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Commit 79da0644 authored by Jens Axboe's avatar Jens Axboe
Browse files

Revert "block: improve queue_should_plug() by looking at IO depths" 



This reverts commit fb1e7538.

"Benjamin S." <sbenni@gmx.de> reports that the patch in question
causes a big drop in sequential throughput for him, dropping from
200MB/sec down to only 70MB/sec.

Needs to be investigated more fully, for now lets just revert the
offending commit.

Conflicts:

	include/linux/blkdev.h

Signed-off-by: default avatarJens Axboe <jens.axboe@oracle.com>
parent 9f3a6284

block/blk-core.c

+2 −9
Original line number Diff line number Diff line
@@ -1147,7 +1147,7 @@ void init_request_from_bio(struct request *req, struct bio *bio) 
 */

static inline bool queue_should_plug(struct request_queue *q)

{

	return !(blk_queue_nonrot(q) && blk_queue_queuing(q));

	return !(blk_queue_nonrot(q) && blk_queue_tagged(q));

}



static int __make_request(struct request_queue *q, struct bio *bio)
@@ -1859,15 +1859,8 @@ void blk_dequeue_request(struct request *rq) 
	 * and to it is freed is accounted as io that is in progress at

	 * the driver side.

	 */

	if (blk_account_rq(rq)) {

	if (blk_account_rq(rq))

		q->in_flight[rq_is_sync(rq)]++;

		/*

		 * Mark this device as supporting hardware queuing, if

		 * we have more IOs in flight than 4.

		 */

		if (!blk_queue_queuing(q) && queue_in_flight(q) > 4)

			set_bit(QUEUE_FLAG_CQ, &q->queue_flags);

	}

}



/**

include/linux/blkdev.h

+1 −3
Original line number Diff line number Diff line
@@ -461,8 +461,7 @@ struct request_queue 
#define QUEUE_FLAG_NONROT      14	/* non-rotational device (SSD) */

#define QUEUE_FLAG_VIRT        QUEUE_FLAG_NONROT /* paravirt device */

#define QUEUE_FLAG_IO_STAT     15	/* do IO stats */

#define QUEUE_FLAG_CQ	       16	/* hardware does queuing */

#define QUEUE_FLAG_DISCARD     17	/* supports DISCARD */

#define QUEUE_FLAG_DISCARD     16	/* supports DISCARD */



#define QUEUE_FLAG_DEFAULT	((1 << QUEUE_FLAG_IO_STAT) |		\

				 (1 << QUEUE_FLAG_CLUSTER) |		\
@@ -586,7 +585,6 @@ enum { 


#define blk_queue_plugged(q)	test_bit(QUEUE_FLAG_PLUGGED, &(q)->queue_flags)

#define blk_queue_tagged(q)	test_bit(QUEUE_FLAG_QUEUED, &(q)->queue_flags)

#define blk_queue_queuing(q)	test_bit(QUEUE_FLAG_CQ, &(q)->queue_flags)

#define blk_queue_stopped(q)	test_bit(QUEUE_FLAG_STOPPED, &(q)->queue_flags)

#define blk_queue_nomerges(q)	test_bit(QUEUE_FLAG_NOMERGES, &(q)->queue_flags)

#define blk_queue_nonrot(q)	test_bit(QUEUE_FLAG_NONROT, &(q)->queue_flags)