// SPDX-License-Identifier: GPL-2.0
/*
* The Kyber I/O scheduler. Controls latency by throttling queue depths using
* scalable techniques.
*
* Copyright (C) 2017 Facebook
*/
#include <linux/kernel.h>
#include <linux/blkdev.h>
#include <linux/module.h>
#include <linux/sbitmap.h>
#include <trace/events/block.h>
#include "elevator.h"
#include "blk.h"
#include "blk-mq.h"
#include "blk-mq-debugfs.h"
#include "blk-mq-sched.h"
#define CREATE_TRACE_POINTS
#include <trace/events/kyber.h>
/*
* Scheduling domains: the device is divided into multiple domains based on the
* request type.
*/
enum {
KYBER_READ,
KYBER_WRITE,
KYBER_DISCARD,
KYBER_OTHER,
KYBER_NUM_DOMAINS,
};
static const char *kyber_domain_names[] = {
[KYBER_READ] = "READ",
[KYBER_WRITE] = "WRITE",
[KYBER_DISCARD] = "DISCARD",
[KYBER_OTHER] = "OTHER",
};
enum {
/*
* In order to prevent starvation of synchronous requests by a flood of
* asynchronous requests, we reserve 25% of requests for synchronous
* operations.
*/
KYBER_ASYNC_PERCENT = 75,
};
/*
* Maximum device-wide depth for each scheduling domain.
*
* Even for fast devices with lots of tags like NVMe, you can saturate the
* device with only a fraction of the maximum possible queue depth. So, we cap
* these to a reasonable value.
*/
static const unsigned int kyber_depth[] = {
[KYBER_READ] = 256,
[KYBER_WRITE] = 128,
[KYBER_DISCARD] = 64,
[KYBER_OTHER] = 16,
};
/*
* Default latency targets for each scheduling domain.
*/
static const u64 kyber_latency_targets[] = {
[KYBER_READ] = 2ULL * NSEC_PER_MSEC,
[KYBER_WRITE] = 10ULL * NSEC_PER_MSEC,
[KYBER_DISCARD] = 5ULL * NSEC_PER_SEC,
};
/*
* Batch size (number of requests we'll dispatch in a row) for each scheduling
* domain.
*/
static const unsigned int kyber_batch_size[] = {
[KYBER_READ] = 16,
[KYBER_WRITE] = 8,
[KYBER_DISCARD] = 1,
[KYBER_OTHER] = 1,
};
/*
* Requests latencies are recorded in a histogram with buckets defined relative
* to the target latency:
*
* <= 1/4 * target latency
* <= 1/2 * target latency
* <= 3/4 * target latency
* <= target latency
* <= 1 1/4 * target latency
* <= 1 1/2 * target latency
* <= 1 3/4 * target latency
* > 1 3/4 * target latency
*/
enum {
/*
* The width of the latency histogram buckets is
* 1 / (1 << KYBER_LATENCY_SHIFT) * target latency.
*/
KYBER_LATENCY_SHIFT = 2,
/*
* The first (1 << KYBER_LATENCY_SHIFT) buckets are <= target latency,
* thus, "good".
*/
KYBER_GOOD_BUCKETS = 1 << KYBER_LATENCY_SHIFT,
/* There are also (1 << KYBER_LATENCY_SHIFT) "bad" buckets. */
KYBER_LATENCY_BUCKETS = 2 << KYBER_LATENCY_SHIFT,
};
/*
* We measure both the total latency and the I/O latency (i.e., latency after
* submitting to the device).
*/
enum {
KYBER_TOTAL_LATENCY,
KYBER_IO_LATENCY,
};
static const char *kyber_latency_type_names[] = {
[KYBER_TOTAL_LATENCY] = "total",
[KYBER_IO_LATENCY] = "I/O",
};
/*
* Per-cpu latency histograms: total latency and I/O latency for each scheduling
* domain except for KYBER_OTHER.
*/
struct kyber_cpu_latency {
atomic_t buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
};
/*
* There is a same mapping between ctx & hctx and kcq & khd,
* we use request->mq_ctx->index_hw to index the kcq in khd.
*/
struct kyber_ctx_queue {
/*
* Used to ensure operations on rq_list and kcq_map to be an atmoic one.
* Also protect the rqs on rq_list when merge.
*/
spinlock_t lock;
struct list_head rq_list[KYBER_NUM_DOMAINS];
} ____cacheline_aligned_in_smp;
struct kyber_queue_data {
struct request_queue *q;
dev_t dev;
/*
* Each scheduling domain has a limited number of in-flight requests
* device-wide, limited by these tokens.
*/
struct sbitmap_queue domain_tokens[KYBER_NUM_DOMAINS];
/*
* Async request percentage, converted to per-word depth for
* sbitmap_get_shallow().
*/
unsigned int async_depth;
struct kyber_cpu_latency __percpu *cpu_latency;
/* Timer for stats aggregation and adjusting domain tokens. */
struct timer_list timer;
unsigned int latency_buckets[KYBER_OTHER][2][KYBER_LATENCY_BUCKETS];
unsigned long latency_timeout[KYBER_OTHER];
int domain_p99[KYBER_OTHER];
/* Target latencies in nanoseconds. */
u64 latency_targets[KYBER_OTHER];
};
struct kyber_hctx_data {
spinlock_t lock;
struct list_head rqs[KYBER_NUM_DOMAINS];
unsigned int cur_domain;
unsigned int batching;
struct kyber_ctx_queue *kcqs;
struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
struct sbq_wait domain_wait[KYBER_NUM_DOMAINS];
struct sbq_wait_state *domain_ws[KYBER_NUM_DOMAINS];
atomic_t wait_index[KYBER_NUM_DOMAINS];
};
static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
void *key);
static unsigned int kyber_sched_domain(blk_opf_t opf)
{
switch (opf & REQ_OP_MASK) {
case REQ_OP_READ:
return KYBER_READ;
case REQ_OP_WRITE:
return KYBER_WRITE;
case REQ_OP_DISCARD:
return KYBER_DISCARD;
default:
return KYBER_OTHER;
}
}
static void flush_latency_buckets(struct kyber_queue_data *kqd,
struct kyber_cpu_latency *cpu_latency,
unsigned int sched_domain, unsigned int type)
{
unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
unsigned int bucket;
for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
}
/*
* Calculate the histogram bucket with the given percentile rank, or -1 if there
* aren't enough samples yet.
*/
static int calculate_percentile(struct kyber_queue_data *kqd,
unsigned int sched_domain, unsigned int type,
unsigned int percentile)
{
unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
unsigned int bucket, samples = 0, percentile_samples;
for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
samples += buckets[bucket];
if (!samples)
return -1;
/*
* We do the calculation once we have 500 samples or one second passes
* since the first sample was recorded, whichever comes first.
*/
if (!kqd->latency_timeout[sched_domain])
kqd->latency_timeout[sched_domain] = max(jiffies + HZ, 1UL);
if (samples < 500 &&
time_is_after_jiffies(kqd->latency_timeout[sched_domain])) {
return -1;
}
kqd->latency_timeout[sched_domain] = 0;
percentile_samples = DIV_ROUND_UP(samples * percentile, 100);
for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS - 1; bucket++) {
if (buckets[bucket] >= percentile_samples)
break;
percentile_samples -= buckets[bucket];
}
memset(buckets, 0, sizeof(kqd->latency_buckets[sched_domain][type]));
trace_kyber_latency(kqd->dev, kyber_domain_names[sched_domain],
kyber_latency_type_names[type], percentile,
bucket + 1, 1 << KYBER_LATENCY_SHIFT, samples);
return bucket;
}
static void kyber_resize_domain(struct kyber_queue_data *kqd,
unsigned int sched_domain, unsigned int depth)
{
depth = clamp(depth, 1U, kyber_depth[sched_domain]);
if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
trace_kyber_adjust(kqd->dev, kyber_domain_names[sched_domain],
depth);
}
}
static void kyber_timer_fn(struct timer_list *t)
{
struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
unsigned int sched_domain;
int cpu;
bool bad = false;
/* Sum all of the per-cpu latency histograms. */
for_each_online_cpu(cpu) {
struct kyber_cpu_latency *cpu_latency;
cpu_latency = per_cpu_ptr(kqd->cpu_latency, cpu);
for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
flush_latency_buckets(kqd, cpu_latency, sched_domain,
KYBER_TOTAL_LATENCY);
flush_latency_buckets(kqd, cpu_latency, sched_domain,
KYBER_IO_LATENCY);
}
}
/*
* Check if any domains have a high I/O latency, which might indicate
* congestion in the device. Note that we use the p90; we don't want to
* be too sensitive to outliers here.
*/
for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
int p90;
p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
90);
if (p90 >= KYBER_GOOD_BUCKETS)
bad = true;
}
/*
* Adjust the scheduling domain depths. If we determined that there was
* congestion, we throttle all domains with good latencies. Either way,
* we ease up on throttling domains with bad latencies.
*/
for (sched_domain = 0; sched_domain < KYBER_OTHER; sched_domain++) {
unsigned int orig_depth, depth;
int p99;
p99 = calculate_percentile(kqd, sched_domain,
KYBER_TOTAL_LATENCY, 99);
/*
* This is kind of subtle: different domains will not
* necessarily have enough samples to calculate the latency
* percentiles during the same window, so we have to remember
* the p99 for the next time we observe congestion; once we do,
* we don't want to throttle again until we get more data, so we
* reset it to -1.
*/
if (bad) {
if (p99 < 0)
p99 = kqd->domain_p99[sched_domain];
kqd->domain_p99[sched_domain] = -1;
} else if (p99 >= 0) {
kqd->domain_p99[sched_domain] = p99;
}
if (p99 < 0)
continue;
/*
* If this domain has bad latency, throttle less. Otherwise,
* throttle more iff we determined that there is congestion.
*
* The new depth is scaled linearly with the p99 latency vs the
* latency target. E.g., if the p99 is 3/4 of the target, then
* we throttle down to 3/4 of the current depth, and if the p99
* is 2x the target, then we double the depth.
*/
if (bad || p99 >= KYBER_GOOD_BUCKETS) {
orig_depth = kqd->domain_tokens[sched_domain].sb.depth;
depth = (orig_depth * (p99 + 1)) >> KYBER_LATENCY_SHIFT;
kyber_resize_domain(kqd, sched_domain, depth);
}
}
}
static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
{
struct kyber_queue_data *kqd;
int ret = -ENOMEM;
int i;
kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
if (!kqd)
goto err;
kqd->q = q;
kqd->dev = disk_devt(q->disk);
kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
GFP_KERNEL | __GFP_ZERO);
if (!kqd->cpu_latency)
goto err_kqd;
timer_setup(&kqd->timer, kyber_timer_fn, 0);
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
WARN_ON(!kyber_depth[i]);
WARN_ON(!kyber_batch_size[i]);
ret = sbitmap_queue_init_node(&kqd->domain_tokens[i],
kyber_depth[i], -1, false,
GFP_KERNEL, q->node);
if (ret) {
while (--i >= 0)
sbitmap_queue_free(&kqd->domain_tokens[i]);
goto err_buckets;
}
}
for (i = 0; i < KYBER_OTHER; i++) {
kqd->domain_p99[i] = -1;
kqd->latency_targets[i] = kyber_latency_targets[i];
}
return kqd;
err_buckets:
free_percpu(kqd->cpu_latency);
err_kqd:
kfree(kqd);
err:
return ERR_PTR(ret);
}
static int kyber_init_sched(struct request_queue *q, struct elevator_type *e)
{
struct kyber_queue_data *kqd;
struct elevator_queue *eq;
eq = elevator_alloc(q, e);
if (!eq)
return -ENOMEM;
kqd = kyber_queue_data_alloc(q);
if (IS_ERR(kqd)) {
kobject_put(&eq->kobj);
return PTR_ERR(kqd);
}
blk_stat_enable_accounting(q);
blk_queue_flag_clear(QUEUE_FLAG_SQ_SCHED, q);
eq->elevator_data = kqd;
q->elevator = eq;
return 0;
}
static void kyber_exit_sched(struct elevator_queue *e)
{
struct kyber_queue_data *kqd = e->elevator_data;
int i;
timer_shutdown_sync(&kqd->timer);
blk_stat_disable_accounting(kqd->q);
for (i = 0; i < KYBER_NUM_DOMAINS; i++)
sbitmap_queue_free(&kqd->domain_tokens[i]);
free_percpu(kqd->cpu_latency);
kfree(kqd);
}
static void kyber_ctx_queue_init(struct kyber_ctx_queue *kcq)
{
unsigned int i;
spin_lock_init(&kcq->lock);
for (i = 0; i < KYBER_NUM_DOMAINS; i++)
INIT_LIST_HEAD(&kcq->rq_list[i]);
}
static void kyber_depth_updated(struct blk_mq_hw_ctx *hctx)
{
struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
struct blk_mq_tags *tags = hctx->sched_tags;
unsigned int shift = tags->bitmap_tags.sb.shift;
kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
sbitmap_queue_min_shallow_depth(&tags->bitmap_tags, kqd->async_depth);
}
static int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
{
struct kyber_hctx_data *khd;
int i;
khd = kmalloc_node(sizeof(*khd), GFP_KERNEL, hctx->numa_node);
if (!khd)
return -ENOMEM;
khd->kcqs = kmalloc_array_node(hctx->nr_ctx,
sizeof(struct kyber_ctx_queue),
GFP_KERNEL, hctx->numa_node);
if (!khd->kcqs)
goto err_khd;
for (i = 0; i < hctx->nr_ctx; i++)
kyber_ctx_queue_init(&khd->kcqs[i]);
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
if (sbitmap_init_node(&khd->kcq_map[i], hctx->nr_ctx,
ilog2(8), GFP_KERNEL, hctx->numa_node,
false, false)) {
while (--i >= 0)
sbitmap_free(&khd->kcq_map[i]);
goto err_kcqs;
}
}
spin_lock_init(&khd->lock);
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
INIT_LIST_HEAD(&khd->rqs[i]);
khd->domain_wait[i].sbq = NULL;
init_waitqueue_func_entry(&khd->domain_wait[i].wait,
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;
kyber_depth_updated(hctx);
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(blk_opf_t opf, 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(opf)) {
struct kyber_queue_data *kqd = data->q->elevator->elevator_data;
data->shallow_depth = kqd->async_depth;
}
}
static bool kyber_bio_merge(struct request_queue *q, struct bio *bio,
unsigned int nr_segs)
{
struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, bio->bi_opf, ctx);
struct kyber_hctx_data *khd = hctx->sched_data;
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_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
spin_unlock(&kcq->lock);
return merged;
}
static void kyber_prepare_request(struct request *rq)
{
rq_set_domain_token(rq, -1);
}
static void kyber_insert_requests(struct blk_mq_hw_ctx *hctx,
struct list_head *rq_list,
blk_insert_t flags)
{
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);
trace_block_rq_insert(rq);
if (flags & BLK_MQ_INSERT_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]);
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->dev,
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->dev,
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,
.depth_updated = kyber_depth_updated,
},
#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");
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