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![Tejun Heo](/assets/img/avatar_default.png)
io.weight is gonna be another rq_qos cgroup mechanism. Let's rename RQ_QOS_CGROUP which is being used by io.latency to RQ_QOS_LATENCY in preparation. Signed-off-by: Tejun Heo <tj@kernel.org> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1052 lines
28 KiB
C
1052 lines
28 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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* Block rq-qos base io controller
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*
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* This works similar to wbt with a few exceptions
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*
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* - It's bio based, so the latency covers the whole block layer in addition to
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* the actual io.
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* - We will throttle all IO that comes in here if we need to.
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* - We use the mean latency over the 100ms window. This is because writes can
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* be particularly fast, which could give us a false sense of the impact of
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* other workloads on our protected workload.
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* - By default there's no throttling, we set the queue_depth to UINT_MAX so
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* that we can have as many outstanding bio's as we're allowed to. Only at
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* throttle time do we pay attention to the actual queue depth.
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*
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* The hierarchy works like the cpu controller does, we track the latency at
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* every configured node, and each configured node has it's own independent
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* queue depth. This means that we only care about our latency targets at the
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* peer level. Some group at the bottom of the hierarchy isn't going to affect
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* a group at the end of some other path if we're only configred at leaf level.
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*
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* Consider the following
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*
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* root blkg
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* / \
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* fast (target=5ms) slow (target=10ms)
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* / \ / \
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* a b normal(15ms) unloved
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*
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* "a" and "b" have no target, but their combined io under "fast" cannot exceed
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* an average latency of 5ms. If it does then we will throttle the "slow"
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* group. In the case of "normal", if it exceeds its 15ms target, we will
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* throttle "unloved", but nobody else.
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*
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* In this example "fast", "slow", and "normal" will be the only groups actually
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* accounting their io latencies. We have to walk up the heirarchy to the root
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* on every submit and complete so we can do the appropriate stat recording and
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* adjust the queue depth of ourselves if needed.
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*
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* There are 2 ways we throttle IO.
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*
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* 1) Queue depth throttling. As we throttle down we will adjust the maximum
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* number of IO's we're allowed to have in flight. This starts at (u64)-1 down
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* to 1. If the group is only ever submitting IO for itself then this is the
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* only way we throttle.
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*
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* 2) Induced delay throttling. This is for the case that a group is generating
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* IO that has to be issued by the root cg to avoid priority inversion. So think
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* REQ_META or REQ_SWAP. If we are already at qd == 1 and we're getting a lot
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* of work done for us on behalf of the root cg and are being asked to scale
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* down more then we induce a latency at userspace return. We accumulate the
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* total amount of time we need to be punished by doing
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*
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* total_time += min_lat_nsec - actual_io_completion
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*
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* and then at throttle time will do
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*
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* throttle_time = min(total_time, NSEC_PER_SEC)
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*
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* This induced delay will throttle back the activity that is generating the
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* root cg issued io's, wethere that's some metadata intensive operation or the
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* group is using so much memory that it is pushing us into swap.
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*
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* Copyright (C) 2018 Josef Bacik
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*/
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#include <linux/kernel.h>
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#include <linux/blk_types.h>
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#include <linux/backing-dev.h>
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#include <linux/module.h>
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#include <linux/timer.h>
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#include <linux/memcontrol.h>
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#include <linux/sched/loadavg.h>
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#include <linux/sched/signal.h>
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#include <trace/events/block.h>
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#include <linux/blk-mq.h>
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#include "blk-rq-qos.h"
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#include "blk-stat.h"
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#include "blk.h"
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#define DEFAULT_SCALE_COOKIE 1000000U
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static struct blkcg_policy blkcg_policy_iolatency;
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struct iolatency_grp;
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struct blk_iolatency {
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struct rq_qos rqos;
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struct timer_list timer;
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atomic_t enabled;
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};
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static inline struct blk_iolatency *BLKIOLATENCY(struct rq_qos *rqos)
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{
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return container_of(rqos, struct blk_iolatency, rqos);
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}
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static inline bool blk_iolatency_enabled(struct blk_iolatency *blkiolat)
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{
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return atomic_read(&blkiolat->enabled) > 0;
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}
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struct child_latency_info {
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spinlock_t lock;
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/* Last time we adjusted the scale of everybody. */
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u64 last_scale_event;
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/* The latency that we missed. */
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u64 scale_lat;
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/* Total io's from all of our children for the last summation. */
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u64 nr_samples;
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/* The guy who actually changed the latency numbers. */
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struct iolatency_grp *scale_grp;
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/* Cookie to tell if we need to scale up or down. */
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atomic_t scale_cookie;
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};
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struct percentile_stats {
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u64 total;
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u64 missed;
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};
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struct latency_stat {
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union {
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struct percentile_stats ps;
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struct blk_rq_stat rqs;
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};
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};
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struct iolatency_grp {
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struct blkg_policy_data pd;
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struct latency_stat __percpu *stats;
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struct latency_stat cur_stat;
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struct blk_iolatency *blkiolat;
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struct rq_depth rq_depth;
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struct rq_wait rq_wait;
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atomic64_t window_start;
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atomic_t scale_cookie;
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u64 min_lat_nsec;
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u64 cur_win_nsec;
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/* total running average of our io latency. */
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u64 lat_avg;
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/* Our current number of IO's for the last summation. */
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u64 nr_samples;
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bool ssd;
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struct child_latency_info child_lat;
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};
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#define BLKIOLATENCY_MIN_WIN_SIZE (100 * NSEC_PER_MSEC)
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#define BLKIOLATENCY_MAX_WIN_SIZE NSEC_PER_SEC
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/*
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* These are the constants used to fake the fixed-point moving average
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* calculation just like load average. The call to calc_load() folds
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* (FIXED_1 (2048) - exp_factor) * new_sample into lat_avg. The sampling
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* window size is bucketed to try to approximately calculate average
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* latency such that 1/exp (decay rate) is [1 min, 2.5 min) when windows
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* elapse immediately. Note, windows only elapse with IO activity. Idle
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* periods extend the most recent window.
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*/
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#define BLKIOLATENCY_NR_EXP_FACTORS 5
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#define BLKIOLATENCY_EXP_BUCKET_SIZE (BLKIOLATENCY_MAX_WIN_SIZE / \
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(BLKIOLATENCY_NR_EXP_FACTORS - 1))
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static const u64 iolatency_exp_factors[BLKIOLATENCY_NR_EXP_FACTORS] = {
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2045, // exp(1/600) - 600 samples
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2039, // exp(1/240) - 240 samples
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2031, // exp(1/120) - 120 samples
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2023, // exp(1/80) - 80 samples
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2014, // exp(1/60) - 60 samples
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};
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static inline struct iolatency_grp *pd_to_lat(struct blkg_policy_data *pd)
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{
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return pd ? container_of(pd, struct iolatency_grp, pd) : NULL;
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}
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static inline struct iolatency_grp *blkg_to_lat(struct blkcg_gq *blkg)
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{
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return pd_to_lat(blkg_to_pd(blkg, &blkcg_policy_iolatency));
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}
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static inline struct blkcg_gq *lat_to_blkg(struct iolatency_grp *iolat)
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{
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return pd_to_blkg(&iolat->pd);
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}
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static inline void latency_stat_init(struct iolatency_grp *iolat,
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struct latency_stat *stat)
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{
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if (iolat->ssd) {
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stat->ps.total = 0;
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stat->ps.missed = 0;
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} else
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blk_rq_stat_init(&stat->rqs);
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}
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static inline void latency_stat_sum(struct iolatency_grp *iolat,
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struct latency_stat *sum,
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struct latency_stat *stat)
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{
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if (iolat->ssd) {
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sum->ps.total += stat->ps.total;
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sum->ps.missed += stat->ps.missed;
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} else
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blk_rq_stat_sum(&sum->rqs, &stat->rqs);
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}
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static inline void latency_stat_record_time(struct iolatency_grp *iolat,
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u64 req_time)
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{
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struct latency_stat *stat = get_cpu_ptr(iolat->stats);
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if (iolat->ssd) {
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if (req_time >= iolat->min_lat_nsec)
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stat->ps.missed++;
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stat->ps.total++;
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} else
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blk_rq_stat_add(&stat->rqs, req_time);
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put_cpu_ptr(stat);
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}
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static inline bool latency_sum_ok(struct iolatency_grp *iolat,
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struct latency_stat *stat)
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{
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if (iolat->ssd) {
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u64 thresh = div64_u64(stat->ps.total, 10);
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thresh = max(thresh, 1ULL);
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return stat->ps.missed < thresh;
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}
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return stat->rqs.mean <= iolat->min_lat_nsec;
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}
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static inline u64 latency_stat_samples(struct iolatency_grp *iolat,
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struct latency_stat *stat)
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{
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if (iolat->ssd)
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return stat->ps.total;
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return stat->rqs.nr_samples;
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}
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static inline void iolat_update_total_lat_avg(struct iolatency_grp *iolat,
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struct latency_stat *stat)
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{
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int exp_idx;
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if (iolat->ssd)
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return;
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/*
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* calc_load() takes in a number stored in fixed point representation.
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* Because we are using this for IO time in ns, the values stored
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* are significantly larger than the FIXED_1 denominator (2048).
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* Therefore, rounding errors in the calculation are negligible and
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* can be ignored.
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*/
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exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
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div64_u64(iolat->cur_win_nsec,
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BLKIOLATENCY_EXP_BUCKET_SIZE));
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iolat->lat_avg = calc_load(iolat->lat_avg,
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iolatency_exp_factors[exp_idx],
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stat->rqs.mean);
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}
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static void iolat_cleanup_cb(struct rq_wait *rqw, void *private_data)
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{
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atomic_dec(&rqw->inflight);
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wake_up(&rqw->wait);
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}
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static bool iolat_acquire_inflight(struct rq_wait *rqw, void *private_data)
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{
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struct iolatency_grp *iolat = private_data;
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return rq_wait_inc_below(rqw, iolat->rq_depth.max_depth);
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}
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static void __blkcg_iolatency_throttle(struct rq_qos *rqos,
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struct iolatency_grp *iolat,
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bool issue_as_root,
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bool use_memdelay)
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{
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struct rq_wait *rqw = &iolat->rq_wait;
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unsigned use_delay = atomic_read(&lat_to_blkg(iolat)->use_delay);
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if (use_delay)
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blkcg_schedule_throttle(rqos->q, use_memdelay);
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/*
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* To avoid priority inversions we want to just take a slot if we are
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* issuing as root. If we're being killed off there's no point in
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* delaying things, we may have been killed by OOM so throttling may
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* make recovery take even longer, so just let the IO's through so the
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* task can go away.
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*/
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if (issue_as_root || fatal_signal_pending(current)) {
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atomic_inc(&rqw->inflight);
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return;
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}
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rq_qos_wait(rqw, iolat, iolat_acquire_inflight, iolat_cleanup_cb);
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}
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#define SCALE_DOWN_FACTOR 2
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#define SCALE_UP_FACTOR 4
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static inline unsigned long scale_amount(unsigned long qd, bool up)
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{
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return max(up ? qd >> SCALE_UP_FACTOR : qd >> SCALE_DOWN_FACTOR, 1UL);
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}
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/*
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* We scale the qd down faster than we scale up, so we need to use this helper
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* to adjust the scale_cookie accordingly so we don't prematurely get
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* scale_cookie at DEFAULT_SCALE_COOKIE and unthrottle too much.
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*
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* Each group has their own local copy of the last scale cookie they saw, so if
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* the global scale cookie goes up or down they know which way they need to go
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* based on their last knowledge of it.
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*/
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static void scale_cookie_change(struct blk_iolatency *blkiolat,
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struct child_latency_info *lat_info,
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bool up)
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{
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unsigned long qd = blkiolat->rqos.q->nr_requests;
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unsigned long scale = scale_amount(qd, up);
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unsigned long old = atomic_read(&lat_info->scale_cookie);
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unsigned long max_scale = qd << 1;
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unsigned long diff = 0;
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if (old < DEFAULT_SCALE_COOKIE)
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diff = DEFAULT_SCALE_COOKIE - old;
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if (up) {
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if (scale + old > DEFAULT_SCALE_COOKIE)
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atomic_set(&lat_info->scale_cookie,
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DEFAULT_SCALE_COOKIE);
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else if (diff > qd)
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atomic_inc(&lat_info->scale_cookie);
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else
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atomic_add(scale, &lat_info->scale_cookie);
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} else {
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/*
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* We don't want to dig a hole so deep that it takes us hours to
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* dig out of it. Just enough that we don't throttle/unthrottle
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* with jagged workloads but can still unthrottle once pressure
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* has sufficiently dissipated.
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*/
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if (diff > qd) {
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if (diff < max_scale)
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atomic_dec(&lat_info->scale_cookie);
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} else {
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atomic_sub(scale, &lat_info->scale_cookie);
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}
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}
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}
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/*
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* Change the queue depth of the iolatency_grp. We add/subtract 1/16th of the
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* queue depth at a time so we don't get wild swings and hopefully dial in to
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* fairer distribution of the overall queue depth.
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*/
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static void scale_change(struct iolatency_grp *iolat, bool up)
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{
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unsigned long qd = iolat->blkiolat->rqos.q->nr_requests;
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unsigned long scale = scale_amount(qd, up);
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unsigned long old = iolat->rq_depth.max_depth;
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if (old > qd)
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old = qd;
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if (up) {
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if (old == 1 && blkcg_unuse_delay(lat_to_blkg(iolat)))
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return;
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if (old < qd) {
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old += scale;
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old = min(old, qd);
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iolat->rq_depth.max_depth = old;
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wake_up_all(&iolat->rq_wait.wait);
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}
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} else {
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old >>= 1;
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iolat->rq_depth.max_depth = max(old, 1UL);
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}
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}
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/* Check our parent and see if the scale cookie has changed. */
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static void check_scale_change(struct iolatency_grp *iolat)
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{
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struct iolatency_grp *parent;
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struct child_latency_info *lat_info;
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unsigned int cur_cookie;
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unsigned int our_cookie = atomic_read(&iolat->scale_cookie);
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u64 scale_lat;
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unsigned int old;
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int direction = 0;
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if (lat_to_blkg(iolat)->parent == NULL)
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return;
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parent = blkg_to_lat(lat_to_blkg(iolat)->parent);
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if (!parent)
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return;
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lat_info = &parent->child_lat;
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cur_cookie = atomic_read(&lat_info->scale_cookie);
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scale_lat = READ_ONCE(lat_info->scale_lat);
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if (cur_cookie < our_cookie)
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direction = -1;
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else if (cur_cookie > our_cookie)
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direction = 1;
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else
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return;
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old = atomic_cmpxchg(&iolat->scale_cookie, our_cookie, cur_cookie);
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/* Somebody beat us to the punch, just bail. */
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if (old != our_cookie)
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return;
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if (direction < 0 && iolat->min_lat_nsec) {
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u64 samples_thresh;
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if (!scale_lat || iolat->min_lat_nsec <= scale_lat)
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return;
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/*
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* Sometimes high priority groups are their own worst enemy, so
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* instead of taking it out on some poor other group that did 5%
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* or less of the IO's for the last summation just skip this
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* scale down event.
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*/
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samples_thresh = lat_info->nr_samples * 5;
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samples_thresh = max(1ULL, div64_u64(samples_thresh, 100));
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if (iolat->nr_samples <= samples_thresh)
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return;
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}
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/* We're as low as we can go. */
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if (iolat->rq_depth.max_depth == 1 && direction < 0) {
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blkcg_use_delay(lat_to_blkg(iolat));
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return;
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}
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/* We're back to the default cookie, unthrottle all the things. */
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if (cur_cookie == DEFAULT_SCALE_COOKIE) {
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blkcg_clear_delay(lat_to_blkg(iolat));
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iolat->rq_depth.max_depth = UINT_MAX;
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wake_up_all(&iolat->rq_wait.wait);
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return;
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}
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scale_change(iolat, direction > 0);
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}
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static void blkcg_iolatency_throttle(struct rq_qos *rqos, struct bio *bio)
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{
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struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
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struct blkcg_gq *blkg = bio->bi_blkg;
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bool issue_as_root = bio_issue_as_root_blkg(bio);
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if (!blk_iolatency_enabled(blkiolat))
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return;
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while (blkg && blkg->parent) {
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struct iolatency_grp *iolat = blkg_to_lat(blkg);
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if (!iolat) {
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blkg = blkg->parent;
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continue;
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}
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check_scale_change(iolat);
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__blkcg_iolatency_throttle(rqos, iolat, issue_as_root,
|
|
(bio->bi_opf & REQ_SWAP) == REQ_SWAP);
|
|
blkg = blkg->parent;
|
|
}
|
|
if (!timer_pending(&blkiolat->timer))
|
|
mod_timer(&blkiolat->timer, jiffies + HZ);
|
|
}
|
|
|
|
static void iolatency_record_time(struct iolatency_grp *iolat,
|
|
struct bio_issue *issue, u64 now,
|
|
bool issue_as_root)
|
|
{
|
|
u64 start = bio_issue_time(issue);
|
|
u64 req_time;
|
|
|
|
/*
|
|
* Have to do this so we are truncated to the correct time that our
|
|
* issue is truncated to.
|
|
*/
|
|
now = __bio_issue_time(now);
|
|
|
|
if (now <= start)
|
|
return;
|
|
|
|
req_time = now - start;
|
|
|
|
/*
|
|
* We don't want to count issue_as_root bio's in the cgroups latency
|
|
* statistics as it could skew the numbers downwards.
|
|
*/
|
|
if (unlikely(issue_as_root && iolat->rq_depth.max_depth != UINT_MAX)) {
|
|
u64 sub = iolat->min_lat_nsec;
|
|
if (req_time < sub)
|
|
blkcg_add_delay(lat_to_blkg(iolat), now, sub - req_time);
|
|
return;
|
|
}
|
|
|
|
latency_stat_record_time(iolat, req_time);
|
|
}
|
|
|
|
#define BLKIOLATENCY_MIN_ADJUST_TIME (500 * NSEC_PER_MSEC)
|
|
#define BLKIOLATENCY_MIN_GOOD_SAMPLES 5
|
|
|
|
static void iolatency_check_latencies(struct iolatency_grp *iolat, u64 now)
|
|
{
|
|
struct blkcg_gq *blkg = lat_to_blkg(iolat);
|
|
struct iolatency_grp *parent;
|
|
struct child_latency_info *lat_info;
|
|
struct latency_stat stat;
|
|
unsigned long flags;
|
|
int cpu;
|
|
|
|
latency_stat_init(iolat, &stat);
|
|
preempt_disable();
|
|
for_each_online_cpu(cpu) {
|
|
struct latency_stat *s;
|
|
s = per_cpu_ptr(iolat->stats, cpu);
|
|
latency_stat_sum(iolat, &stat, s);
|
|
latency_stat_init(iolat, s);
|
|
}
|
|
preempt_enable();
|
|
|
|
parent = blkg_to_lat(blkg->parent);
|
|
if (!parent)
|
|
return;
|
|
|
|
lat_info = &parent->child_lat;
|
|
|
|
iolat_update_total_lat_avg(iolat, &stat);
|
|
|
|
/* Everything is ok and we don't need to adjust the scale. */
|
|
if (latency_sum_ok(iolat, &stat) &&
|
|
atomic_read(&lat_info->scale_cookie) == DEFAULT_SCALE_COOKIE)
|
|
return;
|
|
|
|
/* Somebody beat us to the punch, just bail. */
|
|
spin_lock_irqsave(&lat_info->lock, flags);
|
|
|
|
latency_stat_sum(iolat, &iolat->cur_stat, &stat);
|
|
lat_info->nr_samples -= iolat->nr_samples;
|
|
lat_info->nr_samples += latency_stat_samples(iolat, &iolat->cur_stat);
|
|
iolat->nr_samples = latency_stat_samples(iolat, &iolat->cur_stat);
|
|
|
|
if ((lat_info->last_scale_event >= now ||
|
|
now - lat_info->last_scale_event < BLKIOLATENCY_MIN_ADJUST_TIME))
|
|
goto out;
|
|
|
|
if (latency_sum_ok(iolat, &iolat->cur_stat) &&
|
|
latency_sum_ok(iolat, &stat)) {
|
|
if (latency_stat_samples(iolat, &iolat->cur_stat) <
|
|
BLKIOLATENCY_MIN_GOOD_SAMPLES)
|
|
goto out;
|
|
if (lat_info->scale_grp == iolat) {
|
|
lat_info->last_scale_event = now;
|
|
scale_cookie_change(iolat->blkiolat, lat_info, true);
|
|
}
|
|
} else if (lat_info->scale_lat == 0 ||
|
|
lat_info->scale_lat >= iolat->min_lat_nsec) {
|
|
lat_info->last_scale_event = now;
|
|
if (!lat_info->scale_grp ||
|
|
lat_info->scale_lat > iolat->min_lat_nsec) {
|
|
WRITE_ONCE(lat_info->scale_lat, iolat->min_lat_nsec);
|
|
lat_info->scale_grp = iolat;
|
|
}
|
|
scale_cookie_change(iolat->blkiolat, lat_info, false);
|
|
}
|
|
latency_stat_init(iolat, &iolat->cur_stat);
|
|
out:
|
|
spin_unlock_irqrestore(&lat_info->lock, flags);
|
|
}
|
|
|
|
static void blkcg_iolatency_done_bio(struct rq_qos *rqos, struct bio *bio)
|
|
{
|
|
struct blkcg_gq *blkg;
|
|
struct rq_wait *rqw;
|
|
struct iolatency_grp *iolat;
|
|
u64 window_start;
|
|
u64 now = ktime_to_ns(ktime_get());
|
|
bool issue_as_root = bio_issue_as_root_blkg(bio);
|
|
bool enabled = false;
|
|
int inflight = 0;
|
|
|
|
blkg = bio->bi_blkg;
|
|
if (!blkg || !bio_flagged(bio, BIO_TRACKED))
|
|
return;
|
|
|
|
iolat = blkg_to_lat(bio->bi_blkg);
|
|
if (!iolat)
|
|
return;
|
|
|
|
enabled = blk_iolatency_enabled(iolat->blkiolat);
|
|
if (!enabled)
|
|
return;
|
|
|
|
while (blkg && blkg->parent) {
|
|
iolat = blkg_to_lat(blkg);
|
|
if (!iolat) {
|
|
blkg = blkg->parent;
|
|
continue;
|
|
}
|
|
rqw = &iolat->rq_wait;
|
|
|
|
inflight = atomic_dec_return(&rqw->inflight);
|
|
WARN_ON_ONCE(inflight < 0);
|
|
/*
|
|
* If bi_status is BLK_STS_AGAIN, the bio wasn't actually
|
|
* submitted, so do not account for it.
|
|
*/
|
|
if (iolat->min_lat_nsec && bio->bi_status != BLK_STS_AGAIN) {
|
|
iolatency_record_time(iolat, &bio->bi_issue, now,
|
|
issue_as_root);
|
|
window_start = atomic64_read(&iolat->window_start);
|
|
if (now > window_start &&
|
|
(now - window_start) >= iolat->cur_win_nsec) {
|
|
if (atomic64_cmpxchg(&iolat->window_start,
|
|
window_start, now) == window_start)
|
|
iolatency_check_latencies(iolat, now);
|
|
}
|
|
}
|
|
wake_up(&rqw->wait);
|
|
blkg = blkg->parent;
|
|
}
|
|
}
|
|
|
|
static void blkcg_iolatency_exit(struct rq_qos *rqos)
|
|
{
|
|
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
|
|
|
|
del_timer_sync(&blkiolat->timer);
|
|
blkcg_deactivate_policy(rqos->q, &blkcg_policy_iolatency);
|
|
kfree(blkiolat);
|
|
}
|
|
|
|
static struct rq_qos_ops blkcg_iolatency_ops = {
|
|
.throttle = blkcg_iolatency_throttle,
|
|
.done_bio = blkcg_iolatency_done_bio,
|
|
.exit = blkcg_iolatency_exit,
|
|
};
|
|
|
|
static void blkiolatency_timer_fn(struct timer_list *t)
|
|
{
|
|
struct blk_iolatency *blkiolat = from_timer(blkiolat, t, timer);
|
|
struct blkcg_gq *blkg;
|
|
struct cgroup_subsys_state *pos_css;
|
|
u64 now = ktime_to_ns(ktime_get());
|
|
|
|
rcu_read_lock();
|
|
blkg_for_each_descendant_pre(blkg, pos_css,
|
|
blkiolat->rqos.q->root_blkg) {
|
|
struct iolatency_grp *iolat;
|
|
struct child_latency_info *lat_info;
|
|
unsigned long flags;
|
|
u64 cookie;
|
|
|
|
/*
|
|
* We could be exiting, don't access the pd unless we have a
|
|
* ref on the blkg.
|
|
*/
|
|
if (!blkg_tryget(blkg))
|
|
continue;
|
|
|
|
iolat = blkg_to_lat(blkg);
|
|
if (!iolat)
|
|
goto next;
|
|
|
|
lat_info = &iolat->child_lat;
|
|
cookie = atomic_read(&lat_info->scale_cookie);
|
|
|
|
if (cookie >= DEFAULT_SCALE_COOKIE)
|
|
goto next;
|
|
|
|
spin_lock_irqsave(&lat_info->lock, flags);
|
|
if (lat_info->last_scale_event >= now)
|
|
goto next_lock;
|
|
|
|
/*
|
|
* We scaled down but don't have a scale_grp, scale up and carry
|
|
* on.
|
|
*/
|
|
if (lat_info->scale_grp == NULL) {
|
|
scale_cookie_change(iolat->blkiolat, lat_info, true);
|
|
goto next_lock;
|
|
}
|
|
|
|
/*
|
|
* It's been 5 seconds since our last scale event, clear the
|
|
* scale grp in case the group that needed the scale down isn't
|
|
* doing any IO currently.
|
|
*/
|
|
if (now - lat_info->last_scale_event >=
|
|
((u64)NSEC_PER_SEC * 5))
|
|
lat_info->scale_grp = NULL;
|
|
next_lock:
|
|
spin_unlock_irqrestore(&lat_info->lock, flags);
|
|
next:
|
|
blkg_put(blkg);
|
|
}
|
|
rcu_read_unlock();
|
|
}
|
|
|
|
int blk_iolatency_init(struct request_queue *q)
|
|
{
|
|
struct blk_iolatency *blkiolat;
|
|
struct rq_qos *rqos;
|
|
int ret;
|
|
|
|
blkiolat = kzalloc(sizeof(*blkiolat), GFP_KERNEL);
|
|
if (!blkiolat)
|
|
return -ENOMEM;
|
|
|
|
rqos = &blkiolat->rqos;
|
|
rqos->id = RQ_QOS_LATENCY;
|
|
rqos->ops = &blkcg_iolatency_ops;
|
|
rqos->q = q;
|
|
|
|
rq_qos_add(q, rqos);
|
|
|
|
ret = blkcg_activate_policy(q, &blkcg_policy_iolatency);
|
|
if (ret) {
|
|
rq_qos_del(q, rqos);
|
|
kfree(blkiolat);
|
|
return ret;
|
|
}
|
|
|
|
timer_setup(&blkiolat->timer, blkiolatency_timer_fn, 0);
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* return 1 for enabling iolatency, return -1 for disabling iolatency, otherwise
|
|
* return 0.
|
|
*/
|
|
static int iolatency_set_min_lat_nsec(struct blkcg_gq *blkg, u64 val)
|
|
{
|
|
struct iolatency_grp *iolat = blkg_to_lat(blkg);
|
|
u64 oldval = iolat->min_lat_nsec;
|
|
|
|
iolat->min_lat_nsec = val;
|
|
iolat->cur_win_nsec = max_t(u64, val << 4, BLKIOLATENCY_MIN_WIN_SIZE);
|
|
iolat->cur_win_nsec = min_t(u64, iolat->cur_win_nsec,
|
|
BLKIOLATENCY_MAX_WIN_SIZE);
|
|
|
|
if (!oldval && val)
|
|
return 1;
|
|
if (oldval && !val) {
|
|
blkcg_clear_delay(blkg);
|
|
return -1;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static void iolatency_clear_scaling(struct blkcg_gq *blkg)
|
|
{
|
|
if (blkg->parent) {
|
|
struct iolatency_grp *iolat = blkg_to_lat(blkg->parent);
|
|
struct child_latency_info *lat_info;
|
|
if (!iolat)
|
|
return;
|
|
|
|
lat_info = &iolat->child_lat;
|
|
spin_lock(&lat_info->lock);
|
|
atomic_set(&lat_info->scale_cookie, DEFAULT_SCALE_COOKIE);
|
|
lat_info->last_scale_event = 0;
|
|
lat_info->scale_grp = NULL;
|
|
lat_info->scale_lat = 0;
|
|
spin_unlock(&lat_info->lock);
|
|
}
|
|
}
|
|
|
|
static ssize_t iolatency_set_limit(struct kernfs_open_file *of, char *buf,
|
|
size_t nbytes, loff_t off)
|
|
{
|
|
struct blkcg *blkcg = css_to_blkcg(of_css(of));
|
|
struct blkcg_gq *blkg;
|
|
struct blkg_conf_ctx ctx;
|
|
struct iolatency_grp *iolat;
|
|
char *p, *tok;
|
|
u64 lat_val = 0;
|
|
u64 oldval;
|
|
int ret;
|
|
int enable = 0;
|
|
|
|
ret = blkg_conf_prep(blkcg, &blkcg_policy_iolatency, buf, &ctx);
|
|
if (ret)
|
|
return ret;
|
|
|
|
iolat = blkg_to_lat(ctx.blkg);
|
|
p = ctx.body;
|
|
|
|
ret = -EINVAL;
|
|
while ((tok = strsep(&p, " "))) {
|
|
char key[16];
|
|
char val[21]; /* 18446744073709551616 */
|
|
|
|
if (sscanf(tok, "%15[^=]=%20s", key, val) != 2)
|
|
goto out;
|
|
|
|
if (!strcmp(key, "target")) {
|
|
u64 v;
|
|
|
|
if (!strcmp(val, "max"))
|
|
lat_val = 0;
|
|
else if (sscanf(val, "%llu", &v) == 1)
|
|
lat_val = v * NSEC_PER_USEC;
|
|
else
|
|
goto out;
|
|
} else {
|
|
goto out;
|
|
}
|
|
}
|
|
|
|
/* Walk up the tree to see if our new val is lower than it should be. */
|
|
blkg = ctx.blkg;
|
|
oldval = iolat->min_lat_nsec;
|
|
|
|
enable = iolatency_set_min_lat_nsec(blkg, lat_val);
|
|
if (enable) {
|
|
WARN_ON_ONCE(!blk_get_queue(blkg->q));
|
|
blkg_get(blkg);
|
|
}
|
|
|
|
if (oldval != iolat->min_lat_nsec) {
|
|
iolatency_clear_scaling(blkg);
|
|
}
|
|
|
|
ret = 0;
|
|
out:
|
|
blkg_conf_finish(&ctx);
|
|
if (ret == 0 && enable) {
|
|
struct iolatency_grp *tmp = blkg_to_lat(blkg);
|
|
struct blk_iolatency *blkiolat = tmp->blkiolat;
|
|
|
|
blk_mq_freeze_queue(blkg->q);
|
|
|
|
if (enable == 1)
|
|
atomic_inc(&blkiolat->enabled);
|
|
else if (enable == -1)
|
|
atomic_dec(&blkiolat->enabled);
|
|
else
|
|
WARN_ON_ONCE(1);
|
|
|
|
blk_mq_unfreeze_queue(blkg->q);
|
|
|
|
blkg_put(blkg);
|
|
blk_put_queue(blkg->q);
|
|
}
|
|
return ret ?: nbytes;
|
|
}
|
|
|
|
static u64 iolatency_prfill_limit(struct seq_file *sf,
|
|
struct blkg_policy_data *pd, int off)
|
|
{
|
|
struct iolatency_grp *iolat = pd_to_lat(pd);
|
|
const char *dname = blkg_dev_name(pd->blkg);
|
|
|
|
if (!dname || !iolat->min_lat_nsec)
|
|
return 0;
|
|
seq_printf(sf, "%s target=%llu\n",
|
|
dname, div_u64(iolat->min_lat_nsec, NSEC_PER_USEC));
|
|
return 0;
|
|
}
|
|
|
|
static int iolatency_print_limit(struct seq_file *sf, void *v)
|
|
{
|
|
blkcg_print_blkgs(sf, css_to_blkcg(seq_css(sf)),
|
|
iolatency_prfill_limit,
|
|
&blkcg_policy_iolatency, seq_cft(sf)->private, false);
|
|
return 0;
|
|
}
|
|
|
|
static size_t iolatency_ssd_stat(struct iolatency_grp *iolat, char *buf,
|
|
size_t size)
|
|
{
|
|
struct latency_stat stat;
|
|
int cpu;
|
|
|
|
latency_stat_init(iolat, &stat);
|
|
preempt_disable();
|
|
for_each_online_cpu(cpu) {
|
|
struct latency_stat *s;
|
|
s = per_cpu_ptr(iolat->stats, cpu);
|
|
latency_stat_sum(iolat, &stat, s);
|
|
}
|
|
preempt_enable();
|
|
|
|
if (iolat->rq_depth.max_depth == UINT_MAX)
|
|
return scnprintf(buf, size, " missed=%llu total=%llu depth=max",
|
|
(unsigned long long)stat.ps.missed,
|
|
(unsigned long long)stat.ps.total);
|
|
return scnprintf(buf, size, " missed=%llu total=%llu depth=%u",
|
|
(unsigned long long)stat.ps.missed,
|
|
(unsigned long long)stat.ps.total,
|
|
iolat->rq_depth.max_depth);
|
|
}
|
|
|
|
static size_t iolatency_pd_stat(struct blkg_policy_data *pd, char *buf,
|
|
size_t size)
|
|
{
|
|
struct iolatency_grp *iolat = pd_to_lat(pd);
|
|
unsigned long long avg_lat;
|
|
unsigned long long cur_win;
|
|
|
|
if (!blkcg_debug_stats)
|
|
return 0;
|
|
|
|
if (iolat->ssd)
|
|
return iolatency_ssd_stat(iolat, buf, size);
|
|
|
|
avg_lat = div64_u64(iolat->lat_avg, NSEC_PER_USEC);
|
|
cur_win = div64_u64(iolat->cur_win_nsec, NSEC_PER_MSEC);
|
|
if (iolat->rq_depth.max_depth == UINT_MAX)
|
|
return scnprintf(buf, size, " depth=max avg_lat=%llu win=%llu",
|
|
avg_lat, cur_win);
|
|
|
|
return scnprintf(buf, size, " depth=%u avg_lat=%llu win=%llu",
|
|
iolat->rq_depth.max_depth, avg_lat, cur_win);
|
|
}
|
|
|
|
|
|
static struct blkg_policy_data *iolatency_pd_alloc(gfp_t gfp,
|
|
struct request_queue *q,
|
|
struct blkcg *blkcg)
|
|
{
|
|
struct iolatency_grp *iolat;
|
|
|
|
iolat = kzalloc_node(sizeof(*iolat), gfp, q->node);
|
|
if (!iolat)
|
|
return NULL;
|
|
iolat->stats = __alloc_percpu_gfp(sizeof(struct latency_stat),
|
|
__alignof__(struct latency_stat), gfp);
|
|
if (!iolat->stats) {
|
|
kfree(iolat);
|
|
return NULL;
|
|
}
|
|
return &iolat->pd;
|
|
}
|
|
|
|
static void iolatency_pd_init(struct blkg_policy_data *pd)
|
|
{
|
|
struct iolatency_grp *iolat = pd_to_lat(pd);
|
|
struct blkcg_gq *blkg = lat_to_blkg(iolat);
|
|
struct rq_qos *rqos = blkcg_rq_qos(blkg->q);
|
|
struct blk_iolatency *blkiolat = BLKIOLATENCY(rqos);
|
|
u64 now = ktime_to_ns(ktime_get());
|
|
int cpu;
|
|
|
|
if (blk_queue_nonrot(blkg->q))
|
|
iolat->ssd = true;
|
|
else
|
|
iolat->ssd = false;
|
|
|
|
for_each_possible_cpu(cpu) {
|
|
struct latency_stat *stat;
|
|
stat = per_cpu_ptr(iolat->stats, cpu);
|
|
latency_stat_init(iolat, stat);
|
|
}
|
|
|
|
latency_stat_init(iolat, &iolat->cur_stat);
|
|
rq_wait_init(&iolat->rq_wait);
|
|
spin_lock_init(&iolat->child_lat.lock);
|
|
iolat->rq_depth.queue_depth = blkg->q->nr_requests;
|
|
iolat->rq_depth.max_depth = UINT_MAX;
|
|
iolat->rq_depth.default_depth = iolat->rq_depth.queue_depth;
|
|
iolat->blkiolat = blkiolat;
|
|
iolat->cur_win_nsec = 100 * NSEC_PER_MSEC;
|
|
atomic64_set(&iolat->window_start, now);
|
|
|
|
/*
|
|
* We init things in list order, so the pd for the parent may not be
|
|
* init'ed yet for whatever reason.
|
|
*/
|
|
if (blkg->parent && blkg_to_pd(blkg->parent, &blkcg_policy_iolatency)) {
|
|
struct iolatency_grp *parent = blkg_to_lat(blkg->parent);
|
|
atomic_set(&iolat->scale_cookie,
|
|
atomic_read(&parent->child_lat.scale_cookie));
|
|
} else {
|
|
atomic_set(&iolat->scale_cookie, DEFAULT_SCALE_COOKIE);
|
|
}
|
|
|
|
atomic_set(&iolat->child_lat.scale_cookie, DEFAULT_SCALE_COOKIE);
|
|
}
|
|
|
|
static void iolatency_pd_offline(struct blkg_policy_data *pd)
|
|
{
|
|
struct iolatency_grp *iolat = pd_to_lat(pd);
|
|
struct blkcg_gq *blkg = lat_to_blkg(iolat);
|
|
struct blk_iolatency *blkiolat = iolat->blkiolat;
|
|
int ret;
|
|
|
|
ret = iolatency_set_min_lat_nsec(blkg, 0);
|
|
if (ret == 1)
|
|
atomic_inc(&blkiolat->enabled);
|
|
if (ret == -1)
|
|
atomic_dec(&blkiolat->enabled);
|
|
iolatency_clear_scaling(blkg);
|
|
}
|
|
|
|
static void iolatency_pd_free(struct blkg_policy_data *pd)
|
|
{
|
|
struct iolatency_grp *iolat = pd_to_lat(pd);
|
|
free_percpu(iolat->stats);
|
|
kfree(iolat);
|
|
}
|
|
|
|
static struct cftype iolatency_files[] = {
|
|
{
|
|
.name = "latency",
|
|
.flags = CFTYPE_NOT_ON_ROOT,
|
|
.seq_show = iolatency_print_limit,
|
|
.write = iolatency_set_limit,
|
|
},
|
|
{}
|
|
};
|
|
|
|
static struct blkcg_policy blkcg_policy_iolatency = {
|
|
.dfl_cftypes = iolatency_files,
|
|
.pd_alloc_fn = iolatency_pd_alloc,
|
|
.pd_init_fn = iolatency_pd_init,
|
|
.pd_offline_fn = iolatency_pd_offline,
|
|
.pd_free_fn = iolatency_pd_free,
|
|
.pd_stat_fn = iolatency_pd_stat,
|
|
};
|
|
|
|
static int __init iolatency_init(void)
|
|
{
|
|
return blkcg_policy_register(&blkcg_policy_iolatency);
|
|
}
|
|
|
|
static void __exit iolatency_exit(void)
|
|
{
|
|
return blkcg_policy_unregister(&blkcg_policy_iolatency);
|
|
}
|
|
|
|
module_init(iolatency_init);
|
|
module_exit(iolatency_exit);
|