[erlang-questions] Dirty CPU schedulers stuck at zero utilization

Frank Muller <>
Wed Jan 16 13:48:15 CET 2019


Thanks Rickard.

@Jonas: did the PR2093 help in your case?

/Frank

On 2019-01-15 23:11, Jesse Stimpson wrote:
> > Behavior of the schedulers appears to have the same issue with 2093
> patch.
> >
> > But I did notice something new in the msacc output. There is a very
> > brief period, at approx the same time as the normal schedulers usage
> > spikes, where all the dirty cpu schedulers have a significant sleep
> > time. I've included timestamped excerpts below, starting with the
> > increase in dirty cpu sleep, and ending with a "steady state"
> utilization.
> >
>
> We just released OTP-21.2.3 containing PR-2093.
>
> I don't think PR-2093 cause the spikes. This change does not affect how
> work is moved between normal and dirty schedulers, only prevents the
> "loss" of dirty schedulers.
>
> If a process is scheduled on a dirty scheduler it wont make progress
> until it has executed on a dirty scheduler and vice versa (for normal
> schedulers). This is the same both before and after PR-2093. Since dirty
> schedulers aren't "lost" after PR-2093 progress of such processes will
> happen earlier which of course change the behavior, but that is due to
> the work load.
>
> Regards,
> Rickard
>
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