*** REVERTED *** From ac8fa4196d205ac8fff3f8932bddbad4f16e4110 Mon Sep 17 00:00:00 2001 From: NeilBrown Date: Thu, 19 Feb 2015 16:55:00 +1100 Subject: md: allow resync to go faster when there is competing IO. When md notices non-sync IO happening while it is trying to resync (or reshape or recover) it slows down to the set minimum. The default minimum might have made sense many years ago but the drives have become faster. Changing the default to match the times isn't really a long term solution. This patch changes the code so that instead of waiting until the speed has dropped to the target, it just waits until pending requests have completed. This means that the delay inserted is a function of the speed of the devices. Testing shows that: - for some loads, the resync speed is unchanged. For those loads increasing the minimum doesn't change the speed either. So this is a good result. To increase resync speed under such loads we would probably need to increase the resync window size. - for other loads, resync speed does increase to a reasonable fraction (e.g. 20%) of maximum possible, and throughput of the load only drops a little bit (e.g. 10%) - for other loads, throughput of the non-sync load drops quite a bit more. These seem to be latency-sensitive loads. So it isn't a perfect solution, but it is mostly an improvement. Signed-off-by: NeilBrown --- drivers/md/md.c | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-) diff -Naurp b/drivers/md/md.c a/drivers/md/md.c --- b/drivers/md/md.c 2016-01-10 18:01:32.000000000 -0500 +++ a/drivers/md/md.c 2016-01-30 19:14:27.709811836 -0500 @@ -8036,18 +8036,11 @@ void md_do_sync(struct md_thread *thread /((jiffies-mddev->resync_mark)/HZ +1) +1; if (currspeed > speed_min(mddev)) { - if (currspeed > speed_max(mddev)) { + if ((currspeed > speed_max(mddev)) || + !is_mddev_idle(mddev, 0)) { msleep(500); goto repeat; } - if (!is_mddev_idle(mddev, 0)) { - /* - * Give other IO more of a chance. - * The faster the devices, the less we wait. - */ - wait_event(mddev->recovery_wait, - !atomic_read(&mddev->recovery_active)); - } } } printk(KERN_INFO "md: %s: %s %s.\n",mdname(mddev), desc,