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blk-mq: dequeue request one by one from sw queue if hctx is busy

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It won't be efficient to dequeue request one by one from sw queue,
but we have to do that when queue is busy for better merge performance.

This patch takes the Exponential Weighted Moving Average(EWMA) to figure
out if queue is busy, then only dequeue request one by one from sw queue
when queue is busy.

Fixes: b347689ffb ("blk-mq-sched: improve dispatching from sw queue")
Cc: Kashyap Desai <kashyap.desai@broadcom.com>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Omar Sandoval <osandov@fb.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bart.vanassche@wdc.com>
Cc: Hannes Reinecke <hare@suse.de>
Reported-by: Kashyap Desai <kashyap.desai@broadcom.com>
Tested-by: Kashyap Desai <kashyap.desai@broadcom.com>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Ming Lei
2018-07-03 09:03:16 -06:00
committed by Jens Axboe
parent d893ff8603
commit 6e76871730
4 changed files with 45 additions and 11 deletions
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3
include/linux/blk-mq.h
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@@ -35,9 +35,10 @@ struct blk_mq_hw_ctx {
struct sbitmap ctx_map;
struct blk_mq_ctx *dispatch_from;
unsigned int dispatch_busy;
struct blk_mq_ctx **ctxs;
unsigned int nr_ctx;
struct blk_mq_ctx **ctxs;
spinlock_t dispatch_wait_lock;
wait_queue_entry_t dispatch_wait;