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authorAlan D. Brunelle <Alan.Brunelle@hp.com>2010-01-29 09:04:08 +0100
committerJens Axboe <jens.axboe@oracle.com>2010-01-29 09:04:08 +0100
commit488991e28e55b4fbca8067edf0259f69d1a6f92c (patch)
treefea5e0aca42e338137cc050e66aaeb5f539e3d21 /block
parent47483e25205f1f8d79784f0f7c733941bc080ec0 (diff)
downloadlinux-2.6.34-ux500-488991e28e55b4fbca8067edf0259f69d1a6f92c.tar.gz
block: Added in stricter no merge semantics for block I/O
Updated 'nomerges' tunable to accept a value of '2' - indicating that _no_ merges at all are to be attempted (not even the simple one-hit cache). The following table illustrates the additional benefit - 5 minute runs of a random I/O load were applied to a dozen devices on a 16-way x86_64 system. nomerges Throughput %System Improvement (tput / %sys) -------- ------------ ----------- ------------------------- 0 12.45 MB/sec 0.669365609 1 12.50 MB/sec 0.641519199 0.40% / 2.71% 2 12.52 MB/sec 0.639849750 0.56% / 2.96% Signed-off-by: Alan D. Brunelle <alan.brunelle@hp.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
Diffstat (limited to 'block')
-rw-r--r--block/blk-sysfs.c11
-rw-r--r--block/elevator.c11
2 files changed, 17 insertions, 5 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 8606c9543fd..e85442415db 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -189,7 +189,8 @@ static ssize_t queue_nonrot_store(struct request_queue *q, const char *page,
static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
{
- return queue_var_show(blk_queue_nomerges(q), page);
+ return queue_var_show((blk_queue_nomerges(q) << 1) |
+ blk_queue_noxmerges(q), page);
}
static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
@@ -199,10 +200,12 @@ static ssize_t queue_nomerges_store(struct request_queue *q, const char *page,
ssize_t ret = queue_var_store(&nm, page, count);
spin_lock_irq(q->queue_lock);
- if (nm)
+ queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
+ queue_flag_clear(QUEUE_FLAG_NOXMERGES, q);
+ if (nm == 2)
queue_flag_set(QUEUE_FLAG_NOMERGES, q);
- else
- queue_flag_clear(QUEUE_FLAG_NOMERGES, q);
+ else if (nm)
+ queue_flag_set(QUEUE_FLAG_NOXMERGES, q);
spin_unlock_irq(q->queue_lock);
return ret;
diff --git a/block/elevator.c b/block/elevator.c
index 9ad5ccc4c5e..ee3a883840f 100644
--- a/block/elevator.c
+++ b/block/elevator.c
@@ -474,6 +474,15 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
int ret;
/*
+ * Levels of merges:
+ * nomerges: No merges at all attempted
+ * noxmerges: Only simple one-hit cache try
+ * merges: All merge tries attempted
+ */
+ if (blk_queue_nomerges(q))
+ return ELEVATOR_NO_MERGE;
+
+ /*
* First try one-hit cache.
*/
if (q->last_merge) {
@@ -484,7 +493,7 @@ int elv_merge(struct request_queue *q, struct request **req, struct bio *bio)
}
}
- if (blk_queue_nomerges(q))
+ if (blk_queue_noxmerges(q))
return ELEVATOR_NO_MERGE;
/*