On Fri, 18 Mar 2022 11:26:41 +0900, Shin'ichiro Kawasaki wrote:
> When IO requests are made continuously and the target block device
> handles requests faster than request arrival, the request dispatch loop
> keeps on repeating to dispatch the arriving requests very long time,
> more than a minute. Since the loop runs as a workqueue worker task, the
> very long loop duration triggers workqueue watchdog timeout and BUG [1].
>
> To avoid the very long loop duration, break the loop periodically. When
> opportunity to dispatch requests still exists, check need_resched(). If
> need_resched() returns true, the dispatch loop already consumed its time
> slice, then reschedule the dispatch work and break the loop. With heavy
> IO load, need_resched() does not return true for 20~30 seconds. To cover
> such case, check time spent in the dispatch loop with jiffies. If more
> than 1 second is spent, reschedule the dispatch work and break the loop.
>
> [...]
Applied, thanks!
[1/1] block: limit request dispatch loop duration
commit: 572299f03afd676dd4e20669cdaf5ed0fe1379d4
Best regards,
--
Jens Axboe
