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Commit d87447d8 authored by Paolo Valente's avatar Paolo Valente Committed by Jens Axboe
Browse files

block, bfq: fix sequential rq detection in rate estimation 



In bfq_update_peak_rate, to check whether an I/O request rq is
sequential, only the seek distance of rq w.r.t. the last request
dispatched is controlled. This is not sufficient for non-rotational
storage, where the size of rq is at least as relevant. This commit adds
the missing control.

Signed-off-by: default avatarPaolo Valente <paolo.valente@linaro.org>
Signed-off-by: default avatarJens Axboe <axboe@kernel.dk>
parent 530c4cbb

block/bfq-iosched.c

+7 −5
Original line number Diff line number Diff line
@@ -235,6 +235,11 @@ static struct kmem_cache *bfq_pool; 


#define BFQQ_SEEK_THR		(sector_t)(8 * 100)

#define BFQQ_SECT_THR_NONROT	(sector_t)(2 * 32)

#define BFQ_RQ_SEEKY(bfqd, last_pos, rq) \

	(get_sdist(last_pos, rq) >			\

	 BFQQ_SEEK_THR &&				\

	 (!blk_queue_nonrot(bfqd->queue) ||		\

	  blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT))

#define BFQQ_CLOSE_THR		(sector_t)(8 * 1024)

#define BFQQ_SEEKY(bfqq)	(hweight32(bfqq->seek_history) > 19)
@@ -2754,7 +2759,7 @@ static void bfq_update_peak_rate(struct bfq_data *bfqd, struct request *rq) 


	if ((bfqd->rq_in_driver > 0 ||

		now_ns - bfqd->last_completion < BFQ_MIN_TT)

	     && get_sdist(bfqd->last_position, rq) < BFQQ_SEEK_THR)

	    && !BFQ_RQ_SEEKY(bfqd, bfqd->last_position, rq))

		bfqd->sequential_samples++;



	bfqd->tot_sectors_dispatched += blk_rq_sectors(rq);
@@ -4511,10 +4516,7 @@ bfq_update_io_seektime(struct bfq_data *bfqd, struct bfq_queue *bfqq, 
		       struct request *rq)

{

	bfqq->seek_history <<= 1;

	bfqq->seek_history |=

		get_sdist(bfqq->last_request_pos, rq) > BFQQ_SEEK_THR &&

		(!blk_queue_nonrot(bfqd->queue) ||

		 blk_rq_sectors(rq) < BFQQ_SECT_THR_NONROT);

	bfqq->seek_history |= BFQ_RQ_SEEKY(bfqd, bfqq->last_request_pos, rq);

}



static void bfq_update_has_short_ttime(struct bfq_data *bfqd,