On Thu, 21 Sep 2023 17:45:24 -0400 Mike Snitzer <snitzer@xxxxxxxxxx> wrote: > I just verified that 6.5.0 does have this DM core fix (needed to > prevent excessive splitting of discard IO.. which could cause fstrim > to take longer for a DM device), but again 6.5.0 has this fix so it > isn't relevant: > be04c14a1bd2 dm: use op specific max_sectors when splitting abnormal io > > Given your use of 'writemostly' I'm inferring you're using lvm2's > raid1 that uses MD raid1 code in terms of the dm-raid target. > > Discards (more generic term for fstrim) are considered writes, so > writemostly really shouldn't matter... but I know that there have been > issues with MD's writemostly code (identified by others relatively > recently). > > All said: hopefully someone more MD oriented can review your report > and help you further. > > Mike I've reported that write-mostly TRIM gets split into 1MB pieces, which can be an order of magnitude slower on some SSDs: https://www.spinics.net/lists/raid/msg72471.html Nobody cared to reply, investigate or fix. Maybe your system hasn't frozen too, just taking its time in processing all the tiny split requests. -- With respect, Roman
