On Mon, 6 Mar 2023, Bart Van Assche wrote:
> On 3/6/23 10:02, Mikulas Patocka wrote:
> > On Tue, 28 Feb 2023, yangerkun wrote:
> > > It's ok to fix the softlockup, but for async write encrypt,
> > > kcryptd_crypt_write_io_submit will add bio to write_tree, and once we
> > > call cond_resched before every kcryptd_io_write, the write performance
> > > may be poor while we meet a high cpu usage scene.
> >
> > Hi
> >
> > To fix this problem, find the PID of the process "dmcrypt_write" and
> > change its priority to -20, for example "renice -n -20 -p 34748".
> >
> > This is the proper way how to fix it; locking up the process for one
> > second is not.
> >
> > We used to have high-priority workqueues by default, but it caused audio
> > playback skipping, so we had to revert it - see
> > f612b2132db529feac4f965f28a1b9258ea7c22b.
> >
> > Perhaps we should add an option to have high-priority kernel threads?
>
> Would calling cond_resched() every n iterations instead of every iteration
> help? From mm/swapfile.c:
>
> if (unlikely(--latency_ration < 0)) {
> cond_resched();
> latency_ration = LATENCY_LIMIT;
> }
>
> Thanks,
>
> Bart.
I think that if this helps, it is really a bug in the scheduler... It
shouldn't switch tasks so often.
Mikulas
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