From 102a0743326a03cd1a1202ceda21e175b7d3575c Mon Sep 17 00:00:00 2001
From: hc <hc@nodka.com>
Date: Tue, 20 Feb 2024 01:20:52 +0000
Subject: [PATCH] add new system file
---
kernel/block/kyber-iosched.c | 611 ++++++++++++++++++++++++++++++-------------------------
1 files changed, 334 insertions(+), 277 deletions(-)
diff --git a/kernel/block/kyber-iosched.c b/kernel/block/kyber-iosched.c
index a1660ba..54e6de6 100644
--- a/kernel/block/kyber-iosched.c
+++ b/kernel/block/kyber-iosched.c
@@ -1,20 +1,9 @@
+// SPDX-License-Identifier: GPL-2.0
/*
* The Kyber I/O scheduler. Controls latency by throttling queue depths using
* scalable techniques.
*
* Copyright (C) 2017 Facebook
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public
- * License v2 as published by the Free Software Foundation.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * General Public License for more details.
- *
- * You should have received a copy of the GNU General Public License
- * along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
#include <linux/kernel.h>
@@ -29,19 +18,30 @@
#include "blk-mq-debugfs.h"
#include "blk-mq-sched.h"
#include "blk-mq-tag.h"
-#include "blk-stat.h"
-/* Scheduling domains. */
+#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_SYNC_WRITE,
- KYBER_OTHER, /* Async writes, discard, etc. */
+ KYBER_WRITE,
+ KYBER_DISCARD,
+ KYBER_OTHER,
KYBER_NUM_DOMAINS,
};
-enum {
- KYBER_MIN_DEPTH = 256,
+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
@@ -51,25 +51,87 @@
};
/*
- * Initial device-wide depths for each scheduling domain.
+ * 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.
+ * 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_SYNC_WRITE] = 128,
- [KYBER_OTHER] = 64,
+ [KYBER_WRITE] = 128,
+ [KYBER_DISCARD] = 64,
+ [KYBER_OTHER] = 16,
};
/*
- * Scheduling domain batch sizes. We favor reads.
+ * 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_SYNC_WRITE] = 8,
- [KYBER_OTHER] = 8,
+ [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];
};
/*
@@ -88,12 +150,9 @@
struct kyber_queue_data {
struct request_queue *q;
- struct blk_stat_callback *cb;
-
/*
- * The device is divided into multiple scheduling domains based on the
- * request type. Each domain has a fixed number of in-flight requests of
- * that type device-wide, limited by these tokens.
+ * 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];
@@ -103,8 +162,19 @@
*/
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 read_lat_nsec, write_lat_nsec;
+ u64 latency_targets[KYBER_OTHER];
};
struct kyber_hctx_data {
@@ -114,7 +184,7 @@
unsigned int batching;
struct kyber_ctx_queue *kcqs;
struct sbitmap kcq_map[KYBER_NUM_DOMAINS];
- wait_queue_entry_t domain_wait[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];
};
@@ -124,233 +194,219 @@
static unsigned int kyber_sched_domain(unsigned int op)
{
- if ((op & REQ_OP_MASK) == REQ_OP_READ)
+ switch (op & REQ_OP_MASK) {
+ case REQ_OP_READ:
return KYBER_READ;
- else if ((op & REQ_OP_MASK) == REQ_OP_WRITE && op_is_sync(op))
- return KYBER_SYNC_WRITE;
- else
+ case REQ_OP_WRITE:
+ return KYBER_WRITE;
+ case REQ_OP_DISCARD:
+ return KYBER_DISCARD;
+ default:
return KYBER_OTHER;
+ }
}
-enum {
- NONE = 0,
- GOOD = 1,
- GREAT = 2,
- BAD = -1,
- AWFUL = -2,
-};
-
-#define IS_GOOD(status) ((status) > 0)
-#define IS_BAD(status) ((status) < 0)
-
-static int kyber_lat_status(struct blk_stat_callback *cb,
- unsigned int sched_domain, u64 target)
+static void flush_latency_buckets(struct kyber_queue_data *kqd,
+ struct kyber_cpu_latency *cpu_latency,
+ unsigned int sched_domain, unsigned int type)
{
- u64 latency;
+ unsigned int *buckets = kqd->latency_buckets[sched_domain][type];
+ atomic_t *cpu_buckets = cpu_latency->buckets[sched_domain][type];
+ unsigned int bucket;
- if (!cb->stat[sched_domain].nr_samples)
- return NONE;
-
- latency = cb->stat[sched_domain].mean;
- if (latency >= 2 * target)
- return AWFUL;
- else if (latency > target)
- return BAD;
- else if (latency <= target / 2)
- return GREAT;
- else /* (latency <= target) */
- return GOOD;
+ for (bucket = 0; bucket < KYBER_LATENCY_BUCKETS; bucket++)
+ buckets[bucket] += atomic_xchg(&cpu_buckets[bucket], 0);
}
/*
- * Adjust the read or synchronous write depth given the status of reads and
- * writes. The goal is that the latencies of the two domains are fair (i.e., if
- * one is good, then the other is good).
+ * Calculate the histogram bucket with the given percentile rank, or -1 if there
+ * aren't enough samples yet.
*/
-static void kyber_adjust_rw_depth(struct kyber_queue_data *kqd,
- unsigned int sched_domain, int this_status,
- int other_status)
+static int calculate_percentile(struct kyber_queue_data *kqd,
+ unsigned int sched_domain, unsigned int type,
+ unsigned int percentile)
{
- unsigned int orig_depth, depth;
+ 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;
/*
- * If this domain had no samples, or reads and writes are both good or
- * both bad, don't adjust the depth.
+ * We do the calculation once we have 500 samples or one second passes
+ * since the first sample was recorded, whichever comes first.
*/
- if (this_status == NONE ||
- (IS_GOOD(this_status) && IS_GOOD(other_status)) ||
- (IS_BAD(this_status) && IS_BAD(other_status)))
- return;
-
- orig_depth = depth = kqd->domain_tokens[sched_domain].sb.depth;
-
- if (other_status == NONE) {
- depth++;
- } else {
- switch (this_status) {
- case GOOD:
- if (other_status == AWFUL)
- depth -= max(depth / 4, 1U);
- else
- depth -= max(depth / 8, 1U);
- break;
- case GREAT:
- if (other_status == AWFUL)
- depth /= 2;
- else
- depth -= max(depth / 4, 1U);
- break;
- case BAD:
- depth++;
- break;
- case AWFUL:
- if (other_status == GREAT)
- depth += 2;
- else
- depth++;
- break;
- }
+ 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->q, 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 != orig_depth)
+ if (depth != kqd->domain_tokens[sched_domain].sb.depth) {
sbitmap_queue_resize(&kqd->domain_tokens[sched_domain], depth);
+ trace_kyber_adjust(kqd->q, kyber_domain_names[sched_domain],
+ depth);
+ }
}
-/*
- * Adjust the depth of other requests given the status of reads and synchronous
- * writes. As long as either domain is doing fine, we don't throttle, but if
- * both domains are doing badly, we throttle heavily.
- */
-static void kyber_adjust_other_depth(struct kyber_queue_data *kqd,
- int read_status, int write_status,
- bool have_samples)
+static void kyber_timer_fn(struct timer_list *t)
{
- unsigned int orig_depth, depth;
- int status;
+ struct kyber_queue_data *kqd = from_timer(kqd, t, timer);
+ unsigned int sched_domain;
+ int cpu;
+ bool bad = false;
- orig_depth = depth = kqd->domain_tokens[KYBER_OTHER].sb.depth;
+ /* Sum all of the per-cpu latency histograms. */
+ for_each_online_cpu(cpu) {
+ struct kyber_cpu_latency *cpu_latency;
- if (read_status == NONE && write_status == NONE) {
- depth += 2;
- } else if (have_samples) {
- if (read_status == NONE)
- status = write_status;
- else if (write_status == NONE)
- status = read_status;
- else
- status = max(read_status, write_status);
- switch (status) {
- case GREAT:
- depth += 2;
- break;
- case GOOD:
- depth++;
- break;
- case BAD:
- depth -= max(depth / 4, 1U);
- break;
- case AWFUL:
- depth /= 2;
- break;
+ 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);
}
}
- depth = clamp(depth, 1U, kyber_depth[KYBER_OTHER]);
- if (depth != orig_depth)
- sbitmap_queue_resize(&kqd->domain_tokens[KYBER_OTHER], depth);
-}
+ /*
+ * 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;
-/*
- * Apply heuristics for limiting queue depths based on gathered latency
- * statistics.
- */
-static void kyber_stat_timer_fn(struct blk_stat_callback *cb)
-{
- struct kyber_queue_data *kqd = cb->data;
- int read_status, write_status;
-
- read_status = kyber_lat_status(cb, KYBER_READ, kqd->read_lat_nsec);
- write_status = kyber_lat_status(cb, KYBER_SYNC_WRITE, kqd->write_lat_nsec);
-
- kyber_adjust_rw_depth(kqd, KYBER_READ, read_status, write_status);
- kyber_adjust_rw_depth(kqd, KYBER_SYNC_WRITE, write_status, read_status);
- kyber_adjust_other_depth(kqd, read_status, write_status,
- cb->stat[KYBER_OTHER].nr_samples != 0);
+ p90 = calculate_percentile(kqd, sched_domain, KYBER_IO_LATENCY,
+ 90);
+ if (p90 >= KYBER_GOOD_BUCKETS)
+ bad = true;
+ }
/*
- * Continue monitoring latencies if we aren't hitting the targets or
- * we're still throttling other requests.
+ * 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.
*/
- if (!blk_stat_is_active(kqd->cb) &&
- ((IS_BAD(read_status) || IS_BAD(write_status) ||
- kqd->domain_tokens[KYBER_OTHER].sb.depth < kyber_depth[KYBER_OTHER])))
- blk_stat_activate_msecs(kqd->cb, 100);
+ 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 unsigned int kyber_sched_tags_shift(struct kyber_queue_data *kqd)
+static unsigned int kyber_sched_tags_shift(struct request_queue *q)
{
/*
* All of the hardware queues have the same depth, so we can just grab
* the shift of the first one.
*/
- return kqd->q->queue_hw_ctx[0]->sched_tags->bitmap_tags.sb.shift;
-}
-
-static int kyber_bucket_fn(const struct request *rq)
-{
- return kyber_sched_domain(rq->cmd_flags);
+ return q->queue_hw_ctx[0]->sched_tags->bitmap_tags->sb.shift;
}
static struct kyber_queue_data *kyber_queue_data_alloc(struct request_queue *q)
{
struct kyber_queue_data *kqd;
- unsigned int max_tokens;
unsigned int shift;
int ret = -ENOMEM;
int i;
- kqd = kmalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
+ kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
if (!kqd)
goto err;
+
kqd->q = q;
- kqd->cb = blk_stat_alloc_callback(kyber_stat_timer_fn, kyber_bucket_fn,
- KYBER_NUM_DOMAINS, kqd);
- if (!kqd->cb)
+ kqd->cpu_latency = alloc_percpu_gfp(struct kyber_cpu_latency,
+ GFP_KERNEL | __GFP_ZERO);
+ if (!kqd->cpu_latency)
goto err_kqd;
- /*
- * The maximum number of tokens for any scheduling domain is at least
- * the queue depth of a single hardware queue. If the hardware doesn't
- * have many tags, still provide a reasonable number.
- */
- max_tokens = max_t(unsigned int, q->tag_set->queue_depth,
- KYBER_MIN_DEPTH);
+ 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],
- max_tokens, -1, false, GFP_KERNEL,
- q->node);
+ kyber_depth[i], -1, false,
+ GFP_KERNEL, q->node);
if (ret) {
while (--i >= 0)
sbitmap_queue_free(&kqd->domain_tokens[i]);
- goto err_cb;
+ goto err_buckets;
}
- sbitmap_queue_resize(&kqd->domain_tokens[i], kyber_depth[i]);
}
- shift = kyber_sched_tags_shift(kqd);
- kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
+ for (i = 0; i < KYBER_OTHER; i++) {
+ kqd->domain_p99[i] = -1;
+ kqd->latency_targets[i] = kyber_latency_targets[i];
+ }
- kqd->read_lat_nsec = 2000000ULL;
- kqd->write_lat_nsec = 10000000ULL;
+ shift = kyber_sched_tags_shift(q);
+ kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
return kqd;
-err_cb:
- blk_stat_free_callback(kqd->cb);
+err_buckets:
+ free_percpu(kqd->cpu_latency);
err_kqd:
kfree(kqd);
err:
@@ -372,10 +428,10 @@
return PTR_ERR(kqd);
}
+ blk_stat_enable_accounting(q);
+
eq->elevator_data = kqd;
q->elevator = eq;
-
- blk_stat_add_callback(q, kqd->cb);
return 0;
}
@@ -383,14 +439,13 @@
static void kyber_exit_sched(struct elevator_queue *e)
{
struct kyber_queue_data *kqd = e->elevator_data;
- struct request_queue *q = kqd->q;
int i;
- blk_stat_remove_callback(q, kqd->cb);
+ del_timer_sync(&kqd->timer);
for (i = 0; i < KYBER_NUM_DOMAINS; i++)
sbitmap_queue_free(&kqd->domain_tokens[i]);
- blk_stat_free_callback(kqd->cb);
+ free_percpu(kqd->cpu_latency);
kfree(kqd);
}
@@ -435,10 +490,11 @@
for (i = 0; i < KYBER_NUM_DOMAINS; i++) {
INIT_LIST_HEAD(&khd->rqs[i]);
- init_waitqueue_func_entry(&khd->domain_wait[i],
+ khd->domain_wait[i].sbq = NULL;
+ init_waitqueue_func_entry(&khd->domain_wait[i].wait,
kyber_domain_wake);
- khd->domain_wait[i].private = hctx;
- INIT_LIST_HEAD(&khd->domain_wait[i].entry);
+ khd->domain_wait[i].wait.private = hctx;
+ INIT_LIST_HEAD(&khd->domain_wait[i].wait.entry);
atomic_set(&khd->wait_index[i], 0);
}
@@ -446,7 +502,7 @@
khd->batching = 0;
hctx->sched_data = khd;
- sbitmap_queue_min_shallow_depth(&hctx->sched_tags->bitmap_tags,
+ sbitmap_queue_min_shallow_depth(hctx->sched_tags->bitmap_tags,
kqd->async_depth);
return 0;
@@ -506,24 +562,25 @@
}
}
-static bool kyber_bio_merge(struct blk_mq_hw_ctx *hctx, struct bio *bio)
+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 blk_mq_ctx *ctx = blk_mq_get_ctx(hctx->queue);
- struct kyber_ctx_queue *kcq = &khd->kcqs[ctx->index_hw];
+ 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);
+ merged = blk_bio_list_merge(hctx->queue, rq_list, bio, nr_segs);
spin_unlock(&kcq->lock);
- blk_mq_put_ctx(ctx);
return merged;
}
-static void kyber_prepare_request(struct request *rq, struct bio *bio)
+static void kyber_prepare_request(struct request *rq)
{
rq_set_domain_token(rq, -1);
}
@@ -536,7 +593,7 @@
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 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);
@@ -545,7 +602,7 @@
else
list_move_tail(&rq->queuelist, head);
sbitmap_set_bit(&khd->kcq_map[sched_domain],
- rq->mq_ctx->index_hw);
+ rq->mq_ctx->index_hw[hctx->type]);
blk_mq_sched_request_inserted(rq);
spin_unlock(&kcq->lock);
}
@@ -558,41 +615,44 @@
rq_clear_domain_token(kqd, rq);
}
-static void kyber_completed_request(struct request *rq)
+static void add_latency_sample(struct kyber_cpu_latency *cpu_latency,
+ unsigned int sched_domain, unsigned int type,
+ u64 target, u64 latency)
{
- struct request_queue *q = rq->q;
- struct kyber_queue_data *kqd = q->elevator->elevator_data;
- unsigned int sched_domain;
- u64 now, latency, target;
+ unsigned int bucket;
+ u64 divisor;
- /*
- * 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 (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;
}
- /* If we are already monitoring latencies, don't check again. */
- if (blk_stat_is_active(kqd->cb))
+ 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;
- now = ktime_get_ns();
- if (now < rq->io_start_time_ns)
- 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);
- latency = now - rq->io_start_time_ns;
-
- if (latency > target)
- blk_stat_activate_msecs(kqd->cb, 10);
+ timer_reduce(&kqd->timer, jiffies + HZ / 10);
}
struct flush_kcq_data {
@@ -629,12 +689,13 @@
flush_busy_kcq, &data);
}
-static int kyber_domain_wake(wait_queue_entry_t *wait, unsigned mode, int flags,
+static int kyber_domain_wake(wait_queue_entry_t *wqe, unsigned mode, int flags,
void *key)
{
- struct blk_mq_hw_ctx *hctx = READ_ONCE(wait->private);
+ struct blk_mq_hw_ctx *hctx = READ_ONCE(wqe->private);
+ struct sbq_wait *wait = container_of(wqe, struct sbq_wait, wait);
- list_del_init(&wait->entry);
+ sbitmap_del_wait_queue(wait);
blk_mq_run_hw_queue(hctx, true);
return 1;
}
@@ -645,7 +706,7 @@
{
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 *wait = &khd->domain_wait[sched_domain];
struct sbq_wait_state *ws;
int nr;
@@ -656,11 +717,11 @@
* 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)) {
+ 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;
- add_wait_queue(&ws->wait, wait);
+ sbitmap_add_wait_queue(domain_tokens, ws, wait);
/*
* Try again in case a token was freed before we got on the wait
@@ -676,10 +737,10 @@
* 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)) {
+ if (nr >= 0 && !list_empty_careful(&wait->wait.entry)) {
ws = khd->domain_ws[sched_domain];
spin_lock_irq(&ws->wait.lock);
- list_del_init(&wait->entry);
+ sbitmap_del_wait_queue(wait);
spin_unlock_irq(&ws->wait.lock);
}
@@ -713,6 +774,9 @@
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);
@@ -723,6 +787,9 @@
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]);
}
}
@@ -790,17 +857,17 @@
return false;
}
-#define KYBER_LAT_SHOW_STORE(op) \
-static ssize_t kyber_##op##_lat_show(struct elevator_queue *e, \
- char *page) \
+#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->op##_lat_nsec); \
+ return sprintf(page, "%llu\n", kqd->latency_targets[domain]); \
} \
\
-static ssize_t kyber_##op##_lat_store(struct elevator_queue *e, \
- const char *page, size_t count) \
+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; \
@@ -810,12 +877,12 @@
if (ret) \
return ret; \
\
- kqd->op##_lat_nsec = nsec; \
+ kqd->latency_targets[domain] = nsec; \
\
return count; \
}
-KYBER_LAT_SHOW_STORE(read);
-KYBER_LAT_SHOW_STORE(write);
+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)
@@ -876,13 +943,14 @@
{ \
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_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_SYNC_WRITE, sync_write)
+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
@@ -900,20 +968,7 @@
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;
- }
+ seq_printf(m, "%s\n", kyber_domain_names[khd->cur_domain]);
return 0;
}
@@ -930,7 +985,8 @@
{#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(write),
+ KYBER_QUEUE_DOMAIN_ATTRS(discard),
KYBER_QUEUE_DOMAIN_ATTRS(other),
{"async_depth", 0400, kyber_async_depth_show},
{},
@@ -942,7 +998,8 @@
{#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(write),
+ KYBER_HCTX_DOMAIN_ATTRS(discard),
KYBER_HCTX_DOMAIN_ATTRS(other),
{"cur_domain", 0400, kyber_cur_domain_show},
{"batching", 0400, kyber_batching_show},
@@ -952,7 +1009,7 @@
#endif
static struct elevator_type kyber_sched = {
- .ops.mq = {
+ .ops = {
.init_sched = kyber_init_sched,
.exit_sched = kyber_exit_sched,
.init_hctx = kyber_init_hctx,
@@ -967,13 +1024,13 @@
.dispatch_request = kyber_dispatch_request,
.has_work = kyber_has_work,
},
- .uses_mq = true,
#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_features = ELEVATOR_F_MQ_AWARE,
.elevator_owner = THIS_MODULE,
};
--
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