From 7ac504472263180745ac94242f1d253eb7284e48 Mon Sep 17 00:00:00 2001 From: Tomasz Majchrzak Date: Mon, 13 Jun 2016 15:51:19 +0200 Subject: raid1/raid10: slow down resync if there is non-resync activity pending A performance drop of mkfs has been observed on RAID10 during resync since commit 09314799e4f0 ("md: remove 'go_faster' option from ->sync_request()"). Resync sends so many IOs it slows down non-resync IOs significantly (few times). Add a short delay to a resync. The previous long sleep (1s) has proven unnecessary, even very short delay brings performance right. The change also applied to raid1. The problem has not been observed on raid1, however it shares barriers code with raid10 so it might be an issue for some setup too. Suggested-by: NeilBrown Link: http://lkml.kernel.org/r/20160609134555.GA9104@proton.igk.intel.com Signed-off-by: Tomasz Majchrzak Signed-off-by: Shaohua Li diff --git a/drivers/md/raid1.c b/drivers/md/raid1.c index c7c8cde..358a08e 100644 --- a/drivers/md/raid1.c +++ b/drivers/md/raid1.c @@ -2535,6 +2535,13 @@ static sector_t raid1_sync_request(struct mddev *mddev, sector_t sector_nr, return sync_blocks; } + /* + * If there is non-resync activity waiting for a turn, then let it + * though before starting on this new sync request. + */ + if (conf->nr_waiting) + schedule_timeout_uninterruptible(1); + /* we are incrementing sector_nr below. To be safe, we check against * sector_nr + two times RESYNC_SECTORS */ diff --git a/drivers/md/raid10.c b/drivers/md/raid10.c index c7de2a5..3578d3a 100644 --- a/drivers/md/raid10.c +++ b/drivers/md/raid10.c @@ -2912,6 +2912,13 @@ static sector_t raid10_sync_request(struct mddev *mddev, sector_t sector_nr, max_sector > (sector_nr | chunk_mask)) max_sector = (sector_nr | chunk_mask) + 1; + /* + * If there is non-resync activity waiting for a turn, then let it + * though before starting on this new sync request. + */ + if (conf->nr_waiting) + schedule_timeout_uninterruptible(1); + /* Again, very different code for resync and recovery. * Both must result in an r10bio with a list of bios that * have bi_end_io, bi_sector, bi_bdev set, -- cgit v0.10.2