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? Thanks, David
