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![Jianchao Wang](/assets/img/avatar_default.png)
Currently, kyber is very unfriendly with merging. kyber depends on ctx rq_list to do merging, however, most of time, it will not leave any requests in ctx rq_list. This is because even if tokens of one domain is used up, kyber will try to dispatch requests from other domain and flush the rq_list there. To improve this, we setup kyber_ctx_queue (kcq) which is similar with ctx, but it has rq_lists for different domain and build same mapping between kcq and khd as the ctx & hctx. Then we could merge, insert and dispatch for different domains separately. At the same time, only flush the rq_list of kcq when get domain token successfully. Then if one domain token is used up, the requests could be left in the rq_list of that domain and maybe merged with following io. Following is my test result on machine with 8 cores and NVMe card INTEL SSDPEKKR128G7 fio size=256m ioengine=libaio iodepth=64 direct=1 numjobs=8 seq/random +------+---------------------------------------------------------------+ |patch?| bw(MB/s) | iops | slat(usec) | clat(usec) | merge | +----------------------------------------------------------------------+ | w/o | 606/612 | 151k/153k | 6.89/7.03 | 3349.21/3305.40 | 0/0 | +----------------------------------------------------------------------+ | w/ | 1083/616 | 277k/154k | 4.93/6.95 | 1830.62/3279.95 | 223k/3k | +----------------------------------------------------------------------+ When set numjobs to 16, the bw and iops could reach 1662MB/s and 425k on my platform. Signed-off-by: Jianchao Wang <jianchao.w.wang@oracle.com> Tested-by: Holger Hoffstätte <holger@applied-asynchrony.com> Reviewed-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Jens Axboe <axboe@kernel.dk>
995 lines
25 KiB
C
995 lines
25 KiB
C
/*
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* The Kyber I/O scheduler. Controls latency by throttling queue depths using
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* scalable techniques.
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*
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* Copyright (C) 2017 Facebook
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public
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* License v2 as published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <https://www.gnu.org/licenses/>.
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*/
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#include <linux/kernel.h>
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#include <linux/blkdev.h>
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#include <linux/blk-mq.h>
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#include <linux/elevator.h>
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#include <linux/module.h>
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#include <linux/sbitmap.h>
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#include "blk.h"
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#include "blk-mq.h"
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#include "blk-mq-debugfs.h"
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#include "blk-mq-sched.h"
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#include "blk-mq-tag.h"
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#include "blk-stat.h"
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/* Scheduling domains. */
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enum {
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KYBER_READ,
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KYBER_SYNC_WRITE,
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KYBER_OTHER, /* Async writes, discard, etc. */
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KYBER_NUM_DOMAINS,
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};
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enum {
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KYBER_MIN_DEPTH = 256,
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/*
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* In order to prevent starvation of synchronous requests by a flood of
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* asynchronous requests, we reserve 25% of requests for synchronous
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* operations.
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*/
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KYBER_ASYNC_PERCENT = 75,
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};
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/*
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* Initial device-wide depths for each scheduling domain.
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*
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* Even for fast devices with lots of tags like NVMe, you can saturate
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* the device with only a fraction of the maximum possible queue depth.
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* So, we cap these to a reasonable value.
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*/
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static const unsigned int kyber_depth[] = {
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[KYBER_READ] = 256,
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[KYBER_SYNC_WRITE] = 128,
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[KYBER_OTHER] = 64,
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};
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/*
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* Scheduling domain batch sizes. We favor reads.
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*/
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static const unsigned int kyber_batch_size[] = {
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[KYBER_READ] = 16,
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[KYBER_SYNC_WRITE] = 8,
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[KYBER_OTHER] = 8,
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};
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/*
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* There is a same mapping between ctx & hctx and kcq & khd,
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* we use request->mq_ctx->index_hw to index the kcq in khd.
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*/
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struct kyber_ctx_queue {
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/*
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* Used to ensure operations on rq_list and kcq_map to be an atmoic one.
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* Also protect the rqs on rq_list when merge.
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*/
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spinlock_t lock;
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struct list_head rq_list[KYBER_NUM_DOMAINS];
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} ____cacheline_aligned_in_smp;
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struct kyber_queue_data {
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struct request_queue *q;
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struct blk_stat_callback *cb;
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/*
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* The device is divided into multiple scheduling domains based on the
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* request type. Each domain has a fixed number of in-flight requests of
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* that type device-wide, limited by these tokens.
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*/
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struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
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/*
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* Async request percentage, converted to per-word depth for
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* sbitmap_get_shallow().
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*/
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unsigned int async_depth;
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/* Target latencies in nanoseconds. */
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u64 read_lat_nsec, write_lat_nsec;
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};
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struct kyber_hctx_data {
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spinlock_t lock;
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struct list_head rqs[KYBER_NUM_DOMAINS];
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unsigned int cur_domain;
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unsigned int batching;
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struct kyber_ctx_queue *kcqs;
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struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
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wait_queue_entry_t domain_wait[KYBER_NUM_DOMAINS];
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struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
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atomic_t wait_index[KYBER_NUM_DOMAINS];
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};
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static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
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void *key);
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static unsigned int kyber_sched_domain(unsigned int op)
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{
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if ((op & REQ_OP_MASK) == REQ_OP_READ)
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return KYBER_READ;
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else if ((op & REQ_OP_MASK) == REQ_OP_WRITE && op_is_sync(op))
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return KYBER_SYNC_WRITE;
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else
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return KYBER_OTHER;
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}
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enum {
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NONE = 0,
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GOOD = 1,
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GREAT = 2,
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BAD = -1,
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AWFUL = -2,
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};
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#define IS_GOOD(status) ((status) > 0)
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#define IS_BAD(status) ((status) < 0)
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static int kyber_lat_status(struct blk_stat_callback *cb,
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unsigned int sched_domain, u64 target)
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{
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u64 latency;
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if (!cb->stat[sched_domain].nr_samples)
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return NONE;
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latency = cb->stat[sched_domain].mean;
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if (latency >= 2 * target)
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return AWFUL;
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else if (latency > target)
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return BAD;
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else if (latency <= target / 2)
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return GREAT;
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else /* (latency <= target) */
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return GOOD;
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}
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/*
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* Adjust the read or synchronous write depth given the status of reads and
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* writes. The goal is that the latencies of the two domains are fair (i.e., if
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* one is good, then the other is good).
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*/
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static void kyber_adjust_rw_depth(struct kyber_queue_data *kqd,
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unsigned int sched_domain, int this_status,
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int other_status)
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{
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unsigned int orig_depth, depth;
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/*
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* If this domain had no samples, or reads and writes are both good or
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* both bad, don't adjust the depth.
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*/
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if (this_status == NONE ||
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(IS_GOOD(this_status) && IS_GOOD(other_status)) ||
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(IS_BAD(this_status) && IS_BAD(other_status)))
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return;
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orig_depth = depth = kqd->domain_tokens[sched_domain].sb.depth;
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if (other_status == NONE) {
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depth++;
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} else {
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switch (this_status) {
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case GOOD:
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if (other_status == AWFUL)
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depth -= max(depth / 4, 1U);
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else
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depth -= max(depth / 8, 1U);
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break;
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case GREAT:
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if (other_status == AWFUL)
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depth /= 2;
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else
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depth -= max(depth / 4, 1U);
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break;
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case BAD:
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depth++;
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break;
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case AWFUL:
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if (other_status == GREAT)
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depth += 2;
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else
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depth++;
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break;
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}
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}
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depth = clamp(depth, 1U, kyber_depth[sched_domain]);
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if (depth != orig_depth)
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sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
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}
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/*
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* Adjust the depth of other requests given the status of reads and synchronous
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* writes. As long as either domain is doing fine, we don't throttle, but if
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* both domains are doing badly, we throttle heavily.
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*/
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static void kyber_adjust_other_depth(struct kyber_queue_data *kqd,
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int read_status, int write_status,
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bool have_samples)
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{
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unsigned int orig_depth, depth;
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int status;
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orig_depth = depth = kqd->domain_tokens[KYBER_OTHER].sb.depth;
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if (read_status == NONE && write_status == NONE) {
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depth += 2;
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} else if (have_samples) {
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if (read_status == NONE)
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status = write_status;
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else if (write_status == NONE)
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status = read_status;
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else
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status = max(read_status, write_status);
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switch (status) {
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case GREAT:
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depth += 2;
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break;
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case GOOD:
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depth++;
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break;
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case BAD:
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depth -= max(depth / 4, 1U);
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break;
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case AWFUL:
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depth /= 2;
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break;
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}
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}
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depth = clamp(depth, 1U, kyber_depth[KYBER_OTHER]);
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if (depth != orig_depth)
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sbitmap_queue_resize(&kqd->domain_tokens[KYBER_OTHER], depth);
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}
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/*
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* Apply heuristics for limiting queue depths based on gathered latency
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* statistics.
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*/
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static void kyber_stat_timer_fn(struct blk_stat_callback *cb)
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{
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struct kyber_queue_data *kqd = cb->data;
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int read_status, write_status;
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read_status = kyber_lat_status(cb, KYBER_READ, kqd->read_lat_nsec);
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write_status = kyber_lat_status(cb, KYBER_SYNC_WRITE, kqd->write_lat_nsec);
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kyber_adjust_rw_depth(kqd, KYBER_READ, read_status, write_status);
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kyber_adjust_rw_depth(kqd, KYBER_SYNC_WRITE, write_status, read_status);
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kyber_adjust_other_depth(kqd, read_status, write_status,
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cb->stat[KYBER_OTHER].nr_samples != 0);
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/*
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* Continue monitoring latencies if we aren't hitting the targets or
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* we're still throttling other requests.
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*/
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if (!blk_stat_is_active(kqd->cb) &&
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((IS_BAD(read_status) || IS_BAD(write_status) ||
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kqd->domain_tokens[KYBER_OTHER].sb.depth < kyber_depth[KYBER_OTHER])))
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blk_stat_activate_msecs(kqd->cb, 100);
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}
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static unsigned int kyber_sched_tags_shift(struct kyber_queue_data *kqd)
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{
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/*
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* All of the hardware queues have the same depth, so we can just grab
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* the shift of the first one.
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*/
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return kqd->q->queue_hw_ctx[0]->sched_tags->bitmap_tags.sb.shift;
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}
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static int kyber_bucket_fn(const struct request *rq)
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{
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return kyber_sched_domain(rq->cmd_flags);
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}
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static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
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{
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struct kyber_queue_data *kqd;
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unsigned int max_tokens;
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unsigned int shift;
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int ret = -ENOMEM;
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int i;
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kqd = kmalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
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if (!kqd)
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goto err;
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kqd->q = q;
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kqd->cb = blk_stat_alloc_callback(kyber_stat_timer_fn, kyber_bucket_fn,
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KYBER_NUM_DOMAINS, kqd);
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if (!kqd->cb)
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goto err_kqd;
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/*
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* The maximum number of tokens for any scheduling domain is at least
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* the queue depth of a single hardware queue. If the hardware doesn't
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* have many tags, still provide a reasonable number.
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*/
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max_tokens = max_t(unsigned int, q->tag_set->queue_depth,
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KYBER_MIN_DEPTH);
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
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WARN_ON(!kyber_depth[i]);
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WARN_ON(!kyber_batch_size[i]);
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ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
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max_tokens, -1, false, GFP_KERNEL,
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q->node);
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if (ret) {
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while (--i >= 0)
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sbitmap_queue_free(&kqd->domain_tokens[i]);
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goto err_cb;
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}
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sbitmap_queue_resize(&kqd->domain_tokens[i], kyber_depth[i]);
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}
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shift = kyber_sched_tags_shift(kqd);
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kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
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kqd->read_lat_nsec = 2000000ULL;
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kqd->write_lat_nsec = 10000000ULL;
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return kqd;
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err_cb:
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blk_stat_free_callback(kqd->cb);
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err_kqd:
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kfree(kqd);
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err:
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return ERR_PTR(ret);
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}
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static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)
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{
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struct kyber_queue_data *kqd;
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struct elevator_queue *eq;
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eq = elevator_alloc(q, e);
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if (!eq)
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return -ENOMEM;
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kqd = kyber_queue_data_alloc(q);
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if (IS_ERR(kqd)) {
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kobject_put(&eq->kobj);
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return PTR_ERR(kqd);
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}
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eq->elevator_data = kqd;
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q->elevator = eq;
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blk_stat_add_callback(q, kqd->cb);
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return 0;
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}
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static void kyber_exit_sched(struct elevator_queue *e)
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{
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struct kyber_queue_data *kqd = e->elevator_data;
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struct request_queue *q = kqd->q;
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int i;
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blk_stat_remove_callback(q, kqd->cb);
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for (i = 0; i < KYBER_NUM_DOMAINS; i++)
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sbitmap_queue_free(&kqd->domain_tokens[i]);
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blk_stat_free_callback(kqd->cb);
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kfree(kqd);
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}
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static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
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{
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unsigned int i;
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spin_lock_init(&kcq->lock);
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for (i = 0; i < KYBER_NUM_DOMAINS; i++)
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INIT_LIST_HEAD(&kcq->rq_list[i]);
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}
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static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
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{
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struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
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struct kyber_hctx_data *khd;
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int i;
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khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
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if (!khd)
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return -ENOMEM;
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khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
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sizeof(struct kyber_ctx_queue),
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GFP_KERNEL, hctx->numa_node);
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if (!khd->kcqs)
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goto err_khd;
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for (i = 0; i < hctx->nr_ctx; i++)
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kyber_ctx_queue_init(&khd->kcqs[i]);
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
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if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
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ilog2(8), GFP_KERNEL, hctx->numa_node)) {
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while (--i >= 0)
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sbitmap_free(&khd->kcq_map[i]);
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goto err_kcqs;
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}
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}
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spin_lock_init(&khd->lock);
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for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
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INIT_LIST_HEAD(&khd->rqs[i]);
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init_waitqueue_func_entry(&khd->domain_wait[i],
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kyber_domain_wake);
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khd->domain_wait[i].private = hctx;
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INIT_LIST_HEAD(&khd->domain_wait[i].entry);
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atomic_set(&khd->wait_index[i], 0);
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}
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khd->cur_domain = 0;
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khd->batching = 0;
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hctx->sched_data = khd;
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sbitmap_queue_min_shallow_depth(&hctx->sched_tags->bitmap_tags,
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kqd->async_depth);
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return 0;
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err_kcqs:
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kfree(khd->kcqs);
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err_khd:
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kfree(khd);
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return -ENOMEM;
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}
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static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
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{
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struct kyber_hctx_data *khd = hctx->sched_data;
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int i;
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for (i = 0; i < KYBER_NUM_DOMAINS; i++)
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sbitmap_free(&khd->kcq_map[i]);
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kfree(khd->kcqs);
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kfree(hctx->sched_data);
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}
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static int rq_get_domain_token(struct request *rq)
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{
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return (long)rq->elv.priv[0];
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}
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static void rq_set_domain_token(struct request *rq, int token)
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{
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rq->elv.priv[0] = (void *)(long)token;
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}
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static void rq_clear_domain_token(struct kyber_queue_data *kqd,
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struct request *rq)
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{
|
|
unsigned int sched_domain;
|
|
int nr;
|
|
|
|
nr = rq_get_domain_token(rq);
|
|
if (nr != -1) {
|
|
sched_domain = kyber_sched_domain(rq->cmd_flags);
|
|
sbitmap_queue_clear(&kqd->domain_tokens[sched_domain], nr,
|
|
rq->mq_ctx->cpu);
|
|
}
|
|
}
|
|
|
|
static void kyber_limit_depth(unsigned int op, struct blk_mq_alloc_data *data)
|
|
{
|
|
/*
|
|
* We use the scheduler tags as per-hardware queue queueing tokens.
|
|
* Async requests can be limited at this stage.
|
|
*/
|
|
if (!op_is_sync(op)) {
|
|
struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
|
|
|
|
data->shallow_depth = kqd->async_depth;
|
|
}
|
|
}
|
|
|
|
static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
|
|
{
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
struct blk_mq_ctx *ctx = blk_mq_get_ctx(hctx->queue);
|
|
struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw];
|
|
unsigned int sched_domain = kyber_sched_domain(bio->bi_opf);
|
|
struct list_head *rq_list = &kcq->rq_list[sched_domain];
|
|
bool merged;
|
|
|
|
spin_lock(&kcq->lock);
|
|
merged = blk_mq_bio_list_merge(hctx->queue, rq_list, bio);
|
|
spin_unlock(&kcq->lock);
|
|
blk_mq_put_ctx(ctx);
|
|
|
|
return merged;
|
|
}
|
|
|
|
static void kyber_prepare_request(struct request *rq, struct bio *bio)
|
|
{
|
|
rq_set_domain_token(rq, -1);
|
|
}
|
|
|
|
static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
|
|
struct list_head *rq_list, bool at_head)
|
|
{
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
struct request *rq, *next;
|
|
|
|
list_for_each_entry_safe(rq, next, rq_list, queuelist) {
|
|
unsigned int sched_domain = kyber_sched_domain(rq->cmd_flags);
|
|
struct kyber_ctx_queue *kcq = &khd->kcqs[rq->mq_ctx->index_hw];
|
|
struct list_head *head = &kcq->rq_list[sched_domain];
|
|
|
|
spin_lock(&kcq->lock);
|
|
if (at_head)
|
|
list_move(&rq->queuelist, head);
|
|
else
|
|
list_move_tail(&rq->queuelist, head);
|
|
sbitmap_set_bit(&khd->kcq_map[sched_domain],
|
|
rq->mq_ctx->index_hw);
|
|
blk_mq_sched_request_inserted(rq);
|
|
spin_unlock(&kcq->lock);
|
|
}
|
|
}
|
|
|
|
static void kyber_finish_request(struct request *rq)
|
|
{
|
|
struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
|
|
|
|
rq_clear_domain_token(kqd, rq);
|
|
}
|
|
|
|
static void kyber_completed_request(struct request *rq)
|
|
{
|
|
struct request_queue *q = rq->q;
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data;
|
|
unsigned int sched_domain;
|
|
u64 now, latency, target;
|
|
|
|
/*
|
|
* Check if this request met our latency goal. If not, quickly gather
|
|
* some statistics and start throttling.
|
|
*/
|
|
sched_domain = kyber_sched_domain(rq->cmd_flags);
|
|
switch (sched_domain) {
|
|
case KYBER_READ:
|
|
target = kqd->read_lat_nsec;
|
|
break;
|
|
case KYBER_SYNC_WRITE:
|
|
target = kqd->write_lat_nsec;
|
|
break;
|
|
default:
|
|
return;
|
|
}
|
|
|
|
/* If we are already monitoring latencies, don't check again. */
|
|
if (blk_stat_is_active(kqd->cb))
|
|
return;
|
|
|
|
now = ktime_get_ns();
|
|
if (now < rq->io_start_time_ns)
|
|
return;
|
|
|
|
latency = now - rq->io_start_time_ns;
|
|
|
|
if (latency > target)
|
|
blk_stat_activate_msecs(kqd->cb, 10);
|
|
}
|
|
|
|
struct flush_kcq_data {
|
|
struct kyber_hctx_data *khd;
|
|
unsigned int sched_domain;
|
|
struct list_head *list;
|
|
};
|
|
|
|
static bool flush_busy_kcq(struct sbitmap *sb, unsigned int bitnr, void *data)
|
|
{
|
|
struct flush_kcq_data *flush_data = data;
|
|
struct kyber_ctx_queue *kcq = &flush_data->khd->kcqs[bitnr];
|
|
|
|
spin_lock(&kcq->lock);
|
|
list_splice_tail_init(&kcq->rq_list[flush_data->sched_domain],
|
|
flush_data->list);
|
|
sbitmap_clear_bit(sb, bitnr);
|
|
spin_unlock(&kcq->lock);
|
|
|
|
return true;
|
|
}
|
|
|
|
static void kyber_flush_busy_kcqs(struct kyber_hctx_data *khd,
|
|
unsigned int sched_domain,
|
|
struct list_head *list)
|
|
{
|
|
struct flush_kcq_data data = {
|
|
.khd = khd,
|
|
.sched_domain = sched_domain,
|
|
.list = list,
|
|
};
|
|
|
|
sbitmap_for_each_set(&khd->kcq_map[sched_domain],
|
|
flush_busy_kcq, &data);
|
|
}
|
|
|
|
static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
|
|
void *key)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx = READ_ONCE(wait->private);
|
|
|
|
list_del_init(&wait->entry);
|
|
blk_mq_run_hw_queue(hctx, true);
|
|
return 1;
|
|
}
|
|
|
|
static int kyber_get_domain_token(struct kyber_queue_data *kqd,
|
|
struct kyber_hctx_data *khd,
|
|
struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
unsigned int sched_domain = khd->cur_domain;
|
|
struct sbitmap_queue *domain_tokens = &kqd->domain_tokens[sched_domain];
|
|
wait_queue_entry_t *wait = &khd->domain_wait[sched_domain];
|
|
struct sbq_wait_state *ws;
|
|
int nr;
|
|
|
|
nr = __sbitmap_queue_get(domain_tokens);
|
|
|
|
/*
|
|
* If we failed to get a domain token, make sure the hardware queue is
|
|
* run when one becomes available. Note that this is serialized on
|
|
* khd->lock, but we still need to be careful about the waker.
|
|
*/
|
|
if (nr < 0 && list_empty_careful(&wait->entry)) {
|
|
ws = sbq_wait_ptr(domain_tokens,
|
|
&khd->wait_index[sched_domain]);
|
|
khd->domain_ws[sched_domain] = ws;
|
|
add_wait_queue(&ws->wait, wait);
|
|
|
|
/*
|
|
* Try again in case a token was freed before we got on the wait
|
|
* queue.
|
|
*/
|
|
nr = __sbitmap_queue_get(domain_tokens);
|
|
}
|
|
|
|
/*
|
|
* If we got a token while we were on the wait queue, remove ourselves
|
|
* from the wait queue to ensure that all wake ups make forward
|
|
* progress. It's possible that the waker already deleted the entry
|
|
* between the !list_empty_careful() check and us grabbing the lock, but
|
|
* list_del_init() is okay with that.
|
|
*/
|
|
if (nr >= 0 && !list_empty_careful(&wait->entry)) {
|
|
ws = khd->domain_ws[sched_domain];
|
|
spin_lock_irq(&ws->wait.lock);
|
|
list_del_init(&wait->entry);
|
|
spin_unlock_irq(&ws->wait.lock);
|
|
}
|
|
|
|
return nr;
|
|
}
|
|
|
|
static struct request *
|
|
kyber_dispatch_cur_domain(struct kyber_queue_data *kqd,
|
|
struct kyber_hctx_data *khd,
|
|
struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct list_head *rqs;
|
|
struct request *rq;
|
|
int nr;
|
|
|
|
rqs = &khd->rqs[khd->cur_domain];
|
|
|
|
/*
|
|
* If we already have a flushed request, then we just need to get a
|
|
* token for it. Otherwise, if there are pending requests in the kcqs,
|
|
* flush the kcqs, but only if we can get a token. If not, we should
|
|
* leave the requests in the kcqs so that they can be merged. Note that
|
|
* khd->lock serializes the flushes, so if we observed any bit set in
|
|
* the kcq_map, we will always get a request.
|
|
*/
|
|
rq = list_first_entry_or_null(rqs, struct request, queuelist);
|
|
if (rq) {
|
|
nr = kyber_get_domain_token(kqd, khd, hctx);
|
|
if (nr >= 0) {
|
|
khd->batching++;
|
|
rq_set_domain_token(rq, nr);
|
|
list_del_init(&rq->queuelist);
|
|
return rq;
|
|
}
|
|
} else if (sbitmap_any_bit_set(&khd->kcq_map[khd->cur_domain])) {
|
|
nr = kyber_get_domain_token(kqd, khd, hctx);
|
|
if (nr >= 0) {
|
|
kyber_flush_busy_kcqs(khd, khd->cur_domain, rqs);
|
|
rq = list_first_entry(rqs, struct request, queuelist);
|
|
khd->batching++;
|
|
rq_set_domain_token(rq, nr);
|
|
list_del_init(&rq->queuelist);
|
|
return rq;
|
|
}
|
|
}
|
|
|
|
/* There were either no pending requests or no tokens. */
|
|
return NULL;
|
|
}
|
|
|
|
static struct request *kyber_dispatch_request(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
struct request *rq;
|
|
int i;
|
|
|
|
spin_lock(&khd->lock);
|
|
|
|
/*
|
|
* First, if we are still entitled to batch, try to dispatch a request
|
|
* from the batch.
|
|
*/
|
|
if (khd->batching < kyber_batch_size[khd->cur_domain]) {
|
|
rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
|
|
if (rq)
|
|
goto out;
|
|
}
|
|
|
|
/*
|
|
* Either,
|
|
* 1. We were no longer entitled to a batch.
|
|
* 2. The domain we were batching didn't have any requests.
|
|
* 3. The domain we were batching was out of tokens.
|
|
*
|
|
* Start another batch. Note that this wraps back around to the original
|
|
* domain if no other domains have requests or tokens.
|
|
*/
|
|
khd->batching = 0;
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
|
|
if (khd->cur_domain == KYBER_NUM_DOMAINS - 1)
|
|
khd->cur_domain = 0;
|
|
else
|
|
khd->cur_domain++;
|
|
|
|
rq = kyber_dispatch_cur_domain(kqd, khd, hctx);
|
|
if (rq)
|
|
goto out;
|
|
}
|
|
|
|
rq = NULL;
|
|
out:
|
|
spin_unlock(&khd->lock);
|
|
return rq;
|
|
}
|
|
|
|
static bool kyber_has_work(struct blk_mq_hw_ctx *hctx)
|
|
{
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
int i;
|
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
|
|
if (!list_empty_careful(&khd->rqs[i]) ||
|
|
sbitmap_any_bit_set(&khd->kcq_map[i]))
|
|
return true;
|
|
}
|
|
|
|
return false;
|
|
}
|
|
|
|
#define KYBER_LAT_SHOW_STORE(op) \
|
|
static ssize_t kyber_##op##_lat_show(struct elevator_queue *e, \
|
|
char *page) \
|
|
{ \
|
|
struct kyber_queue_data *kqd = e->elevator_data; \
|
|
\
|
|
return sprintf(page, "%llu\n", kqd->op##_lat_nsec); \
|
|
} \
|
|
\
|
|
static ssize_t kyber_##op##_lat_store(struct elevator_queue *e, \
|
|
const char *page, size_t count) \
|
|
{ \
|
|
struct kyber_queue_data *kqd = e->elevator_data; \
|
|
unsigned long long nsec; \
|
|
int ret; \
|
|
\
|
|
ret = kstrtoull(page, 10, &nsec); \
|
|
if (ret) \
|
|
return ret; \
|
|
\
|
|
kqd->op##_lat_nsec = nsec; \
|
|
\
|
|
return count; \
|
|
}
|
|
KYBER_LAT_SHOW_STORE(read);
|
|
KYBER_LAT_SHOW_STORE(write);
|
|
#undef KYBER_LAT_SHOW_STORE
|
|
|
|
#define KYBER_LAT_ATTR(op) __ATTR(op##_lat_nsec, 0644, kyber_##op##_lat_show, kyber_##op##_lat_store)
|
|
static struct elv_fs_entry kyber_sched_attrs[] = {
|
|
KYBER_LAT_ATTR(read),
|
|
KYBER_LAT_ATTR(write),
|
|
__ATTR_NULL
|
|
};
|
|
#undef KYBER_LAT_ATTR
|
|
|
|
#ifdef CONFIG_BLK_DEBUG_FS
|
|
#define KYBER_DEBUGFS_DOMAIN_ATTRS(domain, name) \
|
|
static int kyber_##name##_tokens_show(void *data, struct seq_file *m) \
|
|
{ \
|
|
struct request_queue *q = data; \
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data; \
|
|
\
|
|
sbitmap_queue_show(&kqd->domain_tokens[domain], m); \
|
|
return 0; \
|
|
} \
|
|
\
|
|
static void *kyber_##name##_rqs_start(struct seq_file *m, loff_t *pos) \
|
|
__acquires(&khd->lock) \
|
|
{ \
|
|
struct blk_mq_hw_ctx *hctx = m->private; \
|
|
struct kyber_hctx_data *khd = hctx->sched_data; \
|
|
\
|
|
spin_lock(&khd->lock); \
|
|
return seq_list_start(&khd->rqs[domain], *pos); \
|
|
} \
|
|
\
|
|
static void *kyber_##name##_rqs_next(struct seq_file *m, void *v, \
|
|
loff_t *pos) \
|
|
{ \
|
|
struct blk_mq_hw_ctx *hctx = m->private; \
|
|
struct kyber_hctx_data *khd = hctx->sched_data; \
|
|
\
|
|
return seq_list_next(v, &khd->rqs[domain], pos); \
|
|
} \
|
|
\
|
|
static void kyber_##name##_rqs_stop(struct seq_file *m, void *v) \
|
|
__releases(&khd->lock) \
|
|
{ \
|
|
struct blk_mq_hw_ctx *hctx = m->private; \
|
|
struct kyber_hctx_data *khd = hctx->sched_data; \
|
|
\
|
|
spin_unlock(&khd->lock); \
|
|
} \
|
|
\
|
|
static const struct seq_operations kyber_##name##_rqs_seq_ops = { \
|
|
.start = kyber_##name##_rqs_start, \
|
|
.next = kyber_##name##_rqs_next, \
|
|
.stop = kyber_##name##_rqs_stop, \
|
|
.show = blk_mq_debugfs_rq_show, \
|
|
}; \
|
|
\
|
|
static int kyber_##name##_waiting_show(void *data, struct seq_file *m) \
|
|
{ \
|
|
struct blk_mq_hw_ctx *hctx = data; \
|
|
struct kyber_hctx_data *khd = hctx->sched_data; \
|
|
wait_queue_entry_t *wait = &khd->domain_wait[domain]; \
|
|
\
|
|
seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \
|
|
return 0; \
|
|
}
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_SYNC_WRITE, sync_write)
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_OTHER, other)
|
|
#undef KYBER_DEBUGFS_DOMAIN_ATTRS
|
|
|
|
static int kyber_async_depth_show(void *data, struct seq_file *m)
|
|
{
|
|
struct request_queue *q = data;
|
|
struct kyber_queue_data *kqd = q->elevator->elevator_data;
|
|
|
|
seq_printf(m, "%u\n", kqd->async_depth);
|
|
return 0;
|
|
}
|
|
|
|
static int kyber_cur_domain_show(void *data, struct seq_file *m)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx = data;
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
|
|
switch (khd->cur_domain) {
|
|
case KYBER_READ:
|
|
seq_puts(m, "READ\n");
|
|
break;
|
|
case KYBER_SYNC_WRITE:
|
|
seq_puts(m, "SYNC_WRITE\n");
|
|
break;
|
|
case KYBER_OTHER:
|
|
seq_puts(m, "OTHER\n");
|
|
break;
|
|
default:
|
|
seq_printf(m, "%u\n", khd->cur_domain);
|
|
break;
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static int kyber_batching_show(void *data, struct seq_file *m)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx = data;
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
|
|
seq_printf(m, "%u\n", khd->batching);
|
|
return 0;
|
|
}
|
|
|
|
#define KYBER_QUEUE_DOMAIN_ATTRS(name) \
|
|
{#name "_tokens", 0400, kyber_##name##_tokens_show}
|
|
static const struct blk_mq_debugfs_attr kyber_queue_debugfs_attrs[] = {
|
|
KYBER_QUEUE_DOMAIN_ATTRS(read),
|
|
KYBER_QUEUE_DOMAIN_ATTRS(sync_write),
|
|
KYBER_QUEUE_DOMAIN_ATTRS(other),
|
|
{"async_depth", 0400, kyber_async_depth_show},
|
|
{},
|
|
};
|
|
#undef KYBER_QUEUE_DOMAIN_ATTRS
|
|
|
|
#define KYBER_HCTX_DOMAIN_ATTRS(name) \
|
|
{#name "_rqs", 0400, .seq_ops = &kyber_##name##_rqs_seq_ops}, \
|
|
{#name "_waiting", 0400, kyber_##name##_waiting_show}
|
|
static const struct blk_mq_debugfs_attr kyber_hctx_debugfs_attrs[] = {
|
|
KYBER_HCTX_DOMAIN_ATTRS(read),
|
|
KYBER_HCTX_DOMAIN_ATTRS(sync_write),
|
|
KYBER_HCTX_DOMAIN_ATTRS(other),
|
|
{"cur_domain", 0400, kyber_cur_domain_show},
|
|
{"batching", 0400, kyber_batching_show},
|
|
{},
|
|
};
|
|
#undef KYBER_HCTX_DOMAIN_ATTRS
|
|
#endif
|
|
|
|
static struct elevator_type kyber_sched = {
|
|
.ops.mq = {
|
|
.init_sched = kyber_init_sched,
|
|
.exit_sched = kyber_exit_sched,
|
|
.init_hctx = kyber_init_hctx,
|
|
.exit_hctx = kyber_exit_hctx,
|
|
.limit_depth = kyber_limit_depth,
|
|
.bio_merge = kyber_bio_merge,
|
|
.prepare_request = kyber_prepare_request,
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.insert_requests = kyber_insert_requests,
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.finish_request = kyber_finish_request,
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.requeue_request = kyber_finish_request,
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|
.completed_request = kyber_completed_request,
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|
.dispatch_request = kyber_dispatch_request,
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.has_work = kyber_has_work,
|
|
},
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|
.uses_mq = true,
|
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#ifdef CONFIG_BLK_DEBUG_FS
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|
.queue_debugfs_attrs = kyber_queue_debugfs_attrs,
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.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
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|
#endif
|
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.elevator_attrs = kyber_sched_attrs,
|
|
.elevator_name = "kyber",
|
|
.elevator_owner = THIS_MODULE,
|
|
};
|
|
|
|
static int __init kyber_init(void)
|
|
{
|
|
return elv_register(&kyber_sched);
|
|
}
|
|
|
|
static void __exit kyber_exit(void)
|
|
{
|
|
elv_unregister(&kyber_sched);
|
|
}
|
|
|
|
module_init(kyber_init);
|
|
module_exit(kyber_exit);
|
|
|
|
MODULE_AUTHOR("Omar Sandoval");
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|
MODULE_LICENSE("GPL");
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|
MODULE_DESCRIPTION("Kyber I/O scheduler");
|