diff options
| author | Jens Axboe <axboe@kernel.dk> | 2017-06-20 17:56:13 -0600 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2017-06-21 10:17:49 -0600 |
| commit | 8e8320c9315c47a6a090188720ccff32a6a6ba18 (patch) | |
| tree | e407c7eb7afd9d09aea9355426a2942a295be946 /block/blk-mq.c | |
| parent | ec2f0fadde446e0ebe28c779ffcac655228b8f1e (diff) | |
| download | linux-8e8320c9315c47a6a090188720ccff32a6a6ba18.tar.gz linux-8e8320c9315c47a6a090188720ccff32a6a6ba18.tar.bz2 linux-8e8320c9315c47a6a090188720ccff32a6a6ba18.zip | |
blk-mq: fix performance regression with shared tags
If we have shared tags enabled, then every IO completion will trigger
a full loop of every queue belonging to a tag set, and every hardware
queue for each of those queues, even if nothing needs to be done.
This causes a massive performance regression if you have a lot of
shared devices.
Instead of doing this huge full scan on every IO, add an atomic
counter to the main queue that tracks how many hardware queues have
been marked as needing a restart. With that, we can avoid looking for
restartable queues, if we don't have to.
Max reports that this restores performance. Before this patch, 4K
IOPS was limited to 22-23K IOPS. With the patch, we are running at
950-970K IOPS.
Fixes: 6d8c6c0f97ad ("blk-mq: Restart a single queue if tag sets are shared")
Reported-by: Max Gurtovoy <maxg@mellanox.com>
Tested-by: Max Gurtovoy <maxg@mellanox.com>
Reviewed-by: Bart Van Assche <bart.vanassche@sandisk.com>
Tested-by: Bart Van Assche <bart.vanassche@wdc.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Diffstat (limited to 'block/blk-mq.c')
| -rw-r--r-- | block/blk-mq.c | 16 |
1 files changed, 13 insertions, 3 deletions
diff --git a/block/blk-mq.c b/block/blk-mq.c index bb66c96850b1..958cedaff8b8 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -2103,20 +2103,30 @@ static void blk_mq_map_swqueue(struct request_queue *q, } } +/* + * Caller needs to ensure that we're either frozen/quiesced, or that + * the queue isn't live yet. + */ static void queue_set_hctx_shared(struct request_queue *q, bool shared) { struct blk_mq_hw_ctx *hctx; int i; queue_for_each_hw_ctx(q, hctx, i) { - if (shared) + if (shared) { + if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) + atomic_inc(&q->shared_hctx_restart); hctx->flags |= BLK_MQ_F_TAG_SHARED; - else + } else { + if (test_bit(BLK_MQ_S_SCHED_RESTART, &hctx->state)) + atomic_dec(&q->shared_hctx_restart); hctx->flags &= ~BLK_MQ_F_TAG_SHARED; + } } } -static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, bool shared) +static void blk_mq_update_tag_set_depth(struct blk_mq_tag_set *set, + bool shared) { struct request_queue *q; |