Messages in this thread Patch in this message | | | Date | Fri, 06 Apr 2012 11:27:01 -0600 | From | Shaohua Li <> | Subject | [PATCH]block: make auto block plug flush threshold per-disk based |
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Subject: block: make auto block plug flush threshold per-disk based
We do auto block plug flush to reduce latency, the threshold is 16 requests. This works well if the task is accessing one or two drives. The problem is if the task is accessing a raid 0 device and the raid disk number is big, say 8 or 16, 16/8 = 2 or 16/16=1, we will have heavy lock contention.
This patch makes the threshold per-disk based. The latency should be still ok accessing one or two drives. The setup with application accessing a lot of drives in the meantime uaually is big machine, avoiding lock contention is more important, because any contention will actually increase latency.
Signed-off-by: Shaohua Li <shli@fusionio.com> --- block/blk-core.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)
Index: linux/block/blk-core.c =================================================================== --- linux.orig/block/blk-core.c 2012-04-06 10:51:29.766932123 -0600 +++ linux/block/blk-core.c 2012-04-06 10:56:46.386929357 -0600 @@ -1277,7 +1277,8 @@ list_for_each_entry_reverse(rq, &plug->list, queuelist) { int el_ret;
- (*request_count)++; + if (rq->q == q) + (*request_count)++;
if (rq->q != q || !blk_rq_merge_ok(rq, bio)) continue;
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