From 488991e28e55b4fbca8067edf0259f69d1a6f92c Mon Sep 17 00:00:00 2001 From: "Alan D. Brunelle" Date: Fri, 29 Jan 2010 09:04:08 +0100 Subject: 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 Signed-off-by: Jens Axboe --- block/blk-sysfs.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'block/blk-sysfs.c') diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c index 8606c9543fdd..e85442415db3 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; -- cgit v1.2.3