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blk-mq: Restart a single queue if tag sets are shared 

To improve scalability, if hardware queues are shared, restart
a single hardware queue in round-robin fashion. Rename
blk_mq_sched_restart_queues() to reflect the new semantics.
Remove blk_mq_sched_mark_restart_queue() because this function
has no callers. Remove flag QUEUE_FLAG_RESTART because this
patch removes the code that uses this flag.

Signed-off-by: Bart Van Assche <bart.vanassche@sandisk.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>
This commit is contained in:
Bart Van Assche 2017-04-07 12:40:09 -06:00 committed by Jens Axboe
parent 6077c2d706
commit 6d8c6c0f97
4 changed files with 55 additions and 27 deletions
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63
block/blk-mq-sched.c
View File

@ -318,25 +318,68 @@ static bool blk_mq_sched_bypass_insert(struct blk_mq_hw_ctx *hctx,
return true;
}
static void blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
static bool blk_mq_sched_restart_hctx(struct blk_mq_hw_ctx *hctx)
{
if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) {
clear_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
if (blk_mq_hctx_has_pending(hctx))
if (blk_mq_hctx_has_pending(hctx)) {
blk_mq_run_hw_queue(hctx, true);
return true;
}
}
return false;
}
void blk_mq_sched_restart_queues(struct blk_mq_hw_ctx *hctx)
{
struct request_queue *q = hctx->queue;
unsigned int i;
/**
* list_for_each_entry_rcu_rr - iterate in a round-robin fashion over rcu list
* @pos: loop cursor.
* @skip: the list element that will not be examined. Iteration starts at
* @skip->next.
* @head: head of the list to examine. This list must have at least one
* element, namely @skip.
* @member: name of the list_head structure within typeof(*pos).
*/
#define list_for_each_entry_rcu_rr(pos, skip, head, member) \
for ((pos) = (skip); \
(pos = (pos)->member.next != (head) ? list_entry_rcu( \
(pos)->member.next, typeof(*pos), member) : \
list_entry_rcu((pos)->member.next->next, typeof(*pos), member)), \
(pos) != (skip); )
if (test_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
if (test_and_clear_bit(QUEUE_FLAG_RESTART, &q->queue_flags)) {
queue_for_each_hw_ctx(q, hctx, i)
blk_mq_sched_restart_hctx(hctx);
/*
* Called after a driver tag has been freed to check whether a hctx needs to
* be restarted. Restarts @hctx if its tag set is not shared. Restarts hardware
* queues in a round-robin fashion if the tag set of @hctx is shared with other
* hardware queues.
*/
void blk_mq_sched_restart(struct blk_mq_hw_ctx *const hctx)
{
struct blk_mq_tags *const tags = hctx->tags;
struct blk_mq_tag_set *const set = hctx->queue->tag_set;
struct request_queue *const queue = hctx->queue, *q;
struct blk_mq_hw_ctx *hctx2;
unsigned int i, j;
if (set->flags & BLK_MQ_F_TAG_SHARED) {
rcu_read_lock();
list_for_each_entry_rcu_rr(q, queue, &set->tag_list,
tag_set_list) {
queue_for_each_hw_ctx(q, hctx2, i)
if (hctx2->tags == tags &&
blk_mq_sched_restart_hctx(hctx2))
goto done;
}
j = hctx->queue_num + 1;
for (i = 0; i < queue->nr_hw_queues; i++, j++) {
if (j == queue->nr_hw_queues)
j = 0;
hctx2 = queue->queue_hw_ctx[j];
if (hctx2->tags == tags &&
blk_mq_sched_restart_hctx(hctx2))
break;
}
done:
rcu_read_unlock();
} else {
blk_mq_sched_restart_hctx(hctx);
}

16
block/blk-mq-sched.h
View File

@ -19,7 +19,7 @@ bool blk_mq_sched_try_merge(struct request_queue *q, struct bio *bio,
struct request **merged_request);
bool __blk_mq_sched_bio_merge(struct request_queue *q, struct bio *bio);
bool blk_mq_sched_try_insert_merge(struct request_queue *q, struct request *rq);
void blk_mq_sched_restart_queues(struct blk_mq_hw_ctx *hctx);
void blk_mq_sched_restart(struct blk_mq_hw_ctx *hctx);
void blk_mq_sched_insert_request(struct request *rq, bool at_head,
bool run_queue, bool async, bool can_block);
@ -136,20 +136,6 @@ static inline void blk_mq_sched_mark_restart_hctx(struct blk_mq_hw_ctx *hctx)
set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
}
/*
* Mark a hardware queue and the request queue it belongs to as needing a
* restart.
*/
static inline void blk_mq_sched_mark_restart_queue(struct blk_mq_hw_ctx *hctx)
{
struct request_queue *q = hctx->queue;
if (!test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state))
set_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);
if (!test_bit(QUEUE_FLAG_RESTART, &q->queue_flags))
set_bit(QUEUE_FLAG_RESTART, &q->queue_flags);
}
static inline bool blk_mq_sched_needs_restart(struct blk_mq_hw_ctx *hctx)
{
return test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state);

2
block/blk-mq.c
View File

@ -348,7 +348,7 @@ void __blk_mq_finish_request(struct blk_mq_hw_ctx *hctx, struct blk_mq_ctx *ctx,
blk_mq_put_tag(hctx, hctx->tags, ctx, rq->tag);
if (sched_tag != -1)
blk_mq_sched_completed_request(hctx, rq);
blk_mq_sched_restart_queues(hctx);
blk_mq_sched_restart(hctx);
blk_queue_exit(q);
}

1
include/linux/blkdev.h
View File

@ -610,7 +610,6 @@ struct request_queue {
#define QUEUE_FLAG_FLUSH_NQ 25 /* flush not queueuable */
#define QUEUE_FLAG_DAX 26 /* device supports DAX */
#define QUEUE_FLAG_STATS 27 /* track rq completion times */
#define QUEUE_FLAG_RESTART 28 /* queue needs restart at completion */
#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \