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authorJens Axboe <axboe@fb.com>2017-01-17 06:03:22 -0700
committerJens Axboe <axboe@fb.com>2017-01-17 10:04:20 -0700
commitbd166ef183c263c5ced656d49ef19c7da4adc774 (patch)
tree449bbd3b4e671b370b96e3846b2281116e7089e9 /block/blk-mq-sched.c
parent2af8cbe30531eca73c8f3ba277f155fc0020b01a (diff)
downloadlinux-bd166ef183c263c5ced656d49ef19c7da4adc774.tar.bz2
blk-mq-sched: add framework for MQ capable IO schedulers
This adds a set of hooks that intercepts the blk-mq path of allocating/inserting/issuing/completing requests, allowing us to develop a scheduler within that framework. We reuse the existing elevator scheduler API on the registration side, but augment that with the scheduler flagging support for the blk-mq interfce, and with a separate set of ops hooks for MQ devices. We split driver and scheduler tags, so we can run the scheduling independently of device queue depth. Signed-off-by: Jens Axboe <axboe@fb.com> Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com> Reviewed-by: Omar Sandoval <osandov@fb.com>
Diffstat (limited to 'block/blk-mq-sched.c')
-rw-r--r--block/blk-mq-sched.c368
1 files changed, 368 insertions, 0 deletions
diff --git a/block/blk-mq-sched.c b/block/blk-mq-sched.c
new file mode 100644
index 000000000000..26759798a0b3
--- /dev/null
+++ b/block/blk-mq-sched.c
@@ -0,0 +1,368 @@
+/*
+ * blk-mq scheduling framework
+ *
+ * Copyright (C) 2016 Jens Axboe
+ */
+#include <linux/kernel.h>
+#include <linux/module.h>
+#include <linux/blk-mq.h>
+
+#include <trace/events/block.h>
+
+#include "blk.h"
+#include "blk-mq.h"
+#include "blk-mq-sched.h"
+#include "blk-mq-tag.h"
+#include "blk-wbt.h"
+
+void blk_mq_sched_free_hctx_data(struct request_queue *q,
+ void (*exit)(struct blk_mq_hw_ctx *))
+{
+ struct blk_mq_hw_ctx *hctx;
+ int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (exit && hctx->sched_data)
+ exit(hctx);
+ kfree(hctx->sched_data);
+ hctx->sched_data = NULL;
+ }
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_free_hctx_data);
+
+int blk_mq_sched_init_hctx_data(struct request_queue *q, size_t size,
+ int (*init)(struct blk_mq_hw_ctx *),
+ void (*exit)(struct blk_mq_hw_ctx *))
+{
+ struct blk_mq_hw_ctx *hctx;
+ int ret;
+ int i;
+
+ queue_for_each_hw_ctx(q, hctx, i) {
+ hctx->sched_data = kmalloc_node(size, GFP_KERNEL, hctx->numa_node);
+ if (!hctx->sched_data) {
+ ret = -ENOMEM;
+ goto error;
+ }
+
+ if (init) {
+ ret = init(hctx);
+ if (ret) {
+ /*
+ * We don't want to give exit() a partially
+ * initialized sched_data. init() must clean up
+ * if it fails.
+ */
+ kfree(hctx->sched_data);
+ hctx->sched_data = NULL;
+ goto error;
+ }
+ }
+ }
+
+ return 0;
+error:
+ blk_mq_sched_free_hctx_data(q, exit);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_init_hctx_data);
+
+static void __blk_mq_sched_assign_ioc(struct request_queue *q,
+ struct request *rq, struct io_context *ioc)
+{
+ struct io_cq *icq;
+
+ spin_lock_irq(q->queue_lock);
+ icq = ioc_lookup_icq(ioc, q);
+ spin_unlock_irq(q->queue_lock);
+
+ if (!icq) {
+ icq = ioc_create_icq(ioc, q, GFP_ATOMIC);
+ if (!icq)
+ return;
+ }
+
+ rq->elv.icq = icq;
+ if (!blk_mq_sched_get_rq_priv(q, rq)) {
+ rq->rq_flags |= RQF_ELVPRIV;
+ get_io_context(icq->ioc);
+ return;
+ }
+
+ rq->elv.icq = NULL;
+}
+
+static void blk_mq_sched_assign_ioc(struct request_queue *q,
+ struct request *rq, struct bio *bio)
+{
+ struct io_context *ioc;
+
+ ioc = rq_ioc(bio);
+ if (ioc)
+ __blk_mq_sched_assign_ioc(q, rq, ioc);
+}
+
+struct request *blk_mq_sched_get_request(struct request_queue *q,
+ struct bio *bio,
+ unsigned int op,
+ struct blk_mq_alloc_data *data)
+{
+ struct elevator_queue *e = q->elevator;
+ struct blk_mq_hw_ctx *hctx;
+ struct blk_mq_ctx *ctx;
+ struct request *rq;
+ const bool is_flush = op & (REQ_PREFLUSH | REQ_FUA);
+
+ blk_queue_enter_live(q);
+ ctx = blk_mq_get_ctx(q);
+ hctx = blk_mq_map_queue(q, ctx->cpu);
+
+ blk_mq_set_alloc_data(data, q, 0, ctx, hctx);
+
+ if (e) {
+ data->flags |= BLK_MQ_REQ_INTERNAL;
+
+ /*
+ * Flush requests are special and go directly to the
+ * dispatch list.
+ */
+ if (!is_flush && e->type->ops.mq.get_request) {
+ rq = e->type->ops.mq.get_request(q, op, data);
+ if (rq)
+ rq->rq_flags |= RQF_QUEUED;
+ } else
+ rq = __blk_mq_alloc_request(data, op);
+ } else {
+ rq = __blk_mq_alloc_request(data, op);
+ data->hctx->tags->rqs[rq->tag] = rq;
+ }
+
+ if (rq) {
+ if (!is_flush) {
+ rq->elv.icq = NULL;
+ if (e && e->type->icq_cache)
+ blk_mq_sched_assign_ioc(q, rq, bio);
+ }
+ data->hctx->queued++;
+ return rq;
+ }
+
+ blk_queue_exit(q);
+ return NULL;
+}
+
+void blk_mq_sched_put_request(struct request *rq)
+{
+ struct request_queue *q = rq->q;
+ struct elevator_queue *e = q->elevator;
+
+ if (rq->rq_flags & RQF_ELVPRIV) {
+ blk_mq_sched_put_rq_priv(rq->q, rq);
+ if (rq->elv.icq) {
+ put_io_context(rq->elv.icq->ioc);
+ rq->elv.icq = NULL;
+ }
+ }
+
+ if ((rq->rq_flags & RQF_QUEUED) && e && e->type->ops.mq.put_request)
+ e->type->ops.mq.put_request(rq);
+ else
+ blk_mq_finish_request(rq);
+}
+
+void blk_mq_sched_dispatch_requests(struct blk_mq_hw_ctx *hctx)
+{
+ struct elevator_queue *e = hctx->queue->elevator;
+ LIST_HEAD(rq_list);
+
+ if (unlikely(blk_mq_hctx_stopped(hctx)))
+ return;
+
+ hctx->run++;
+
+ /*
+ * If we have previous entries on our dispatch list, grab them first for
+ * more fair dispatch.
+ */
+ if (!list_empty_careful(&hctx->dispatch)) {
+ spin_lock(&hctx->lock);
+ if (!list_empty(&hctx->dispatch))
+ list_splice_init(&hctx->dispatch, &rq_list);
+ spin_unlock(&hctx->lock);
+ }
+
+ /*
+ * Only ask the scheduler for requests, if we didn't have residual
+ * requests from the dispatch list. This is to avoid the case where
+ * we only ever dispatch a fraction of the requests available because
+ * of low device queue depth. Once we pull requests out of the IO
+ * scheduler, we can no longer merge or sort them. So it's best to
+ * leave them there for as long as we can. Mark the hw queue as
+ * needing a restart in that case.
+ */
+ if (list_empty(&rq_list)) {
+ if (e && e->type->ops.mq.dispatch_requests)
+ e->type->ops.mq.dispatch_requests(hctx, &rq_list);
+ else
+ blk_mq_flush_busy_ctxs(hctx, &rq_list);
+ } else
+ blk_mq_sched_mark_restart(hctx);
+
+ blk_mq_dispatch_rq_list(hctx, &rq_list);
+}
+
+void blk_mq_sched_move_to_dispatch(struct blk_mq_hw_ctx *hctx,
+ struct list_head *rq_list,
+ struct request *(*get_rq)(struct blk_mq_hw_ctx *))
+{
+ do {
+ struct request *rq;
+
+ rq = get_rq(hctx);
+ if (!rq)
+ break;
+
+ list_add_tail(&rq->queuelist, rq_list);
+ } while (1);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_move_to_dispatch);
+
+bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio)
+{
+ struct request *rq;
+ int ret;
+
+ ret = elv_merge(q, &rq, bio);
+ if (ret == ELEVATOR_BACK_MERGE) {
+ if (!blk_mq_sched_allow_merge(q, rq, bio))
+ return false;
+ if (bio_attempt_back_merge(q, rq, bio)) {
+ if (!attempt_back_merge(q, rq))
+ elv_merged_request(q, rq, ret);
+ return true;
+ }
+ } else if (ret == ELEVATOR_FRONT_MERGE) {
+ if (!blk_mq_sched_allow_merge(q, rq, bio))
+ return false;
+ if (bio_attempt_front_merge(q, rq, bio)) {
+ if (!attempt_front_merge(q, rq))
+ elv_merged_request(q, rq, ret);
+ return true;
+ }
+ }
+
+ return false;
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_try_merge);
+
+bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio)
+{
+ struct elevator_queue *e = q->elevator;
+
+ if (e->type->ops.mq.bio_merge) {
+ struct blk_mq_ctx *ctx = blk_mq_get_ctx(q);
+ struct blk_mq_hw_ctx *hctx = blk_mq_map_queue(q, ctx->cpu);
+
+ blk_mq_put_ctx(ctx);
+ return e->type->ops.mq.bio_merge(hctx, bio);
+ }
+
+ return false;
+}
+
+bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq)
+{
+ return rq_mergeable(rq) && elv_attempt_insert_merge(q, rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_try_insert_merge);
+
+void blk_mq_sched_request_inserted(struct request *rq)
+{
+ trace_block_rq_insert(rq->q, rq);
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_request_inserted);
+
+bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx, struct request *rq)
+{
+ if (rq->tag == -1) {
+ rq->rq_flags |= RQF_SORTED;
+ return false;
+ }
+
+ /*
+ * If we already have a real request tag, send directly to
+ * the dispatch list.
+ */
+ spin_lock(&hctx->lock);
+ list_add(&rq->queuelist, &hctx->dispatch);
+ spin_unlock(&hctx->lock);
+ return true;
+}
+EXPORT_SYMBOL_GPL(blk_mq_sched_bypass_insert);
+
+static void blk_mq_sched_free_tags(struct blk_mq_tag_set *set,
+ struct blk_mq_hw_ctx *hctx,
+ unsigned int hctx_idx)
+{
+ if (hctx->sched_tags) {
+ blk_mq_free_rqs(set, hctx->sched_tags, hctx_idx);
+ blk_mq_free_rq_map(hctx->sched_tags);
+ hctx->sched_tags = NULL;
+ }
+}
+
+int blk_mq_sched_setup(struct request_queue *q)
+{
+ struct blk_mq_tag_set *set = q->tag_set;
+ struct blk_mq_hw_ctx *hctx;
+ int ret, i;
+
+ /*
+ * Default to 256, since we don't split into sync/async like the
+ * old code did. Additionally, this is a per-hw queue depth.
+ */
+ q->nr_requests = 2 * BLKDEV_MAX_RQ;
+
+ /*
+ * We're switching to using an IO scheduler, so setup the hctx
+ * scheduler tags and switch the request map from the regular
+ * tags to scheduler tags. First allocate what we need, so we
+ * can safely fail and fallback, if needed.
+ */
+ ret = 0;
+ queue_for_each_hw_ctx(q, hctx, i) {
+ hctx->sched_tags = blk_mq_alloc_rq_map(set, i, q->nr_requests, 0);
+ if (!hctx->sched_tags) {
+ ret = -ENOMEM;
+ break;
+ }
+ ret = blk_mq_alloc_rqs(set, hctx->sched_tags, i, q->nr_requests);
+ if (ret)
+ break;
+ }
+
+ /*
+ * If we failed, free what we did allocate
+ */
+ if (ret) {
+ queue_for_each_hw_ctx(q, hctx, i) {
+ if (!hctx->sched_tags)
+ continue;
+ blk_mq_sched_free_tags(set, hctx, i);
+ }
+
+ return ret;
+ }
+
+ return 0;
+}
+
+void blk_mq_sched_teardown(struct request_queue *q)
+{
+ struct blk_mq_tag_set *set = q->tag_set;
+ struct blk_mq_hw_ctx *hctx;
+ int i;
+
+ queue_for_each_hw_ctx(q, hctx, i)
+ blk_mq_sched_free_tags(set, hctx, i);
+}