On 2023/12/8 00:19, David Disseldorp wrote:
On Thu, 7 Dec 2023 20:19:00 +1030, Qu Wenruo wrote:
On 2023/12/7 17:50, David Disseldorp wrote:
btrfs/282 fails intermittently under some circumstances. This patchset
adds dmdelay to make storage latencies more uniform and slightly
increases throttled rate tolerances.
My concern using dm_delay is, is the delay per-merged-bio or something else?
If the delay is only per-bio (after merge), then I'm afraid it would not
be good enough.
The dmdelay device presents itself as a regular block device, so I think
delay_map()->delay_bio() handling comes after any merges.
The bio plug we use in scrub can have much higher chance to result a
difference in the scrub speed.
We may want a delay behavior which can take bio size into consideration
at least.
Should we manipulate it a bit by fiddling with queue/max_sectors_kb and
queue/nomerges?
I'm not sure if delay is our best friend.
If we have something to limits the read/write speed directly that would
be the best case.
Unfortunately I didn't see a dm-throttle in upstream, can we limit the
IO speed on certain device using cgroup?
Thanks,
Qu
Thanks, David
