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-rw-r--r--block/kyber-iosched.c1051
1 files changed, 1051 insertions, 0 deletions
diff --git a/block/kyber-iosched.c b/block/kyber-iosched.c
new file mode 100644
index 000000000..7f9ef773b
--- /dev/null
+++ b/block/kyber-iosched.c
@@ -0,0 +1,1051 @@
+// 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/blk-mq.h>
+#include <linux/elevator.h>
+#include <linux/module.h>
+#include <linux/sbitmap.h>
+
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-debugfs.h"
+#include "blk-mq-sched.h"
+#include "blk-mq-tag.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;
+
+ /*
+ * 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(unsigned int op)
+{
+ switch (op & 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->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 != 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);
+ }
+}
+
+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 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 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 shift;
+ int ret = -ENOMEM;
+ int i;
+
+ kqd = kzalloc_node(sizeof(*kqd), GFP_KERNEL, q->node);
+ if (!kqd)
+ goto err;
+
+ kqd->q = q;
+
+ 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];
+ }
+
+ shift = kyber_sched_tags_shift(q);
+ kqd->async_depth = (1U << shift) * KYBER_ASYNC_PERCENT / 100U;
+
+ 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);
+
+ 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;
+
+ del_timer_sync(&kqd->timer);
+
+ 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 int kyber_init_hctx(struct blk_mq_hw_ctx *hctx, unsigned int hctx_idx)
+{
+ struct kyber_queue_data *kqd = hctx->queue->elevator->elevator_data;
+ 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)) {
+ 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;
+ 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 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, 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");
generated by cgit v1.2.3 (git 2.39.1) at 2024-12-28 09:27:23 +0000