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8c16567d86
All these files have some form of the usual GPLv2 boilerplate. Switch them to use SPDX tags instead. Reviewed-by: Chaitanya Kulkarni <chaitanya.kulkarni@wdc.com> Signed-off-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Jens Axboe <axboe@kernel.dk>
1051 lines
28 KiB
C
1051 lines
28 KiB
C
// SPDX-License-Identifier: GPL-2.0
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/*
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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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#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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#define CREATE_TRACE_POINTS
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#include <trace/events/kyber.h>
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/*
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* Scheduling domains: the device is divided into multiple domains based on the
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* request type.
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*/
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enum {
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KYBER_READ,
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KYBER_WRITE,
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KYBER_DISCARD,
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KYBER_OTHER,
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KYBER_NUM_DOMAINS,
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};
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static const char *kyber_domain_names[] = {
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[KYBER_READ] = "READ",
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[KYBER_WRITE] = "WRITE",
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[KYBER_DISCARD] = "DISCARD",
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[KYBER_OTHER] = "OTHER",
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};
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enum {
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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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* Maximum device-wide depth 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 the
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* device with only a fraction of the maximum possible queue depth. So, we cap
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* 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_WRITE] = 128,
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[KYBER_DISCARD] = 64,
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[KYBER_OTHER] = 16,
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};
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/*
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* Default latency targets for each scheduling domain.
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*/
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static const u64 kyber_latency_targets[] = {
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[KYBER_READ] = 2ULL * NSEC_PER_MSEC,
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[KYBER_WRITE] = 10ULL * NSEC_PER_MSEC,
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[KYBER_DISCARD] = 5ULL * NSEC_PER_SEC,
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};
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/*
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* Batch size (number of requests we'll dispatch in a row) for each scheduling
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* domain.
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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_WRITE] = 8,
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[KYBER_DISCARD] = 1,
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[KYBER_OTHER] = 1,
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};
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/*
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* Requests latencies are recorded in a histogram with buckets defined relative
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* to the target latency:
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*
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* <= 1/4 * target latency
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* <= 1/2 * target latency
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* <= 3/4 * target latency
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* <= target latency
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* <= 1 1/4 * target latency
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* <= 1 1/2 * target latency
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* <= 1 3/4 * target latency
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* > 1 3/4 * target latency
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*/
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enum {
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/*
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* The width of the latency histogram buckets is
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* 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.
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*/
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KYBER_LATENCY_SHIFT = 2,
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/*
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* The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,
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* thus, "good".
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*/
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KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT,
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/* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */
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KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT,
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};
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/*
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* We measure both the total latency and the I/O latency (i.e., latency after
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* submitting to the device).
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*/
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enum {
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KYBER_TOTAL_LATENCY,
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KYBER_IO_LATENCY,
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};
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static const char *kyber_latency_type_names[] = {
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[KYBER_TOTAL_LATENCY] = "total",
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[KYBER_IO_LATENCY] = "I/O",
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};
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/*
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* Per-cpu latency histograms: total latency and I/O latency for each scheduling
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* domain except for KYBER_OTHER.
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*/
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struct kyber_cpu_latency {
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atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
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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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/*
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* Each scheduling domain has a limited number of in-flight requests
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* 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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struct kyber_cpu_latency __percpu *cpu_latency;
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/* Timer for stats aggregation and adjusting domain tokens. */
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struct timer_list timer;
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unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
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unsigned long latency_timeout[KYBER_OTHER];
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int domain_p99[KYBER_OTHER];
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/* Target latencies in nanoseconds. */
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u64 latency_targets[KYBER_OTHER];
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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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struct sbq_wait 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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switch (op & REQ_OP_MASK) {
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case REQ_OP_READ:
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return KYBER_READ;
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case REQ_OP_WRITE:
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return KYBER_WRITE;
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case REQ_OP_DISCARD:
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return KYBER_DISCARD;
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default:
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return KYBER_OTHER;
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}
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}
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static void flush_latency_buckets(struct kyber_queue_data *kqd,
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struct kyber_cpu_latency *cpu_latency,
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unsigned int sched_domain, unsigned int type)
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{
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unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
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atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
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unsigned int bucket;
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
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buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
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}
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/*
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* Calculate the histogram bucket with the given percentile rank, or -1 if there
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* aren't enough samples yet.
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*/
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static int calculate_percentile(struct kyber_queue_data *kqd,
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unsigned int sched_domain, unsigned int type,
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unsigned int percentile)
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{
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unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
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unsigned int bucket, samples = 0, percentile_samples;
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
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samples += buckets[bucket];
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if (!samples)
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return -1;
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/*
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* We do the calculation once we have 500 samples or one second passes
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* since the first sample was recorded, whichever comes first.
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*/
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if (!kqd->latency_timeout[sched_domain])
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kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
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if (samples < 500 &&
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time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
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return -1;
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}
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kqd->latency_timeout[sched_domain] = 0;
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percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
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for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
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if (buckets[bucket] >= percentile_samples)
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break;
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percentile_samples -= buckets[bucket];
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}
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memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
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trace_kyber_latency(kqd->q, kyber_domain_names[sched_domain],
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kyber_latency_type_names[type], percentile,
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bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
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return bucket;
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}
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static void kyber_resize_domain(struct kyber_queue_data *kqd,
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unsigned int sched_domain, unsigned int depth)
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{
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depth = clamp(depth, 1U, kyber_depth[sched_domain]);
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if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
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sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
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trace_kyber_adjust(kqd->q, kyber_domain_names[sched_domain],
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depth);
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}
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}
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static void kyber_timer_fn(struct timer_list *t)
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{
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struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
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unsigned int sched_domain;
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int cpu;
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bool bad = false;
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/* Sum all of the per-cpu latency histograms. */
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for_each_online_cpu(cpu) {
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struct kyber_cpu_latency *cpu_latency;
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cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
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flush_latency_buckets(kqd, cpu_latency, sched_domain,
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KYBER_TOTAL_LATENCY);
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flush_latency_buckets(kqd, cpu_latency, sched_domain,
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KYBER_IO_LATENCY);
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}
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}
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/*
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* Check if any domains have a high I/O latency, which might indicate
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* congestion in the device. Note that we use the p90; we don't want to
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* be too sensitive to outliers here.
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*/
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
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int p90;
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p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
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90);
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if (p90 >= KYBER_GOOD_BUCKETS)
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bad = true;
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}
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/*
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* Adjust the scheduling domain depths. If we determined that there was
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* congestion, we throttle all domains with good latencies. Either way,
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* we ease up on throttling domains with bad latencies.
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*/
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for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
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unsigned int orig_depth, depth;
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int p99;
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p99 = calculate_percentile(kqd, sched_domain,
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KYBER_TOTAL_LATENCY, 99);
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/*
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* This is kind of subtle: different domains will not
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* necessarily have enough samples to calculate the latency
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* percentiles during the same window, so we have to remember
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* the p99 for the next time we observe congestion; once we do,
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* we don't want to throttle again until we get more data, so we
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* reset it to -1.
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*/
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if (bad) {
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if (p99 < 0)
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p99 = kqd->domain_p99[sched_domain];
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kqd->domain_p99[sched_domain] = -1;
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} else if (p99 >= 0) {
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kqd->domain_p99[sched_domain] = p99;
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}
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if (p99 < 0)
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continue;
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/*
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* If this domain has bad latency, throttle less. Otherwise,
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* throttle more iff we determined that there is congestion.
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*
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* The new depth is scaled linearly with the p99 latency vs the
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* latency target. E.g., if the p99 is 3/4 of the target, then
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* we throttle down to 3/4 of the current depth, and if the p99
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* is 2x the target, then we double the depth.
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*/
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if (bad || p99 >= KYBER_GOOD_BUCKETS) {
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orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
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depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
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kyber_resize_domain(kqd, sched_domain, depth);
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}
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}
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}
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static unsigned int kyber_sched_tags_shift(struct request_queue *q)
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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 q->queue_hw_ctx[0]->sched_tags->bitmap_tags.sb.shift;
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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 shift;
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int ret = -ENOMEM;
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int i;
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kqd = kzalloc_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->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
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GFP_KERNEL | __GFP_ZERO);
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if (!kqd->cpu_latency)
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goto err_kqd;
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timer_setup(&kqd->timer, kyber_timer_fn, 0);
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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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kyber_depth[i], -1, false,
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GFP_KERNEL, 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_buckets;
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}
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}
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for (i = 0; i < KYBER_OTHER; i++) {
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kqd->domain_p99[i] = -1;
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kqd->latency_targets[i] = kyber_latency_targets[i];
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}
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shift = kyber_sched_tags_shift(q);
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kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
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return kqd;
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err_buckets:
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free_percpu(kqd->cpu_latency);
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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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blk_stat_enable_accounting(q);
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eq->elevator_data = kqd;
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q->elevator = eq;
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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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int i;
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del_timer_sync(&kqd->timer);
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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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free_percpu(kqd->cpu_latency);
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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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|
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spin_lock_init(&khd->lock);
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|
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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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khd->domain_wait[i].sbq = NULL;
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init_waitqueue_func_entry(&khd->domain_wait[i].wait,
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kyber_domain_wake);
|
|
khd->domain_wait[i].wait.private = hctx;
|
|
INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
|
|
atomic_set(&khd->wait_index[i], 0);
|
|
}
|
|
|
|
khd->cur_domain = 0;
|
|
khd->batching = 0;
|
|
|
|
hctx->sched_data = khd;
|
|
sbitmap_queue_min_shallow_depth(&hctx->sched_tags->bitmap_tags,
|
|
kqd->async_depth);
|
|
|
|
return 0;
|
|
|
|
err_kcqs:
|
|
kfree(khd->kcqs);
|
|
err_khd:
|
|
kfree(khd);
|
|
return -ENOMEM;
|
|
}
|
|
|
|
static void kyber_exit_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
|
|
{
|
|
struct kyber_hctx_data *khd = hctx->sched_data;
|
|
int i;
|
|
|
|
for (i = 0; i < KYBER_NUM_DOMAINS; i++)
|
|
sbitmap_free(&khd->kcq_map[i]);
|
|
kfree(khd->kcqs);
|
|
kfree(hctx->sched_data);
|
|
}
|
|
|
|
static int rq_get_domain_token(struct request *rq)
|
|
{
|
|
return (long)rq->elv.priv[0];
|
|
}
|
|
|
|
static void rq_set_domain_token(struct request *rq, int token)
|
|
{
|
|
rq->elv.priv[0] = (void *)(long)token;
|
|
}
|
|
|
|
static void rq_clear_domain_token(struct kyber_queue_data *kqd,
|
|
struct request *rq)
|
|
{
|
|
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[hctx->type]];
|
|
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[hctx->type]];
|
|
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[hctx->type]);
|
|
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 add_latency_sample(struct kyber_cpu_latency *cpu_latency,
|
|
unsigned int sched_domain, unsigned int type,
|
|
u64 target, u64 latency)
|
|
{
|
|
unsigned int bucket;
|
|
u64 divisor;
|
|
|
|
if (latency > 0) {
|
|
divisor = max_t(u64, target >> KYBER_LATENCY_SHIFT, 1);
|
|
bucket = min_t(unsigned int, div64_u64(latency - 1, divisor),
|
|
KYBER_LATENCY_BUCKETS - 1);
|
|
} else {
|
|
bucket = 0;
|
|
}
|
|
|
|
atomic_inc(&cpu_latency->buckets[sched_domain][type][bucket]);
|
|
}
|
|
|
|
static void kyber_completed_request(struct request *rq, u64 now)
|
|
{
|
|
struct kyber_queue_data *kqd = rq->q->elevator->elevator_data;
|
|
struct kyber_cpu_latency *cpu_latency;
|
|
unsigned int sched_domain;
|
|
u64 target;
|
|
|
|
sched_domain = kyber_sched_domain(rq->cmd_flags);
|
|
if (sched_domain == KYBER_OTHER)
|
|
return;
|
|
|
|
cpu_latency = get_cpu_ptr(kqd->cpu_latency);
|
|
target = kqd->latency_targets[sched_domain];
|
|
add_latency_sample(cpu_latency, sched_domain, KYBER_TOTAL_LATENCY,
|
|
target, now - rq->start_time_ns);
|
|
add_latency_sample(cpu_latency, sched_domain, KYBER_IO_LATENCY, target,
|
|
now - rq->io_start_time_ns);
|
|
put_cpu_ptr(kqd->cpu_latency);
|
|
|
|
timer_reduce(&kqd->timer, jiffies + HZ / 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 *wqe, unsigned mode, int flags,
|
|
void *key)
|
|
{
|
|
struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
|
|
struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
|
|
|
|
sbitmap_del_wait_queue(wait);
|
|
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];
|
|
struct sbq_wait *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->wait.entry)) {
|
|
ws = sbq_wait_ptr(domain_tokens,
|
|
&khd->wait_index[sched_domain]);
|
|
khd->domain_ws[sched_domain] = ws;
|
|
sbitmap_add_wait_queue(domain_tokens, ws, 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->wait.entry)) {
|
|
ws = khd->domain_ws[sched_domain];
|
|
spin_lock_irq(&ws->wait.lock);
|
|
sbitmap_del_wait_queue(wait);
|
|
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 {
|
|
trace_kyber_throttled(kqd->q,
|
|
kyber_domain_names[khd->cur_domain]);
|
|
}
|
|
} 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;
|
|
} else {
|
|
trace_kyber_throttled(kqd->q,
|
|
kyber_domain_names[khd->cur_domain]);
|
|
}
|
|
}
|
|
|
|
/* 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(domain, name) \
|
|
static ssize_t kyber_##name##_lat_show(struct elevator_queue *e, \
|
|
char *page) \
|
|
{ \
|
|
struct kyber_queue_data *kqd = e->elevator_data; \
|
|
\
|
|
return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \
|
|
} \
|
|
\
|
|
static ssize_t kyber_##name##_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->latency_targets[domain] = nsec; \
|
|
\
|
|
return count; \
|
|
}
|
|
KYBER_LAT_SHOW_STORE(KYBER_READ, read);
|
|
KYBER_LAT_SHOW_STORE(KYBER_WRITE, 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].wait; \
|
|
\
|
|
seq_printf(m, "%d\n", !list_empty_careful(&wait->entry)); \
|
|
return 0; \
|
|
}
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_READ, read)
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_WRITE, write)
|
|
KYBER_DEBUGFS_DOMAIN_ATTRS(KYBER_DISCARD, discard)
|
|
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;
|
|
|
|
seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
|
|
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(write),
|
|
KYBER_QUEUE_DOMAIN_ATTRS(discard),
|
|
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(write),
|
|
KYBER_HCTX_DOMAIN_ATTRS(discard),
|
|
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 = {
|
|
.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,
|
|
.insert_requests = kyber_insert_requests,
|
|
.finish_request = kyber_finish_request,
|
|
.requeue_request = kyber_finish_request,
|
|
.completed_request = kyber_completed_request,
|
|
.dispatch_request = kyber_dispatch_request,
|
|
.has_work = kyber_has_work,
|
|
},
|
|
#ifdef CONFIG_BLK_DEBUG_FS
|
|
.queue_debugfs_attrs = kyber_queue_debugfs_attrs,
|
|
.hctx_debugfs_attrs = kyber_hctx_debugfs_attrs,
|
|
#endif
|
|
.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");
|
|
MODULE_LICENSE("GPL");
|
|
MODULE_DESCRIPTION("Kyber I/O scheduler");
|