Re: [PATCH] sched/fair: check for idle core

[Julia Lawall]

On Wed, 21 Oct 2020, Peter Zijlstra wrote:

> On Wed, Oct 21, 2020 at 01:56:55PM +0200, Julia Lawall wrote:
> > Prior to 5.8, my machine was using intel_pstate and had few background
> > tasks.  Thus the problem wasn't visible in practice.  Starting with 5.8
> > the kernel decided that intel_cpufreq would be more appropriate, which
> > introduced kworkers every 0.004 seconds on all cores.
>
> That still doesn't make any sense. Are you running the legacy on-demand
> thing or something?
>
> Rafael, Srinivas, Viresh, how come it defaults to that?

The relevant commits are 33aa46f252c7, and 39a188b88332 that fixes a small
bug.  I have a Intel(R) Xeon(R) CPU E7-8870 v4 @ 2.10GHz that does not
have the HWP feature, even though the cores seemed to be able to change
their frequencies at the hardware level.

julia