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

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This reverts commit fb1e75389b.

"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: Jens Axboe <jens.axboe@oracle.com>
This commit is contained in:
Jens Axboe 2010-02-23 08:40:43 +01:00
parent 9f3a628488
commit 79da0644a8
2 changed files with 3 additions and 12 deletions
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11
block/blk-core.c
View file

@ -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);
}
}
/**

4
include/linux/blkdev.h
View file

@ -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)