if necessary and allowed, puts it on the idle
|
|
* tree.
|
|
*/
|
|
static bool __bfq_deactivate_entity(struct bfq_entity *entity,
|
|
bool ins_into_idle_tree)
|
|
{
|
|
struct bfq_sched_data *sd = entity->sched_data;
|
|
struct bfq_service_tree *st = bfq_entity_service_tree(entity);
|
|
int is_in_service = entity == sd->in_service_entity;
|
|
|
|
if (!entity->on_st) /* entity never activated, or already inactive */
|
|
return false;
|
|
|
|
if (is_in_service)
|
|
bfq_calc_finish(entity, entity->service);
|
|
|
|
if (entity->tree == &st->active)
|
|
bfq_active_extract(st, entity);
|
|
else if (!is_in_service && entity->tree == &st->idle)
|
|
bfq_idle_extract(st, entity);
|
|
|
|
if (!ins_into_idle_tree || !bfq_gt(entity->finish, st->vtime))
|
|
bfq_forget_entity(st, entity, is_in_service);
|
|
else
|
|
bfq_idle_insert(st, entity);
|
|
|
|
return true;
|
|
}
|
|
|
|
/**
|
|
* bfq_deactivate_entity - deactivate an entity representing a bfq_queue.
|
|
* @entity: the entity to deactivate.
|
|
* @ins_into_idle_tree: true if the entity can be put on the idle tree
|
|
*/
|
|
static void bfq_deactivate_entity(struct bfq_entity *entity,
|
|
bool ins_into_idle_tree,
|
|
bool expiration)
|
|
{
|
|
struct bfq_sched_data *sd;
|
|
struct bfq_entity *parent = NULL;
|
|
|
|
for_each_entity_safe(entity, parent) {
|
|
sd = entity->sched_data;
|
|
|
|
if (!__bfq_deactivate_entity(entity, ins_into_idle_tree)) {
|
|
/*
|
|
* entity is not in any tree any more, so
|
|
* this deactivation is a no-op, and there is
|
|
* nothing to change for upper-level entities
|
|
* (in case of expiration, this can never
|
|
* happen).
|
|
*/
|
|
return;
|
|
}
|
|
|
|
if (sd->next_in_service == entity)
|
|
/*
|
|
* entity was the next_in_service entity,
|
|
* then, since entity has just been
|
|
* deactivated, a new one must be found.
|
|
*/
|
|
bfq_update_next_in_service(sd, NULL);
|
|
|
|
if (sd->next_in_service)
|
|
/*
|
|
* The parent entity is still backlogged,
|
|
* because next_in_service is not NULL. So, no
|
|
* further upwards deactivation must be
|
|
* performed. Yet, next_in_service has
|
|
* changed. Then the schedule does need to be
|
|
* updated upwards.
|
|
*/
|
|
break;
|
|
|
|
/*
|
|
* If we get here, then the parent is no more
|
|
* backlogged and we need to propagate the
|
|
* deactivation upwards. Thus let the loop go on.
|
|
*/
|
|
|
|
/*
|
|
* Also let parent be queued into the idle tree on
|
|
* deactivation, to preserve service guarantees, and
|
|
* assuming that who invoked this function does not
|
|
* need parent entities too to be removed completely.
|
|
*/
|
|
ins_into_idle_tree = true;
|
|
}
|
|
|
|
/*
|
|
* If the deactivation loop is fully executed, then there are
|
|
* no more entities to touch and next loop is not executed at
|
|
* all. Otherwise, requeue remaining entities if they are
|
|
* about to stop receiving service, or reposition them if this
|
|
* is not the case.
|
|
*/
|
|
entity = parent;
|
|
for_each_entity(entity) {
|
|
/*
|
|
* Invoke __bfq_requeue_entity on entity, even if
|
|
* already active, to requeue/reposition it in the
|
|
* active tree (because sd->next_in_service has
|
|
* changed)
|
|
*/
|
|
__bfq_requeue_entity(entity);
|
|
|
|
sd = entity->sched_data;
|
|
if (!bfq_update_next_in_service(sd, entity) &&
|
|
!expiration)
|
|
/*
|
|
* next_in_service unchanged or not causing
|
|
* any change in entity->parent->sd, and no
|
|
* requeueing needed for expiration: stop
|
|
* here.
|
|
*/
|
|
break;
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bfq_calc_vtime_jump - compute the value to which the vtime should jump,
|
|
* if needed, to have at least one entity eligible.
|
|
* @st: the service tree to act upon.
|
|
*
|
|
* Assumes that st is not empty.
|
|
*/
|
|
static u64 bfq_calc_vtime_jump(struct bfq_service_tree *st)
|
|
{
|
|
struct bfq_entity *root_entity = bfq_root_active_entity(&st->active);
|
|
|
|
if (bfq_gt(root_entity->min_start, st->vtime))
|
|
return root_entity->min_start;
|
|
|
|
return st->vtime;
|
|
}
|
|
|
|
static void bfq_update_vtime(struct bfq_service_tree *st, u64 new_value)
|
|
{
|
|
if (new_value > st->vtime) {
|
|
st->vtime = new_value;
|
|
bfq_forget_idle(st);
|
|
}
|
|
}
|
|
|
|
/**
|
|
* bfq_first_active_entity - find the eligible entity with
|
|
* the smallest finish time
|
|
* @st: the service tree to select from.
|
|
* @vtime: the system virtual to use as a reference for eligibility
|
|
*
|
|
* This function searches the first schedulable entity, starting from the
|
|
* root of the tree and going on the left every time on this side there is
|
|
* a subtree with at least one eligible (start >= vtime) entity. The path on
|
|
* the right is followed only if a) the left subtree contains no eligible
|
|
* entities and b) no eligible entity has been found yet.
|
|
*/
|
|
static struct bfq_entity *bfq_first_active_entity(struct bfq_service_tree *st,
|
|
u64 vtime)
|
|
{
|
|
struct bfq_entity *entry, *first = NULL;
|
|
struct rb_node *node = st->active.rb_node;
|
|
|
|
while (node) {
|
|
entry = rb_entry(node, struct bfq_entity, rb_node);
|
|
left:
|
|
if (!bfq_gt(entry->start, vtime))
|
|
first = entry;
|
|
|
|
if (node->rb_left) {
|
|
entry = rb_entry(node->rb_left,
|
|
struct bfq_entity, rb_node);
|
|
if (!bfq_gt(entry->min_start, vtime)) {
|
|
node = node->rb_left;
|
|
goto left;
|
|
}
|
|
}
|
|
if (first)
|
|
break;
|
|
node = node->rb_right;
|
|
}
|
|
|
|
return first;
|
|
}
|
|
|
|
/**
|
|
* __bfq_lookup_next_entity - return the first eligible entity in @st.
|
|
* @st: the service tree.
|
|
*
|
|
* If there is no in-service entity for the sched_data st belongs to,
|
|
* then return the entity that will be set in service if:
|
|
* 1) the parent entity this st belongs to is set in service;
|
|
* 2) no entity belonging to such parent entity undergoes a state change
|
|
* that would influence the timestamps of the entity (e.g., becomes idle,
|
|
* becomes backlogged, changes its budget, ...).
|
|
*
|
|
* In this first case, update the virtual time in @st too (see the
|
|
* comments on this update inside the function).
|
|
*
|
|
* In constrast, if there is an in-service entity, then return the
|
|
* entity that would be set in service if not only the above
|
|
* conditions, but also the next one held true: the currently
|
|
* in-service entity, on expiration,
|
|
* 1) gets a finish time equal to the current one, or
|
|
* 2) is not eligible any more, or
|
|
* 3) is idle.
|
|
*/
|
|
static struct bfq_entity *
|
|
__bfq_lookup_next_entity(struct bfq_service_tree *st, bool in_service)
|
|
{
|
|
struct bfq_entity *entity;
|
|
u64 new_vtime;
|
|
|
|
if (RB_EMPTY_ROOT(&st->active))
|
|
return NULL;
|
|
|
|
/*
|
|
* Get the value of the system virtual time for which at
|
|
* least one entity is eligible.
|
|
*/
|
|
new_vtime = bfq_calc_vtime_jump(st);
|
|
|
|
/*
|
|
* If there is no in-service entity for the sched_data this
|
|
* active tree belongs to, then push the system virtual time
|
|
* up to the value that guarantees that at least one entity is
|
|
* eligible. If, instead, there is an in-service entity, then
|
|
* do not make any such update, because there is already an
|
|
* eligible entity, namely the in-service one (even if the
|
|
* entity is not on st, because it was extracted when set in
|
|
* service).
|
|
*/
|
|
if (!in_service)
|
|
bfq_update_vtime(st, new_vtime);
|
|
|
|
entity = bfq_first_active_entity(st, new_vtime);
|
|
|
|
return entity;
|
|
}
|
|
|
|
/**
|
|
* bfq_lookup_next_entity - return the first eligible entity in @sd.
|
|
* @sd: the sched_data.
|
|
*
|
|
* This function is invoked when there has been a change in the trees
|
|
* for sd, and we need know what is the new next entity after this
|
|
* change.
|
|
*/
|
|
static struct bfq_entity *bfq_lookup_next_entity(struct bfq_sched_data *sd)
|
|
{
|
|
struct bfq_service_tree *st = sd->service_tree;
|
|
struct bfq_service_tree *idle_class_st = st + (BFQ_IOPRIO_CLASSES - 1);
|
|
struct bfq_entity *entity = NULL;
|
|
int class_idx = 0;
|
|
|
|
/*
|
|
* Choose from idle class, if needed to guarantee a minimum
|
|
* bandwidth to this class (and if there is some active entity
|
|
* in idle class). This should also mitigate
|
|
* priority-inversion problems in case a low priority task is
|
|
* holding file system resources.
|
|
*/
|
|
if (time_is_before_jiffies(sd->bfq_class_idle_last_service +
|
|
BFQ_CL_IDLE_TIMEOUT)) {
|
|
if (!RB_EMPTY_ROOT(&idle_class_st->active))
|
|
class_idx = BFQ_IOPRIO_CLASSES - 1;
|
|
/* About to be served if backlogged, or not yet backlogged */
|
|
sd->bfq_class_idle_last_service = jiffies;
|
|
}
|
|
|
|
/*
|
|
* Find the next entity to serve for the highest-priority
|
|
* class, unless the idle class needs to be served.
|
|
*/
|
|
for (; class_idx < BFQ_IOPRIO_CLASSES; class_idx++) {
|
|
entity = __bfq_lookup_next_entity(st + class_idx,
|
|
sd->in_service_entity);
|
|
|
|
if (entity)
|
|
break;
|
|
}
|
|
|
|
if (!entity)
|
|
return NULL;
|
|
|
|
return entity;
|
|
}
|
|
|
|
static bool next_queue_may_preempt(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_sched_data *sd = &bfqd->root_group->sched_data;
|
|
|
|
return sd->next_in_service != sd->in_service_entity;
|
|
}
|
|
|
|
/*
|
|
* Get next queue for service.
|
|
*/
|
|
static struct bfq_queue *bfq_get_next_queue(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_entity *entity = NULL;
|
|
struct bfq_sched_data *sd;
|
|
struct bfq_queue *bfqq;
|
|
|
|
if (bfqd->busy_queues == 0)
|
|
return NULL;
|
|
|
|
/*
|
|
* Traverse the path from the root to the leaf entity to
|
|
* serve. Set in service all the entities visited along the
|
|
* way.
|
|
*/
|
|
sd = &bfqd->root_group->sched_data;
|
|
for (; sd ; sd = entity->my_sched_data) {
|
|
/*
|
|
* WARNING. We are about to set the in-service entity
|
|
* to sd->next_in_service, i.e., to the (cached) value
|
|
* returned by bfq_lookup_next_entity(sd) the last
|
|
* time it was invoked, i.e., the last time when the
|
|
* service order in sd changed as a consequence of the
|
|
* activation or deactivation of an entity. In this
|
|
* respect, if we execute bfq_lookup_next_entity(sd)
|
|
* in this very moment, it may, although with low
|
|
* probability, yield a different entity than that
|
|
* pointed to by sd->next_in_service. This rare event
|
|
* happens in case there was no CLASS_IDLE entity to
|
|
* serve for sd when bfq_lookup_next_entity(sd) was
|
|
* invoked for the last time, while there is now one
|
|
* such entity.
|
|
*
|
|
* If the above event happens, then the scheduling of
|
|
* such entity in CLASS_IDLE is postponed until the
|
|
* service of the sd->next_in_service entity
|
|
* finishes. In fact, when the latter is expired,
|
|
* bfq_lookup_next_entity(sd) gets called again,
|
|
* exactly to update sd->next_in_service.
|
|
*/
|
|
|
|
/* Make next_in_service entity become in_service_entity */
|
|
entity = sd->next_in_service;
|
|
sd->in_service_entity = entity;
|
|
|
|
/*
|
|
* Reset the accumulator of the amount of service that
|
|
* the entity is about to receive.
|
|
*/
|
|
entity->service = 0;
|
|
|
|
/*
|
|
* If entity is no longer a candidate for next
|
|
* service, then we extract it from its active tree,
|
|
* for the following reason. To further boost the
|
|
* throughput in some special case, BFQ needs to know
|
|
* which is the next candidate entity to serve, while
|
|
* there is already an entity in service. In this
|
|
* respect, to make it easy to compute/update the next
|
|
* candidate entity to serve after the current
|
|
* candidate has been set in service, there is a case
|
|
* where it is necessary to extract the current
|
|
* candidate from its service tree. Such a case is
|
|
* when the entity just set in service cannot be also
|
|
* a candidate for next service. Details about when
|
|
* this conditions holds are reported in the comments
|
|
* on the function bfq_no_longer_next_in_service()
|
|
* invoked below.
|
|
*/
|
|
if (bfq_no_longer_next_in_service(entity))
|
|
bfq_active_extract(bfq_entity_service_tree(entity),
|
|
entity);
|
|
|
|
/*
|
|
* For the same reason why we may have just extracted
|
|
* entity from its active tree, we may need to update
|
|
* next_in_service for the sched_data of entity too,
|
|
* regardless of whether entity has been extracted.
|
|
* In fact, even if entity has not been extracted, a
|
|
* descendant entity may get extracted. Such an event
|
|
* would cause a change in next_in_service for the
|
|
* level of the descendant entity, and thus possibly
|
|
* back to upper levels.
|
|
*
|
|
* We cannot perform the resulting needed update
|
|
* before the end of this loop, because, to know which
|
|
* is the correct next-to-serve candidate entity for
|
|
* each level, we need first to find the leaf entity
|
|
* to set in service. In fact, only after we know
|
|
* which is the next-to-serve leaf entity, we can
|
|
* discover whether the parent entity of the leaf
|
|
* entity becomes the next-to-serve, and so on.
|
|
*/
|
|
|
|
}
|
|
|
|
bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
/*
|
|
* We can finally update all next-to-serve entities along the
|
|
* path from the leaf entity just set in service to the root.
|
|
*/
|
|
for_each_entity(entity) {
|
|
struct bfq_sched_data *sd = entity->sched_data;
|
|
|
|
if (!bfq_update_next_in_service(sd, NULL))
|
|
break;
|
|
}
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
static void __bfq_bfqd_reset_in_service(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_queue *in_serv_bfqq = bfqd->in_service_queue;
|
|
struct bfq_entity *in_serv_entity = &in_serv_bfqq->entity;
|
|
struct bfq_entity *entity = in_serv_entity;
|
|
|
|
if (bfqd->in_service_bic) {
|
|
/*
|
|
* Schedule the release of a reference to
|
|
* bfqd->in_service_bic->icq.ioc to right after the
|
|
* scheduler lock is released. This ioc is not
|
|
* released immediately, to not risk to possibly take
|
|
* an ioc->lock while holding the scheduler lock.
|
|
*/
|
|
bfqd->ioc_to_put = bfqd->in_service_bic->icq.ioc;
|
|
bfqd->in_service_bic = NULL;
|
|
}
|
|
|
|
bfq_clear_bfqq_wait_request(in_serv_bfqq);
|
|
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
|
|
bfqd->in_service_queue = NULL;
|
|
|
|
/*
|
|
* When this function is called, all in-service entities have
|
|
* been properly deactivated or requeued, so we can safely
|
|
* execute the final step: reset in_service_entity along the
|
|
* path from entity to the root.
|
|
*/
|
|
for_each_entity(entity)
|
|
entity->sched_data->in_service_entity = NULL;
|
|
|
|
/*
|
|
* in_serv_entity is no longer in service, so, if it is in no
|
|
* service tree either, then release the service reference to
|
|
* the queue it represents (taken with bfq_get_entity).
|
|
*/
|
|
if (!in_serv_entity->on_st)
|
|
bfq_put_queue(in_serv_bfqq);
|
|
}
|
|
|
|
static void bfq_deactivate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
bool ins_into_idle_tree, bool expiration)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
bfq_deactivate_entity(entity, ins_into_idle_tree, expiration);
|
|
}
|
|
|
|
static void bfq_activate_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
bfq_activate_requeue_entity(entity, bfq_bfqq_non_blocking_wait_rq(bfqq),
|
|
false);
|
|
bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
|
|
}
|
|
|
|
static void bfq_requeue_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
bfq_activate_requeue_entity(entity, false,
|
|
bfqq == bfqd->in_service_queue);
|
|
}
|
|
|
|
static void bfqg_stats_update_dequeue(struct bfq_group *bfqg);
|
|
|
|
/*
|
|
* Called when the bfqq no longer has requests pending, remove it from
|
|
* the service tree. As a special case, it can be invoked during an
|
|
* expiration.
|
|
*/
|
|
static void bfq_del_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
bool expiration)
|
|
{
|
|
bfq_log_bfqq(bfqd, bfqq, "del from busy");
|
|
|
|
bfq_clear_bfqq_busy(bfqq);
|
|
|
|
bfqd->busy_queues--;
|
|
|
|
if (bfqq->wr_coeff > 1)
|
|
bfqd->wr_busy_queues--;
|
|
|
|
bfqg_stats_update_dequeue(bfqq_group(bfqq));
|
|
|
|
bfq_deactivate_bfqq(bfqd, bfqq, true, expiration);
|
|
}
|
|
|
|
/*
|
|
* Called when an inactive queue receives a new request.
|
|
*/
|
|
static void bfq_add_bfqq_busy(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
bfq_log_bfqq(bfqd, bfqq, "add to busy");
|
|
|
|
bfq_activate_bfqq(bfqd, bfqq);
|
|
|
|
bfq_mark_bfqq_busy(bfqq);
|
|
bfqd->busy_queues++;
|
|
|
|
if (bfqq->wr_coeff > 1)
|
|
bfqd->wr_busy_queues++;
|
|
}
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
|
|
/* bfqg stats flags */
|
|
enum bfqg_stats_flags {
|
|
BFQG_stats_waiting = 0,
|
|
BFQG_stats_idling,
|
|
BFQG_stats_empty,
|
|
};
|
|
|
|
#define BFQG_FLAG_FNS(name) \
|
|
static void bfqg_stats_mark_##name(struct bfqg_stats *stats) \
|
|
{ \
|
|
stats->flags |= (1 << BFQG_stats_##name); \
|
|
} \
|
|
static void bfqg_stats_clear_##name(struct bfqg_stats *stats) \
|
|
{ \
|
|
stats->flags &= ~(1 << BFQG_stats_##name); \
|
|
} \
|
|
static int bfqg_stats_##name(struct bfqg_stats *stats) \
|
|
{ \
|
|
return (stats->flags & (1 << BFQG_stats_##name)) != 0; \
|
|
} \
|
|
|
|
BFQG_FLAG_FNS(waiting)
|
|
BFQG_FLAG_FNS(idling)
|
|
BFQG_FLAG_FNS(empty)
|
|
#undef BFQG_FLAG_FNS
|
|
|
|
/* This should be called with the queue_lock held. */
|
|
static void bfqg_stats_update_group_wait_time(struct bfqg_stats *stats)
|
|
{
|
|
unsigned long long now;
|
|
|
|
if (!bfqg_stats_waiting(stats))
|
|
return;
|
|
|
|
now = sched_clock();
|
|
if (time_after64(now, stats->start_group_wait_time))
|
|
blkg_stat_add(&stats->group_wait_time,
|
|
now - stats->start_group_wait_time);
|
|
bfqg_stats_clear_waiting(stats);
|
|
}
|
|
|
|
/* This should be called with the queue_lock held. */
|
|
static void bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
|
|
struct bfq_group *curr_bfqg)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
|
|
if (bfqg_stats_waiting(stats))
|
|
return;
|
|
if (bfqg == curr_bfqg)
|
|
return;
|
|
stats->start_group_wait_time = sched_clock();
|
|
bfqg_stats_mark_waiting(stats);
|
|
}
|
|
|
|
/* This should be called with the queue_lock held. */
|
|
static void bfqg_stats_end_empty_time(struct bfqg_stats *stats)
|
|
{
|
|
unsigned long long now;
|
|
|
|
if (!bfqg_stats_empty(stats))
|
|
return;
|
|
|
|
now = sched_clock();
|
|
if (time_after64(now, stats->start_empty_time))
|
|
blkg_stat_add(&stats->empty_time,
|
|
now - stats->start_empty_time);
|
|
bfqg_stats_clear_empty(stats);
|
|
}
|
|
|
|
static void bfqg_stats_update_dequeue(struct bfq_group *bfqg)
|
|
{
|
|
blkg_stat_add(&bfqg->stats.dequeue, 1);
|
|
}
|
|
|
|
static void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
|
|
if (blkg_rwstat_total(&stats->queued))
|
|
return;
|
|
|
|
/*
|
|
* group is already marked empty. This can happen if bfqq got new
|
|
* request in parent group and moved to this group while being added
|
|
* to service tree. Just ignore the event and move on.
|
|
*/
|
|
if (bfqg_stats_empty(stats))
|
|
return;
|
|
|
|
stats->start_empty_time = sched_clock();
|
|
bfqg_stats_mark_empty(stats);
|
|
}
|
|
|
|
static void bfqg_stats_update_idle_time(struct bfq_group *bfqg)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
|
|
if (bfqg_stats_idling(stats)) {
|
|
unsigned long long now = sched_clock();
|
|
|
|
if (time_after64(now, stats->start_idle_time))
|
|
blkg_stat_add(&stats->idle_time,
|
|
now - stats->start_idle_time);
|
|
bfqg_stats_clear_idling(stats);
|
|
}
|
|
}
|
|
|
|
static void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
|
|
stats->start_idle_time = sched_clock();
|
|
bfqg_stats_mark_idling(stats);
|
|
}
|
|
|
|
static void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
|
|
blkg_stat_add(&stats->avg_queue_size_sum,
|
|
blkg_rwstat_total(&stats->queued));
|
|
blkg_stat_add(&stats->avg_queue_size_samples, 1);
|
|
bfqg_stats_update_group_wait_time(stats);
|
|
}
|
|
|
|
/*
|
|
* blk-cgroup policy-related handlers
|
|
* The following functions help in converting between blk-cgroup
|
|
* internal structures and BFQ-specific structures.
|
|
*/
|
|
|
|
static struct bfq_group *pd_to_bfqg(struct blkg_policy_data *pd)
|
|
{
|
|
return pd ? container_of(pd, struct bfq_group, pd) : NULL;
|
|
}
|
|
|
|
static struct blkcg_gq *bfqg_to_blkg(struct bfq_group *bfqg)
|
|
{
|
|
return pd_to_blkg(&bfqg->pd);
|
|
}
|
|
|
|
static struct blkcg_policy blkcg_policy_bfq;
|
|
|
|
static struct bfq_group *blkg_to_bfqg(struct blkcg_gq *blkg)
|
|
{
|
|
return pd_to_bfqg(blkg_to_pd(blkg, &blkcg_policy_bfq));
|
|
}
|
|
|
|
/*
|
|
* bfq_group handlers
|
|
* The following functions help in navigating the bfq_group hierarchy
|
|
* by allowing to find the parent of a bfq_group or the bfq_group
|
|
* associated to a bfq_queue.
|
|
*/
|
|
|
|
static struct bfq_group *bfqg_parent(struct bfq_group *bfqg)
|
|
{
|
|
struct blkcg_gq *pblkg = bfqg_to_blkg(bfqg)->parent;
|
|
|
|
return pblkg ? blkg_to_bfqg(pblkg) : NULL;
|
|
}
|
|
|
|
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *group_entity = bfqq->entity.parent;
|
|
|
|
return group_entity ? container_of(group_entity, struct bfq_group,
|
|
entity) :
|
|
bfqq->bfqd->root_group;
|
|
}
|
|
|
|
/*
|
|
* The following two functions handle get and put of a bfq_group by
|
|
* wrapping the related blk-cgroup hooks.
|
|
*/
|
|
|
|
static void bfqg_get(struct bfq_group *bfqg)
|
|
{
|
|
return blkg_get(bfqg_to_blkg(bfqg));
|
|
}
|
|
|
|
static void bfqg_put(struct bfq_group *bfqg)
|
|
{
|
|
return blkg_put(bfqg_to_blkg(bfqg));
|
|
}
|
|
|
|
static void bfqg_stats_update_io_add(struct bfq_group *bfqg,
|
|
struct bfq_queue *bfqq,
|
|
unsigned int op)
|
|
{
|
|
blkg_rwstat_add(&bfqg->stats.queued, op, 1);
|
|
bfqg_stats_end_empty_time(&bfqg->stats);
|
|
if (!(bfqq == ((struct bfq_data *)bfqg->bfqd)->in_service_queue))
|
|
bfqg_stats_set_start_group_wait_time(bfqg, bfqq_group(bfqq));
|
|
}
|
|
|
|
static void bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op)
|
|
{
|
|
blkg_rwstat_add(&bfqg->stats.queued, op, -1);
|
|
}
|
|
|
|
static void bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op)
|
|
{
|
|
blkg_rwstat_add(&bfqg->stats.merged, op, 1);
|
|
}
|
|
|
|
static void bfqg_stats_update_completion(struct bfq_group *bfqg,
|
|
uint64_t start_time, uint64_t io_start_time,
|
|
unsigned int op)
|
|
{
|
|
struct bfqg_stats *stats = &bfqg->stats;
|
|
unsigned long long now = sched_clock();
|
|
|
|
if (time_after64(now, io_start_time))
|
|
blkg_rwstat_add(&stats->service_time, op,
|
|
now - io_start_time);
|
|
if (time_after64(io_start_time, start_time))
|
|
blkg_rwstat_add(&stats->wait_time, op,
|
|
io_start_time - start_time);
|
|
}
|
|
|
|
/* @stats = 0 */
|
|
static void bfqg_stats_reset(struct bfqg_stats *stats)
|
|
{
|
|
/* queued stats shouldn't be cleared */
|
|
blkg_rwstat_reset(&stats->merged);
|
|
blkg_rwstat_reset(&stats->service_time);
|
|
blkg_rwstat_reset(&stats->wait_time);
|
|
blkg_stat_reset(&stats->time);
|
|
blkg_stat_reset(&stats->avg_queue_size_sum);
|
|
blkg_stat_reset(&stats->avg_queue_size_samples);
|
|
blkg_stat_reset(&stats->dequeue);
|
|
blkg_stat_reset(&stats->group_wait_time);
|
|
blkg_stat_reset(&stats->idle_time);
|
|
blkg_stat_reset(&stats->empty_time);
|
|
}
|
|
|
|
/* @to += @from */
|
|
static void bfqg_stats_add_aux(struct bfqg_stats *to, struct bfqg_stats *from)
|
|
{
|
|
if (!to || !from)
|
|
return;
|
|
|
|
/* queued stats shouldn't be cleared */
|
|
blkg_rwstat_add_aux(&to->merged, &from->merged);
|
|
blkg_rwstat_add_aux(&to->service_time, &from->service_time);
|
|
blkg_rwstat_add_aux(&to->wait_time, &from->wait_time);
|
|
blkg_stat_add_aux(&from->time, &from->time);
|
|
blkg_stat_add_aux(&to->avg_queue_size_sum, &from->avg_queue_size_sum);
|
|
blkg_stat_add_aux(&to->avg_queue_size_samples,
|
|
&from->avg_queue_size_samples);
|
|
blkg_stat_add_aux(&to->dequeue, &from->dequeue);
|
|
blkg_stat_add_aux(&to->group_wait_time, &from->group_wait_time);
|
|
blkg_stat_add_aux(&to->idle_time, &from->idle_time);
|
|
blkg_stat_add_aux(&to->empty_time, &from->empty_time);
|
|
}
|
|
|
|
/*
|
|
* Transfer @bfqg's stats to its parent's aux counts so that the ancestors'
|
|
* recursive stats can still account for the amount used by this bfqg after
|
|
* it's gone.
|
|
*/
|
|
static void bfqg_stats_xfer_dead(struct bfq_group *bfqg)
|
|
{
|
|
struct bfq_group *parent;
|
|
|
|
if (!bfqg) /* root_group */
|
|
return;
|
|
|
|
parent = bfqg_parent(bfqg);
|
|
|
|
lockdep_assert_held(bfqg_to_blkg(bfqg)->q->queue_lock);
|
|
|
|
if (unlikely(!parent))
|
|
return;
|
|
|
|
bfqg_stats_add_aux(&parent->stats, &bfqg->stats);
|
|
bfqg_stats_reset(&bfqg->stats);
|
|
}
|
|
|
|
static void bfq_init_entity(struct bfq_entity *entity,
|
|
struct bfq_group *bfqg)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
entity->weight = entity->new_weight;
|
|
entity->orig_weight = entity->new_weight;
|
|
if (bfqq) {
|
|
bfqq->ioprio = bfqq->new_ioprio;
|
|
bfqq->ioprio_class = bfqq->new_ioprio_class;
|
|
bfqg_get(bfqg);
|
|
}
|
|
entity->parent = bfqg->my_entity; /* NULL for root group */
|
|
entity->sched_data = &bfqg->sched_data;
|
|
}
|
|
|
|
static void bfqg_stats_exit(struct bfqg_stats *stats)
|
|
{
|
|
blkg_rwstat_exit(&stats->merged);
|
|
blkg_rwstat_exit(&stats->service_time);
|
|
blkg_rwstat_exit(&stats->wait_time);
|
|
blkg_rwstat_exit(&stats->queued);
|
|
blkg_stat_exit(&stats->time);
|
|
blkg_stat_exit(&stats->avg_queue_size_sum);
|
|
blkg_stat_exit(&stats->avg_queue_size_samples);
|
|
blkg_stat_exit(&stats->dequeue);
|
|
blkg_stat_exit(&stats->group_wait_time);
|
|
blkg_stat_exit(&stats->idle_time);
|
|
blkg_stat_exit(&stats->empty_time);
|
|
}
|
|
|
|
static int bfqg_stats_init(struct bfqg_stats *stats, gfp_t gfp)
|
|
{
|
|
if (blkg_rwstat_init(&stats->merged, gfp) ||
|
|
blkg_rwstat_init(&stats->service_time, gfp) ||
|
|
blkg_rwstat_init(&stats->wait_time, gfp) ||
|
|
blkg_rwstat_init(&stats->queued, gfp) ||
|
|
blkg_stat_init(&stats->time, gfp) ||
|
|
blkg_stat_init(&stats->avg_queue_size_sum, gfp) ||
|
|
blkg_stat_init(&stats->avg_queue_size_samples, gfp) ||
|
|
blkg_stat_init(&stats->dequeue, gfp) ||
|
|
blkg_stat_init(&stats->group_wait_time, gfp) ||
|
|
blkg_stat_init(&stats->idle_time, gfp) ||
|
|
blkg_stat_init(&stats->empty_time, gfp)) {
|
|
bfqg_stats_exit(stats);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
static struct bfq_group_data *cpd_to_bfqgd(struct blkcg_policy_data *cpd)
|
|
{
|
|
return cpd ? container_of(cpd, struct bfq_group_data, pd) : NULL;
|
|
}
|
|
|
|
static struct bfq_group_data *blkcg_to_bfqgd(struct blkcg *blkcg)
|
|
{
|
|
return cpd_to_bfqgd(blkcg_to_cpd(blkcg, &blkcg_policy_bfq));
|
|
}
|
|
|
|
static struct blkcg_policy_data *bfq_cpd_alloc(gfp_t gfp)
|
|
{
|
|
struct bfq_group_data *bgd;
|
|
|
|
bgd = kzalloc(sizeof(*bgd), gfp);
|
|
if (!bgd)
|
|
return NULL;
|
|
return &bgd->pd;
|
|
}
|
|
|
|
static void bfq_cpd_init(struct blkcg_policy_data *cpd)
|
|
{
|
|
struct bfq_group_data *d = cpd_to_bfqgd(cpd);
|
|
|
|
d->weight = cgroup_subsys_on_dfl(io_cgrp_subsys) ?
|
|
CGROUP_WEIGHT_DFL : BFQ_WEIGHT_LEGACY_DFL;
|
|
}
|
|
|
|
static void bfq_cpd_free(struct blkcg_policy_data *cpd)
|
|
{
|
|
kfree(cpd_to_bfqgd(cpd));
|
|
}
|
|
|
|
static struct blkg_policy_data *bfq_pd_alloc(gfp_t gfp, int node)
|
|
{
|
|
struct bfq_group *bfqg;
|
|
|
|
bfqg = kzalloc_node(sizeof(*bfqg), gfp, node);
|
|
if (!bfqg)
|
|
return NULL;
|
|
|
|
if (bfqg_stats_init(&bfqg->stats, gfp)) {
|
|
kfree(bfqg);
|
|
return NULL;
|
|
}
|
|
|
|
return &bfqg->pd;
|
|
}
|
|
|
|
static void bfq_pd_init(struct blkg_policy_data *pd)
|
|
{
|
|
struct blkcg_gq *blkg = pd_to_blkg(pd);
|
|
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
|
|
struct bfq_data *bfqd = blkg->q->elevator->elevator_data;
|
|
struct bfq_entity *entity = &bfqg->entity;
|
|
struct bfq_group_data *d = blkcg_to_bfqgd(blkg->blkcg);
|
|
|
|
entity->orig_weight = entity->weight = entity->new_weight = d->weight;
|
|
entity->my_sched_data = &bfqg->sched_data;
|
|
bfqg->my_entity = entity; /*
|
|
* the root_group's will be set to NULL
|
|
* in bfq_init_queue()
|
|
*/
|
|
bfqg->bfqd = bfqd;
|
|
bfqg->rq_pos_tree = RB_ROOT;
|
|
}
|
|
|
|
static void bfq_pd_free(struct blkg_policy_data *pd)
|
|
{
|
|
struct bfq_group *bfqg = pd_to_bfqg(pd);
|
|
|
|
bfqg_stats_exit(&bfqg->stats);
|
|
return kfree(bfqg);
|
|
}
|
|
|
|
static void bfq_pd_reset_stats(struct blkg_policy_data *pd)
|
|
{
|
|
struct bfq_group *bfqg = pd_to_bfqg(pd);
|
|
|
|
bfqg_stats_reset(&bfqg->stats);
|
|
}
|
|
|
|
static void bfq_group_set_parent(struct bfq_group *bfqg,
|
|
struct bfq_group *parent)
|
|
{
|
|
struct bfq_entity *entity;
|
|
|
|
entity = &bfqg->entity;
|
|
entity->parent = parent->my_entity;
|
|
entity->sched_data = &parent->sched_data;
|
|
}
|
|
|
|
static struct bfq_group *bfq_lookup_bfqg(struct bfq_data *bfqd,
|
|
struct blkcg *blkcg)
|
|
{
|
|
struct blkcg_gq *blkg;
|
|
|
|
blkg = blkg_lookup(blkcg, bfqd->queue);
|
|
if (likely(blkg))
|
|
return blkg_to_bfqg(blkg);
|
|
return NULL;
|
|
}
|
|
|
|
static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
|
|
struct blkcg *blkcg)
|
|
{
|
|
struct bfq_group *bfqg, *parent;
|
|
struct bfq_entity *entity;
|
|
|
|
bfqg = bfq_lookup_bfqg(bfqd, blkcg);
|
|
|
|
if (unlikely(!bfqg))
|
|
return NULL;
|
|
|
|
/*
|
|
* Update chain of bfq_groups as we might be handling a leaf group
|
|
* which, along with some of its relatives, has not been hooked yet
|
|
* to the private hierarchy of BFQ.
|
|
*/
|
|
entity = &bfqg->entity;
|
|
for_each_entity(entity) {
|
|
bfqg = container_of(entity, struct bfq_group, entity);
|
|
if (bfqg != bfqd->root_group) {
|
|
parent = bfqg_parent(bfqg);
|
|
if (!parent)
|
|
parent = bfqd->root_group;
|
|
bfq_group_set_parent(bfqg, parent);
|
|
}
|
|
}
|
|
|
|
return bfqg;
|
|
}
|
|
|
|
static void bfq_pos_tree_add_move(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq);
|
|
static void bfq_bfqq_expire(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
bool compensate,
|
|
enum bfqq_expiration reason);
|
|
|
|
/**
|
|
* bfq_bfqq_move - migrate @bfqq to @bfqg.
|
|
* @bfqd: queue descriptor.
|
|
* @bfqq: the queue to move.
|
|
* @bfqg: the group to move to.
|
|
*
|
|
* Move @bfqq to @bfqg, deactivating it from its old group and reactivating
|
|
* it on the new one. Avoid putting the entity on the old group idle tree.
|
|
*
|
|
* Must be called under the queue lock; the cgroup owning @bfqg must
|
|
* not disappear (by now this just means that we are called under
|
|
* rcu_read_lock()).
|
|
*/
|
|
static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
struct bfq_group *bfqg)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
/* If bfqq is empty, then bfq_bfqq_expire also invokes
|
|
* bfq_del_bfqq_busy, thereby removing bfqq and its entity
|
|
* from data structures related to current group. Otherwise we
|
|
* need to remove bfqq explicitly with bfq_deactivate_bfqq, as
|
|
* we do below.
|
|
*/
|
|
if (bfqq == bfqd->in_service_queue)
|
|
bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
|
|
false, BFQQE_PREEMPTED);
|
|
|
|
if (bfq_bfqq_busy(bfqq))
|
|
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
|
|
else if (entity->on_st)
|
|
bfq_put_idle_entity(bfq_entity_service_tree(entity), entity);
|
|
bfqg_put(bfqq_group(bfqq));
|
|
|
|
/*
|
|
* Here we use a reference to bfqg. We don't need a refcounter
|
|
* as the cgroup reference will not be dropped, so that its
|
|
* destroy() callback will not be invoked.
|
|
*/
|
|
entity->parent = bfqg->my_entity;
|
|
entity->sched_data = &bfqg->sched_data;
|
|
bfqg_get(bfqg);
|
|
|
|
if (bfq_bfqq_busy(bfqq)) {
|
|
bfq_pos_tree_add_move(bfqd, bfqq);
|
|
bfq_activate_bfqq(bfqd, bfqq);
|
|
}
|
|
|
|
if (!bfqd->in_service_queue && !bfqd->rq_in_driver)
|
|
bfq_schedule_dispatch(bfqd);
|
|
}
|
|
|
|
/**
|
|
* __bfq_bic_change_cgroup - move @bic to @cgroup.
|
|
* @bfqd: the queue descriptor.
|
|
* @bic: the bic to move.
|
|
* @blkcg: the blk-cgroup to move to.
|
|
*
|
|
* Move bic to blkcg, assuming that bfqd->queue is locked; the caller
|
|
* has to make sure that the reference to cgroup is valid across the call.
|
|
*
|
|
* NOTE: an alternative approach might have been to store the current
|
|
* cgroup in bfqq and getting a reference to it, reducing the lookup
|
|
* time here, at the price of slightly more complex code.
|
|
*/
|
|
static struct bfq_group *__bfq_bic_change_cgroup(struct bfq_data *bfqd,
|
|
struct bfq_io_cq *bic,
|
|
struct blkcg *blkcg)
|
|
{
|
|
struct bfq_queue *async_bfqq = bic_to_bfqq(bic, 0);
|
|
struct bfq_queue *sync_bfqq = bic_to_bfqq(bic, 1);
|
|
struct bfq_group *bfqg;
|
|
struct bfq_entity *entity;
|
|
|
|
bfqg = bfq_find_set_group(bfqd, blkcg);
|
|
|
|
if (unlikely(!bfqg))
|
|
bfqg = bfqd->root_group;
|
|
|
|
if (async_bfqq) {
|
|
entity = &async_bfqq->entity;
|
|
|
|
if (entity->sched_data != &bfqg->sched_data) {
|
|
bic_set_bfqq(bic, NULL, 0);
|
|
bfq_log_bfqq(bfqd, async_bfqq,
|
|
"bic_change_group: %p %d",
|
|
async_bfqq, async_bfqq->ref);
|
|
bfq_put_queue(async_bfqq);
|
|
}
|
|
}
|
|
|
|
if (sync_bfqq) {
|
|
entity = &sync_bfqq->entity;
|
|
if (entity->sched_data != &bfqg->sched_data)
|
|
bfq_bfqq_move(bfqd, sync_bfqq, bfqg);
|
|
}
|
|
|
|
return bfqg;
|
|
}
|
|
|
|
static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio)
|
|
{
|
|
struct bfq_data *bfqd = bic_to_bfqd(bic);
|
|
struct bfq_group *bfqg = NULL;
|
|
uint64_t serial_nr;
|
|
|
|
rcu_read_lock();
|
|
serial_nr = bio_blkcg(bio)->css.serial_nr;
|
|
|
|
/*
|
|
* Check whether blkcg has changed. The condition may trigger
|
|
* spuriously on a newly created cic but there's no harm.
|
|
*/
|
|
if (unlikely(!bfqd) || likely(bic->blkcg_serial_nr == serial_nr))
|
|
goto out;
|
|
|
|
bfqg = __bfq_bic_change_cgroup(bfqd, bic, bio_blkcg(bio));
|
|
bic->blkcg_serial_nr = serial_nr;
|
|
out:
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
/**
|
|
* bfq_flush_idle_tree - deactivate any entity on the idle tree of @st.
|
|
* @st: the service tree being flushed.
|
|
*/
|
|
static void bfq_flush_idle_tree(struct bfq_service_tree *st)
|
|
{
|
|
struct bfq_entity *entity = st->first_idle;
|
|
|
|
for (; entity ; entity = st->first_idle)
|
|
__bfq_deactivate_entity(entity, false);
|
|
}
|
|
|
|
/**
|
|
* bfq_reparent_leaf_entity - move leaf entity to the root_group.
|
|
* @bfqd: the device data structure with the root group.
|
|
* @entity: the entity to move.
|
|
*/
|
|
static void bfq_reparent_leaf_entity(struct bfq_data *bfqd,
|
|
struct bfq_entity *entity)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
|
|
}
|
|
|
|
/**
|
|
* bfq_reparent_active_entities - move to the root group all active
|
|
* entities.
|
|
* @bfqd: the device data structure with the root group.
|
|
* @bfqg: the group to move from.
|
|
* @st: the service tree with the entities.
|
|
*
|
|
* Needs queue_lock to be taken and reference to be valid over the call.
|
|
*/
|
|
static void bfq_reparent_active_entities(struct bfq_data *bfqd,
|
|
struct bfq_group *bfqg,
|
|
struct bfq_service_tree *st)
|
|
{
|
|
struct rb_root *active = &st->active;
|
|
struct bfq_entity *entity = NULL;
|
|
|
|
if (!RB_EMPTY_ROOT(&st->active))
|
|
entity = bfq_entity_of(rb_first(active));
|
|
|
|
for (; entity ; entity = bfq_entity_of(rb_first(active)))
|
|
bfq_reparent_leaf_entity(bfqd, entity);
|
|
|
|
if (bfqg->sched_data.in_service_entity)
|
|
bfq_reparent_leaf_entity(bfqd,
|
|
bfqg->sched_data.in_service_entity);
|
|
}
|
|
|
|
/**
|
|
* bfq_pd_offline - deactivate the entity associated with @pd,
|
|
* and reparent its children entities.
|
|
* @pd: descriptor of the policy going offline.
|
|
*
|
|
* blkio already grabs the queue_lock for us, so no need to use
|
|
* RCU-based magic
|
|
*/
|
|
static void bfq_pd_offline(struct blkg_policy_data *pd)
|
|
{
|
|
struct bfq_service_tree *st;
|
|
struct bfq_group *bfqg = pd_to_bfqg(pd);
|
|
struct bfq_data *bfqd = bfqg->bfqd;
|
|
struct bfq_entity *entity = bfqg->my_entity;
|
|
unsigned long flags;
|
|
int i;
|
|
|
|
if (!entity) /* root group */
|
|
return;
|
|
|
|
spin_lock_irqsave(&bfqd->lock, flags);
|
|
/*
|
|
* Empty all service_trees belonging to this group before
|
|
* deactivating the group itself.
|
|
*/
|
|
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++) {
|
|
st = bfqg->sched_data.service_tree + i;
|
|
|
|
/*
|
|
* The idle tree may still contain bfq_queues belonging
|
|
* to exited task because they never migrated to a different
|
|
* cgroup from the one being destroyed now. No one else
|
|
* can access them so it's safe to act without any lock.
|
|
*/
|
|
bfq_flush_idle_tree(st);
|
|
|
|
/*
|
|
* It may happen that some queues are still active
|
|
* (busy) upon group destruction (if the corresponding
|
|
* processes have been forced to terminate). We move
|
|
* all the leaf entities corresponding to these queues
|
|
* to the root_group.
|
|
* Also, it may happen that the group has an entity
|
|
* in service, which is disconnected from the active
|
|
* tree: it must be moved, too.
|
|
* There is no need to put the sync queues, as the
|
|
* scheduler has taken no reference.
|
|
*/
|
|
bfq_reparent_active_entities(bfqd, bfqg, st);
|
|
}
|
|
|
|
__bfq_deactivate_entity(entity, false);
|
|
bfq_put_async_queues(bfqd, bfqg);
|
|
|
|
bfq_unlock_put_ioc_restore(bfqd, flags);
|
|
/*
|
|
* @blkg is going offline and will be ignored by
|
|
* blkg_[rw]stat_recursive_sum(). Transfer stats to the parent so
|
|
* that they don't get lost. If IOs complete after this point, the
|
|
* stats for them will be lost. Oh well...
|
|
*/
|
|
bfqg_stats_xfer_dead(bfqg);
|
|
}
|
|
|
|
static void bfq_end_wr_async(struct bfq_data *bfqd)
|
|
{
|
|
struct blkcg_gq *blkg;
|
|
|
|
list_for_each_entry(blkg, &bfqd->queue->blkg_list, q_node) {
|
|
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
|
|
|
|
bfq_end_wr_async_queues(bfqd, bfqg);
|
|
}
|
|
bfq_end_wr_async_queues(bfqd, bfqd->root_group);
|
|
}
|
|
|
|
static int bfq_io_show_weight(struct seq_file *sf, void *v)
|
|
{
|
|
struct blkcg *blkcg = css_to_blkcg(seq_css(sf));
|
|
struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
|
|
unsigned int val = 0;
|
|
|
|
if (bfqgd)
|
|
val = bfqgd->weight;
|
|
|
|
seq_printf(sf, "%u\n", val);
|
|
|
|
return 0;
|
|
}
|
|
|
|
static int bfq_io_set_weight_legacy(struct cgroup_subsys_state *css,
|
|
struct cftype *cftype,
|
|
u64 val)
|
|
{
|
|
struct blkcg *blkcg = css_to_blkcg(css);
|
|
struct bfq_group_data *bfqgd = blkcg_to_bfqgd(blkcg);
|
|
struct blkcg_gq *blkg;
|
|
int ret = -ERANGE;
|
|
|
|
if (val < BFQ_MIN_WEIGHT || val > BFQ_MAX_WEIGHT)
|
|
return ret;
|
|
|
|
ret = 0;
|
|
spin_lock_irq(&blkcg->lock);
|
|
bfqgd->weight = (unsigned short)val;
|
|
hlist_for_each_entry(blkg, &blkcg->blkg_list, blkcg_node) {
|
|
struct bfq_group *bfqg = blkg_to_bfqg(blkg);
|
|
|
|
if (!bfqg)
|
|
continue;
|
|
/*
|
|
* Setting the prio_changed flag of the entity
|
|
* to 1 with new_weight == weight would re-set
|
|
* the value of the weight to its ioprio mapping.
|
|
* Set the flag only if necessary.
|
|
*/
|
|
if ((unsigned short)val != bfqg->entity.new_weight) {
|
|
bfqg->entity.new_weight = (unsigned short)val;
|
|
/*
|
|
* Make sure that the above new value has been
|
|
* stored in bfqg->entity.new_weight before
|
|
* setting the prio_changed flag. In fact,
|
|
* this flag may be read asynchronously (in
|
|
* critical sections protected by a different
|
|
* lock than that held here), and finding this
|
|
* flag set may cause the execution of the code
|
|
* for updating parameters whose value may
|
|
* depend also on bfqg->entity.new_weight (in
|
|
* __bfq_entity_update_weight_prio).
|
|
* This barrier makes sure that the new value
|
|
* of bfqg->entity.new_weight is correctly
|
|
* seen in that code.
|
|
*/
|
|
smp_wmb();
|
|
bfqg->entity.prio_changed = 1;
|
|
}
|
|
}
|
|
spin_unlock_irq(&blkcg->lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static ssize_t bfq_io_set_weight(struct kernfs_open_file *of,
|
|
char *buf, size_t nbytes,
|
|
loff_t off)
|
|
{
|
|
u64 weight;
|
|
/* First unsigned long found in the file is used */
|
|
int ret = kstrtoull(strim(buf), 0, &weight);
|
|
|
|
if (ret)
|
|
return ret;
|
|
|
|
return bfq_io_set_weight_legacy(of_css(of), NULL, weight);
|
|
}
|
|
|
|
static int bfqg_print_stat(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_stat,
|
|
&blkcg_policy_bfq, seq_cft(sf)->private, false);
|
|
return 0;
|
|
}
|
|
|
|
static int bfqg_print_rwstat(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)), blkg_prfill_rwstat,
|
|
&blkcg_policy_bfq, seq_cft(sf)->private, true);
|
|
return 0;
|
|
}
|
|
|
|
static u64 bfqg_prfill_stat_recursive(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
u64 sum = blkg_stat_recursive_sum(pd_to_blkg(pd),
|
|
&blkcg_policy_bfq, off);
|
|
return __blkg_prfill_u64(sf, pd, sum);
|
|
}
|
|
|
|
static u64 bfqg_prfill_rwstat_recursive(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
struct blkg_rwstat sum = blkg_rwstat_recursive_sum(pd_to_blkg(pd),
|
|
&blkcg_policy_bfq,
|
|
off);
|
|
return __blkg_prfill_rwstat(sf, pd, &sum);
|
|
}
|
|
|
|
static int bfqg_print_stat_recursive(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
bfqg_prfill_stat_recursive, &blkcg_policy_bfq,
|
|
seq_cft(sf)->private, false);
|
|
return 0;
|
|
}
|
|
|
|
static int bfqg_print_rwstat_recursive(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
bfqg_prfill_rwstat_recursive, &blkcg_policy_bfq,
|
|
seq_cft(sf)->private, true);
|
|
return 0;
|
|
}
|
|
|
|
static u64 bfqg_prfill_sectors(struct seq_file *sf, struct blkg_policy_data *pd,
|
|
int off)
|
|
{
|
|
u64 sum = blkg_rwstat_total(&pd->blkg->stat_bytes);
|
|
|
|
return __blkg_prfill_u64(sf, pd, sum >> 9);
|
|
}
|
|
|
|
static int bfqg_print_stat_sectors(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
bfqg_prfill_sectors, &blkcg_policy_bfq, 0, false);
|
|
return 0;
|
|
}
|
|
|
|
static u64 bfqg_prfill_sectors_recursive(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
struct blkg_rwstat tmp = blkg_rwstat_recursive_sum(pd->blkg, NULL,
|
|
offsetof(struct blkcg_gq, stat_bytes));
|
|
u64 sum = atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_READ]) +
|
|
atomic64_read(&tmp.aux_cnt[BLKG_RWSTAT_WRITE]);
|
|
|
|
return __blkg_prfill_u64(sf, pd, sum >> 9);
|
|
}
|
|
|
|
static int bfqg_print_stat_sectors_recursive(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
bfqg_prfill_sectors_recursive, &blkcg_policy_bfq, 0,
|
|
false);
|
|
return 0;
|
|
}
|
|
|
|
static u64 bfqg_prfill_avg_queue_size(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
struct bfq_group *bfqg = pd_to_bfqg(pd);
|
|
u64 samples = blkg_stat_read(&bfqg->stats.avg_queue_size_samples);
|
|
u64 v = 0;
|
|
|
|
if (samples) {
|
|
v = blkg_stat_read(&bfqg->stats.avg_queue_size_sum);
|
|
v = div64_u64(v, samples);
|
|
}
|
|
__blkg_prfill_u64(sf, pd, v);
|
|
return 0;
|
|
}
|
|
|
|
/* print avg_queue_size */
|
|
static int bfqg_print_avg_queue_size(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
bfqg_prfill_avg_queue_size, &blkcg_policy_bfq,
|
|
0, false);
|
|
return 0;
|
|
}
|
|
|
|
static struct bfq_group *
|
|
bfq_create_group_hierarchy(struct bfq_data *bfqd, int node)
|
|
{
|
|
int ret;
|
|
|
|
ret = blkcg_activate_policy(bfqd->queue, &blkcg_policy_bfq);
|
|
if (ret)
|
|
return NULL;
|
|
|
|
return blkg_to_bfqg(bfqd->queue->root_blkg);
|
|
}
|
|
|
|
static struct cftype bfq_blkcg_legacy_files[] = {
|
|
{
|
|
.name = "bfq.weight",
|
|
.flags = CFTYPE_NOT_ON_ROOT,
|
|
.seq_show = bfq_io_show_weight,
|
|
.write_u64 = bfq_io_set_weight_legacy,
|
|
},
|
|
|
|
/* statistics, covers only the tasks in the bfqg */
|
|
{
|
|
.name = "bfq.time",
|
|
.private = offsetof(struct bfq_group, stats.time),
|
|
.seq_show = bfqg_print_stat,
|
|
},
|
|
{
|
|
.name = "bfq.sectors",
|
|
.seq_show = bfqg_print_stat_sectors,
|
|
},
|
|
{
|
|
.name = "bfq.io_service_bytes",
|
|
.private = (unsigned long)&blkcg_policy_bfq,
|
|
.seq_show = blkg_print_stat_bytes,
|
|
},
|
|
{
|
|
.name = "bfq.io_serviced",
|
|
.private = (unsigned long)&blkcg_policy_bfq,
|
|
.seq_show = blkg_print_stat_ios,
|
|
},
|
|
{
|
|
.name = "bfq.io_service_time",
|
|
.private = offsetof(struct bfq_group, stats.service_time),
|
|
.seq_show = bfqg_print_rwstat,
|
|
},
|
|
{
|
|
.name = "bfq.io_wait_time",
|
|
.private = offsetof(struct bfq_group, stats.wait_time),
|
|
.seq_show = bfqg_print_rwstat,
|
|
},
|
|
{
|
|
.name = "bfq.io_merged",
|
|
.private = offsetof(struct bfq_group, stats.merged),
|
|
.seq_show = bfqg_print_rwstat,
|
|
},
|
|
{
|
|
.name = "bfq.io_queued",
|
|
.private = offsetof(struct bfq_group, stats.queued),
|
|
.seq_show = bfqg_print_rwstat,
|
|
},
|
|
|
|
/* the same statictics which cover the bfqg and its descendants */
|
|
{
|
|
.name = "bfq.time_recursive",
|
|
.private = offsetof(struct bfq_group, stats.time),
|
|
.seq_show = bfqg_print_stat_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.sectors_recursive",
|
|
.seq_show = bfqg_print_stat_sectors_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_service_bytes_recursive",
|
|
.private = (unsigned long)&blkcg_policy_bfq,
|
|
.seq_show = blkg_print_stat_bytes_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_serviced_recursive",
|
|
.private = (unsigned long)&blkcg_policy_bfq,
|
|
.seq_show = blkg_print_stat_ios_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_service_time_recursive",
|
|
.private = offsetof(struct bfq_group, stats.service_time),
|
|
.seq_show = bfqg_print_rwstat_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_wait_time_recursive",
|
|
.private = offsetof(struct bfq_group, stats.wait_time),
|
|
.seq_show = bfqg_print_rwstat_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_merged_recursive",
|
|
.private = offsetof(struct bfq_group, stats.merged),
|
|
.seq_show = bfqg_print_rwstat_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.io_queued_recursive",
|
|
.private = offsetof(struct bfq_group, stats.queued),
|
|
.seq_show = bfqg_print_rwstat_recursive,
|
|
},
|
|
{
|
|
.name = "bfq.avg_queue_size",
|
|
.seq_show = bfqg_print_avg_queue_size,
|
|
},
|
|
{
|
|
.name = "bfq.group_wait_time",
|
|
.private = offsetof(struct bfq_group, stats.group_wait_time),
|
|
.seq_show = bfqg_print_stat,
|
|
},
|
|
{
|
|
.name = "bfq.idle_time",
|
|
.private = offsetof(struct bfq_group, stats.idle_time),
|
|
.seq_show = bfqg_print_stat,
|
|
},
|
|
{
|
|
.name = "bfq.empty_time",
|
|
.private = offsetof(struct bfq_group, stats.empty_time),
|
|
.seq_show = bfqg_print_stat,
|
|
},
|
|
{
|
|
.name = "bfq.dequeue",
|
|
.private = offsetof(struct bfq_group, stats.dequeue),
|
|
.seq_show = bfqg_print_stat,
|
|
},
|
|
{ } /* terminate */
|
|
};
|
|
|
|
static struct cftype bfq_blkg_files[] = {
|
|
{
|
|
.name = "bfq.weight",
|
|
.flags = CFTYPE_NOT_ON_ROOT,
|
|
.seq_show = bfq_io_show_weight,
|
|
.write = bfq_io_set_weight,
|
|
},
|
|
{} /* terminate */
|
|
};
|
|
|
|
#else /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
|
|
static inline void bfqg_stats_update_io_add(struct bfq_group *bfqg,
|
|
struct bfq_queue *bfqq, unsigned int op) { }
|
|
static inline void
|
|
bfqg_stats_update_io_remove(struct bfq_group *bfqg, unsigned int op) { }
|
|
static inline void
|
|
bfqg_stats_update_io_merged(struct bfq_group *bfqg, unsigned int op) { }
|
|
static inline void bfqg_stats_update_completion(struct bfq_group *bfqg,
|
|
uint64_t start_time, uint64_t io_start_time,
|
|
unsigned int op) { }
|
|
static inline void
|
|
bfqg_stats_set_start_group_wait_time(struct bfq_group *bfqg,
|
|
struct bfq_group *curr_bfqg) { }
|
|
static inline void bfqg_stats_end_empty_time(struct bfqg_stats *stats) { }
|
|
static inline void bfqg_stats_update_dequeue(struct bfq_group *bfqg) { }
|
|
static inline void bfqg_stats_set_start_empty_time(struct bfq_group *bfqg) { }
|
|
static inline void bfqg_stats_update_idle_time(struct bfq_group *bfqg) { }
|
|
static inline void bfqg_stats_set_start_idle_time(struct bfq_group *bfqg) { }
|
|
static inline void bfqg_stats_update_avg_queue_size(struct bfq_group *bfqg) { }
|
|
|
|
static void bfq_bfqq_move(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
struct bfq_group *bfqg) {}
|
|
|
|
static void bfq_init_entity(struct bfq_entity *entity,
|
|
struct bfq_group *bfqg)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_entity_to_bfqq(entity);
|
|
|
|
entity->weight = entity->new_weight;
|
|
entity->orig_weight = entity->new_weight;
|
|
if (bfqq) {
|
|
bfqq->ioprio = bfqq->new_ioprio;
|
|
bfqq->ioprio_class = bfqq->new_ioprio_class;
|
|
}
|
|
entity->sched_data = &bfqg->sched_data;
|
|
}
|
|
|
|
static void bfq_bic_update_cgroup(struct bfq_io_cq *bic, struct bio *bio) {}
|
|
|
|
static void bfq_end_wr_async(struct bfq_data *bfqd)
|
|
{
|
|
bfq_end_wr_async_queues(bfqd, bfqd->root_group);
|
|
}
|
|
|
|
static struct bfq_group *bfq_find_set_group(struct bfq_data *bfqd,
|
|
struct blkcg *blkcg)
|
|
{
|
|
return bfqd->root_group;
|
|
}
|
|
|
|
static struct bfq_group *bfqq_group(struct bfq_queue *bfqq)
|
|
{
|
|
return bfqq->bfqd->root_group;
|
|
}
|
|
|
|
static struct bfq_group *bfq_create_group_hierarchy(struct bfq_data *bfqd,
|
|
int node)
|
|
{
|
|
struct bfq_group *bfqg;
|
|
int i;
|
|
|
|
bfqg = kmalloc_node(sizeof(*bfqg), GFP_KERNEL | __GFP_ZERO, node);
|
|
if (!bfqg)
|
|
return NULL;
|
|
|
|
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
|
|
bfqg->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
|
|
|
|
return bfqg;
|
|
}
|
|
#endif /* CONFIG_BFQ_GROUP_IOSCHED */
|
|
|
|
#define bfq_class_idle(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_IDLE)
|
|
#define bfq_class_rt(bfqq) ((bfqq)->ioprio_class == IOPRIO_CLASS_RT)
|
|
|
|
#define bfq_sample_valid(samples) ((samples) > 80)
|
|
|
|
/*
|
|
* Lifted from AS - choose which of rq1 and rq2 that is best served now.
|
|
* We choose the request that is closesr to the head right now. Distance
|
|
* behind the head is penalized and only allowed to a certain extent.
|
|
*/
|
|
static struct request *bfq_choose_req(struct bfq_data *bfqd,
|
|
struct request *rq1,
|
|
struct request *rq2,
|
|
sector_t last)
|
|
{
|
|
sector_t s1, s2, d1 = 0, d2 = 0;
|
|
unsigned long back_max;
|
|
#define BFQ_RQ1_WRAP 0x01 /* request 1 wraps */
|
|
#define BFQ_RQ2_WRAP 0x02 /* request 2 wraps */
|
|
unsigned int wrap = 0; /* bit mask: requests behind the disk head? */
|
|
|
|
if (!rq1 || rq1 == rq2)
|
|
return rq2;
|
|
if (!rq2)
|
|
return rq1;
|
|
|
|
if (rq_is_sync(rq1) && !rq_is_sync(rq2))
|
|
return rq1;
|
|
else if (rq_is_sync(rq2) && !rq_is_sync(rq1))
|
|
return rq2;
|
|
if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META))
|
|
return rq1;
|
|
else if ((rq2->cmd_flags & REQ_META) && !(rq1->cmd_flags & REQ_META))
|
|
return rq2;
|
|
|
|
s1 = blk_rq_pos(rq1);
|
|
s2 = blk_rq_pos(rq2);
|
|
|
|
/*
|
|
* By definition, 1KiB is 2 sectors.
|
|
*/
|
|
back_max = bfqd->bfq_back_max * 2;
|
|
|
|
/*
|
|
* Strict one way elevator _except_ in the case where we allow
|
|
* short backward seeks which are biased as twice the cost of a
|
|
* similar forward seek.
|
|
*/
|
|
if (s1 >= last)
|
|
d1 = s1 - last;
|
|
else if (s1 + back_max >= last)
|
|
d1 = (last - s1) * bfqd->bfq_back_penalty;
|
|
else
|
|
wrap |= BFQ_RQ1_WRAP;
|
|
|
|
if (s2 >= last)
|
|
d2 = s2 - last;
|
|
else if (s2 + back_max >= last)
|
|
d2 = (last - s2) * bfqd->bfq_back_penalty;
|
|
else
|
|
wrap |= BFQ_RQ2_WRAP;
|
|
|
|
/* Found required data */
|
|
|
|
/*
|
|
* By doing switch() on the bit mask "wrap" we avoid having to
|
|
* check two variables for all permutations: --> faster!
|
|
*/
|
|
switch (wrap) {
|
|
case 0: /* common case for CFQ: rq1 and rq2 not wrapped */
|
|
if (d1 < d2)
|
|
return rq1;
|
|
else if (d2 < d1)
|
|
return rq2;
|
|
|
|
if (s1 >= s2)
|
|
return rq1;
|
|
else
|
|
return rq2;
|
|
|
|
case BFQ_RQ2_WRAP:
|
|
return rq1;
|
|
case BFQ_RQ1_WRAP:
|
|
return rq2;
|
|
case BFQ_RQ1_WRAP|BFQ_RQ2_WRAP: /* both rqs wrapped */
|
|
default:
|
|
/*
|
|
* Since both rqs are wrapped,
|
|
* start with the one that's further behind head
|
|
* (--> only *one* back seek required),
|
|
* since back seek takes more time than forward.
|
|
*/
|
|
if (s1 <= s2)
|
|
return rq1;
|
|
else
|
|
return rq2;
|
|
}
|
|
}
|
|
|
|
static struct bfq_queue *
|
|
bfq_rq_pos_tree_lookup(struct bfq_data *bfqd, struct rb_root *root,
|
|
sector_t sector, struct rb_node **ret_parent,
|
|
struct rb_node ***rb_link)
|
|
{
|
|
struct rb_node **p, *parent;
|
|
struct bfq_queue *bfqq = NULL;
|
|
|
|
parent = NULL;
|
|
p = &root->rb_node;
|
|
while (*p) {
|
|
struct rb_node **n;
|
|
|
|
parent = *p;
|
|
bfqq = rb_entry(parent, struct bfq_queue, pos_node);
|
|
|
|
/*
|
|
* Sort strictly based on sector. Smallest to the left,
|
|
* largest to the right.
|
|
*/
|
|
if (sector > blk_rq_pos(bfqq->next_rq))
|
|
n = &(*p)->rb_right;
|
|
else if (sector < blk_rq_pos(bfqq->next_rq))
|
|
n = &(*p)->rb_left;
|
|
else
|
|
break;
|
|
p = n;
|
|
bfqq = NULL;
|
|
}
|
|
|
|
*ret_parent = parent;
|
|
if (rb_link)
|
|
*rb_link = p;
|
|
|
|
bfq_log(bfqd, "rq_pos_tree_lookup %llu: returning %d",
|
|
(unsigned long long)sector,
|
|
bfqq ? bfqq->pid : 0);
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
static void bfq_pos_tree_add_move(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
struct rb_node **p, *parent;
|
|
struct bfq_queue *__bfqq;
|
|
|
|
if (bfqq->pos_root) {
|
|
rb_erase(&bfqq->pos_node, bfqq->pos_root);
|
|
bfqq->pos_root = NULL;
|
|
}
|
|
|
|
if (bfq_class_idle(bfqq))
|
|
return;
|
|
if (!bfqq->next_rq)
|
|
return;
|
|
|
|
bfqq->pos_root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
|
|
__bfqq = bfq_rq_pos_tree_lookup(bfqd, bfqq->pos_root,
|
|
blk_rq_pos(bfqq->next_rq), &parent, &p);
|
|
if (!__bfqq) {
|
|
rb_link_node(&bfqq->pos_node, parent, p);
|
|
rb_insert_color(&bfqq->pos_node, bfqq->pos_root);
|
|
} else
|
|
bfqq->pos_root = NULL;
|
|
}
|
|
|
|
/*
|
|
* Return expired entry, or NULL to just start from scratch in rbtree.
|
|
*/
|
|
static struct request *bfq_check_fifo(struct bfq_queue *bfqq,
|
|
struct request *last)
|
|
{
|
|
struct request *rq;
|
|
|
|
if (bfq_bfqq_fifo_expire(bfqq))
|
|
return NULL;
|
|
|
|
bfq_mark_bfqq_fifo_expire(bfqq);
|
|
|
|
rq = rq_entry_fifo(bfqq->fifo.next);
|
|
|
|
if (rq == last || ktime_get_ns() < rq->fifo_time)
|
|
return NULL;
|
|
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "check_fifo: returned %p", rq);
|
|
return rq;
|
|
}
|
|
|
|
static struct request *bfq_find_next_rq(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
struct request *last)
|
|
{
|
|
struct rb_node *rbnext = rb_next(&last->rb_node);
|
|
struct rb_node *rbprev = rb_prev(&last->rb_node);
|
|
struct request *next, *prev = NULL;
|
|
|
|
/* Follow expired path, else get first next available. */
|
|
next = bfq_check_fifo(bfqq, last);
|
|
if (next)
|
|
return next;
|
|
|
|
if (rbprev)
|
|
prev = rb_entry_rq(rbprev);
|
|
|
|
if (rbnext)
|
|
next = rb_entry_rq(rbnext);
|
|
else {
|
|
rbnext = rb_first(&bfqq->sort_list);
|
|
if (rbnext && rbnext != &last->rb_node)
|
|
next = rb_entry_rq(rbnext);
|
|
}
|
|
|
|
return bfq_choose_req(bfqd, next, prev, blk_rq_pos(last));
|
|
}
|
|
|
|
/* see the definition of bfq_async_charge_factor for details */
|
|
static unsigned long bfq_serv_to_charge(struct request *rq,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
if (bfq_bfqq_sync(bfqq) || bfqq->wr_coeff > 1)
|
|
return blk_rq_sectors(rq);
|
|
|
|
/*
|
|
* If there are no weight-raised queues, then amplify service
|
|
* by just the async charge factor; otherwise amplify service
|
|
* by twice the async charge factor, to further reduce latency
|
|
* for weight-raised queues.
|
|
*/
|
|
if (bfqq->bfqd->wr_busy_queues == 0)
|
|
return blk_rq_sectors(rq) * bfq_async_charge_factor;
|
|
|
|
return blk_rq_sectors(rq) * 2 * bfq_async_charge_factor;
|
|
}
|
|
|
|
/**
|
|
* bfq_updated_next_req - update the queue after a new next_rq selection.
|
|
* @bfqd: the device data the queue belongs to.
|
|
* @bfqq: the queue to update.
|
|
*
|
|
* If the first request of a queue changes we make sure that the queue
|
|
* has enough budget to serve at least its first request (if the
|
|
* request has grown). We do this because if the queue has not enough
|
|
* budget for its first request, it has to go through two dispatch
|
|
* rounds to actually get it dispatched.
|
|
*/
|
|
static void bfq_updated_next_req(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
struct request *next_rq = bfqq->next_rq;
|
|
unsigned long new_budget;
|
|
|
|
if (!next_rq)
|
|
return;
|
|
|
|
if (bfqq == bfqd->in_service_queue)
|
|
/*
|
|
* In order not to break guarantees, budgets cannot be
|
|
* changed after an entity has been selected.
|
|
*/
|
|
return;
|
|
|
|
new_budget = max_t(unsigned long, bfqq->max_budget,
|
|
bfq_serv_to_charge(next_rq, bfqq));
|
|
if (entity->budget != new_budget) {
|
|
entity->budget = new_budget;
|
|
bfq_log_bfqq(bfqd, bfqq, "updated next rq: new budget %lu",
|
|
new_budget);
|
|
bfq_requeue_bfqq(bfqd, bfqq);
|
|
}
|
|
}
|
|
|
|
static void
|
|
bfq_bfqq_resume_state(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
|
|
{
|
|
if (bic->saved_idle_window)
|
|
bfq_mark_bfqq_idle_window(bfqq);
|
|
else
|
|
bfq_clear_bfqq_idle_window(bfqq);
|
|
|
|
if (bic->saved_IO_bound)
|
|
bfq_mark_bfqq_IO_bound(bfqq);
|
|
else
|
|
bfq_clear_bfqq_IO_bound(bfqq);
|
|
|
|
bfqq->ttime = bic->saved_ttime;
|
|
bfqq->wr_coeff = bic->saved_wr_coeff;
|
|
bfqq->wr_start_at_switch_to_srt = bic->saved_wr_start_at_switch_to_srt;
|
|
bfqq->last_wr_start_finish = bic->saved_last_wr_start_finish;
|
|
bfqq->wr_cur_max_time = bic->saved_wr_cur_max_time;
|
|
|
|
if (bfqq->wr_coeff > 1 &&
|
|
time_is_before_jiffies(bfqq->last_wr_start_finish +
|
|
bfqq->wr_cur_max_time)) {
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq,
|
|
"resume state: switching off wr");
|
|
|
|
bfqq->wr_coeff = 1;
|
|
}
|
|
|
|
/* make sure weight will be updated, however we got here */
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
|
|
static int bfqq_process_refs(struct bfq_queue *bfqq)
|
|
{
|
|
return bfqq->ref - bfqq->allocated - bfqq->entity.on_st;
|
|
}
|
|
|
|
static int bfq_bfqq_budget_left(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
return entity->budget - entity->service;
|
|
}
|
|
|
|
/*
|
|
* If enough samples have been computed, return the current max budget
|
|
* stored in bfqd, which is dynamically updated according to the
|
|
* estimated disk peak rate; otherwise return the default max budget
|
|
*/
|
|
static int bfq_max_budget(struct bfq_data *bfqd)
|
|
{
|
|
if (bfqd->budgets_assigned < bfq_stats_min_budgets)
|
|
return bfq_default_max_budget;
|
|
else
|
|
return bfqd->bfq_max_budget;
|
|
}
|
|
|
|
/*
|
|
* Return min budget, which is a fraction of the current or default
|
|
* max budget (trying with 1/32)
|
|
*/
|
|
static int bfq_min_budget(struct bfq_data *bfqd)
|
|
{
|
|
if (bfqd->budgets_assigned < bfq_stats_min_budgets)
|
|
return bfq_default_max_budget / 32;
|
|
else
|
|
return bfqd->bfq_max_budget / 32;
|
|
}
|
|
|
|
static void bfq_bfqq_expire(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
bool compensate,
|
|
enum bfqq_expiration reason);
|
|
|
|
/*
|
|
* The next function, invoked after the input queue bfqq switches from
|
|
* idle to busy, updates the budget of bfqq. The function also tells
|
|
* whether the in-service queue should be expired, by returning
|
|
* true. The purpose of expiring the in-service queue is to give bfqq
|
|
* the chance to possibly preempt the in-service queue, and the reason
|
|
* for preempting the in-service queue is to achieve one of the two
|
|
* goals below.
|
|
*
|
|
* 1. Guarantee to bfqq its reserved bandwidth even if bfqq has
|
|
* expired because it has remained idle. In particular, bfqq may have
|
|
* expired for one of the following two reasons:
|
|
*
|
|
* - BFQQE_NO_MORE_REQUESTS bfqq did not enjoy any device idling
|
|
* and did not make it to issue a new request before its last
|
|
* request was served;
|
|
*
|
|
* - BFQQE_TOO_IDLE bfqq did enjoy device idling, but did not issue
|
|
* a new request before the expiration of the idling-time.
|
|
*
|
|
* Even if bfqq has expired for one of the above reasons, the process
|
|
* associated with the queue may be however issuing requests greedily,
|
|
* and thus be sensitive to the bandwidth it receives (bfqq may have
|
|
* remained idle for other reasons: CPU high load, bfqq not enjoying
|
|
* idling, I/O throttling somewhere in the path from the process to
|
|
* the I/O scheduler, ...). But if, after every expiration for one of
|
|
* the above two reasons, bfqq has to wait for the service of at least
|
|
* one full budget of another queue before being served again, then
|
|
* bfqq is likely to get a much lower bandwidth or resource time than
|
|
* its reserved ones. To address this issue, two countermeasures need
|
|
* to be taken.
|
|
*
|
|
* First, the budget and the timestamps of bfqq need to be updated in
|
|
* a special way on bfqq reactivation: they need to be updated as if
|
|
* bfqq did not remain idle and did not expire. In fact, if they are
|
|
* computed as if bfqq expired and remained idle until reactivation,
|
|
* then the process associated with bfqq is treated as if, instead of
|
|
* being greedy, it stopped issuing requests when bfqq remained idle,
|
|
* and restarts issuing requests only on this reactivation. In other
|
|
* words, the scheduler does not help the process recover the "service
|
|
* hole" between bfqq expiration and reactivation. As a consequence,
|
|
* the process receives a lower bandwidth than its reserved one. In
|
|
* contrast, to recover this hole, the budget must be updated as if
|
|
* bfqq was not expired at all before this reactivation, i.e., it must
|
|
* be set to the value of the remaining budget when bfqq was
|
|
* expired. Along the same line, timestamps need to be assigned the
|
|
* value they had the last time bfqq was selected for service, i.e.,
|
|
* before last expiration. Thus timestamps need to be back-shifted
|
|
* with respect to their normal computation (see [1] for more details
|
|
* on this tricky aspect).
|
|
*
|
|
* Secondly, to allow the process to recover the hole, the in-service
|
|
* queue must be expired too, to give bfqq the chance to preempt it
|
|
* immediately. In fact, if bfqq has to wait for a full budget of the
|
|
* in-service queue to be completed, then it may become impossible to
|
|
* let the process recover the hole, even if the back-shifted
|
|
* timestamps of bfqq are lower than those of the in-service queue. If
|
|
* this happens for most or all of the holes, then the process may not
|
|
* receive its reserved bandwidth. In this respect, it is worth noting
|
|
* that, being the service of outstanding requests unpreemptible, a
|
|
* little fraction of the holes may however be unrecoverable, thereby
|
|
* causing a little loss of bandwidth.
|
|
*
|
|
* The last important point is detecting whether bfqq does need this
|
|
* bandwidth recovery. In this respect, the next function deems the
|
|
* process associated with bfqq greedy, and thus allows it to recover
|
|
* the hole, if: 1) the process is waiting for the arrival of a new
|
|
* request (which implies that bfqq expired for one of the above two
|
|
* reasons), and 2) such a request has arrived soon. The first
|
|
* condition is controlled through the flag non_blocking_wait_rq,
|
|
* while the second through the flag arrived_in_time. If both
|
|
* conditions hold, then the function computes the budget in the
|
|
* above-described special way, and signals that the in-service queue
|
|
* should be expired. Timestamp back-shifting is done later in
|
|
* __bfq_activate_entity.
|
|
*
|
|
* 2. Reduce latency. Even if timestamps are not backshifted to let
|
|
* the process associated with bfqq recover a service hole, bfqq may
|
|
* however happen to have, after being (re)activated, a lower finish
|
|
* timestamp than the in-service queue. That is, the next budget of
|
|
* bfqq may have to be completed before the one of the in-service
|
|
* queue. If this is the case, then preempting the in-service queue
|
|
* allows this goal to be achieved, apart from the unpreemptible,
|
|
* outstanding requests mentioned above.
|
|
*
|
|
* Unfortunately, regardless of which of the above two goals one wants
|
|
* to achieve, service trees need first to be updated to know whether
|
|
* the in-service queue must be preempted. To have service trees
|
|
* correctly updated, the in-service queue must be expired and
|
|
* rescheduled, and bfqq must be scheduled too. This is one of the
|
|
* most costly operations (in future versions, the scheduling
|
|
* mechanism may be re-designed in such a way to make it possible to
|
|
* know whether preemption is needed without needing to update service
|
|
* trees). In addition, queue preemptions almost always cause random
|
|
* I/O, and thus loss of throughput. Because of these facts, the next
|
|
* function adopts the following simple scheme to avoid both costly
|
|
* operations and too frequent preemptions: it requests the expiration
|
|
* of the in-service queue (unconditionally) only for queues that need
|
|
* to recover a hole, or that either are weight-raised or deserve to
|
|
* be weight-raised.
|
|
*/
|
|
static bool bfq_bfqq_update_budg_for_activation(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
bool arrived_in_time,
|
|
bool wr_or_deserves_wr)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
if (bfq_bfqq_non_blocking_wait_rq(bfqq) && arrived_in_time) {
|
|
/*
|
|
* We do not clear the flag non_blocking_wait_rq here, as
|
|
* the latter is used in bfq_activate_bfqq to signal
|
|
* that timestamps need to be back-shifted (and is
|
|
* cleared right after).
|
|
*/
|
|
|
|
/*
|
|
* In next assignment we rely on that either
|
|
* entity->service or entity->budget are not updated
|
|
* on expiration if bfqq is empty (see
|
|
* __bfq_bfqq_recalc_budget). Thus both quantities
|
|
* remain unchanged after such an expiration, and the
|
|
* following statement therefore assigns to
|
|
* entity->budget the remaining budget on such an
|
|
* expiration. For clarity, entity->service is not
|
|
* updated on expiration in any case, and, in normal
|
|
* operation, is reset only when bfqq is selected for
|
|
* service (see bfq_get_next_queue).
|
|
*/
|
|
entity->budget = min_t(unsigned long,
|
|
bfq_bfqq_budget_left(bfqq),
|
|
bfqq->max_budget);
|
|
|
|
return true;
|
|
}
|
|
|
|
entity->budget = max_t(unsigned long, bfqq->max_budget,
|
|
bfq_serv_to_charge(bfqq->next_rq, bfqq));
|
|
bfq_clear_bfqq_non_blocking_wait_rq(bfqq);
|
|
return wr_or_deserves_wr;
|
|
}
|
|
|
|
static unsigned int bfq_wr_duration(struct bfq_data *bfqd)
|
|
{
|
|
u64 dur;
|
|
|
|
if (bfqd->bfq_wr_max_time > 0)
|
|
return bfqd->bfq_wr_max_time;
|
|
|
|
dur = bfqd->RT_prod;
|
|
do_div(dur, bfqd->peak_rate);
|
|
|
|
/*
|
|
* Limit duration between 3 and 13 seconds. Tests show that
|
|
* higher values than 13 seconds often yield the opposite of
|
|
* the desired result, i.e., worsen responsiveness by letting
|
|
* non-interactive and non-soft-real-time applications
|
|
* preserve weight raising for a too long time interval.
|
|
*
|
|
* On the other end, lower values than 3 seconds make it
|
|
* difficult for most interactive tasks to complete their jobs
|
|
* before weight-raising finishes.
|
|
*/
|
|
if (dur > msecs_to_jiffies(13000))
|
|
dur = msecs_to_jiffies(13000);
|
|
else if (dur < msecs_to_jiffies(3000))
|
|
dur = msecs_to_jiffies(3000);
|
|
|
|
return dur;
|
|
}
|
|
|
|
static void bfq_update_bfqq_wr_on_rq_arrival(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
unsigned int old_wr_coeff,
|
|
bool wr_or_deserves_wr,
|
|
bool interactive,
|
|
bool soft_rt)
|
|
{
|
|
if (old_wr_coeff == 1 && wr_or_deserves_wr) {
|
|
/* start a weight-raising period */
|
|
if (interactive) {
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
|
|
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
|
|
} else {
|
|
bfqq->wr_start_at_switch_to_srt = jiffies;
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff *
|
|
BFQ_SOFTRT_WEIGHT_FACTOR;
|
|
bfqq->wr_cur_max_time =
|
|
bfqd->bfq_wr_rt_max_time;
|
|
}
|
|
|
|
/*
|
|
* If needed, further reduce budget to make sure it is
|
|
* close to bfqq's backlog, so as to reduce the
|
|
* scheduling-error component due to a too large
|
|
* budget. Do not care about throughput consequences,
|
|
* but only about latency. Finally, do not assign a
|
|
* too small budget either, to avoid increasing
|
|
* latency by causing too frequent expirations.
|
|
*/
|
|
bfqq->entity.budget = min_t(unsigned long,
|
|
bfqq->entity.budget,
|
|
2 * bfq_min_budget(bfqd));
|
|
} else if (old_wr_coeff > 1) {
|
|
if (interactive) { /* update wr coeff and duration */
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
|
|
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
|
|
} else if (soft_rt) {
|
|
/*
|
|
* The application is now or still meeting the
|
|
* requirements for being deemed soft rt. We
|
|
* can then correctly and safely (re)charge
|
|
* the weight-raising duration for the
|
|
* application with the weight-raising
|
|
* duration for soft rt applications.
|
|
*
|
|
* In particular, doing this recharge now, i.e.,
|
|
* before the weight-raising period for the
|
|
* application finishes, reduces the probability
|
|
* of the following negative scenario:
|
|
* 1) the weight of a soft rt application is
|
|
* raised at startup (as for any newly
|
|
* created application),
|
|
* 2) since the application is not interactive,
|
|
* at a certain time weight-raising is
|
|
* stopped for the application,
|
|
* 3) at that time the application happens to
|
|
* still have pending requests, and hence
|
|
* is destined to not have a chance to be
|
|
* deemed soft rt before these requests are
|
|
* completed (see the comments to the
|
|
* function bfq_bfqq_softrt_next_start()
|
|
* for details on soft rt detection),
|
|
* 4) these pending requests experience a high
|
|
* latency because the application is not
|
|
* weight-raised while they are pending.
|
|
*/
|
|
if (bfqq->wr_cur_max_time !=
|
|
bfqd->bfq_wr_rt_max_time) {
|
|
bfqq->wr_start_at_switch_to_srt =
|
|
bfqq->last_wr_start_finish;
|
|
|
|
bfqq->wr_cur_max_time =
|
|
bfqd->bfq_wr_rt_max_time;
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff *
|
|
BFQ_SOFTRT_WEIGHT_FACTOR;
|
|
}
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
}
|
|
}
|
|
}
|
|
|
|
static bool bfq_bfqq_idle_for_long_time(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
return bfqq->dispatched == 0 &&
|
|
time_is_before_jiffies(
|
|
bfqq->budget_timeout +
|
|
bfqd->bfq_wr_min_idle_time);
|
|
}
|
|
|
|
static void bfq_bfqq_handle_idle_busy_switch(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
int old_wr_coeff,
|
|
struct request *rq,
|
|
bool *interactive)
|
|
{
|
|
bool soft_rt, wr_or_deserves_wr, bfqq_wants_to_preempt,
|
|
idle_for_long_time = bfq_bfqq_idle_for_long_time(bfqd, bfqq),
|
|
/*
|
|
* See the comments on
|
|
* bfq_bfqq_update_budg_for_activation for
|
|
* details on the usage of the next variable.
|
|
*/
|
|
arrived_in_time = ktime_get_ns() <=
|
|
bfqq->ttime.last_end_request +
|
|
bfqd->bfq_slice_idle * 3;
|
|
|
|
bfqg_stats_update_io_add(bfqq_group(RQ_BFQQ(rq)), bfqq, rq->cmd_flags);
|
|
|
|
/*
|
|
* bfqq deserves to be weight-raised if:
|
|
* - it is sync,
|
|
* - it has been idle for enough time or is soft real-time,
|
|
* - is linked to a bfq_io_cq (it is not shared in any sense).
|
|
*/
|
|
soft_rt = bfqd->bfq_wr_max_softrt_rate > 0 &&
|
|
time_is_before_jiffies(bfqq->soft_rt_next_start);
|
|
*interactive = idle_for_long_time;
|
|
wr_or_deserves_wr = bfqd->low_latency &&
|
|
(bfqq->wr_coeff > 1 ||
|
|
(bfq_bfqq_sync(bfqq) &&
|
|
bfqq->bic && (*interactive || soft_rt)));
|
|
|
|
/*
|
|
* Using the last flag, update budget and check whether bfqq
|
|
* may want to preempt the in-service queue.
|
|
*/
|
|
bfqq_wants_to_preempt =
|
|
bfq_bfqq_update_budg_for_activation(bfqd, bfqq,
|
|
arrived_in_time,
|
|
wr_or_deserves_wr);
|
|
|
|
if (!bfq_bfqq_IO_bound(bfqq)) {
|
|
if (arrived_in_time) {
|
|
bfqq->requests_within_timer++;
|
|
if (bfqq->requests_within_timer >=
|
|
bfqd->bfq_requests_within_timer)
|
|
bfq_mark_bfqq_IO_bound(bfqq);
|
|
} else
|
|
bfqq->requests_within_timer = 0;
|
|
}
|
|
|
|
if (bfqd->low_latency) {
|
|
if (unlikely(time_is_after_jiffies(bfqq->split_time)))
|
|
/* wraparound */
|
|
bfqq->split_time =
|
|
jiffies - bfqd->bfq_wr_min_idle_time - 1;
|
|
|
|
if (time_is_before_jiffies(bfqq->split_time +
|
|
bfqd->bfq_wr_min_idle_time)) {
|
|
bfq_update_bfqq_wr_on_rq_arrival(bfqd, bfqq,
|
|
old_wr_coeff,
|
|
wr_or_deserves_wr,
|
|
*interactive,
|
|
soft_rt);
|
|
|
|
if (old_wr_coeff != bfqq->wr_coeff)
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
}
|
|
|
|
bfqq->last_idle_bklogged = jiffies;
|
|
bfqq->service_from_backlogged = 0;
|
|
bfq_clear_bfqq_softrt_update(bfqq);
|
|
|
|
bfq_add_bfqq_busy(bfqd, bfqq);
|
|
|
|
/*
|
|
* Expire in-service queue only if preemption may be needed
|
|
* for guarantees. In this respect, the function
|
|
* next_queue_may_preempt just checks a simple, necessary
|
|
* condition, and not a sufficient condition based on
|
|
* timestamps. In fact, for the latter condition to be
|
|
* evaluated, timestamps would need first to be updated, and
|
|
* this operation is quite costly (see the comments on the
|
|
* function bfq_bfqq_update_budg_for_activation).
|
|
*/
|
|
if (bfqd->in_service_queue && bfqq_wants_to_preempt &&
|
|
bfqd->in_service_queue->wr_coeff < bfqq->wr_coeff &&
|
|
next_queue_may_preempt(bfqd))
|
|
bfq_bfqq_expire(bfqd, bfqd->in_service_queue,
|
|
false, BFQQE_PREEMPTED);
|
|
}
|
|
|
|
static void bfq_add_request(struct request *rq)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq);
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
struct request *next_rq, *prev;
|
|
unsigned int old_wr_coeff = bfqq->wr_coeff;
|
|
bool interactive = false;
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "add_request %d", rq_is_sync(rq));
|
|
bfqq->queued[rq_is_sync(rq)]++;
|
|
bfqd->queued++;
|
|
|
|
elv_rb_add(&bfqq->sort_list, rq);
|
|
|
|
/*
|
|
* Check if this request is a better next-serve candidate.
|
|
*/
|
|
prev = bfqq->next_rq;
|
|
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, rq, bfqd->last_position);
|
|
bfqq->next_rq = next_rq;
|
|
|
|
/*
|
|
* Adjust priority tree position, if next_rq changes.
|
|
*/
|
|
if (prev != bfqq->next_rq)
|
|
bfq_pos_tree_add_move(bfqd, bfqq);
|
|
|
|
if (!bfq_bfqq_busy(bfqq)) /* switching to busy ... */
|
|
bfq_bfqq_handle_idle_busy_switch(bfqd, bfqq, old_wr_coeff,
|
|
rq, &interactive);
|
|
else {
|
|
if (bfqd->low_latency && old_wr_coeff == 1 && !rq_is_sync(rq) &&
|
|
time_is_before_jiffies(
|
|
bfqq->last_wr_start_finish +
|
|
bfqd->bfq_wr_min_inter_arr_async)) {
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
|
|
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
|
|
|
|
bfqd->wr_busy_queues++;
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
if (prev != bfqq->next_rq)
|
|
bfq_updated_next_req(bfqd, bfqq);
|
|
}
|
|
|
|
/*
|
|
* Assign jiffies to last_wr_start_finish in the following
|
|
* cases:
|
|
*
|
|
* . if bfqq is not going to be weight-raised, because, for
|
|
* non weight-raised queues, last_wr_start_finish stores the
|
|
* arrival time of the last request; as of now, this piece
|
|
* of information is used only for deciding whether to
|
|
* weight-raise async queues
|
|
*
|
|
* . if bfqq is not weight-raised, because, if bfqq is now
|
|
* switching to weight-raised, then last_wr_start_finish
|
|
* stores the time when weight-raising starts
|
|
*
|
|
* . if bfqq is interactive, because, regardless of whether
|
|
* bfqq is currently weight-raised, the weight-raising
|
|
* period must start or restart (this case is considered
|
|
* separately because it is not detected by the above
|
|
* conditions, if bfqq is already weight-raised)
|
|
*
|
|
* last_wr_start_finish has to be updated also if bfqq is soft
|
|
* real-time, because the weight-raising period is constantly
|
|
* restarted on idle-to-busy transitions for these queues, but
|
|
* this is already done in bfq_bfqq_handle_idle_busy_switch if
|
|
* needed.
|
|
*/
|
|
if (bfqd->low_latency &&
|
|
(old_wr_coeff == 1 || bfqq->wr_coeff == 1 || interactive))
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
}
|
|
|
|
static struct request *bfq_find_rq_fmerge(struct bfq_data *bfqd,
|
|
struct bio *bio,
|
|
struct request_queue *q)
|
|
{
|
|
struct bfq_queue *bfqq = bfqd->bio_bfqq;
|
|
|
|
|
|
if (bfqq)
|
|
return elv_rb_find(&bfqq->sort_list, bio_end_sector(bio));
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static sector_t get_sdist(sector_t last_pos, struct request *rq)
|
|
{
|
|
if (last_pos)
|
|
return abs(blk_rq_pos(rq) - last_pos);
|
|
|
|
return 0;
|
|
}
|
|
|
|
#if 0 /* Still not clear if we can do without next two functions */
|
|
static void bfq_activate_request(struct request_queue *q, struct request *rq)
|
|
{
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
|
|
bfqd->rq_in_driver++;
|
|
}
|
|
|
|
static void bfq_deactivate_request(struct request_queue *q, struct request *rq)
|
|
{
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
|
|
bfqd->rq_in_driver--;
|
|
}
|
|
#endif
|
|
|
|
static void bfq_remove_request(struct request_queue *q,
|
|
struct request *rq)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq);
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
const int sync = rq_is_sync(rq);
|
|
|
|
if (bfqq->next_rq == rq) {
|
|
bfqq->next_rq = bfq_find_next_rq(bfqd, bfqq, rq);
|
|
bfq_updated_next_req(bfqd, bfqq);
|
|
}
|
|
|
|
if (rq->queuelist.prev != &rq->queuelist)
|
|
list_del_init(&rq->queuelist);
|
|
bfqq->queued[sync]--;
|
|
bfqd->queued--;
|
|
elv_rb_del(&bfqq->sort_list, rq);
|
|
|
|
elv_rqhash_del(q, rq);
|
|
if (q->last_merge == rq)
|
|
q->last_merge = NULL;
|
|
|
|
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
|
|
bfqq->next_rq = NULL;
|
|
|
|
if (bfq_bfqq_busy(bfqq) && bfqq != bfqd->in_service_queue) {
|
|
bfq_del_bfqq_busy(bfqd, bfqq, false);
|
|
/*
|
|
* bfqq emptied. In normal operation, when
|
|
* bfqq is empty, bfqq->entity.service and
|
|
* bfqq->entity.budget must contain,
|
|
* respectively, the service received and the
|
|
* budget used last time bfqq emptied. These
|
|
* facts do not hold in this case, as at least
|
|
* this last removal occurred while bfqq is
|
|
* not in service. To avoid inconsistencies,
|
|
* reset both bfqq->entity.service and
|
|
* bfqq->entity.budget, if bfqq has still a
|
|
* process that may issue I/O requests to it.
|
|
*/
|
|
bfqq->entity.budget = bfqq->entity.service = 0;
|
|
}
|
|
|
|
/*
|
|
* Remove queue from request-position tree as it is empty.
|
|
*/
|
|
if (bfqq->pos_root) {
|
|
rb_erase(&bfqq->pos_node, bfqq->pos_root);
|
|
bfqq->pos_root = NULL;
|
|
}
|
|
}
|
|
|
|
if (rq->cmd_flags & REQ_META)
|
|
bfqq->meta_pending--;
|
|
|
|
bfqg_stats_update_io_remove(bfqq_group(bfqq), rq->cmd_flags);
|
|
}
|
|
|
|
static bool bfq_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
|
|
{
|
|
struct request_queue *q = hctx->queue;
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
struct request *free = NULL;
|
|
/*
|
|
* bfq_bic_lookup grabs the queue_lock: invoke it now and
|
|
* store its return value for later use, to avoid nesting
|
|
* queue_lock inside the bfqd->lock. We assume that the bic
|
|
* returned by bfq_bic_lookup does not go away before
|
|
* bfqd->lock is taken.
|
|
*/
|
|
struct bfq_io_cq *bic = bfq_bic_lookup(bfqd, current->io_context, q);
|
|
bool ret;
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
|
|
if (bic)
|
|
bfqd->bio_bfqq = bic_to_bfqq(bic, op_is_sync(bio->bi_opf));
|
|
else
|
|
bfqd->bio_bfqq = NULL;
|
|
bfqd->bio_bic = bic;
|
|
|
|
ret = blk_mq_sched_try_merge(q, bio, &free);
|
|
|
|
if (free)
|
|
blk_mq_free_request(free);
|
|
spin_unlock_irq(&bfqd->lock);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static int bfq_request_merge(struct request_queue *q, struct request **req,
|
|
struct bio *bio)
|
|
{
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
struct request *__rq;
|
|
|
|
__rq = bfq_find_rq_fmerge(bfqd, bio, q);
|
|
if (__rq && elv_bio_merge_ok(__rq, bio)) {
|
|
*req = __rq;
|
|
return ELEVATOR_FRONT_MERGE;
|
|
}
|
|
|
|
return ELEVATOR_NO_MERGE;
|
|
}
|
|
|
|
static void bfq_request_merged(struct request_queue *q, struct request *req,
|
|
enum elv_merge type)
|
|
{
|
|
if (type == ELEVATOR_FRONT_MERGE &&
|
|
rb_prev(&req->rb_node) &&
|
|
blk_rq_pos(req) <
|
|
blk_rq_pos(container_of(rb_prev(&req->rb_node),
|
|
struct request, rb_node))) {
|
|
struct bfq_queue *bfqq = RQ_BFQQ(req);
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
struct request *prev, *next_rq;
|
|
|
|
/* Reposition request in its sort_list */
|
|
elv_rb_del(&bfqq->sort_list, req);
|
|
elv_rb_add(&bfqq->sort_list, req);
|
|
|
|
/* Choose next request to be served for bfqq */
|
|
prev = bfqq->next_rq;
|
|
next_rq = bfq_choose_req(bfqd, bfqq->next_rq, req,
|
|
bfqd->last_position);
|
|
bfqq->next_rq = next_rq;
|
|
/*
|
|
* If next_rq changes, update both the queue's budget to
|
|
* fit the new request and the queue's position in its
|
|
* rq_pos_tree.
|
|
*/
|
|
if (prev != bfqq->next_rq) {
|
|
bfq_updated_next_req(bfqd, bfqq);
|
|
bfq_pos_tree_add_move(bfqd, bfqq);
|
|
}
|
|
}
|
|
}
|
|
|
|
static void bfq_requests_merged(struct request_queue *q, struct request *rq,
|
|
struct request *next)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq), *next_bfqq = RQ_BFQQ(next);
|
|
|
|
if (!RB_EMPTY_NODE(&rq->rb_node))
|
|
goto end;
|
|
spin_lock_irq(&bfqq->bfqd->lock);
|
|
|
|
/*
|
|
* If next and rq belong to the same bfq_queue and next is older
|
|
* than rq, then reposition rq in the fifo (by substituting next
|
|
* with rq). Otherwise, if next and rq belong to different
|
|
* bfq_queues, never reposition rq: in fact, we would have to
|
|
* reposition it with respect to next's position in its own fifo,
|
|
* which would most certainly be too expensive with respect to
|
|
* the benefits.
|
|
*/
|
|
if (bfqq == next_bfqq &&
|
|
!list_empty(&rq->queuelist) && !list_empty(&next->queuelist) &&
|
|
next->fifo_time < rq->fifo_time) {
|
|
list_del_init(&rq->queuelist);
|
|
list_replace_init(&next->queuelist, &rq->queuelist);
|
|
rq->fifo_time = next->fifo_time;
|
|
}
|
|
|
|
if (bfqq->next_rq == next)
|
|
bfqq->next_rq = rq;
|
|
|
|
bfq_remove_request(q, next);
|
|
|
|
spin_unlock_irq(&bfqq->bfqd->lock);
|
|
end:
|
|
bfqg_stats_update_io_merged(bfqq_group(bfqq), next->cmd_flags);
|
|
}
|
|
|
|
/* Must be called with bfqq != NULL */
|
|
static void bfq_bfqq_end_wr(struct bfq_queue *bfqq)
|
|
{
|
|
if (bfq_bfqq_busy(bfqq))
|
|
bfqq->bfqd->wr_busy_queues--;
|
|
bfqq->wr_coeff = 1;
|
|
bfqq->wr_cur_max_time = 0;
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
/*
|
|
* Trigger a weight change on the next invocation of
|
|
* __bfq_entity_update_weight_prio.
|
|
*/
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
|
|
static void bfq_end_wr_async_queues(struct bfq_data *bfqd,
|
|
struct bfq_group *bfqg)
|
|
{
|
|
int i, j;
|
|
|
|
for (i = 0; i < 2; i++)
|
|
for (j = 0; j < IOPRIO_BE_NR; j++)
|
|
if (bfqg->async_bfqq[i][j])
|
|
bfq_bfqq_end_wr(bfqg->async_bfqq[i][j]);
|
|
if (bfqg->async_idle_bfqq)
|
|
bfq_bfqq_end_wr(bfqg->async_idle_bfqq);
|
|
}
|
|
|
|
static void bfq_end_wr(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_queue *bfqq;
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
|
|
list_for_each_entry(bfqq, &bfqd->active_list, bfqq_list)
|
|
bfq_bfqq_end_wr(bfqq);
|
|
list_for_each_entry(bfqq, &bfqd->idle_list, bfqq_list)
|
|
bfq_bfqq_end_wr(bfqq);
|
|
bfq_end_wr_async(bfqd);
|
|
|
|
spin_unlock_irq(&bfqd->lock);
|
|
}
|
|
|
|
static sector_t bfq_io_struct_pos(void *io_struct, bool request)
|
|
{
|
|
if (request)
|
|
return blk_rq_pos(io_struct);
|
|
else
|
|
return ((struct bio *)io_struct)->bi_iter.bi_sector;
|
|
}
|
|
|
|
static int bfq_rq_close_to_sector(void *io_struct, bool request,
|
|
sector_t sector)
|
|
{
|
|
return abs(bfq_io_struct_pos(io_struct, request) - sector) <=
|
|
BFQQ_CLOSE_THR;
|
|
}
|
|
|
|
static struct bfq_queue *bfqq_find_close(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
sector_t sector)
|
|
{
|
|
struct rb_root *root = &bfq_bfqq_to_bfqg(bfqq)->rq_pos_tree;
|
|
struct rb_node *parent, *node;
|
|
struct bfq_queue *__bfqq;
|
|
|
|
if (RB_EMPTY_ROOT(root))
|
|
return NULL;
|
|
|
|
/*
|
|
* First, if we find a request starting at the end of the last
|
|
* request, choose it.
|
|
*/
|
|
__bfqq = bfq_rq_pos_tree_lookup(bfqd, root, sector, &parent, NULL);
|
|
if (__bfqq)
|
|
return __bfqq;
|
|
|
|
/*
|
|
* If the exact sector wasn't found, the parent of the NULL leaf
|
|
* will contain the closest sector (rq_pos_tree sorted by
|
|
* next_request position).
|
|
*/
|
|
__bfqq = rb_entry(parent, struct bfq_queue, pos_node);
|
|
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
|
|
return __bfqq;
|
|
|
|
if (blk_rq_pos(__bfqq->next_rq) < sector)
|
|
node = rb_next(&__bfqq->pos_node);
|
|
else
|
|
node = rb_prev(&__bfqq->pos_node);
|
|
if (!node)
|
|
return NULL;
|
|
|
|
__bfqq = rb_entry(node, struct bfq_queue, pos_node);
|
|
if (bfq_rq_close_to_sector(__bfqq->next_rq, true, sector))
|
|
return __bfqq;
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static struct bfq_queue *bfq_find_close_cooperator(struct bfq_data *bfqd,
|
|
struct bfq_queue *cur_bfqq,
|
|
sector_t sector)
|
|
{
|
|
struct bfq_queue *bfqq;
|
|
|
|
/*
|
|
* We shall notice if some of the queues are cooperating,
|
|
* e.g., working closely on the same area of the device. In
|
|
* that case, we can group them together and: 1) don't waste
|
|
* time idling, and 2) serve the union of their requests in
|
|
* the best possible order for throughput.
|
|
*/
|
|
bfqq = bfqq_find_close(bfqd, cur_bfqq, sector);
|
|
if (!bfqq || bfqq == cur_bfqq)
|
|
return NULL;
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
static struct bfq_queue *
|
|
bfq_setup_merge(struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
|
|
{
|
|
int process_refs, new_process_refs;
|
|
struct bfq_queue *__bfqq;
|
|
|
|
/*
|
|
* If there are no process references on the new_bfqq, then it is
|
|
* unsafe to follow the ->new_bfqq chain as other bfqq's in the chain
|
|
* may have dropped their last reference (not just their last process
|
|
* reference).
|
|
*/
|
|
if (!bfqq_process_refs(new_bfqq))
|
|
return NULL;
|
|
|
|
/* Avoid a circular list and skip interim queue merges. */
|
|
while ((__bfqq = new_bfqq->new_bfqq)) {
|
|
if (__bfqq == bfqq)
|
|
return NULL;
|
|
new_bfqq = __bfqq;
|
|
}
|
|
|
|
process_refs = bfqq_process_refs(bfqq);
|
|
new_process_refs = bfqq_process_refs(new_bfqq);
|
|
/*
|
|
* If the process for the bfqq has gone away, there is no
|
|
* sense in merging the queues.
|
|
*/
|
|
if (process_refs == 0 || new_process_refs == 0)
|
|
return NULL;
|
|
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "scheduling merge with queue %d",
|
|
new_bfqq->pid);
|
|
|
|
/*
|
|
* Merging is just a redirection: the requests of the process
|
|
* owning one of the two queues are redirected to the other queue.
|
|
* The latter queue, in its turn, is set as shared if this is the
|
|
* first time that the requests of some process are redirected to
|
|
* it.
|
|
*
|
|
* We redirect bfqq to new_bfqq and not the opposite, because we
|
|
* are in the context of the process owning bfqq, hence we have
|
|
* the io_cq of this process. So we can immediately configure this
|
|
* io_cq to redirect the requests of the process to new_bfqq.
|
|
*
|
|
* NOTE, even if new_bfqq coincides with the in-service queue, the
|
|
* io_cq of new_bfqq is not available, because, if the in-service
|
|
* queue is shared, bfqd->in_service_bic may not point to the
|
|
* io_cq of the in-service queue.
|
|
* Redirecting the requests of the process owning bfqq to the
|
|
* currently in-service queue is in any case the best option, as
|
|
* we feed the in-service queue with new requests close to the
|
|
* last request served and, by doing so, hopefully increase the
|
|
* throughput.
|
|
*/
|
|
bfqq->new_bfqq = new_bfqq;
|
|
new_bfqq->ref += process_refs;
|
|
return new_bfqq;
|
|
}
|
|
|
|
static bool bfq_may_be_close_cooperator(struct bfq_queue *bfqq,
|
|
struct bfq_queue *new_bfqq)
|
|
{
|
|
if (bfq_class_idle(bfqq) || bfq_class_idle(new_bfqq) ||
|
|
(bfqq->ioprio_class != new_bfqq->ioprio_class))
|
|
return false;
|
|
|
|
/*
|
|
* If either of the queues has already been detected as seeky,
|
|
* then merging it with the other queue is unlikely to lead to
|
|
* sequential I/O.
|
|
*/
|
|
if (BFQQ_SEEKY(bfqq) || BFQQ_SEEKY(new_bfqq))
|
|
return false;
|
|
|
|
/*
|
|
* Interleaved I/O is known to be done by (some) applications
|
|
* only for reads, so it does not make sense to merge async
|
|
* queues.
|
|
*/
|
|
if (!bfq_bfqq_sync(bfqq) || !bfq_bfqq_sync(new_bfqq))
|
|
return false;
|
|
|
|
return true;
|
|
}
|
|
|
|
/*
|
|
* If this function returns true, then bfqq cannot be merged. The idea
|
|
* is that true cooperation happens very early after processes start
|
|
* to do I/O. Usually, late cooperations are just accidental false
|
|
* positives. In case bfqq is weight-raised, such false positives
|
|
* would evidently degrade latency guarantees for bfqq.
|
|
*/
|
|
static bool wr_from_too_long(struct bfq_queue *bfqq)
|
|
{
|
|
return bfqq->wr_coeff > 1 &&
|
|
time_is_before_jiffies(bfqq->last_wr_start_finish +
|
|
msecs_to_jiffies(100));
|
|
}
|
|
|
|
/*
|
|
* Attempt to schedule a merge of bfqq with the currently in-service
|
|
* queue or with a close queue among the scheduled queues. Return
|
|
* NULL if no merge was scheduled, a pointer to the shared bfq_queue
|
|
* structure otherwise.
|
|
*
|
|
* The OOM queue is not allowed to participate to cooperation: in fact, since
|
|
* the requests temporarily redirected to the OOM queue could be redirected
|
|
* again to dedicated queues at any time, the state needed to correctly
|
|
* handle merging with the OOM queue would be quite complex and expensive
|
|
* to maintain. Besides, in such a critical condition as an out of memory,
|
|
* the benefits of queue merging may be little relevant, or even negligible.
|
|
*
|
|
* Weight-raised queues can be merged only if their weight-raising
|
|
* period has just started. In fact cooperating processes are usually
|
|
* started together. Thus, with this filter we avoid false positives
|
|
* that would jeopardize low-latency guarantees.
|
|
*
|
|
* WARNING: queue merging may impair fairness among non-weight raised
|
|
* queues, for at least two reasons: 1) the original weight of a
|
|
* merged queue may change during the merged state, 2) even being the
|
|
* weight the same, a merged queue may be bloated with many more
|
|
* requests than the ones produced by its originally-associated
|
|
* process.
|
|
*/
|
|
static struct bfq_queue *
|
|
bfq_setup_cooperator(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
void *io_struct, bool request)
|
|
{
|
|
struct bfq_queue *in_service_bfqq, *new_bfqq;
|
|
|
|
if (bfqq->new_bfqq)
|
|
return bfqq->new_bfqq;
|
|
|
|
if (!io_struct ||
|
|
wr_from_too_long(bfqq) ||
|
|
unlikely(bfqq == &bfqd->oom_bfqq))
|
|
return NULL;
|
|
|
|
/* If there is only one backlogged queue, don't search. */
|
|
if (bfqd->busy_queues == 1)
|
|
return NULL;
|
|
|
|
in_service_bfqq = bfqd->in_service_queue;
|
|
|
|
if (!in_service_bfqq || in_service_bfqq == bfqq ||
|
|
!bfqd->in_service_bic || wr_from_too_long(in_service_bfqq) ||
|
|
unlikely(in_service_bfqq == &bfqd->oom_bfqq))
|
|
goto check_scheduled;
|
|
|
|
if (bfq_rq_close_to_sector(io_struct, request, bfqd->last_position) &&
|
|
bfqq->entity.parent == in_service_bfqq->entity.parent &&
|
|
bfq_may_be_close_cooperator(bfqq, in_service_bfqq)) {
|
|
new_bfqq = bfq_setup_merge(bfqq, in_service_bfqq);
|
|
if (new_bfqq)
|
|
return new_bfqq;
|
|
}
|
|
/*
|
|
* Check whether there is a cooperator among currently scheduled
|
|
* queues. The only thing we need is that the bio/request is not
|
|
* NULL, as we need it to establish whether a cooperator exists.
|
|
*/
|
|
check_scheduled:
|
|
new_bfqq = bfq_find_close_cooperator(bfqd, bfqq,
|
|
bfq_io_struct_pos(io_struct, request));
|
|
|
|
if (new_bfqq && !wr_from_too_long(new_bfqq) &&
|
|
likely(new_bfqq != &bfqd->oom_bfqq) &&
|
|
bfq_may_be_close_cooperator(bfqq, new_bfqq))
|
|
return bfq_setup_merge(bfqq, new_bfqq);
|
|
|
|
return NULL;
|
|
}
|
|
|
|
static void bfq_bfqq_save_state(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_io_cq *bic = bfqq->bic;
|
|
|
|
/*
|
|
* If !bfqq->bic, the queue is already shared or its requests
|
|
* have already been redirected to a shared queue; both idle window
|
|
* and weight raising state have already been saved. Do nothing.
|
|
*/
|
|
if (!bic)
|
|
return;
|
|
|
|
bic->saved_ttime = bfqq->ttime;
|
|
bic->saved_idle_window = bfq_bfqq_idle_window(bfqq);
|
|
bic->saved_IO_bound = bfq_bfqq_IO_bound(bfqq);
|
|
bic->saved_wr_coeff = bfqq->wr_coeff;
|
|
bic->saved_wr_start_at_switch_to_srt = bfqq->wr_start_at_switch_to_srt;
|
|
bic->saved_last_wr_start_finish = bfqq->last_wr_start_finish;
|
|
bic->saved_wr_cur_max_time = bfqq->wr_cur_max_time;
|
|
}
|
|
|
|
static void bfq_get_bic_reference(struct bfq_queue *bfqq)
|
|
{
|
|
/*
|
|
* If bfqq->bic has a non-NULL value, the bic to which it belongs
|
|
* is about to begin using a shared bfq_queue.
|
|
*/
|
|
if (bfqq->bic)
|
|
atomic_long_inc(&bfqq->bic->icq.ioc->refcount);
|
|
}
|
|
|
|
static void
|
|
bfq_merge_bfqqs(struct bfq_data *bfqd, struct bfq_io_cq *bic,
|
|
struct bfq_queue *bfqq, struct bfq_queue *new_bfqq)
|
|
{
|
|
bfq_log_bfqq(bfqd, bfqq, "merging with queue %lu",
|
|
(unsigned long)new_bfqq->pid);
|
|
/* Save weight raising and idle window of the merged queues */
|
|
bfq_bfqq_save_state(bfqq);
|
|
bfq_bfqq_save_state(new_bfqq);
|
|
if (bfq_bfqq_IO_bound(bfqq))
|
|
bfq_mark_bfqq_IO_bound(new_bfqq);
|
|
bfq_clear_bfqq_IO_bound(bfqq);
|
|
|
|
/*
|
|
* If bfqq is weight-raised, then let new_bfqq inherit
|
|
* weight-raising. To reduce false positives, neglect the case
|
|
* where bfqq has just been created, but has not yet made it
|
|
* to be weight-raised (which may happen because EQM may merge
|
|
* bfqq even before bfq_add_request is executed for the first
|
|
* time for bfqq).
|
|
*/
|
|
if (new_bfqq->wr_coeff == 1 && bfqq->wr_coeff > 1) {
|
|
new_bfqq->wr_coeff = bfqq->wr_coeff;
|
|
new_bfqq->wr_cur_max_time = bfqq->wr_cur_max_time;
|
|
new_bfqq->last_wr_start_finish = bfqq->last_wr_start_finish;
|
|
new_bfqq->wr_start_at_switch_to_srt =
|
|
bfqq->wr_start_at_switch_to_srt;
|
|
if (bfq_bfqq_busy(new_bfqq))
|
|
bfqd->wr_busy_queues++;
|
|
new_bfqq->entity.prio_changed = 1;
|
|
}
|
|
|
|
if (bfqq->wr_coeff > 1) { /* bfqq has given its wr to new_bfqq */
|
|
bfqq->wr_coeff = 1;
|
|
bfqq->entity.prio_changed = 1;
|
|
if (bfq_bfqq_busy(bfqq))
|
|
bfqd->wr_busy_queues--;
|
|
}
|
|
|
|
bfq_log_bfqq(bfqd, new_bfqq, "merge_bfqqs: wr_busy %d",
|
|
bfqd->wr_busy_queues);
|
|
|
|
/*
|
|
* Grab a reference to the bic, to prevent it from being destroyed
|
|
* before being possibly touched by a bfq_split_bfqq().
|
|
*/
|
|
bfq_get_bic_reference(bfqq);
|
|
bfq_get_bic_reference(new_bfqq);
|
|
/*
|
|
* Merge queues (that is, let bic redirect its requests to new_bfqq)
|
|
*/
|
|
bic_set_bfqq(bic, new_bfqq, 1);
|
|
bfq_mark_bfqq_coop(new_bfqq);
|
|
/*
|
|
* new_bfqq now belongs to at least two bics (it is a shared queue):
|
|
* set new_bfqq->bic to NULL. bfqq either:
|
|
* - does not belong to any bic any more, and hence bfqq->bic must
|
|
* be set to NULL, or
|
|
* - is a queue whose owning bics have already been redirected to a
|
|
* different queue, hence the queue is destined to not belong to
|
|
* any bic soon and bfqq->bic is already NULL (therefore the next
|
|
* assignment causes no harm).
|
|
*/
|
|
new_bfqq->bic = NULL;
|
|
bfqq->bic = NULL;
|
|
/* release process reference to bfqq */
|
|
bfq_put_queue(bfqq);
|
|
}
|
|
|
|
static bool bfq_allow_bio_merge(struct request_queue *q, struct request *rq,
|
|
struct bio *bio)
|
|
{
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
bool is_sync = op_is_sync(bio->bi_opf);
|
|
struct bfq_queue *bfqq = bfqd->bio_bfqq, *new_bfqq;
|
|
|
|
/*
|
|
* Disallow merge of a sync bio into an async request.
|
|
*/
|
|
if (is_sync && !rq_is_sync(rq))
|
|
return false;
|
|
|
|
/*
|
|
* Lookup the bfqq that this bio will be queued with. Allow
|
|
* merge only if rq is queued there.
|
|
*/
|
|
if (!bfqq)
|
|
return false;
|
|
|
|
/*
|
|
* We take advantage of this function to perform an early merge
|
|
* of the queues of possible cooperating processes.
|
|
*/
|
|
new_bfqq = bfq_setup_cooperator(bfqd, bfqq, bio, false);
|
|
if (new_bfqq) {
|
|
/*
|
|
* bic still points to bfqq, then it has not yet been
|
|
* redirected to some other bfq_queue, and a queue
|
|
* merge beween bfqq and new_bfqq can be safely
|
|
* fulfillled, i.e., bic can be redirected to new_bfqq
|
|
* and bfqq can be put.
|
|
*/
|
|
bfq_merge_bfqqs(bfqd, bfqd->bio_bic, bfqq,
|
|
new_bfqq);
|
|
/*
|
|
* If we get here, bio will be queued into new_queue,
|
|
* so use new_bfqq to decide whether bio and rq can be
|
|
* merged.
|
|
*/
|
|
bfqq = new_bfqq;
|
|
|
|
/*
|
|
* Change also bqfd->bio_bfqq, as
|
|
* bfqd->bio_bic now points to new_bfqq, and
|
|
* this function may be invoked again (and then may
|
|
* use again bqfd->bio_bfqq).
|
|
*/
|
|
bfqd->bio_bfqq = bfqq;
|
|
}
|
|
|
|
return bfqq == RQ_BFQQ(rq);
|
|
}
|
|
|
|
/*
|
|
* Set the maximum time for the in-service queue to consume its
|
|
* budget. This prevents seeky processes from lowering the throughput.
|
|
* In practice, a time-slice service scheme is used with seeky
|
|
* processes.
|
|
*/
|
|
static void bfq_set_budget_timeout(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
unsigned int timeout_coeff;
|
|
|
|
if (bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time)
|
|
timeout_coeff = 1;
|
|
else
|
|
timeout_coeff = bfqq->entity.weight / bfqq->entity.orig_weight;
|
|
|
|
bfqd->last_budget_start = ktime_get();
|
|
|
|
bfqq->budget_timeout = jiffies +
|
|
bfqd->bfq_timeout * timeout_coeff;
|
|
}
|
|
|
|
static void __bfq_set_in_service_queue(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
if (bfqq) {
|
|
bfqg_stats_update_avg_queue_size(bfqq_group(bfqq));
|
|
bfq_clear_bfqq_fifo_expire(bfqq);
|
|
|
|
bfqd->budgets_assigned = (bfqd->budgets_assigned * 7 + 256) / 8;
|
|
|
|
if (time_is_before_jiffies(bfqq->last_wr_start_finish) &&
|
|
bfqq->wr_coeff > 1 &&
|
|
bfqq->wr_cur_max_time == bfqd->bfq_wr_rt_max_time &&
|
|
time_is_before_jiffies(bfqq->budget_timeout)) {
|
|
/*
|
|
* For soft real-time queues, move the start
|
|
* of the weight-raising period forward by the
|
|
* time the queue has not received any
|
|
* service. Otherwise, a relatively long
|
|
* service delay is likely to cause the
|
|
* weight-raising period of the queue to end,
|
|
* because of the short duration of the
|
|
* weight-raising period of a soft real-time
|
|
* queue. It is worth noting that this move
|
|
* is not so dangerous for the other queues,
|
|
* because soft real-time queues are not
|
|
* greedy.
|
|
*
|
|
* To not add a further variable, we use the
|
|
* overloaded field budget_timeout to
|
|
* determine for how long the queue has not
|
|
* received service, i.e., how much time has
|
|
* elapsed since the queue expired. However,
|
|
* this is a little imprecise, because
|
|
* budget_timeout is set to jiffies if bfqq
|
|
* not only expires, but also remains with no
|
|
* request.
|
|
*/
|
|
if (time_after(bfqq->budget_timeout,
|
|
bfqq->last_wr_start_finish))
|
|
bfqq->last_wr_start_finish +=
|
|
jiffies - bfqq->budget_timeout;
|
|
else
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
}
|
|
|
|
bfq_set_budget_timeout(bfqd, bfqq);
|
|
bfq_log_bfqq(bfqd, bfqq,
|
|
"set_in_service_queue, cur-budget = %d",
|
|
bfqq->entity.budget);
|
|
}
|
|
|
|
bfqd->in_service_queue = bfqq;
|
|
}
|
|
|
|
/*
|
|
* Get and set a new queue for service.
|
|
*/
|
|
static struct bfq_queue *bfq_set_in_service_queue(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_queue *bfqq = bfq_get_next_queue(bfqd);
|
|
|
|
__bfq_set_in_service_queue(bfqd, bfqq);
|
|
return bfqq;
|
|
}
|
|
|
|
static void bfq_arm_slice_timer(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_queue *bfqq = bfqd->in_service_queue;
|
|
struct bfq_io_cq *bic;
|
|
u32 sl;
|
|
|
|
/* Processes have exited, don't wait. */
|
|
bic = bfqd->in_service_bic;
|
|
if (!bic || atomic_read(&bic->icq.ioc->active_ref) == 0)
|
|
return;
|
|
|
|
bfq_mark_bfqq_wait_request(bfqq);
|
|
|
|
/*
|
|
* We don't want to idle for seeks, but we do want to allow
|
|
* fair distribution of slice time for a process doing back-to-back
|
|
* seeks. So allow a little bit of time for him to submit a new rq.
|
|
*/
|
|
sl = bfqd->bfq_slice_idle;
|
|
/*
|
|
* Unless the queue is being weight-raised, grant only minimum
|
|
* idle time if the queue is seeky. A long idling is preserved
|
|
* for a weight-raised queue, because it is needed for
|
|
* guaranteeing to the queue its reserved share of the
|
|
* throughput.
|
|
*/
|
|
if (BFQQ_SEEKY(bfqq) && bfqq->wr_coeff == 1)
|
|
sl = min_t(u64, sl, BFQ_MIN_TT);
|
|
|
|
bfqd->last_idling_start = ktime_get();
|
|
hrtimer_start(&bfqd->idle_slice_timer, ns_to_ktime(sl),
|
|
HRTIMER_MODE_REL);
|
|
bfqg_stats_set_start_idle_time(bfqq_group(bfqq));
|
|
}
|
|
|
|
/*
|
|
* In autotuning mode, max_budget is dynamically recomputed as the
|
|
* amount of sectors transferred in timeout at the estimated peak
|
|
* rate. This enables BFQ to utilize a full timeslice with a full
|
|
* budget, even if the in-service queue is served at peak rate. And
|
|
* this maximises throughput with sequential workloads.
|
|
*/
|
|
static unsigned long bfq_calc_max_budget(struct bfq_data *bfqd)
|
|
{
|
|
return (u64)bfqd->peak_rate * USEC_PER_MSEC *
|
|
jiffies_to_msecs(bfqd->bfq_timeout)>>BFQ_RATE_SHIFT;
|
|
}
|
|
|
|
/*
|
|
* Update parameters related to throughput and responsiveness, as a
|
|
* function of the estimated peak rate. See comments on
|
|
* bfq_calc_max_budget(), and on T_slow and T_fast arrays.
|
|
*/
|
|
static void update_thr_responsiveness_params(struct bfq_data *bfqd)
|
|
{
|
|
int dev_type = blk_queue_nonrot(bfqd->queue);
|
|
|
|
if (bfqd->bfq_user_max_budget == 0)
|
|
bfqd->bfq_max_budget =
|
|
bfq_calc_max_budget(bfqd);
|
|
|
|
if (bfqd->device_speed == BFQ_BFQD_FAST &&
|
|
bfqd->peak_rate < device_speed_thresh[dev_type]) {
|
|
bfqd->device_speed = BFQ_BFQD_SLOW;
|
|
bfqd->RT_prod = R_slow[dev_type] *
|
|
T_slow[dev_type];
|
|
} else if (bfqd->device_speed == BFQ_BFQD_SLOW &&
|
|
bfqd->peak_rate > device_speed_thresh[dev_type]) {
|
|
bfqd->device_speed = BFQ_BFQD_FAST;
|
|
bfqd->RT_prod = R_fast[dev_type] *
|
|
T_fast[dev_type];
|
|
}
|
|
|
|
bfq_log(bfqd,
|
|
"dev_type %s dev_speed_class = %s (%llu sects/sec), thresh %llu setcs/sec",
|
|
dev_type == 0 ? "ROT" : "NONROT",
|
|
bfqd->device_speed == BFQ_BFQD_FAST ? "FAST" : "SLOW",
|
|
bfqd->device_speed == BFQ_BFQD_FAST ?
|
|
(USEC_PER_SEC*(u64)R_fast[dev_type])>>BFQ_RATE_SHIFT :
|
|
(USEC_PER_SEC*(u64)R_slow[dev_type])>>BFQ_RATE_SHIFT,
|
|
(USEC_PER_SEC*(u64)device_speed_thresh[dev_type])>>
|
|
BFQ_RATE_SHIFT);
|
|
}
|
|
|
|
static void bfq_reset_rate_computation(struct bfq_data *bfqd,
|
|
struct request *rq)
|
|
{
|
|
if (rq != NULL) { /* new rq dispatch now, reset accordingly */
|
|
bfqd->last_dispatch = bfqd->first_dispatch = ktime_get_ns();
|
|
bfqd->peak_rate_samples = 1;
|
|
bfqd->sequential_samples = 0;
|
|
bfqd->tot_sectors_dispatched = bfqd->last_rq_max_size =
|
|
blk_rq_sectors(rq);
|
|
} else /* no new rq dispatched, just reset the number of samples */
|
|
bfqd->peak_rate_samples = 0; /* full re-init on next disp. */
|
|
|
|
bfq_log(bfqd,
|
|
"reset_rate_computation at end, sample %u/%u tot_sects %llu",
|
|
bfqd->peak_rate_samples, bfqd->sequential_samples,
|
|
bfqd->tot_sectors_dispatched);
|
|
}
|
|
|
|
static void bfq_update_rate_reset(struct bfq_data *bfqd, struct request *rq)
|
|
{
|
|
u32 rate, weight, divisor;
|
|
|
|
/*
|
|
* For the convergence property to hold (see comments on
|
|
* bfq_update_peak_rate()) and for the assessment to be
|
|
* reliable, a minimum number of samples must be present, and
|
|
* a minimum amount of time must have elapsed. If not so, do
|
|
* not compute new rate. Just reset parameters, to get ready
|
|
* for a new evaluation attempt.
|
|
*/
|
|
if (bfqd->peak_rate_samples < BFQ_RATE_MIN_SAMPLES ||
|
|
bfqd->delta_from_first < BFQ_RATE_MIN_INTERVAL)
|
|
goto reset_computation;
|
|
|
|
/*
|
|
* If a new request completion has occurred after last
|
|
* dispatch, then, to approximate the rate at which requests
|
|
* have been served by the device, it is more precise to
|
|
* extend the observation interval to the last completion.
|
|
*/
|
|
bfqd->delta_from_first =
|
|
max_t(u64, bfqd->delta_from_first,
|
|
bfqd->last_completion - bfqd->first_dispatch);
|
|
|
|
/*
|
|
* Rate computed in sects/usec, and not sects/nsec, for
|
|
* precision issues.
|
|
*/
|
|
rate = div64_ul(bfqd->tot_sectors_dispatched<<BFQ_RATE_SHIFT,
|
|
div_u64(bfqd->delta_from_first, NSEC_PER_USEC));
|
|
|
|
/*
|
|
* Peak rate not updated if:
|
|
* - the percentage of sequential dispatches is below 3/4 of the
|
|
* total, and rate is below the current estimated peak rate
|
|
* - rate is unreasonably high (> 20M sectors/sec)
|
|
*/
|
|
if ((bfqd->sequential_samples < (3 * bfqd->peak_rate_samples)>>2 &&
|
|
rate <= bfqd->peak_rate) ||
|
|
rate > 20<<BFQ_RATE_SHIFT)
|
|
goto reset_computation;
|
|
|
|
/*
|
|
* We have to update the peak rate, at last! To this purpose,
|
|
* we use a low-pass filter. We compute the smoothing constant
|
|
* of the filter as a function of the 'weight' of the new
|
|
* measured rate.
|
|
*
|
|
* As can be seen in next formulas, we define this weight as a
|
|
* quantity proportional to how sequential the workload is,
|
|
* and to how long the observation time interval is.
|
|
*
|
|
* The weight runs from 0 to 8. The maximum value of the
|
|
* weight, 8, yields the minimum value for the smoothing
|
|
* constant. At this minimum value for the smoothing constant,
|
|
* the measured rate contributes for half of the next value of
|
|
* the estimated peak rate.
|
|
*
|
|
* So, the first step is to compute the weight as a function
|
|
* of how sequential the workload is. Note that the weight
|
|
* cannot reach 9, because bfqd->sequential_samples cannot
|
|
* become equal to bfqd->peak_rate_samples, which, in its
|
|
* turn, holds true because bfqd->sequential_samples is not
|
|
* incremented for the first sample.
|
|
*/
|
|
weight = (9 * bfqd->sequential_samples) / bfqd->peak_rate_samples;
|
|
|
|
/*
|
|
* Second step: further refine the weight as a function of the
|
|
* duration of the observation interval.
|
|
*/
|
|
weight = min_t(u32, 8,
|
|
div_u64(weight * bfqd->delta_from_first,
|
|
BFQ_RATE_REF_INTERVAL));
|
|
|
|
/*
|
|
* Divisor ranging from 10, for minimum weight, to 2, for
|
|
* maximum weight.
|
|
*/
|
|
divisor = 10 - weight;
|
|
|
|
/*
|
|
* Finally, update peak rate:
|
|
*
|
|
* peak_rate = peak_rate * (divisor-1) / divisor + rate / divisor
|
|
*/
|
|
bfqd->peak_rate *= divisor-1;
|
|
bfqd->peak_rate /= divisor;
|
|
rate /= divisor; /* smoothing constant alpha = 1/divisor */
|
|
|
|
bfqd->peak_rate += rate;
|
|
update_thr_responsiveness_params(bfqd);
|
|
|
|
reset_computation:
|
|
bfq_reset_rate_computation(bfqd, rq);
|
|
}
|
|
|
|
/*
|
|
* Update the read/write peak rate (the main quantity used for
|
|
* auto-tuning, see update_thr_responsiveness_params()).
|
|
*
|
|
* It is not trivial to estimate the peak rate (correctly): because of
|
|
* the presence of sw and hw queues between the scheduler and the
|
|
* device components that finally serve I/O requests, it is hard to
|
|
* say exactly when a given dispatched request is served inside the
|
|
* device, and for how long. As a consequence, it is hard to know
|
|
* precisely at what rate a given set of requests is actually served
|
|
* by the device.
|
|
*
|
|
* On the opposite end, the dispatch time of any request is trivially
|
|
* available, and, from this piece of information, the "dispatch rate"
|
|
* of requests can be immediately computed. So, the idea in the next
|
|
* function is to use what is known, namely request dispatch times
|
|
* (plus, when useful, request completion times), to estimate what is
|
|
* unknown, namely in-device request service rate.
|
|
*
|
|
* The main issue is that, because of the above facts, the rate at
|
|
* which a certain set of requests is dispatched over a certain time
|
|
* interval can vary greatly with respect to the rate at which the
|
|
* same requests are then served. But, since the size of any
|
|
* intermediate queue is limited, and the service scheme is lossless
|
|
* (no request is silently dropped), the following obvious convergence
|
|
* property holds: the number of requests dispatched MUST become
|
|
* closer and closer to the number of requests completed as the
|
|
* observation interval grows. This is the key property used in
|
|
* the next function to estimate the peak service rate as a function
|
|
* of the observed dispatch rate. The function assumes to be invoked
|
|
* on every request dispatch.
|
|
*/
|
|
static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq)
|
|
{
|
|
u64 now_ns = ktime_get_ns();
|
|
|
|
if (bfqd->peak_rate_samples == 0) { /* first dispatch */
|
|
bfq_log(bfqd, "update_peak_rate: goto reset, samples %d",
|
|
bfqd->peak_rate_samples);
|
|
bfq_reset_rate_computation(bfqd, rq);
|
|
goto update_last_values; /* will add one sample */
|
|
}
|
|
|
|
/*
|
|
* Device idle for very long: the observation interval lasting
|
|
* up to this dispatch cannot be a valid observation interval
|
|
* for computing a new peak rate (similarly to the late-
|
|
* completion event in bfq_completed_request()). Go to
|
|
* update_rate_and_reset to have the following three steps
|
|
* taken:
|
|
* - close the observation interval at the last (previous)
|
|
* request dispatch or completion
|
|
* - compute rate, if possible, for that observation interval
|
|
* - start a new observation interval with this dispatch
|
|
*/
|
|
if (now_ns - bfqd->last_dispatch > 100*NSEC_PER_MSEC &&
|
|
bfqd->rq_in_driver == 0)
|
|
goto update_rate_and_reset;
|
|
|
|
/* Update sampling information */
|
|
bfqd->peak_rate_samples++;
|
|
|
|
if ((bfqd->rq_in_driver > 0 ||
|
|
now_ns - bfqd->last_completion < BFQ_MIN_TT)
|
|
&& get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR)
|
|
bfqd->sequential_samples++;
|
|
|
|
bfqd->tot_sectors_dispatched += blk_rq_sectors(rq);
|
|
|
|
/* Reset max observed rq size every 32 dispatches */
|
|
if (likely(bfqd->peak_rate_samples % 32))
|
|
bfqd->last_rq_max_size =
|
|
max_t(u32, blk_rq_sectors(rq), bfqd->last_rq_max_size);
|
|
else
|
|
bfqd->last_rq_max_size = blk_rq_sectors(rq);
|
|
|
|
bfqd->delta_from_first = now_ns - bfqd->first_dispatch;
|
|
|
|
/* Target observation interval not yet reached, go on sampling */
|
|
if (bfqd->delta_from_first < BFQ_RATE_REF_INTERVAL)
|
|
goto update_last_values;
|
|
|
|
update_rate_and_reset:
|
|
bfq_update_rate_reset(bfqd, rq);
|
|
update_last_values:
|
|
bfqd->last_position = blk_rq_pos(rq) + blk_rq_sectors(rq);
|
|
bfqd->last_dispatch = now_ns;
|
|
}
|
|
|
|
/*
|
|
* Remove request from internal lists.
|
|
*/
|
|
static void bfq_dispatch_remove(struct request_queue *q, struct request *rq)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq);
|
|
|
|
/*
|
|
* For consistency, the next instruction should have been
|
|
* executed after removing the request from the queue and
|
|
* dispatching it. We execute instead this instruction before
|
|
* bfq_remove_request() (and hence introduce a temporary
|
|
* inconsistency), for efficiency. In fact, should this
|
|
* dispatch occur for a non in-service bfqq, this anticipated
|
|
* increment prevents two counters related to bfqq->dispatched
|
|
* from risking to be, first, uselessly decremented, and then
|
|
* incremented again when the (new) value of bfqq->dispatched
|
|
* happens to be taken into account.
|
|
*/
|
|
bfqq->dispatched++;
|
|
bfq_update_peak_rate(q->elevator->elevator_data, rq);
|
|
|
|
bfq_remove_request(q, rq);
|
|
}
|
|
|
|
static void __bfq_bfqq_expire(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
/*
|
|
* If this bfqq is shared between multiple processes, check
|
|
* to make sure that those processes are still issuing I/Os
|
|
* within the mean seek distance. If not, it may be time to
|
|
* break the queues apart again.
|
|
*/
|
|
if (bfq_bfqq_coop(bfqq) && BFQQ_SEEKY(bfqq))
|
|
bfq_mark_bfqq_split_coop(bfqq);
|
|
|
|
if (RB_EMPTY_ROOT(&bfqq->sort_list)) {
|
|
if (bfqq->dispatched == 0)
|
|
/*
|
|
* Overloading budget_timeout field to store
|
|
* the time at which the queue remains with no
|
|
* backlog and no outstanding request; used by
|
|
* the weight-raising mechanism.
|
|
*/
|
|
bfqq->budget_timeout = jiffies;
|
|
|
|
bfq_del_bfqq_busy(bfqd, bfqq, true);
|
|
} else {
|
|
bfq_requeue_bfqq(bfqd, bfqq);
|
|
/*
|
|
* Resort priority tree of potential close cooperators.
|
|
*/
|
|
bfq_pos_tree_add_move(bfqd, bfqq);
|
|
}
|
|
|
|
/*
|
|
* All in-service entities must have been properly deactivated
|
|
* or requeued before executing the next function, which
|
|
* resets all in-service entites as no more in service.
|
|
*/
|
|
__bfq_bfqd_reset_in_service(bfqd);
|
|
}
|
|
|
|
/**
|
|
* __bfq_bfqq_recalc_budget - try to adapt the budget to the @bfqq behavior.
|
|
* @bfqd: device data.
|
|
* @bfqq: queue to update.
|
|
* @reason: reason for expiration.
|
|
*
|
|
* Handle the feedback on @bfqq budget at queue expiration.
|
|
* See the body for detailed comments.
|
|
*/
|
|
static void __bfq_bfqq_recalc_budget(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
enum bfqq_expiration reason)
|
|
{
|
|
struct request *next_rq;
|
|
int budget, min_budget;
|
|
|
|
min_budget = bfq_min_budget(bfqd);
|
|
|
|
if (bfqq->wr_coeff == 1)
|
|
budget = bfqq->max_budget;
|
|
else /*
|
|
* Use a constant, low budget for weight-raised queues,
|
|
* to help achieve a low latency. Keep it slightly higher
|
|
* than the minimum possible budget, to cause a little
|
|
* bit fewer expirations.
|
|
*/
|
|
budget = 2 * min_budget;
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last budg %d, budg left %d",
|
|
bfqq->entity.budget, bfq_bfqq_budget_left(bfqq));
|
|
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: last max_budg %d, min budg %d",
|
|
budget, bfq_min_budget(bfqd));
|
|
bfq_log_bfqq(bfqd, bfqq, "recalc_budg: sync %d, seeky %d",
|
|
bfq_bfqq_sync(bfqq), BFQQ_SEEKY(bfqd->in_service_queue));
|
|
|
|
if (bfq_bfqq_sync(bfqq) && bfqq->wr_coeff == 1) {
|
|
switch (reason) {
|
|
/*
|
|
* Caveat: in all the following cases we trade latency
|
|
* for throughput.
|
|
*/
|
|
case BFQQE_TOO_IDLE:
|
|
/*
|
|
* This is the only case where we may reduce
|
|
* the budget: if there is no request of the
|
|
* process still waiting for completion, then
|
|
* we assume (tentatively) that the timer has
|
|
* expired because the batch of requests of
|
|
* the process could have been served with a
|
|
* smaller budget. Hence, betting that
|
|
* process will behave in the same way when it
|
|
* becomes backlogged again, we reduce its
|
|
* next budget. As long as we guess right,
|
|
* this budget cut reduces the latency
|
|
* experienced by the process.
|
|
*
|
|
* However, if there are still outstanding
|
|
* requests, then the process may have not yet
|
|
* issued its next request just because it is
|
|
* still waiting for the completion of some of
|
|
* the still outstanding ones. So in this
|
|
* subcase we do not reduce its budget, on the
|
|
* contrary we increase it to possibly boost
|
|
* the throughput, as discussed in the
|
|
* comments to the BUDGET_TIMEOUT case.
|
|
*/
|
|
if (bfqq->dispatched > 0) /* still outstanding reqs */
|
|
budget = min(budget * 2, bfqd->bfq_max_budget);
|
|
else {
|
|
if (budget > 5 * min_budget)
|
|
budget -= 4 * min_budget;
|
|
else
|
|
budget = min_budget;
|
|
}
|
|
break;
|
|
case BFQQE_BUDGET_TIMEOUT:
|
|
/*
|
|
* We double the budget here because it gives
|
|
* the chance to boost the throughput if this
|
|
* is not a seeky process (and has bumped into
|
|
* this timeout because of, e.g., ZBR).
|
|
*/
|
|
budget = min(budget * 2, bfqd->bfq_max_budget);
|
|
break;
|
|
case BFQQE_BUDGET_EXHAUSTED:
|
|
/*
|
|
* The process still has backlog, and did not
|
|
* let either the budget timeout or the disk
|
|
* idling timeout expire. Hence it is not
|
|
* seeky, has a short thinktime and may be
|
|
* happy with a higher budget too. So
|
|
* definitely increase the budget of this good
|
|
* candidate to boost the disk throughput.
|
|
*/
|
|
budget = min(budget * 4, bfqd->bfq_max_budget);
|
|
break;
|
|
case BFQQE_NO_MORE_REQUESTS:
|
|
/*
|
|
* For queues that expire for this reason, it
|
|
* is particularly important to keep the
|
|
* budget close to the actual service they
|
|
* need. Doing so reduces the timestamp
|
|
* misalignment problem described in the
|
|
* comments in the body of
|
|
* __bfq_activate_entity. In fact, suppose
|
|
* that a queue systematically expires for
|
|
* BFQQE_NO_MORE_REQUESTS and presents a
|
|
* new request in time to enjoy timestamp
|
|
* back-shifting. The larger the budget of the
|
|
* queue is with respect to the service the
|
|
* queue actually requests in each service
|
|
* slot, the more times the queue can be
|
|
* reactivated with the same virtual finish
|
|
* time. It follows that, even if this finish
|
|
* time is pushed to the system virtual time
|
|
* to reduce the consequent timestamp
|
|
* misalignment, the queue unjustly enjoys for
|
|
* many re-activations a lower finish time
|
|
* than all newly activated queues.
|
|
*
|
|
* The service needed by bfqq is measured
|
|
* quite precisely by bfqq->entity.service.
|
|
* Since bfqq does not enjoy device idling,
|
|
* bfqq->entity.service is equal to the number
|
|
* of sectors that the process associated with
|
|
* bfqq requested to read/write before waiting
|
|
* for request completions, or blocking for
|
|
* other reasons.
|
|
*/
|
|
budget = max_t(int, bfqq->entity.service, min_budget);
|
|
break;
|
|
default:
|
|
return;
|
|
}
|
|
} else if (!bfq_bfqq_sync(bfqq)) {
|
|
/*
|
|
* Async queues get always the maximum possible
|
|
* budget, as for them we do not care about latency
|
|
* (in addition, their ability to dispatch is limited
|
|
* by the charging factor).
|
|
*/
|
|
budget = bfqd->bfq_max_budget;
|
|
}
|
|
|
|
bfqq->max_budget = budget;
|
|
|
|
if (bfqd->budgets_assigned >= bfq_stats_min_budgets &&
|
|
!bfqd->bfq_user_max_budget)
|
|
bfqq->max_budget = min(bfqq->max_budget, bfqd->bfq_max_budget);
|
|
|
|
/*
|
|
* If there is still backlog, then assign a new budget, making
|
|
* sure that it is large enough for the next request. Since
|
|
* the finish time of bfqq must be kept in sync with the
|
|
* budget, be sure to call __bfq_bfqq_expire() *after* this
|
|
* update.
|
|
*
|
|
* If there is no backlog, then no need to update the budget;
|
|
* it will be updated on the arrival of a new request.
|
|
*/
|
|
next_rq = bfqq->next_rq;
|
|
if (next_rq)
|
|
bfqq->entity.budget = max_t(unsigned long, bfqq->max_budget,
|
|
bfq_serv_to_charge(next_rq, bfqq));
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "head sect: %u, new budget %d",
|
|
next_rq ? blk_rq_sectors(next_rq) : 0,
|
|
bfqq->entity.budget);
|
|
}
|
|
|
|
/*
|
|
* Return true if the process associated with bfqq is "slow". The slow
|
|
* flag is used, in addition to the budget timeout, to reduce the
|
|
* amount of service provided to seeky processes, and thus reduce
|
|
* their chances to lower the throughput. More details in the comments
|
|
* on the function bfq_bfqq_expire().
|
|
*
|
|
* An important observation is in order: as discussed in the comments
|
|
* on the function bfq_update_peak_rate(), with devices with internal
|
|
* queues, it is hard if ever possible to know when and for how long
|
|
* an I/O request is processed by the device (apart from the trivial
|
|
* I/O pattern where a new request is dispatched only after the
|
|
* previous one has been completed). This makes it hard to evaluate
|
|
* the real rate at which the I/O requests of each bfq_queue are
|
|
* served. In fact, for an I/O scheduler like BFQ, serving a
|
|
* bfq_queue means just dispatching its requests during its service
|
|
* slot (i.e., until the budget of the queue is exhausted, or the
|
|
* queue remains idle, or, finally, a timeout fires). But, during the
|
|
* service slot of a bfq_queue, around 100 ms at most, the device may
|
|
* be even still processing requests of bfq_queues served in previous
|
|
* service slots. On the opposite end, the requests of the in-service
|
|
* bfq_queue may be completed after the service slot of the queue
|
|
* finishes.
|
|
*
|
|
* Anyway, unless more sophisticated solutions are used
|
|
* (where possible), the sum of the sizes of the requests dispatched
|
|
* during the service slot of a bfq_queue is probably the only
|
|
* approximation available for the service received by the bfq_queue
|
|
* during its service slot. And this sum is the quantity used in this
|
|
* function to evaluate the I/O speed of a process.
|
|
*/
|
|
static bool bfq_bfqq_is_slow(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
bool compensate, enum bfqq_expiration reason,
|
|
unsigned long *delta_ms)
|
|
{
|
|
ktime_t delta_ktime;
|
|
u32 delta_usecs;
|
|
bool slow = BFQQ_SEEKY(bfqq); /* if delta too short, use seekyness */
|
|
|
|
if (!bfq_bfqq_sync(bfqq))
|
|
return false;
|
|
|
|
if (compensate)
|
|
delta_ktime = bfqd->last_idling_start;
|
|
else
|
|
delta_ktime = ktime_get();
|
|
delta_ktime = ktime_sub(delta_ktime, bfqd->last_budget_start);
|
|
delta_usecs = ktime_to_us(delta_ktime);
|
|
|
|
/* don't use too short time intervals */
|
|
if (delta_usecs < 1000) {
|
|
if (blk_queue_nonrot(bfqd->queue))
|
|
/*
|
|
* give same worst-case guarantees as idling
|
|
* for seeky
|
|
*/
|
|
*delta_ms = BFQ_MIN_TT / NSEC_PER_MSEC;
|
|
else /* charge at least one seek */
|
|
*delta_ms = bfq_slice_idle / NSEC_PER_MSEC;
|
|
|
|
return slow;
|
|
}
|
|
|
|
*delta_ms = delta_usecs / USEC_PER_MSEC;
|
|
|
|
/*
|
|
* Use only long (> 20ms) intervals to filter out excessive
|
|
* spikes in service rate estimation.
|
|
*/
|
|
if (delta_usecs > 20000) {
|
|
/*
|
|
* Caveat for rotational devices: processes doing I/O
|
|
* in the slower disk zones tend to be slow(er) even
|
|
* if not seeky. In this respect, the estimated peak
|
|
* rate is likely to be an average over the disk
|
|
* surface. Accordingly, to not be too harsh with
|
|
* unlucky processes, a process is deemed slow only if
|
|
* its rate has been lower than half of the estimated
|
|
* peak rate.
|
|
*/
|
|
slow = bfqq->entity.service < bfqd->bfq_max_budget / 2;
|
|
}
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "bfq_bfqq_is_slow: slow %d", slow);
|
|
|
|
return slow;
|
|
}
|
|
|
|
/*
|
|
* To be deemed as soft real-time, an application must meet two
|
|
* requirements. First, the application must not require an average
|
|
* bandwidth higher than the approximate bandwidth required to playback or
|
|
* record a compressed high-definition video.
|
|
* The next function is invoked on the completion of the last request of a
|
|
* batch, to compute the next-start time instant, soft_rt_next_start, such
|
|
* that, if the next request of the application does not arrive before
|
|
* soft_rt_next_start, then the above requirement on the bandwidth is met.
|
|
*
|
|
* The second requirement is that the request pattern of the application is
|
|
* isochronous, i.e., that, after issuing a request or a batch of requests,
|
|
* the application stops issuing new requests until all its pending requests
|
|
* have been completed. After that, the application may issue a new batch,
|
|
* and so on.
|
|
* For this reason the next function is invoked to compute
|
|
* soft_rt_next_start only for applications that meet this requirement,
|
|
* whereas soft_rt_next_start is set to infinity for applications that do
|
|
* not.
|
|
*
|
|
* Unfortunately, even a greedy application may happen to behave in an
|
|
* isochronous way if the CPU load is high. In fact, the application may
|
|
* stop issuing requests while the CPUs are busy serving other processes,
|
|
* then restart, then stop again for a while, and so on. In addition, if
|
|
* the disk achieves a low enough throughput with the request pattern
|
|
* issued by the application (e.g., because the request pattern is random
|
|
* and/or the device is slow), then the application may meet the above
|
|
* bandwidth requirement too. To prevent such a greedy application to be
|
|
* deemed as soft real-time, a further rule is used in the computation of
|
|
* soft_rt_next_start: soft_rt_next_start must be higher than the current
|
|
* time plus the maximum time for which the arrival of a request is waited
|
|
* for when a sync queue becomes idle, namely bfqd->bfq_slice_idle.
|
|
* This filters out greedy applications, as the latter issue instead their
|
|
* next request as soon as possible after the last one has been completed
|
|
* (in contrast, when a batch of requests is completed, a soft real-time
|
|
* application spends some time processing data).
|
|
*
|
|
* Unfortunately, the last filter may easily generate false positives if
|
|
* only bfqd->bfq_slice_idle is used as a reference time interval and one
|
|
* or both the following cases occur:
|
|
* 1) HZ is so low that the duration of a jiffy is comparable to or higher
|
|
* than bfqd->bfq_slice_idle. This happens, e.g., on slow devices with
|
|
* HZ=100.
|
|
* 2) jiffies, instead of increasing at a constant rate, may stop increasing
|
|
* for a while, then suddenly 'jump' by several units to recover the lost
|
|
* increments. This seems to happen, e.g., inside virtual machines.
|
|
* To address this issue, we do not use as a reference time interval just
|
|
* bfqd->bfq_slice_idle, but bfqd->bfq_slice_idle plus a few jiffies. In
|
|
* particular we add the minimum number of jiffies for which the filter
|
|
* seems to be quite precise also in embedded systems and KVM/QEMU virtual
|
|
* machines.
|
|
*/
|
|
static unsigned long bfq_bfqq_softrt_next_start(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
return max(bfqq->last_idle_bklogged +
|
|
HZ * bfqq->service_from_backlogged /
|
|
bfqd->bfq_wr_max_softrt_rate,
|
|
jiffies + nsecs_to_jiffies(bfqq->bfqd->bfq_slice_idle) + 4);
|
|
}
|
|
|
|
/*
|
|
* Return the farthest future time instant according to jiffies
|
|
* macros.
|
|
*/
|
|
static unsigned long bfq_greatest_from_now(void)
|
|
{
|
|
return jiffies + MAX_JIFFY_OFFSET;
|
|
}
|
|
|
|
/*
|
|
* Return the farthest past time instant according to jiffies
|
|
* macros.
|
|
*/
|
|
static unsigned long bfq_smallest_from_now(void)
|
|
{
|
|
return jiffies - MAX_JIFFY_OFFSET;
|
|
}
|
|
|
|
/**
|
|
* bfq_bfqq_expire - expire a queue.
|
|
* @bfqd: device owning the queue.
|
|
* @bfqq: the queue to expire.
|
|
* @compensate: if true, compensate for the time spent idling.
|
|
* @reason: the reason causing the expiration.
|
|
*
|
|
* If the process associated with bfqq does slow I/O (e.g., because it
|
|
* issues random requests), we charge bfqq with the time it has been
|
|
* in service instead of the service it has received (see
|
|
* bfq_bfqq_charge_time for details on how this goal is achieved). As
|
|
* a consequence, bfqq will typically get higher timestamps upon
|
|
* reactivation, and hence it will be rescheduled as if it had
|
|
* received more service than what it has actually received. In the
|
|
* end, bfqq receives less service in proportion to how slowly its
|
|
* associated process consumes its budgets (and hence how seriously it
|
|
* tends to lower the throughput). In addition, this time-charging
|
|
* strategy guarantees time fairness among slow processes. In
|
|
* contrast, if the process associated with bfqq is not slow, we
|
|
* charge bfqq exactly with the service it has received.
|
|
*
|
|
* Charging time to the first type of queues and the exact service to
|
|
* the other has the effect of using the WF2Q+ policy to schedule the
|
|
* former on a timeslice basis, without violating service domain
|
|
* guarantees among the latter.
|
|
*/
|
|
static void bfq_bfqq_expire(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
bool compensate,
|
|
enum bfqq_expiration reason)
|
|
{
|
|
bool slow;
|
|
unsigned long delta = 0;
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
int ref;
|
|
|
|
/*
|
|
* Check whether the process is slow (see bfq_bfqq_is_slow).
|
|
*/
|
|
slow = bfq_bfqq_is_slow(bfqd, bfqq, compensate, reason, &delta);
|
|
|
|
/*
|
|
* Increase service_from_backlogged before next statement,
|
|
* because the possible next invocation of
|
|
* bfq_bfqq_charge_time would likely inflate
|
|
* entity->service. In contrast, service_from_backlogged must
|
|
* contain real service, to enable the soft real-time
|
|
* heuristic to correctly compute the bandwidth consumed by
|
|
* bfqq.
|
|
*/
|
|
bfqq->service_from_backlogged += entity->service;
|
|
|
|
/*
|
|
* As above explained, charge slow (typically seeky) and
|
|
* timed-out queues with the time and not the service
|
|
* received, to favor sequential workloads.
|
|
*
|
|
* Processes doing I/O in the slower disk zones will tend to
|
|
* be slow(er) even if not seeky. Therefore, since the
|
|
* estimated peak rate is actually an average over the disk
|
|
* surface, these processes may timeout just for bad luck. To
|
|
* avoid punishing them, do not charge time to processes that
|
|
* succeeded in consuming at least 2/3 of their budget. This
|
|
* allows BFQ to preserve enough elasticity to still perform
|
|
* bandwidth, and not time, distribution with little unlucky
|
|
* or quasi-sequential processes.
|
|
*/
|
|
if (bfqq->wr_coeff == 1 &&
|
|
(slow ||
|
|
(reason == BFQQE_BUDGET_TIMEOUT &&
|
|
bfq_bfqq_budget_left(bfqq) >= entity->budget / 3)))
|
|
bfq_bfqq_charge_time(bfqd, bfqq, delta);
|
|
|
|
if (reason == BFQQE_TOO_IDLE &&
|
|
entity->service <= 2 * entity->budget / 10)
|
|
bfq_clear_bfqq_IO_bound(bfqq);
|
|
|
|
if (bfqd->low_latency && bfqq->wr_coeff == 1)
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
|
|
if (bfqd->low_latency && bfqd->bfq_wr_max_softrt_rate > 0 &&
|
|
RB_EMPTY_ROOT(&bfqq->sort_list)) {
|
|
/*
|
|
* If we get here, and there are no outstanding
|
|
* requests, then the request pattern is isochronous
|
|
* (see the comments on the function
|
|
* bfq_bfqq_softrt_next_start()). Thus we can compute
|
|
* soft_rt_next_start. If, instead, the queue still
|
|
* has outstanding requests, then we have to wait for
|
|
* the completion of all the outstanding requests to
|
|
* discover whether the request pattern is actually
|
|
* isochronous.
|
|
*/
|
|
if (bfqq->dispatched == 0)
|
|
bfqq->soft_rt_next_start =
|
|
bfq_bfqq_softrt_next_start(bfqd, bfqq);
|
|
else {
|
|
/*
|
|
* The application is still waiting for the
|
|
* completion of one or more requests:
|
|
* prevent it from possibly being incorrectly
|
|
* deemed as soft real-time by setting its
|
|
* soft_rt_next_start to infinity. In fact,
|
|
* without this assignment, the application
|
|
* would be incorrectly deemed as soft
|
|
* real-time if:
|
|
* 1) it issued a new request before the
|
|
* completion of all its in-flight
|
|
* requests, and
|
|
* 2) at that time, its soft_rt_next_start
|
|
* happened to be in the past.
|
|
*/
|
|
bfqq->soft_rt_next_start =
|
|
bfq_greatest_from_now();
|
|
/*
|
|
* Schedule an update of soft_rt_next_start to when
|
|
* the task may be discovered to be isochronous.
|
|
*/
|
|
bfq_mark_bfqq_softrt_update(bfqq);
|
|
}
|
|
}
|
|
|
|
bfq_log_bfqq(bfqd, bfqq,
|
|
"expire (%d, slow %d, num_disp %d, idle_win %d)", reason,
|
|
slow, bfqq->dispatched, bfq_bfqq_idle_window(bfqq));
|
|
|
|
/*
|
|
* Increase, decrease or leave budget unchanged according to
|
|
* reason.
|
|
*/
|
|
__bfq_bfqq_recalc_budget(bfqd, bfqq, reason);
|
|
ref = bfqq->ref;
|
|
__bfq_bfqq_expire(bfqd, bfqq);
|
|
|
|
/* mark bfqq as waiting a request only if a bic still points to it */
|
|
if (ref > 1 && !bfq_bfqq_busy(bfqq) &&
|
|
reason != BFQQE_BUDGET_TIMEOUT &&
|
|
reason != BFQQE_BUDGET_EXHAUSTED)
|
|
bfq_mark_bfqq_non_blocking_wait_rq(bfqq);
|
|
}
|
|
|
|
/*
|
|
* Budget timeout is not implemented through a dedicated timer, but
|
|
* just checked on request arrivals and completions, as well as on
|
|
* idle timer expirations.
|
|
*/
|
|
static bool bfq_bfqq_budget_timeout(struct bfq_queue *bfqq)
|
|
{
|
|
return time_is_before_eq_jiffies(bfqq->budget_timeout);
|
|
}
|
|
|
|
/*
|
|
* If we expire a queue that is actively waiting (i.e., with the
|
|
* device idled) for the arrival of a new request, then we may incur
|
|
* the timestamp misalignment problem described in the body of the
|
|
* function __bfq_activate_entity. Hence we return true only if this
|
|
* condition does not hold, or if the queue is slow enough to deserve
|
|
* only to be kicked off for preserving a high throughput.
|
|
*/
|
|
static bool bfq_may_expire_for_budg_timeout(struct bfq_queue *bfqq)
|
|
{
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq,
|
|
"may_budget_timeout: wait_request %d left %d timeout %d",
|
|
bfq_bfqq_wait_request(bfqq),
|
|
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3,
|
|
bfq_bfqq_budget_timeout(bfqq));
|
|
|
|
return (!bfq_bfqq_wait_request(bfqq) ||
|
|
bfq_bfqq_budget_left(bfqq) >= bfqq->entity.budget / 3)
|
|
&&
|
|
bfq_bfqq_budget_timeout(bfqq);
|
|
}
|
|
|
|
/*
|
|
* For a queue that becomes empty, device idling is allowed only if
|
|
* this function returns true for the queue. As a consequence, since
|
|
* device idling plays a critical role in both throughput boosting and
|
|
* service guarantees, the return value of this function plays a
|
|
* critical role in both these aspects as well.
|
|
*
|
|
* In a nutshell, this function returns true only if idling is
|
|
* beneficial for throughput or, even if detrimental for throughput,
|
|
* idling is however necessary to preserve service guarantees (low
|
|
* latency, desired throughput distribution, ...). In particular, on
|
|
* NCQ-capable devices, this function tries to return false, so as to
|
|
* help keep the drives' internal queues full, whenever this helps the
|
|
* device boost the throughput without causing any service-guarantee
|
|
* issue.
|
|
*
|
|
* In more detail, the return value of this function is obtained by,
|
|
* first, computing a number of boolean variables that take into
|
|
* account throughput and service-guarantee issues, and, then,
|
|
* combining these variables in a logical expression. Most of the
|
|
* issues taken into account are not trivial. We discuss these issues
|
|
* individually while introducing the variables.
|
|
*/
|
|
static bool bfq_bfqq_may_idle(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
bool idling_boosts_thr, idling_boosts_thr_without_issues,
|
|
asymmetric_scenario;
|
|
|
|
if (bfqd->strict_guarantees)
|
|
return true;
|
|
|
|
/*
|
|
* The next variable takes into account the cases where idling
|
|
* boosts the throughput.
|
|
*
|
|
* The value of the variable is computed considering that
|
|
* idling is usually beneficial for the throughput if:
|
|
* (a) the device is not NCQ-capable, or
|
|
* (b) regardless of the presence of NCQ, the request pattern
|
|
* for bfqq is I/O-bound (possible throughput losses
|
|
* caused by granting idling to seeky queues are mitigated
|
|
* by the fact that, in all scenarios where boosting
|
|
* throughput is the best thing to do, i.e., in all
|
|
* symmetric scenarios, only a minimal idle time is
|
|
* allowed to seeky queues).
|
|
*/
|
|
idling_boosts_thr = !bfqd->hw_tag || bfq_bfqq_IO_bound(bfqq);
|
|
|
|
/*
|
|
* The value of the next variable,
|
|
* idling_boosts_thr_without_issues, is equal to that of
|
|
* idling_boosts_thr, unless a special case holds. In this
|
|
* special case, described below, idling may cause problems to
|
|
* weight-raised queues.
|
|
*
|
|
* When the request pool is saturated (e.g., in the presence
|
|
* of write hogs), if the processes associated with
|
|
* non-weight-raised queues ask for requests at a lower rate,
|
|
* then processes associated with weight-raised queues have a
|
|
* higher probability to get a request from the pool
|
|
* immediately (or at least soon) when they need one. Thus
|
|
* they have a higher probability to actually get a fraction
|
|
* of the device throughput proportional to their high
|
|
* weight. This is especially true with NCQ-capable drives,
|
|
* which enqueue several requests in advance, and further
|
|
* reorder internally-queued requests.
|
|
*
|
|
* For this reason, we force to false the value of
|
|
* idling_boosts_thr_without_issues if there are weight-raised
|
|
* busy queues. In this case, and if bfqq is not weight-raised,
|
|
* this guarantees that the device is not idled for bfqq (if,
|
|
* instead, bfqq is weight-raised, then idling will be
|
|
* guaranteed by another variable, see below). Combined with
|
|
* the timestamping rules of BFQ (see [1] for details), this
|
|
* behavior causes bfqq, and hence any sync non-weight-raised
|
|
* queue, to get a lower number of requests served, and thus
|
|
* to ask for a lower number of requests from the request
|
|
* pool, before the busy weight-raised queues get served
|
|
* again. This often mitigates starvation problems in the
|
|
* presence of heavy write workloads and NCQ, thereby
|
|
* guaranteeing a higher application and system responsiveness
|
|
* in these hostile scenarios.
|
|
*/
|
|
idling_boosts_thr_without_issues = idling_boosts_thr &&
|
|
bfqd->wr_busy_queues == 0;
|
|
|
|
/*
|
|
* There is then a case where idling must be performed not for
|
|
* throughput concerns, but to preserve service guarantees. To
|
|
* introduce it, we can note that allowing the drive to
|
|
* enqueue more than one request at a time, and hence
|
|
* delegating de facto final scheduling decisions to the
|
|
* drive's internal scheduler, causes loss of control on the
|
|
* actual request service order. In particular, the critical
|
|
* situation is when requests from different processes happens
|
|
* to be present, at the same time, in the internal queue(s)
|
|
* of the drive. In such a situation, the drive, by deciding
|
|
* the service order of the internally-queued requests, does
|
|
* determine also the actual throughput distribution among
|
|
* these processes. But the drive typically has no notion or
|
|
* concern about per-process throughput distribution, and
|
|
* makes its decisions only on a per-request basis. Therefore,
|
|
* the service distribution enforced by the drive's internal
|
|
* scheduler is likely to coincide with the desired
|
|
* device-throughput distribution only in a completely
|
|
* symmetric scenario where: (i) each of these processes must
|
|
* get the same throughput as the others; (ii) all these
|
|
* processes have the same I/O pattern (either sequential or
|
|
* random). In fact, in such a scenario, the drive will tend
|
|
* to treat the requests of each of these processes in about
|
|
* the same way as the requests of the others, and thus to
|
|
* provide each of these processes with about the same
|
|
* throughput (which is exactly the desired throughput
|
|
* distribution). In contrast, in any asymmetric scenario,
|
|
* device idling is certainly needed to guarantee that bfqq
|
|
* receives its assigned fraction of the device throughput
|
|
* (see [1] for details).
|
|
*
|
|
* As for sub-condition (i), actually we check only whether
|
|
* bfqq is being weight-raised. In fact, if bfqq is not being
|
|
* weight-raised, we have that:
|
|
* - if the process associated with bfqq is not I/O-bound, then
|
|
* it is not either latency- or throughput-critical; therefore
|
|
* idling is not needed for bfqq;
|
|
* - if the process asociated with bfqq is I/O-bound, then
|
|
* idling is already granted with bfqq (see the comments on
|
|
* idling_boosts_thr).
|
|
*
|
|
* We do not check sub-condition (ii) at all, i.e., the next
|
|
* variable is true if and only if bfqq is being
|
|
* weight-raised. We do not need to control sub-condition (ii)
|
|
* for the following reason:
|
|
* - if bfqq is being weight-raised, then idling is already
|
|
* guaranteed to bfqq by sub-condition (i);
|
|
* - if bfqq is not being weight-raised, then idling is
|
|
* already guaranteed to bfqq (only) if it matters, i.e., if
|
|
* bfqq is associated to a currently I/O-bound process (see
|
|
* the above comment on sub-condition (i)).
|
|
*
|
|
* As a side note, it is worth considering that the above
|
|
* device-idling countermeasures may however fail in the
|
|
* following unlucky scenario: if idling is (correctly)
|
|
* disabled in a time period during which the symmetry
|
|
* sub-condition holds, and hence the device is allowed to
|
|
* enqueue many requests, but at some later point in time some
|
|
* sub-condition stops to hold, then it may become impossible
|
|
* to let requests be served in the desired order until all
|
|
* the requests already queued in the device have been served.
|
|
*/
|
|
asymmetric_scenario = bfqq->wr_coeff > 1;
|
|
|
|
/*
|
|
* We have now all the components we need to compute the return
|
|
* value of the function, which is true only if both the following
|
|
* conditions hold:
|
|
* 1) bfqq is sync, because idling make sense only for sync queues;
|
|
* 2) idling either boosts the throughput (without issues), or
|
|
* is necessary to preserve service guarantees.
|
|
*/
|
|
return bfq_bfqq_sync(bfqq) &&
|
|
(idling_boosts_thr_without_issues || asymmetric_scenario);
|
|
}
|
|
|
|
/*
|
|
* If the in-service queue is empty but the function bfq_bfqq_may_idle
|
|
* returns true, then:
|
|
* 1) the queue must remain in service and cannot be expired, and
|
|
* 2) the device must be idled to wait for the possible arrival of a new
|
|
* request for the queue.
|
|
* See the comments on the function bfq_bfqq_may_idle for the reasons
|
|
* why performing device idling is the best choice to boost the throughput
|
|
* and preserve service guarantees when bfq_bfqq_may_idle itself
|
|
* returns true.
|
|
*/
|
|
static bool bfq_bfqq_must_idle(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
|
|
return RB_EMPTY_ROOT(&bfqq->sort_list) && bfqd->bfq_slice_idle != 0 &&
|
|
bfq_bfqq_may_idle(bfqq);
|
|
}
|
|
|
|
/*
|
|
* Select a queue for service. If we have a current queue in service,
|
|
* check whether to continue servicing it, or retrieve and set a new one.
|
|
*/
|
|
static struct bfq_queue *bfq_select_queue(struct bfq_data *bfqd)
|
|
{
|
|
struct bfq_queue *bfqq;
|
|
struct request *next_rq;
|
|
enum bfqq_expiration reason = BFQQE_BUDGET_TIMEOUT;
|
|
|
|
bfqq = bfqd->in_service_queue;
|
|
if (!bfqq)
|
|
goto new_queue;
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "select_queue: already in-service queue");
|
|
|
|
if (bfq_may_expire_for_budg_timeout(bfqq) &&
|
|
!bfq_bfqq_wait_request(bfqq) &&
|
|
!bfq_bfqq_must_idle(bfqq))
|
|
goto expire;
|
|
|
|
check_queue:
|
|
/*
|
|
* This loop is rarely executed more than once. Even when it
|
|
* happens, it is much more convenient to re-execute this loop
|
|
* than to return NULL and trigger a new dispatch to get a
|
|
* request served.
|
|
*/
|
|
next_rq = bfqq->next_rq;
|
|
/*
|
|
* If bfqq has requests queued and it has enough budget left to
|
|
* serve them, keep the queue, otherwise expire it.
|
|
*/
|
|
if (next_rq) {
|
|
if (bfq_serv_to_charge(next_rq, bfqq) >
|
|
bfq_bfqq_budget_left(bfqq)) {
|
|
/*
|
|
* Expire the queue for budget exhaustion,
|
|
* which makes sure that the next budget is
|
|
* enough to serve the next request, even if
|
|
* it comes from the fifo expired path.
|
|
*/
|
|
reason = BFQQE_BUDGET_EXHAUSTED;
|
|
goto expire;
|
|
} else {
|
|
/*
|
|
* The idle timer may be pending because we may
|
|
* not disable disk idling even when a new request
|
|
* arrives.
|
|
*/
|
|
if (bfq_bfqq_wait_request(bfqq)) {
|
|
/*
|
|
* If we get here: 1) at least a new request
|
|
* has arrived but we have not disabled the
|
|
* timer because the request was too small,
|
|
* 2) then the block layer has unplugged
|
|
* the device, causing the dispatch to be
|
|
* invoked.
|
|
*
|
|
* Since the device is unplugged, now the
|
|
* requests are probably large enough to
|
|
* provide a reasonable throughput.
|
|
* So we disable idling.
|
|
*/
|
|
bfq_clear_bfqq_wait_request(bfqq);
|
|
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
|
|
bfqg_stats_update_idle_time(bfqq_group(bfqq));
|
|
}
|
|
goto keep_queue;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* No requests pending. However, if the in-service queue is idling
|
|
* for a new request, or has requests waiting for a completion and
|
|
* may idle after their completion, then keep it anyway.
|
|
*/
|
|
if (bfq_bfqq_wait_request(bfqq) ||
|
|
(bfqq->dispatched != 0 && bfq_bfqq_may_idle(bfqq))) {
|
|
bfqq = NULL;
|
|
goto keep_queue;
|
|
}
|
|
|
|
reason = BFQQE_NO_MORE_REQUESTS;
|
|
expire:
|
|
bfq_bfqq_expire(bfqd, bfqq, false, reason);
|
|
new_queue:
|
|
bfqq = bfq_set_in_service_queue(bfqd);
|
|
if (bfqq) {
|
|
bfq_log_bfqq(bfqd, bfqq, "select_queue: checking new queue");
|
|
goto check_queue;
|
|
}
|
|
keep_queue:
|
|
if (bfqq)
|
|
bfq_log_bfqq(bfqd, bfqq, "select_queue: returned this queue");
|
|
else
|
|
bfq_log(bfqd, "select_queue: no queue returned");
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
static void bfq_update_wr_data(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_entity *entity = &bfqq->entity;
|
|
|
|
if (bfqq->wr_coeff > 1) { /* queue is being weight-raised */
|
|
bfq_log_bfqq(bfqd, bfqq,
|
|
"raising period dur %u/%u msec, old coeff %u, w %d(%d)",
|
|
jiffies_to_msecs(jiffies - bfqq->last_wr_start_finish),
|
|
jiffies_to_msecs(bfqq->wr_cur_max_time),
|
|
bfqq->wr_coeff,
|
|
bfqq->entity.weight, bfqq->entity.orig_weight);
|
|
|
|
if (entity->prio_changed)
|
|
bfq_log_bfqq(bfqd, bfqq, "WARN: pending prio change");
|
|
|
|
/*
|
|
* If too much time has elapsed from the beginning of
|
|
* this weight-raising period, then end weight raising.
|
|
*/
|
|
if (time_is_before_jiffies(bfqq->last_wr_start_finish +
|
|
bfqq->wr_cur_max_time)) {
|
|
if (bfqq->wr_cur_max_time != bfqd->bfq_wr_rt_max_time ||
|
|
time_is_before_jiffies(bfqq->wr_start_at_switch_to_srt +
|
|
bfq_wr_duration(bfqd)))
|
|
bfq_bfqq_end_wr(bfqq);
|
|
else {
|
|
/* switch back to interactive wr */
|
|
bfqq->wr_coeff = bfqd->bfq_wr_coeff;
|
|
bfqq->wr_cur_max_time = bfq_wr_duration(bfqd);
|
|
bfqq->last_wr_start_finish =
|
|
bfqq->wr_start_at_switch_to_srt;
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
}
|
|
}
|
|
/* Update weight both if it must be raised and if it must be lowered */
|
|
if ((entity->weight > entity->orig_weight) != (bfqq->wr_coeff > 1))
|
|
__bfq_entity_update_weight_prio(
|
|
bfq_entity_service_tree(entity),
|
|
entity);
|
|
}
|
|
|
|
/*
|
|
* Dispatch next request from bfqq.
|
|
*/
|
|
static struct request *bfq_dispatch_rq_from_bfqq(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
struct request *rq = bfqq->next_rq;
|
|
unsigned long service_to_charge;
|
|
|
|
service_to_charge = bfq_serv_to_charge(rq, bfqq);
|
|
|
|
bfq_bfqq_served(bfqq, service_to_charge);
|
|
|
|
bfq_dispatch_remove(bfqd->queue, rq);
|
|
|
|
/*
|
|
* If weight raising has to terminate for bfqq, then next
|
|
* function causes an immediate update of bfqq's weight,
|
|
* without waiting for next activation. As a consequence, on
|
|
* expiration, bfqq will be timestamped as if has never been
|
|
* weight-raised during this service slot, even if it has
|
|
* received part or even most of the service as a
|
|
* weight-raised queue. This inflates bfqq's timestamps, which
|
|
* is beneficial, as bfqq is then more willing to leave the
|
|
* device immediately to possible other weight-raised queues.
|
|
*/
|
|
bfq_update_wr_data(bfqd, bfqq);
|
|
|
|
if (!bfqd->in_service_bic) {
|
|
atomic_long_inc(&RQ_BIC(rq)->icq.ioc->refcount);
|
|
bfqd->in_service_bic = RQ_BIC(rq);
|
|
}
|
|
|
|
/*
|
|
* Expire bfqq, pretending that its budget expired, if bfqq
|
|
* belongs to CLASS_IDLE and other queues are waiting for
|
|
* service.
|
|
*/
|
|
if (bfqd->busy_queues > 1 && bfq_class_idle(bfqq))
|
|
goto expire;
|
|
|
|
return rq;
|
|
|
|
expire:
|
|
bfq_bfqq_expire(bfqd, bfqq, false, BFQQE_BUDGET_EXHAUSTED);
|
|
return rq;
|
|
}
|
|
|
|
static bool bfq_has_work(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
|
|
|
|
/*
|
|
* Avoiding lock: a race on bfqd->busy_queues should cause at
|
|
* most a call to dispatch for nothing
|
|
*/
|
|
return !list_empty_careful(&bfqd->dispatch) ||
|
|
bfqd->busy_queues > 0;
|
|
}
|
|
|
|
static struct request *__bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
|
|
struct request *rq = NULL;
|
|
struct bfq_queue *bfqq = NULL;
|
|
|
|
if (!list_empty(&bfqd->dispatch)) {
|
|
rq = list_first_entry(&bfqd->dispatch, struct request,
|
|
queuelist);
|
|
list_del_init(&rq->queuelist);
|
|
|
|
bfqq = RQ_BFQQ(rq);
|
|
|
|
if (bfqq) {
|
|
/*
|
|
* Increment counters here, because this
|
|
* dispatch does not follow the standard
|
|
* dispatch flow (where counters are
|
|
* incremented)
|
|
*/
|
|
bfqq->dispatched++;
|
|
|
|
goto inc_in_driver_start_rq;
|
|
}
|
|
|
|
/*
|
|
* We exploit the put_rq_private hook to decrement
|
|
* rq_in_driver, but put_rq_private will not be
|
|
* invoked on this request. So, to avoid unbalance,
|
|
* just start this request, without incrementing
|
|
* rq_in_driver. As a negative consequence,
|
|
* rq_in_driver is deceptively lower than it should be
|
|
* while this request is in service. This may cause
|
|
* bfq_schedule_dispatch to be invoked uselessly.
|
|
*
|
|
* As for implementing an exact solution, the
|
|
* put_request hook, if defined, is probably invoked
|
|
* also on this request. So, by exploiting this hook,
|
|
* we could 1) increment rq_in_driver here, and 2)
|
|
* decrement it in put_request. Such a solution would
|
|
* let the value of the counter be always accurate,
|
|
* but it would entail using an extra interface
|
|
* function. This cost seems higher than the benefit,
|
|
* being the frequency of non-elevator-private
|
|
* requests very low.
|
|
*/
|
|
goto start_rq;
|
|
}
|
|
|
|
bfq_log(bfqd, "dispatch requests: %d busy queues", bfqd->busy_queues);
|
|
|
|
if (bfqd->busy_queues == 0)
|
|
goto exit;
|
|
|
|
/*
|
|
* Force device to serve one request at a time if
|
|
* strict_guarantees is true. Forcing this service scheme is
|
|
* currently the ONLY way to guarantee that the request
|
|
* service order enforced by the scheduler is respected by a
|
|
* queueing device. Otherwise the device is free even to make
|
|
* some unlucky request wait for as long as the device
|
|
* wishes.
|
|
*
|
|
* Of course, serving one request at at time may cause loss of
|
|
* throughput.
|
|
*/
|
|
if (bfqd->strict_guarantees && bfqd->rq_in_driver > 0)
|
|
goto exit;
|
|
|
|
bfqq = bfq_select_queue(bfqd);
|
|
if (!bfqq)
|
|
goto exit;
|
|
|
|
rq = bfq_dispatch_rq_from_bfqq(bfqd, bfqq);
|
|
|
|
if (rq) {
|
|
inc_in_driver_start_rq:
|
|
bfqd->rq_in_driver++;
|
|
start_rq:
|
|
rq->rq_flags |= RQF_STARTED;
|
|
}
|
|
exit:
|
|
return rq;
|
|
}
|
|
|
|
static struct request *bfq_dispatch_request(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct bfq_data *bfqd = hctx->queue->elevator->elevator_data;
|
|
struct request *rq;
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
|
|
rq = __bfq_dispatch_request(hctx);
|
|
bfq_unlock_put_ioc(bfqd);
|
|
|
|
return rq;
|
|
}
|
|
|
|
/*
|
|
* Task holds one reference to the queue, dropped when task exits. Each rq
|
|
* in-flight on this queue also holds a reference, dropped when rq is freed.
|
|
*
|
|
* Scheduler lock must be held here. Recall not to use bfqq after calling
|
|
* this function on it.
|
|
*/
|
|
static void bfq_put_queue(struct bfq_queue *bfqq)
|
|
{
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
struct bfq_group *bfqg = bfqq_group(bfqq);
|
|
#endif
|
|
|
|
if (bfqq->bfqd)
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p %d",
|
|
bfqq, bfqq->ref);
|
|
|
|
bfqq->ref--;
|
|
if (bfqq->ref)
|
|
return;
|
|
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "put_queue: %p freed", bfqq);
|
|
|
|
kmem_cache_free(bfq_pool, bfqq);
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
bfqg_put(bfqg);
|
|
#endif
|
|
}
|
|
|
|
static void bfq_put_cooperator(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_queue *__bfqq, *next;
|
|
|
|
/*
|
|
* If this queue was scheduled to merge with another queue, be
|
|
* sure to drop the reference taken on that queue (and others in
|
|
* the merge chain). See bfq_setup_merge and bfq_merge_bfqqs.
|
|
*/
|
|
__bfqq = bfqq->new_bfqq;
|
|
while (__bfqq) {
|
|
if (__bfqq == bfqq)
|
|
break;
|
|
next = __bfqq->new_bfqq;
|
|
bfq_put_queue(__bfqq);
|
|
__bfqq = next;
|
|
}
|
|
}
|
|
|
|
static void bfq_exit_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq)
|
|
{
|
|
if (bfqq == bfqd->in_service_queue) {
|
|
__bfq_bfqq_expire(bfqd, bfqq);
|
|
bfq_schedule_dispatch(bfqd);
|
|
}
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "exit_bfqq: %p, %d", bfqq, bfqq->ref);
|
|
|
|
bfq_put_cooperator(bfqq);
|
|
|
|
bfq_put_queue(bfqq); /* release process reference */
|
|
}
|
|
|
|
static void bfq_exit_icq_bfqq(struct bfq_io_cq *bic, bool is_sync)
|
|
{
|
|
struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync);
|
|
struct bfq_data *bfqd;
|
|
|
|
if (bfqq)
|
|
bfqd = bfqq->bfqd; /* NULL if scheduler already exited */
|
|
|
|
if (bfqq && bfqd) {
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&bfqd->lock, flags);
|
|
/*
|
|
* If the bic is using a shared queue, put the
|
|
* reference taken on the io_context when the bic
|
|
* started using a shared bfq_queue. This put cannot
|
|
* make ioc->ref_count reach 0, then no ioc->lock
|
|
* risks to be taken (leading to possible deadlock
|
|
* scenarios).
|
|
*/
|
|
if (is_sync && bfq_bfqq_coop(bfqq))
|
|
put_io_context(bic->icq.ioc);
|
|
|
|
bfq_exit_bfqq(bfqd, bfqq);
|
|
bic_set_bfqq(bic, NULL, is_sync);
|
|
bfq_unlock_put_ioc_restore(bfqd, flags);
|
|
}
|
|
}
|
|
|
|
static void bfq_exit_icq(struct io_cq *icq)
|
|
{
|
|
struct bfq_io_cq *bic = icq_to_bic(icq);
|
|
|
|
bfq_exit_icq_bfqq(bic, true);
|
|
bfq_exit_icq_bfqq(bic, false);
|
|
}
|
|
|
|
/*
|
|
* Update the entity prio values; note that the new values will not
|
|
* be used until the next (re)activation.
|
|
*/
|
|
static void
|
|
bfq_set_next_ioprio_data(struct bfq_queue *bfqq, struct bfq_io_cq *bic)
|
|
{
|
|
struct task_struct *tsk = current;
|
|
int ioprio_class;
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
|
|
if (!bfqd)
|
|
return;
|
|
|
|
ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
|
|
switch (ioprio_class) {
|
|
default:
|
|
dev_err(bfqq->bfqd->queue->backing_dev_info->dev,
|
|
"bfq: bad prio class %d\n", ioprio_class);
|
|
case IOPRIO_CLASS_NONE:
|
|
/*
|
|
* No prio set, inherit CPU scheduling settings.
|
|
*/
|
|
bfqq->new_ioprio = task_nice_ioprio(tsk);
|
|
bfqq->new_ioprio_class = task_nice_ioclass(tsk);
|
|
break;
|
|
case IOPRIO_CLASS_RT:
|
|
bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
|
|
bfqq->new_ioprio_class = IOPRIO_CLASS_RT;
|
|
break;
|
|
case IOPRIO_CLASS_BE:
|
|
bfqq->new_ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
|
|
bfqq->new_ioprio_class = IOPRIO_CLASS_BE;
|
|
break;
|
|
case IOPRIO_CLASS_IDLE:
|
|
bfqq->new_ioprio_class = IOPRIO_CLASS_IDLE;
|
|
bfqq->new_ioprio = 7;
|
|
bfq_clear_bfqq_idle_window(bfqq);
|
|
break;
|
|
}
|
|
|
|
if (bfqq->new_ioprio >= IOPRIO_BE_NR) {
|
|
pr_crit("bfq_set_next_ioprio_data: new_ioprio %d\n",
|
|
bfqq->new_ioprio);
|
|
bfqq->new_ioprio = IOPRIO_BE_NR;
|
|
}
|
|
|
|
bfqq->entity.new_weight = bfq_ioprio_to_weight(bfqq->new_ioprio);
|
|
bfqq->entity.prio_changed = 1;
|
|
}
|
|
|
|
static void bfq_check_ioprio_change(struct bfq_io_cq *bic, struct bio *bio)
|
|
{
|
|
struct bfq_data *bfqd = bic_to_bfqd(bic);
|
|
struct bfq_queue *bfqq;
|
|
int ioprio = bic->icq.ioc->ioprio;
|
|
|
|
/*
|
|
* This condition may trigger on a newly created bic, be sure to
|
|
* drop the lock before returning.
|
|
*/
|
|
if (unlikely(!bfqd) || likely(bic->ioprio == ioprio))
|
|
return;
|
|
|
|
bic->ioprio = ioprio;
|
|
|
|
bfqq = bic_to_bfqq(bic, false);
|
|
if (bfqq) {
|
|
/* release process reference on this queue */
|
|
bfq_put_queue(bfqq);
|
|
bfqq = bfq_get_queue(bfqd, bio, BLK_RW_ASYNC, bic);
|
|
bic_set_bfqq(bic, bfqq, false);
|
|
}
|
|
|
|
bfqq = bic_to_bfqq(bic, true);
|
|
if (bfqq)
|
|
bfq_set_next_ioprio_data(bfqq, bic);
|
|
}
|
|
|
|
static void bfq_init_bfqq(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
struct bfq_io_cq *bic, pid_t pid, int is_sync)
|
|
{
|
|
RB_CLEAR_NODE(&bfqq->entity.rb_node);
|
|
INIT_LIST_HEAD(&bfqq->fifo);
|
|
|
|
bfqq->ref = 0;
|
|
bfqq->bfqd = bfqd;
|
|
|
|
if (bic)
|
|
bfq_set_next_ioprio_data(bfqq, bic);
|
|
|
|
if (is_sync) {
|
|
if (!bfq_class_idle(bfqq))
|
|
bfq_mark_bfqq_idle_window(bfqq);
|
|
bfq_mark_bfqq_sync(bfqq);
|
|
} else
|
|
bfq_clear_bfqq_sync(bfqq);
|
|
|
|
/* set end request to minus infinity from now */
|
|
bfqq->ttime.last_end_request = ktime_get_ns() + 1;
|
|
|
|
bfq_mark_bfqq_IO_bound(bfqq);
|
|
|
|
bfqq->pid = pid;
|
|
|
|
/* Tentative initial value to trade off between thr and lat */
|
|
bfqq->max_budget = (2 * bfq_max_budget(bfqd)) / 3;
|
|
bfqq->budget_timeout = bfq_smallest_from_now();
|
|
|
|
bfqq->wr_coeff = 1;
|
|
bfqq->last_wr_start_finish = jiffies;
|
|
bfqq->wr_start_at_switch_to_srt = bfq_smallest_from_now();
|
|
bfqq->split_time = bfq_smallest_from_now();
|
|
|
|
/*
|
|
* Set to the value for which bfqq will not be deemed as
|
|
* soft rt when it becomes backlogged.
|
|
*/
|
|
bfqq->soft_rt_next_start = bfq_greatest_from_now();
|
|
|
|
/* first request is almost certainly seeky */
|
|
bfqq->seek_history = 1;
|
|
}
|
|
|
|
static struct bfq_queue **bfq_async_queue_prio(struct bfq_data *bfqd,
|
|
struct bfq_group *bfqg,
|
|
int ioprio_class, int ioprio)
|
|
{
|
|
switch (ioprio_class) {
|
|
case IOPRIO_CLASS_RT:
|
|
return &bfqg->async_bfqq[0][ioprio];
|
|
case IOPRIO_CLASS_NONE:
|
|
ioprio = IOPRIO_NORM;
|
|
/* fall through */
|
|
case IOPRIO_CLASS_BE:
|
|
return &bfqg->async_bfqq[1][ioprio];
|
|
case IOPRIO_CLASS_IDLE:
|
|
return &bfqg->async_idle_bfqq;
|
|
default:
|
|
return NULL;
|
|
}
|
|
}
|
|
|
|
static struct bfq_queue *bfq_get_queue(struct bfq_data *bfqd,
|
|
struct bio *bio, bool is_sync,
|
|
struct bfq_io_cq *bic)
|
|
{
|
|
const int ioprio = IOPRIO_PRIO_DATA(bic->ioprio);
|
|
const int ioprio_class = IOPRIO_PRIO_CLASS(bic->ioprio);
|
|
struct bfq_queue **async_bfqq = NULL;
|
|
struct bfq_queue *bfqq;
|
|
struct bfq_group *bfqg;
|
|
|
|
rcu_read_lock();
|
|
|
|
bfqg = bfq_find_set_group(bfqd, bio_blkcg(bio));
|
|
if (!bfqg) {
|
|
bfqq = &bfqd->oom_bfqq;
|
|
goto out;
|
|
}
|
|
|
|
if (!is_sync) {
|
|
async_bfqq = bfq_async_queue_prio(bfqd, bfqg, ioprio_class,
|
|
ioprio);
|
|
bfqq = *async_bfqq;
|
|
if (bfqq)
|
|
goto out;
|
|
}
|
|
|
|
bfqq = kmem_cache_alloc_node(bfq_pool,
|
|
GFP_NOWAIT | __GFP_ZERO | __GFP_NOWARN,
|
|
bfqd->queue->node);
|
|
|
|
if (bfqq) {
|
|
bfq_init_bfqq(bfqd, bfqq, bic, current->pid,
|
|
is_sync);
|
|
bfq_init_entity(&bfqq->entity, bfqg);
|
|
bfq_log_bfqq(bfqd, bfqq, "allocated");
|
|
} else {
|
|
bfqq = &bfqd->oom_bfqq;
|
|
bfq_log_bfqq(bfqd, bfqq, "using oom bfqq");
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Pin the queue now that it's allocated, scheduler exit will
|
|
* prune it.
|
|
*/
|
|
if (async_bfqq) {
|
|
bfqq->ref++; /*
|
|
* Extra group reference, w.r.t. sync
|
|
* queue. This extra reference is removed
|
|
* only if bfqq->bfqg disappears, to
|
|
* guarantee that this queue is not freed
|
|
* until its group goes away.
|
|
*/
|
|
bfq_log_bfqq(bfqd, bfqq, "get_queue, bfqq not in async: %p, %d",
|
|
bfqq, bfqq->ref);
|
|
*async_bfqq = bfqq;
|
|
}
|
|
|
|
out:
|
|
bfqq->ref++; /* get a process reference to this queue */
|
|
bfq_log_bfqq(bfqd, bfqq, "get_queue, at end: %p, %d", bfqq, bfqq->ref);
|
|
rcu_read_unlock();
|
|
return bfqq;
|
|
}
|
|
|
|
static void bfq_update_io_thinktime(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_ttime *ttime = &bfqq->ttime;
|
|
u64 elapsed = ktime_get_ns() - bfqq->ttime.last_end_request;
|
|
|
|
elapsed = min_t(u64, elapsed, 2ULL * bfqd->bfq_slice_idle);
|
|
|
|
ttime->ttime_samples = (7*bfqq->ttime.ttime_samples + 256) / 8;
|
|
ttime->ttime_total = div_u64(7*ttime->ttime_total + 256*elapsed, 8);
|
|
ttime->ttime_mean = div64_ul(ttime->ttime_total + 128,
|
|
ttime->ttime_samples);
|
|
}
|
|
|
|
static void
|
|
bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
struct request *rq)
|
|
{
|
|
bfqq->seek_history <<= 1;
|
|
bfqq->seek_history |=
|
|
get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR &&
|
|
(!blk_queue_nonrot(bfqd->queue) ||
|
|
blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT);
|
|
}
|
|
|
|
/*
|
|
* Disable idle window if the process thinks too long or seeks so much that
|
|
* it doesn't matter.
|
|
*/
|
|
static void bfq_update_idle_window(struct bfq_data *bfqd,
|
|
struct bfq_queue *bfqq,
|
|
struct bfq_io_cq *bic)
|
|
{
|
|
int enable_idle;
|
|
|
|
/* Don't idle for async or idle io prio class. */
|
|
if (!bfq_bfqq_sync(bfqq) || bfq_class_idle(bfqq))
|
|
return;
|
|
|
|
/* Idle window just restored, statistics are meaningless. */
|
|
if (time_is_after_eq_jiffies(bfqq->split_time +
|
|
bfqd->bfq_wr_min_idle_time))
|
|
return;
|
|
|
|
enable_idle = bfq_bfqq_idle_window(bfqq);
|
|
|
|
if (atomic_read(&bic->icq.ioc->active_ref) == 0 ||
|
|
bfqd->bfq_slice_idle == 0 ||
|
|
(bfqd->hw_tag && BFQQ_SEEKY(bfqq) &&
|
|
bfqq->wr_coeff == 1))
|
|
enable_idle = 0;
|
|
else if (bfq_sample_valid(bfqq->ttime.ttime_samples)) {
|
|
if (bfqq->ttime.ttime_mean > bfqd->bfq_slice_idle &&
|
|
bfqq->wr_coeff == 1)
|
|
enable_idle = 0;
|
|
else
|
|
enable_idle = 1;
|
|
}
|
|
bfq_log_bfqq(bfqd, bfqq, "update_idle_window: enable_idle %d",
|
|
enable_idle);
|
|
|
|
if (enable_idle)
|
|
bfq_mark_bfqq_idle_window(bfqq);
|
|
else
|
|
bfq_clear_bfqq_idle_window(bfqq);
|
|
}
|
|
|
|
/*
|
|
* Called when a new fs request (rq) is added to bfqq. Check if there's
|
|
* something we should do about it.
|
|
*/
|
|
static void bfq_rq_enqueued(struct bfq_data *bfqd, struct bfq_queue *bfqq,
|
|
struct request *rq)
|
|
{
|
|
struct bfq_io_cq *bic = RQ_BIC(rq);
|
|
|
|
if (rq->cmd_flags & REQ_META)
|
|
bfqq->meta_pending++;
|
|
|
|
bfq_update_io_thinktime(bfqd, bfqq);
|
|
bfq_update_io_seektime(bfqd, bfqq, rq);
|
|
if (bfqq->entity.service > bfq_max_budget(bfqd) / 8 ||
|
|
!BFQQ_SEEKY(bfqq))
|
|
bfq_update_idle_window(bfqd, bfqq, bic);
|
|
|
|
bfq_log_bfqq(bfqd, bfqq,
|
|
"rq_enqueued: idle_window=%d (seeky %d)",
|
|
bfq_bfqq_idle_window(bfqq), BFQQ_SEEKY(bfqq));
|
|
|
|
bfqq->last_request_pos = blk_rq_pos(rq) + blk_rq_sectors(rq);
|
|
|
|
if (bfqq == bfqd->in_service_queue && bfq_bfqq_wait_request(bfqq)) {
|
|
bool small_req = bfqq->queued[rq_is_sync(rq)] == 1 &&
|
|
blk_rq_sectors(rq) < 32;
|
|
bool budget_timeout = bfq_bfqq_budget_timeout(bfqq);
|
|
|
|
/*
|
|
* There is just this request queued: if the request
|
|
* is small and the queue is not to be expired, then
|
|
* just exit.
|
|
*
|
|
* In this way, if the device is being idled to wait
|
|
* for a new request from the in-service queue, we
|
|
* avoid unplugging the device and committing the
|
|
* device to serve just a small request. On the
|
|
* contrary, we wait for the block layer to decide
|
|
* when to unplug the device: hopefully, new requests
|
|
* will be merged to this one quickly, then the device
|
|
* will be unplugged and larger requests will be
|
|
* dispatched.
|
|
*/
|
|
if (small_req && !budget_timeout)
|
|
return;
|
|
|
|
/*
|
|
* A large enough request arrived, or the queue is to
|
|
* be expired: in both cases disk idling is to be
|
|
* stopped, so clear wait_request flag and reset
|
|
* timer.
|
|
*/
|
|
bfq_clear_bfqq_wait_request(bfqq);
|
|
hrtimer_try_to_cancel(&bfqd->idle_slice_timer);
|
|
bfqg_stats_update_idle_time(bfqq_group(bfqq));
|
|
|
|
/*
|
|
* The queue is not empty, because a new request just
|
|
* arrived. Hence we can safely expire the queue, in
|
|
* case of budget timeout, without risking that the
|
|
* timestamps of the queue are not updated correctly.
|
|
* See [1] for more details.
|
|
*/
|
|
if (budget_timeout)
|
|
bfq_bfqq_expire(bfqd, bfqq, false,
|
|
BFQQE_BUDGET_TIMEOUT);
|
|
}
|
|
}
|
|
|
|
static void __bfq_insert_request(struct bfq_data *bfqd, struct request *rq)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq),
|
|
*new_bfqq = bfq_setup_cooperator(bfqd, bfqq, rq, true);
|
|
|
|
if (new_bfqq) {
|
|
if (bic_to_bfqq(RQ_BIC(rq), 1) != bfqq)
|
|
new_bfqq = bic_to_bfqq(RQ_BIC(rq), 1);
|
|
/*
|
|
* Release the request's reference to the old bfqq
|
|
* and make sure one is taken to the shared queue.
|
|
*/
|
|
new_bfqq->allocated++;
|
|
bfqq->allocated--;
|
|
new_bfqq->ref++;
|
|
/*
|
|
* If the bic associated with the process
|
|
* issuing this request still points to bfqq
|
|
* (and thus has not been already redirected
|
|
* to new_bfqq or even some other bfq_queue),
|
|
* then complete the merge and redirect it to
|
|
* new_bfqq.
|
|
*/
|
|
if (bic_to_bfqq(RQ_BIC(rq), 1) == bfqq)
|
|
bfq_merge_bfqqs(bfqd, RQ_BIC(rq),
|
|
bfqq, new_bfqq);
|
|
/*
|
|
* rq is about to be enqueued into new_bfqq,
|
|
* release rq reference on bfqq
|
|
*/
|
|
bfq_put_queue(bfqq);
|
|
rq->elv.priv[1] = new_bfqq;
|
|
bfqq = new_bfqq;
|
|
}
|
|
|
|
bfq_add_request(rq);
|
|
|
|
rq->fifo_time = ktime_get_ns() + bfqd->bfq_fifo_expire[rq_is_sync(rq)];
|
|
list_add_tail(&rq->queuelist, &bfqq->fifo);
|
|
|
|
bfq_rq_enqueued(bfqd, bfqq, rq);
|
|
}
|
|
|
|
static void bfq_insert_request(struct blk_mq_hw_ctx *hctx, struct request *rq,
|
|
bool at_head)
|
|
{
|
|
struct request_queue *q = hctx->queue;
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
if (blk_mq_sched_try_insert_merge(q, rq)) {
|
|
spin_unlock_irq(&bfqd->lock);
|
|
return;
|
|
}
|
|
|
|
spin_unlock_irq(&bfqd->lock);
|
|
|
|
blk_mq_sched_request_inserted(rq);
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
if (at_head || blk_rq_is_passthrough(rq)) {
|
|
if (at_head)
|
|
list_add(&rq->queuelist, &bfqd->dispatch);
|
|
else
|
|
list_add_tail(&rq->queuelist, &bfqd->dispatch);
|
|
} else {
|
|
__bfq_insert_request(bfqd, rq);
|
|
|
|
if (rq_mergeable(rq)) {
|
|
elv_rqhash_add(q, rq);
|
|
if (!q->last_merge)
|
|
q->last_merge = rq;
|
|
}
|
|
}
|
|
|
|
bfq_unlock_put_ioc(bfqd);
|
|
}
|
|
|
|
static void bfq_insert_requests(struct blk_mq_hw_ctx *hctx,
|
|
struct list_head *list, bool at_head)
|
|
{
|
|
while (!list_empty(list)) {
|
|
struct request *rq;
|
|
|
|
rq = list_first_entry(list, struct request, queuelist);
|
|
list_del_init(&rq->queuelist);
|
|
bfq_insert_request(hctx, rq, at_head);
|
|
}
|
|
}
|
|
|
|
static void bfq_update_hw_tag(struct bfq_data *bfqd)
|
|
{
|
|
bfqd->max_rq_in_driver = max_t(int, bfqd->max_rq_in_driver,
|
|
bfqd->rq_in_driver);
|
|
|
|
if (bfqd->hw_tag == 1)
|
|
return;
|
|
|
|
/*
|
|
* This sample is valid if the number of outstanding requests
|
|
* is large enough to allow a queueing behavior. Note that the
|
|
* sum is not exact, as it's not taking into account deactivated
|
|
* requests.
|
|
*/
|
|
if (bfqd->rq_in_driver + bfqd->queued < BFQ_HW_QUEUE_THRESHOLD)
|
|
return;
|
|
|
|
if (bfqd->hw_tag_samples++ < BFQ_HW_QUEUE_SAMPLES)
|
|
return;
|
|
|
|
bfqd->hw_tag = bfqd->max_rq_in_driver > BFQ_HW_QUEUE_THRESHOLD;
|
|
bfqd->max_rq_in_driver = 0;
|
|
bfqd->hw_tag_samples = 0;
|
|
}
|
|
|
|
static void bfq_completed_request(struct bfq_queue *bfqq, struct bfq_data *bfqd)
|
|
{
|
|
u64 now_ns;
|
|
u32 delta_us;
|
|
|
|
bfq_update_hw_tag(bfqd);
|
|
|
|
bfqd->rq_in_driver--;
|
|
bfqq->dispatched--;
|
|
|
|
if (!bfqq->dispatched && !bfq_bfqq_busy(bfqq)) {
|
|
/*
|
|
* Set budget_timeout (which we overload to store the
|
|
* time at which the queue remains with no backlog and
|
|
* no outstanding request; used by the weight-raising
|
|
* mechanism).
|
|
*/
|
|
bfqq->budget_timeout = jiffies;
|
|
}
|
|
|
|
now_ns = ktime_get_ns();
|
|
|
|
bfqq->ttime.last_end_request = now_ns;
|
|
|
|
/*
|
|
* Using us instead of ns, to get a reasonable precision in
|
|
* computing rate in next check.
|
|
*/
|
|
delta_us = div_u64(now_ns - bfqd->last_completion, NSEC_PER_USEC);
|
|
|
|
/*
|
|
* If the request took rather long to complete, and, according
|
|
* to the maximum request size recorded, this completion latency
|
|
* implies that the request was certainly served at a very low
|
|
* rate (less than 1M sectors/sec), then the whole observation
|
|
* interval that lasts up to this time instant cannot be a
|
|
* valid time interval for computing a new peak rate. Invoke
|
|
* bfq_update_rate_reset to have the following three steps
|
|
* taken:
|
|
* - close the observation interval at the last (previous)
|
|
* request dispatch or completion
|
|
* - compute rate, if possible, for that observation interval
|
|
* - reset to zero samples, which will trigger a proper
|
|
* re-initialization of the observation interval on next
|
|
* dispatch
|
|
*/
|
|
if (delta_us > BFQ_MIN_TT/NSEC_PER_USEC &&
|
|
(bfqd->last_rq_max_size<<BFQ_RATE_SHIFT)/delta_us <
|
|
1UL<<(BFQ_RATE_SHIFT - 10))
|
|
bfq_update_rate_reset(bfqd, NULL);
|
|
bfqd->last_completion = now_ns;
|
|
|
|
/*
|
|
* If we are waiting to discover whether the request pattern
|
|
* of the task associated with the queue is actually
|
|
* isochronous, and both requisites for this condition to hold
|
|
* are now satisfied, then compute soft_rt_next_start (see the
|
|
* comments on the function bfq_bfqq_softrt_next_start()). We
|
|
* schedule this delayed check when bfqq expires, if it still
|
|
* has in-flight requests.
|
|
*/
|
|
if (bfq_bfqq_softrt_update(bfqq) && bfqq->dispatched == 0 &&
|
|
RB_EMPTY_ROOT(&bfqq->sort_list))
|
|
bfqq->soft_rt_next_start =
|
|
bfq_bfqq_softrt_next_start(bfqd, bfqq);
|
|
|
|
/*
|
|
* If this is the in-service queue, check if it needs to be expired,
|
|
* or if we want to idle in case it has no pending requests.
|
|
*/
|
|
if (bfqd->in_service_queue == bfqq) {
|
|
if (bfqq->dispatched == 0 && bfq_bfqq_must_idle(bfqq)) {
|
|
bfq_arm_slice_timer(bfqd);
|
|
return;
|
|
} else if (bfq_may_expire_for_budg_timeout(bfqq))
|
|
bfq_bfqq_expire(bfqd, bfqq, false,
|
|
BFQQE_BUDGET_TIMEOUT);
|
|
else if (RB_EMPTY_ROOT(&bfqq->sort_list) &&
|
|
(bfqq->dispatched == 0 ||
|
|
!bfq_bfqq_may_idle(bfqq)))
|
|
bfq_bfqq_expire(bfqd, bfqq, false,
|
|
BFQQE_NO_MORE_REQUESTS);
|
|
}
|
|
}
|
|
|
|
static void bfq_put_rq_priv_body(struct bfq_queue *bfqq)
|
|
{
|
|
bfqq->allocated--;
|
|
|
|
bfq_put_queue(bfqq);
|
|
}
|
|
|
|
static void bfq_put_rq_private(struct request_queue *q, struct request *rq)
|
|
{
|
|
struct bfq_queue *bfqq = RQ_BFQQ(rq);
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
|
|
if (rq->rq_flags & RQF_STARTED)
|
|
bfqg_stats_update_completion(bfqq_group(bfqq),
|
|
rq_start_time_ns(rq),
|
|
rq_io_start_time_ns(rq),
|
|
rq->cmd_flags);
|
|
|
|
if (likely(rq->rq_flags & RQF_STARTED)) {
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&bfqd->lock, flags);
|
|
|
|
bfq_completed_request(bfqq, bfqd);
|
|
bfq_put_rq_priv_body(bfqq);
|
|
|
|
bfq_unlock_put_ioc_restore(bfqd, flags);
|
|
} else {
|
|
/*
|
|
* Request rq may be still/already in the scheduler,
|
|
* in which case we need to remove it. And we cannot
|
|
* defer such a check and removal, to avoid
|
|
* inconsistencies in the time interval from the end
|
|
* of this function to the start of the deferred work.
|
|
* This situation seems to occur only in process
|
|
* context, as a consequence of a merge. In the
|
|
* current version of the code, this implies that the
|
|
* lock is held.
|
|
*/
|
|
|
|
if (!RB_EMPTY_NODE(&rq->rb_node))
|
|
bfq_remove_request(q, rq);
|
|
bfq_put_rq_priv_body(bfqq);
|
|
}
|
|
|
|
rq->elv.priv[0] = NULL;
|
|
rq->elv.priv[1] = NULL;
|
|
}
|
|
|
|
/*
|
|
* Returns NULL if a new bfqq should be allocated, or the old bfqq if this
|
|
* was the last process referring to that bfqq.
|
|
*/
|
|
static struct bfq_queue *
|
|
bfq_split_bfqq(struct bfq_io_cq *bic, struct bfq_queue *bfqq)
|
|
{
|
|
bfq_log_bfqq(bfqq->bfqd, bfqq, "splitting queue");
|
|
|
|
if (bfqq_process_refs(bfqq) == 1) {
|
|
bfqq->pid = current->pid;
|
|
bfq_clear_bfqq_coop(bfqq);
|
|
bfq_clear_bfqq_split_coop(bfqq);
|
|
return bfqq;
|
|
}
|
|
|
|
bic_set_bfqq(bic, NULL, 1);
|
|
|
|
bfq_put_cooperator(bfqq);
|
|
|
|
bfq_put_queue(bfqq);
|
|
return NULL;
|
|
}
|
|
|
|
static struct bfq_queue *bfq_get_bfqq_handle_split(struct bfq_data *bfqd,
|
|
struct bfq_io_cq *bic,
|
|
struct bio *bio,
|
|
bool split, bool is_sync,
|
|
bool *new_queue)
|
|
{
|
|
struct bfq_queue *bfqq = bic_to_bfqq(bic, is_sync);
|
|
|
|
if (likely(bfqq && bfqq != &bfqd->oom_bfqq))
|
|
return bfqq;
|
|
|
|
if (new_queue)
|
|
*new_queue = true;
|
|
|
|
if (bfqq)
|
|
bfq_put_queue(bfqq);
|
|
bfqq = bfq_get_queue(bfqd, bio, is_sync, bic);
|
|
|
|
bic_set_bfqq(bic, bfqq, is_sync);
|
|
if (split && is_sync)
|
|
bfqq->split_time = jiffies;
|
|
|
|
return bfqq;
|
|
}
|
|
|
|
/*
|
|
* Allocate bfq data structures associated with this request.
|
|
*/
|
|
static int bfq_get_rq_private(struct request_queue *q, struct request *rq,
|
|
struct bio *bio)
|
|
{
|
|
struct bfq_data *bfqd = q->elevator->elevator_data;
|
|
struct bfq_io_cq *bic = icq_to_bic(rq->elv.icq);
|
|
const int is_sync = rq_is_sync(rq);
|
|
struct bfq_queue *bfqq;
|
|
bool new_queue = false;
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
|
|
bfq_check_ioprio_change(bic, bio);
|
|
|
|
if (!bic)
|
|
goto queue_fail;
|
|
|
|
bfq_bic_update_cgroup(bic, bio);
|
|
|
|
bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio, false, is_sync,
|
|
&new_queue);
|
|
|
|
if (likely(!new_queue)) {
|
|
/* If the queue was seeky for too long, break it apart. */
|
|
if (bfq_bfqq_coop(bfqq) && bfq_bfqq_split_coop(bfqq)) {
|
|
bfq_log_bfqq(bfqd, bfqq, "breaking apart bfqq");
|
|
bfqq = bfq_split_bfqq(bic, bfqq);
|
|
/*
|
|
* A reference to bic->icq.ioc needs to be
|
|
* released after a queue split. Do not do it
|
|
* immediately, to not risk to possibly take
|
|
* an ioc->lock while holding the scheduler
|
|
* lock.
|
|
*/
|
|
bfqd->ioc_to_put = bic->icq.ioc;
|
|
|
|
if (!bfqq)
|
|
bfqq = bfq_get_bfqq_handle_split(bfqd, bic, bio,
|
|
true, is_sync,
|
|
NULL);
|
|
}
|
|
}
|
|
|
|
bfqq->allocated++;
|
|
bfqq->ref++;
|
|
bfq_log_bfqq(bfqd, bfqq, "get_request %p: bfqq %p, %d",
|
|
rq, bfqq, bfqq->ref);
|
|
|
|
rq->elv.priv[0] = bic;
|
|
rq->elv.priv[1] = bfqq;
|
|
|
|
/*
|
|
* If a bfq_queue has only one process reference, it is owned
|
|
* by only this bic: we can then set bfqq->bic = bic. in
|
|
* addition, if the queue has also just been split, we have to
|
|
* resume its state.
|
|
*/
|
|
if (likely(bfqq != &bfqd->oom_bfqq) && bfqq_process_refs(bfqq) == 1) {
|
|
bfqq->bic = bic;
|
|
if (bfqd->ioc_to_put) { /* if true, there has been a split */
|
|
/*
|
|
* The queue has just been split from a shared
|
|
* queue: restore the idle window and the
|
|
* possible weight raising period.
|
|
*/
|
|
bfq_bfqq_resume_state(bfqq, bic);
|
|
}
|
|
}
|
|
|
|
bfq_unlock_put_ioc(bfqd);
|
|
|
|
return 0;
|
|
|
|
queue_fail:
|
|
spin_unlock_irq(&bfqd->lock);
|
|
|
|
return 1;
|
|
}
|
|
|
|
static void bfq_idle_slice_timer_body(struct bfq_queue *bfqq)
|
|
{
|
|
struct bfq_data *bfqd = bfqq->bfqd;
|
|
enum bfqq_expiration reason;
|
|
unsigned long flags;
|
|
|
|
spin_lock_irqsave(&bfqd->lock, flags);
|
|
bfq_clear_bfqq_wait_request(bfqq);
|
|
|
|
if (bfqq != bfqd->in_service_queue) {
|
|
spin_unlock_irqrestore(&bfqd->lock, flags);
|
|
return;
|
|
}
|
|
|
|
if (bfq_bfqq_budget_timeout(bfqq))
|
|
/*
|
|
* Also here the queue can be safely expired
|
|
* for budget timeout without wasting
|
|
* guarantees
|
|
*/
|
|
reason = BFQQE_BUDGET_TIMEOUT;
|
|
else if (bfqq->queued[0] == 0 && bfqq->queued[1] == 0)
|
|
/*
|
|
* The queue may not be empty upon timer expiration,
|
|
* because we may not disable the timer when the
|
|
* first request of the in-service queue arrives
|
|
* during disk idling.
|
|
*/
|
|
reason = BFQQE_TOO_IDLE;
|
|
else
|
|
goto schedule_dispatch;
|
|
|
|
bfq_bfqq_expire(bfqd, bfqq, true, reason);
|
|
|
|
schedule_dispatch:
|
|
bfq_unlock_put_ioc_restore(bfqd, flags);
|
|
bfq_schedule_dispatch(bfqd);
|
|
}
|
|
|
|
/*
|
|
* Handler of the expiration of the timer running if the in-service queue
|
|
* is idling inside its time slice.
|
|
*/
|
|
static enum hrtimer_restart bfq_idle_slice_timer(struct hrtimer *timer)
|
|
{
|
|
struct bfq_data *bfqd = container_of(timer, struct bfq_data,
|
|
idle_slice_timer);
|
|
struct bfq_queue *bfqq = bfqd->in_service_queue;
|
|
|
|
/*
|
|
* Theoretical race here: the in-service queue can be NULL or
|
|
* different from the queue that was idling if a new request
|
|
* arrives for the current queue and there is a full dispatch
|
|
* cycle that changes the in-service queue. This can hardly
|
|
* happen, but in the worst case we just expire a queue too
|
|
* early.
|
|
*/
|
|
if (bfqq)
|
|
bfq_idle_slice_timer_body(bfqq);
|
|
|
|
return HRTIMER_NORESTART;
|
|
}
|
|
|
|
static void __bfq_put_async_bfqq(struct bfq_data *bfqd,
|
|
struct bfq_queue **bfqq_ptr)
|
|
{
|
|
struct bfq_queue *bfqq = *bfqq_ptr;
|
|
|
|
bfq_log(bfqd, "put_async_bfqq: %p", bfqq);
|
|
if (bfqq) {
|
|
bfq_bfqq_move(bfqd, bfqq, bfqd->root_group);
|
|
|
|
bfq_log_bfqq(bfqd, bfqq, "put_async_bfqq: putting %p, %d",
|
|
bfqq, bfqq->ref);
|
|
bfq_put_queue(bfqq);
|
|
*bfqq_ptr = NULL;
|
|
}
|
|
}
|
|
|
|
/*
|
|
* Release all the bfqg references to its async queues. If we are
|
|
* deallocating the group these queues may still contain requests, so
|
|
* we reparent them to the root cgroup (i.e., the only one that will
|
|
* exist for sure until all the requests on a device are gone).
|
|
*/
|
|
static void bfq_put_async_queues(struct bfq_data *bfqd, struct bfq_group *bfqg)
|
|
{
|
|
int i, j;
|
|
|
|
for (i = 0; i < 2; i++)
|
|
for (j = 0; j < IOPRIO_BE_NR; j++)
|
|
__bfq_put_async_bfqq(bfqd, &bfqg->async_bfqq[i][j]);
|
|
|
|
__bfq_put_async_bfqq(bfqd, &bfqg->async_idle_bfqq);
|
|
}
|
|
|
|
static void bfq_exit_queue(struct elevator_queue *e)
|
|
{
|
|
struct bfq_data *bfqd = e->elevator_data;
|
|
struct bfq_queue *bfqq, *n;
|
|
|
|
hrtimer_cancel(&bfqd->idle_slice_timer);
|
|
|
|
spin_lock_irq(&bfqd->lock);
|
|
list_for_each_entry_safe(bfqq, n, &bfqd->idle_list, bfqq_list)
|
|
bfq_deactivate_bfqq(bfqd, bfqq, false, false);
|
|
spin_unlock_irq(&bfqd->lock);
|
|
|
|
hrtimer_cancel(&bfqd->idle_slice_timer);
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
blkcg_deactivate_policy(bfqd->queue, &blkcg_policy_bfq);
|
|
#else
|
|
spin_lock_irq(&bfqd->lock);
|
|
bfq_put_async_queues(bfqd, bfqd->root_group);
|
|
kfree(bfqd->root_group);
|
|
spin_unlock_irq(&bfqd->lock);
|
|
#endif
|
|
|
|
kfree(bfqd);
|
|
}
|
|
|
|
static void bfq_init_root_group(struct bfq_group *root_group,
|
|
struct bfq_data *bfqd)
|
|
{
|
|
int i;
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
root_group->entity.parent = NULL;
|
|
root_group->my_entity = NULL;
|
|
root_group->bfqd = bfqd;
|
|
#endif
|
|
root_group->rq_pos_tree = RB_ROOT;
|
|
for (i = 0; i < BFQ_IOPRIO_CLASSES; i++)
|
|
root_group->sched_data.service_tree[i] = BFQ_SERVICE_TREE_INIT;
|
|
root_group->sched_data.bfq_class_idle_last_service = jiffies;
|
|
}
|
|
|
|
static int bfq_init_queue(struct request_queue *q, struct elevator_type *e)
|
|
{
|
|
struct bfq_data *bfqd;
|
|
struct elevator_queue *eq;
|
|
|
|
eq = elevator_alloc(q, e);
|
|
if (!eq)
|
|
return -ENOMEM;
|
|
|
|
bfqd = kzalloc_node(sizeof(*bfqd), GFP_KERNEL, q->node);
|
|
if (!bfqd) {
|
|
kobject_put(&eq->kobj);
|
|
return -ENOMEM;
|
|
}
|
|
eq->elevator_data = bfqd;
|
|
|
|
spin_lock_irq(q->queue_lock);
|
|
q->elevator = eq;
|
|
spin_unlock_irq(q->queue_lock);
|
|
|
|
/*
|
|
* Our fallback bfqq if bfq_find_alloc_queue() runs into OOM issues.
|
|
* Grab a permanent reference to it, so that the normal code flow
|
|
* will not attempt to free it.
|
|
*/
|
|
bfq_init_bfqq(bfqd, &bfqd->oom_bfqq, NULL, 1, 0);
|
|
bfqd->oom_bfqq.ref++;
|
|
bfqd->oom_bfqq.new_ioprio = BFQ_DEFAULT_QUEUE_IOPRIO;
|
|
bfqd->oom_bfqq.new_ioprio_class = IOPRIO_CLASS_BE;
|
|
bfqd->oom_bfqq.entity.new_weight =
|
|
bfq_ioprio_to_weight(bfqd->oom_bfqq.new_ioprio);
|
|
/*
|
|
* Trigger weight initialization, according to ioprio, at the
|
|
* oom_bfqq's first activation. The oom_bfqq's ioprio and ioprio
|
|
* class won't be changed any more.
|
|
*/
|
|
bfqd->oom_bfqq.entity.prio_changed = 1;
|
|
|
|
bfqd->queue = q;
|
|
|
|
INIT_LIST_HEAD(&bfqd->dispatch);
|
|
|
|
hrtimer_init(&bfqd->idle_slice_timer, CLOCK_MONOTONIC,
|
|
HRTIMER_MODE_REL);
|
|
bfqd->idle_slice_timer.function = bfq_idle_slice_timer;
|
|
|
|
INIT_LIST_HEAD(&bfqd->active_list);
|
|
INIT_LIST_HEAD(&bfqd->idle_list);
|
|
|
|
bfqd->hw_tag = -1;
|
|
|
|
bfqd->bfq_max_budget = bfq_default_max_budget;
|
|
|
|
bfqd->bfq_fifo_expire[0] = bfq_fifo_expire[0];
|
|
bfqd->bfq_fifo_expire[1] = bfq_fifo_expire[1];
|
|
bfqd->bfq_back_max = bfq_back_max;
|
|
bfqd->bfq_back_penalty = bfq_back_penalty;
|
|
bfqd->bfq_slice_idle = bfq_slice_idle;
|
|
bfqd->bfq_timeout = bfq_timeout;
|
|
|
|
bfqd->bfq_requests_within_timer = 120;
|
|
|
|
bfqd->low_latency = true;
|
|
|
|
/*
|
|
* Trade-off between responsiveness and fairness.
|
|
*/
|
|
bfqd->bfq_wr_coeff = 30;
|
|
bfqd->bfq_wr_rt_max_time = msecs_to_jiffies(300);
|
|
bfqd->bfq_wr_max_time = 0;
|
|
bfqd->bfq_wr_min_idle_time = msecs_to_jiffies(2000);
|
|
bfqd->bfq_wr_min_inter_arr_async = msecs_to_jiffies(500);
|
|
bfqd->bfq_wr_max_softrt_rate = 7000; /*
|
|
* Approximate rate required
|
|
* to playback or record a
|
|
* high-definition compressed
|
|
* video.
|
|
*/
|
|
bfqd->wr_busy_queues = 0;
|
|
|
|
/*
|
|
* Begin by assuming, optimistically, that the device is a
|
|
* high-speed one, and that its peak rate is equal to 2/3 of
|
|
* the highest reference rate.
|
|
*/
|
|
bfqd->RT_prod = R_fast[blk_queue_nonrot(bfqd->queue)] *
|
|
T_fast[blk_queue_nonrot(bfqd->queue)];
|
|
bfqd->peak_rate = R_fast[blk_queue_nonrot(bfqd->queue)] * 2 / 3;
|
|
bfqd->device_speed = BFQ_BFQD_FAST;
|
|
|
|
spin_lock_init(&bfqd->lock);
|
|
|
|
/*
|
|
* The invocation of the next bfq_create_group_hierarchy
|
|
* function is the head of a chain of function calls
|
|
* (bfq_create_group_hierarchy->blkcg_activate_policy->
|
|
* blk_mq_freeze_queue) that may lead to the invocation of the
|
|
* has_work hook function. For this reason,
|
|
* bfq_create_group_hierarchy is invoked only after all
|
|
* scheduler data has been initialized, apart from the fields
|
|
* that can be initialized only after invoking
|
|
* bfq_create_group_hierarchy. This, in particular, enables
|
|
* has_work to correctly return false. Of course, to avoid
|
|
* other inconsistencies, the blk-mq stack must then refrain
|
|
* from invoking further scheduler hooks before this init
|
|
* function is finished.
|
|
*/
|
|
bfqd->root_group = bfq_create_group_hierarchy(bfqd, q->node);
|
|
if (!bfqd->root_group)
|
|
goto out_free;
|
|
bfq_init_root_group(bfqd->root_group, bfqd);
|
|
bfq_init_entity(&bfqd->oom_bfqq.entity, bfqd->root_group);
|
|
|
|
|
|
return 0;
|
|
|
|
out_free:
|
|
kfree(bfqd);
|
|
kobject_put(&eq->kobj);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static void bfq_slab_kill(void)
|
|
{
|
|
kmem_cache_destroy(bfq_pool);
|
|
}
|
|
|
|
static int __init bfq_slab_setup(void)
|
|
{
|
|
bfq_pool = KMEM_CACHE(bfq_queue, 0);
|
|
if (!bfq_pool)
|
|
return -ENOMEM;
|
|
return 0;
|
|
}
|
|
|
|
static ssize_t bfq_var_show(unsigned int var, char *page)
|
|
{
|
|
return sprintf(page, "%u\n", var);
|
|
}
|
|
|
|
static ssize_t bfq_var_store(unsigned long *var, const char *page,
|
|
size_t count)
|
|
{
|
|
unsigned long new_val;
|
|
int ret = kstrtoul(page, 10, &new_val);
|
|
|
|
if (ret == 0)
|
|
*var = new_val;
|
|
|
|
return count;
|
|
}
|
|
|
|
#define SHOW_FUNCTION(__FUNC, __VAR, __CONV) \
|
|
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
|
|
{ \
|
|
struct bfq_data *bfqd = e->elevator_data; \
|
|
u64 __data = __VAR; \
|
|
if (__CONV == 1) \
|
|
__data = jiffies_to_msecs(__data); \
|
|
else if (__CONV == 2) \
|
|
__data = div_u64(__data, NSEC_PER_MSEC); \
|
|
return bfq_var_show(__data, (page)); \
|
|
}
|
|
SHOW_FUNCTION(bfq_fifo_expire_sync_show, bfqd->bfq_fifo_expire[1], 2);
|
|
SHOW_FUNCTION(bfq_fifo_expire_async_show, bfqd->bfq_fifo_expire[0], 2);
|
|
SHOW_FUNCTION(bfq_back_seek_max_show, bfqd->bfq_back_max, 0);
|
|
SHOW_FUNCTION(bfq_back_seek_penalty_show, bfqd->bfq_back_penalty, 0);
|
|
SHOW_FUNCTION(bfq_slice_idle_show, bfqd->bfq_slice_idle, 2);
|
|
SHOW_FUNCTION(bfq_max_budget_show, bfqd->bfq_user_max_budget, 0);
|
|
SHOW_FUNCTION(bfq_timeout_sync_show, bfqd->bfq_timeout, 1);
|
|
SHOW_FUNCTION(bfq_strict_guarantees_show, bfqd->strict_guarantees, 0);
|
|
SHOW_FUNCTION(bfq_low_latency_show, bfqd->low_latency, 0);
|
|
#undef SHOW_FUNCTION
|
|
|
|
#define USEC_SHOW_FUNCTION(__FUNC, __VAR) \
|
|
static ssize_t __FUNC(struct elevator_queue *e, char *page) \
|
|
{ \
|
|
struct bfq_data *bfqd = e->elevator_data; \
|
|
u64 __data = __VAR; \
|
|
__data = div_u64(__data, NSEC_PER_USEC); \
|
|
return bfq_var_show(__data, (page)); \
|
|
}
|
|
USEC_SHOW_FUNCTION(bfq_slice_idle_us_show, bfqd->bfq_slice_idle);
|
|
#undef USEC_SHOW_FUNCTION
|
|
|
|
#define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \
|
|
static ssize_t \
|
|
__FUNC(struct elevator_queue *e, const char *page, size_t count) \
|
|
{ \
|
|
struct bfq_data *bfqd = e->elevator_data; \
|
|
unsigned long uninitialized_var(__data); \
|
|
int ret = bfq_var_store(&__data, (page), count); \
|
|
if (__data < (MIN)) \
|
|
__data = (MIN); \
|
|
else if (__data > (MAX)) \
|
|
__data = (MAX); \
|
|
if (__CONV == 1) \
|
|
*(__PTR) = msecs_to_jiffies(__data); \
|
|
else if (__CONV == 2) \
|
|
*(__PTR) = (u64)__data * NSEC_PER_MSEC; \
|
|
else \
|
|
*(__PTR) = __data; \
|
|
return ret; \
|
|
}
|
|
STORE_FUNCTION(bfq_fifo_expire_sync_store, &bfqd->bfq_fifo_expire[1], 1,
|
|
INT_MAX, 2);
|
|
STORE_FUNCTION(bfq_fifo_expire_async_store, &bfqd->bfq_fifo_expire[0], 1,
|
|
INT_MAX, 2);
|
|
STORE_FUNCTION(bfq_back_seek_max_store, &bfqd->bfq_back_max, 0, INT_MAX, 0);
|
|
STORE_FUNCTION(bfq_back_seek_penalty_store, &bfqd->bfq_back_penalty, 1,
|
|
INT_MAX, 0);
|
|
STORE_FUNCTION(bfq_slice_idle_store, &bfqd->bfq_slice_idle, 0, INT_MAX, 2);
|
|
#undef STORE_FUNCTION
|
|
|
|
#define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \
|
|
static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count)\
|
|
{ \
|
|
struct bfq_data *bfqd = e->elevator_data; \
|
|
unsigned long uninitialized_var(__data); \
|
|
int ret = bfq_var_store(&__data, (page), count); \
|
|
if (__data < (MIN)) \
|
|
__data = (MIN); \
|
|
else if (__data > (MAX)) \
|
|
__data = (MAX); \
|
|
*(__PTR) = (u64)__data * NSEC_PER_USEC; \
|
|
return ret; \
|
|
}
|
|
USEC_STORE_FUNCTION(bfq_slice_idle_us_store, &bfqd->bfq_slice_idle, 0,
|
|
UINT_MAX);
|
|
#undef USEC_STORE_FUNCTION
|
|
|
|
static ssize_t bfq_max_budget_store(struct elevator_queue *e,
|
|
const char *page, size_t count)
|
|
{
|
|
struct bfq_data *bfqd = e->elevator_data;
|
|
unsigned long uninitialized_var(__data);
|
|
int ret = bfq_var_store(&__data, (page), count);
|
|
|
|
if (__data == 0)
|
|
bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
|
|
else {
|
|
if (__data > INT_MAX)
|
|
__data = INT_MAX;
|
|
bfqd->bfq_max_budget = __data;
|
|
}
|
|
|
|
bfqd->bfq_user_max_budget = __data;
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* Leaving this name to preserve name compatibility with cfq
|
|
* parameters, but this timeout is used for both sync and async.
|
|
*/
|
|
static ssize_t bfq_timeout_sync_store(struct elevator_queue *e,
|
|
const char *page, size_t count)
|
|
{
|
|
struct bfq_data *bfqd = e->elevator_data;
|
|
unsigned long uninitialized_var(__data);
|
|
int ret = bfq_var_store(&__data, (page), count);
|
|
|
|
if (__data < 1)
|
|
__data = 1;
|
|
else if (__data > INT_MAX)
|
|
__data = INT_MAX;
|
|
|
|
bfqd->bfq_timeout = msecs_to_jiffies(__data);
|
|
if (bfqd->bfq_user_max_budget == 0)
|
|
bfqd->bfq_max_budget = bfq_calc_max_budget(bfqd);
|
|
|
|
return ret;
|
|
}
|
|
|
|
static ssize_t bfq_strict_guarantees_store(struct elevator_queue *e,
|
|
const char *page, size_t count)
|
|
{
|
|
struct bfq_data *bfqd = e->elevator_data;
|
|
unsigned long uninitialized_var(__data);
|
|
int ret = bfq_var_store(&__data, (page), count);
|
|
|
|
if (__data > 1)
|
|
__data = 1;
|
|
if (!bfqd->strict_guarantees && __data == 1
|
|
&& bfqd->bfq_slice_idle < 8 * NSEC_PER_MSEC)
|
|
bfqd->bfq_slice_idle = 8 * NSEC_PER_MSEC;
|
|
|
|
bfqd->strict_guarantees = __data;
|
|
|
|
return ret;
|
|
}
|
|
|
|
static ssize_t bfq_low_latency_store(struct elevator_queue *e,
|
|
const char *page, size_t count)
|
|
{
|
|
struct bfq_data *bfqd = e->elevator_data;
|
|
unsigned long uninitialized_var(__data);
|
|
int ret = bfq_var_store(&__data, (page), count);
|
|
|
|
if (__data > 1)
|
|
__data = 1;
|
|
if (__data == 0 && bfqd->low_latency != 0)
|
|
bfq_end_wr(bfqd);
|
|
bfqd->low_latency = __data;
|
|
|
|
return ret;
|
|
}
|
|
|
|
#define BFQ_ATTR(name) \
|
|
__ATTR(name, 0644, bfq_##name##_show, bfq_##name##_store)
|
|
|
|
static struct elv_fs_entry bfq_attrs[] = {
|
|
BFQ_ATTR(fifo_expire_sync),
|
|
BFQ_ATTR(fifo_expire_async),
|
|
BFQ_ATTR(back_seek_max),
|
|
BFQ_ATTR(back_seek_penalty),
|
|
BFQ_ATTR(slice_idle),
|
|
BFQ_ATTR(slice_idle_us),
|
|
BFQ_ATTR(max_budget),
|
|
BFQ_ATTR(timeout_sync),
|
|
BFQ_ATTR(strict_guarantees),
|
|
BFQ_ATTR(low_latency),
|
|
__ATTR_NULL
|
|
};
|
|
|
|
static struct elevator_type iosched_bfq_mq = {
|
|
.ops.mq = {
|
|
.get_rq_priv = bfq_get_rq_private,
|
|
.put_rq_priv = bfq_put_rq_private,
|
|
.exit_icq = bfq_exit_icq,
|
|
.insert_requests = bfq_insert_requests,
|
|
.dispatch_request = bfq_dispatch_request,
|
|
.next_request = elv_rb_latter_request,
|
|
.former_request = elv_rb_former_request,
|
|
.allow_merge = bfq_allow_bio_merge,
|
|
.bio_merge = bfq_bio_merge,
|
|
.request_merge = bfq_request_merge,
|
|
.requests_merged = bfq_requests_merged,
|
|
.request_merged = bfq_request_merged,
|
|
.has_work = bfq_has_work,
|
|
.init_sched = bfq_init_queue,
|
|
.exit_sched = bfq_exit_queue,
|
|
},
|
|
|
|
.uses_mq = true,
|
|
.icq_size = sizeof(struct bfq_io_cq),
|
|
.icq_align = __alignof__(struct bfq_io_cq),
|
|
.elevator_attrs = bfq_attrs,
|
|
.elevator_name = "bfq",
|
|
.elevator_owner = THIS_MODULE,
|
|
};
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
static struct blkcg_policy blkcg_policy_bfq = {
|
|
.dfl_cftypes = bfq_blkg_files,
|
|
.legacy_cftypes = bfq_blkcg_legacy_files,
|
|
|
|
.cpd_alloc_fn = bfq_cpd_alloc,
|
|
.cpd_init_fn = bfq_cpd_init,
|
|
.cpd_bind_fn = bfq_cpd_init,
|
|
.cpd_free_fn = bfq_cpd_free,
|
|
|
|
.pd_alloc_fn = bfq_pd_alloc,
|
|
.pd_init_fn = bfq_pd_init,
|
|
.pd_offline_fn = bfq_pd_offline,
|
|
.pd_free_fn = bfq_pd_free,
|
|
.pd_reset_stats_fn = bfq_pd_reset_stats,
|
|
};
|
|
#endif
|
|
|
|
static int __init bfq_init(void)
|
|
{
|
|
int ret;
|
|
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
ret = blkcg_policy_register(&blkcg_policy_bfq);
|
|
if (ret)
|
|
return ret;
|
|
#endif
|
|
|
|
ret = -ENOMEM;
|
|
if (bfq_slab_setup())
|
|
goto err_pol_unreg;
|
|
|
|
/*
|
|
* Times to load large popular applications for the typical
|
|
* systems installed on the reference devices (see the
|
|
* comments before the definitions of the next two
|
|
* arrays). Actually, we use slightly slower values, as the
|
|
* estimated peak rate tends to be smaller than the actual
|
|
* peak rate. The reason for this last fact is that estimates
|
|
* are computed over much shorter time intervals than the long
|
|
* intervals typically used for benchmarking. Why? First, to
|
|
* adapt more quickly to variations. Second, because an I/O
|
|
* scheduler cannot rely on a peak-rate-evaluation workload to
|
|
* be run for a long time.
|
|
*/
|
|
T_slow[0] = msecs_to_jiffies(3500); /* actually 4 sec */
|
|
T_slow[1] = msecs_to_jiffies(6000); /* actually 6.5 sec */
|
|
T_fast[0] = msecs_to_jiffies(7000); /* actually 8 sec */
|
|
T_fast[1] = msecs_to_jiffies(2500); /* actually 3 sec */
|
|
|
|
/*
|
|
* Thresholds that determine the switch between speed classes
|
|
* (see the comments before the definition of the array
|
|
* device_speed_thresh). These thresholds are biased towards
|
|
* transitions to the fast class. This is safer than the
|
|
* opposite bias. In fact, a wrong transition to the slow
|
|
* class results in short weight-raising periods, because the
|
|
* speed of the device then tends to be higher that the
|
|
* reference peak rate. On the opposite end, a wrong
|
|
* transition to the fast class tends to increase
|
|
* weight-raising periods, because of the opposite reason.
|
|
*/
|
|
device_speed_thresh[0] = (4 * R_slow[0]) / 3;
|
|
device_speed_thresh[1] = (4 * R_slow[1]) / 3;
|
|
|
|
ret = elv_register(&iosched_bfq_mq);
|
|
if (ret)
|
|
goto err_pol_unreg;
|
|
|
|
return 0;
|
|
|
|
err_pol_unreg:
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
blkcg_policy_unregister(&blkcg_policy_bfq);
|
|
#endif
|
|
return ret;
|
|
}
|
|
|
|
static void __exit bfq_exit(void)
|
|
{
|
|
elv_unregister(&iosched_bfq_mq);
|
|
#ifdef CONFIG_BFQ_GROUP_IOSCHED
|
|
blkcg_policy_unregister(&blkcg_policy_bfq);
|
|
#endif
|
|
bfq_slab_kill();
|
|
}
|
|
|
|
module_init(bfq_init);
|
|
module_exit(bfq_exit);
|
|
|
|
MODULE_AUTHOR("Paolo Valente");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("MQ Budget Fair Queueing I/O Scheduler");
|