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 <neilb@suse.com>
Link: http://lkml.kernel.org/r/20160609134555.GA9104@proton.igk.intel.com
Signed-off-by: Tomasz Majchrzak <tomasz.majchrzak@intel.com>
Signed-off-by: Shaohua Li <shli@fb.com>
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 @@
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
*/