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authorJens Axboe <jens.axboe@oracle.com>2009-07-30 08:18:24 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-09-11 14:33:31 +0200
commitfb1e75389bd06fd5987e9cda1b4e0305c782f854 (patch)
tree6658e13f80d4f6450f5a69c82d3bf1b590ecf234
parent1f98a13f623e0ef666690a18c1250335fc6d7ef1 (diff)
block: improve queue_should_plug() by looking at IO depths
Instead of just checking whether this device uses block layer tagging, we can improve the detection by looking at the maximum queue depth it has reached. If that crosses 4, then deem it a queuing device. This is important on high IOPS devices, since plugging hurts the performance there (it can be as much as 10-15% of the sys time). Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--block/blk-core.c11
-rw-r--r--include/linux/blkdev.h2
2 files changed, 11 insertions, 2 deletions
diff --git a/block/blk-core.c b/block/blk-core.c
index 52559715cb9..93051d15163 100644
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -1146,7 +1146,7 @@ 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_tagged(q));
+ return !(blk_queue_nonrot(q) && blk_queue_queuing(q));
}
static int __make_request(struct request_queue *q, struct bio *bio)
@@ -1857,8 +1857,15 @@ 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 88edb62def8..98b45633a27 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -459,6 +459,7 @@ 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_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_CLUSTER) | \
@@ -581,6 +582,7 @@ 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)