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Subject[ 002/184] Revert "block: improve queue_should_plug() by
2.6.32-longterm review patch.  If anyone has any objections, please let me know.

------------------
looking at IO depths"

From: Jens Axboe <jens.axboe@oracle.com>

This reverts commit fb1e75389bd06fd5987e9cda1b4e0305c782f854.

"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>
(cherry picked from commit 79da0644a8e0838522828f106e4049639eea6baf)
Cc: Thomas Bork <tom@eisfair.net>
Signed-off-by: Willy Tarreau <w@1wt.eu>
---
block/blk-core.c | 11 ++---------
include/linux/blkdev.h | 4 +---
2 files changed, 3 insertions(+), 12 deletions(-)

diff --git a/block/blk-core.c b/block/blk-core.c
index cffd737..00ac586 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1149,7 +1149,7 @@ 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)
@@ -1861,15 +1861,8 @@ 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);
- }
}

/**
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5eb6cb0..ec9c10b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -456,8 +456,7 @@ 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_STACKABLE) | \
@@ -580,7 +579,6 @@ 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)
--
1.7.12.2.21.g234cd45.dirty




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