[Scheduler] CFS - What happens to each task's slice if nr_running * min_granularity > sched_latency?

Evan T Mesterhazy etm2131 at columbia.edu
Tue Apr 7 11:02:47 EDT 2020

Interesting, thanks Rik. I assumed that couldn't be correct, since it would
result in lower priority tasks receiving a slice less than the
- which I assumed CFS explicitly aims to prevent.

Thanks for taking a look.

On Fri, Apr 3, 2020 at 1:51 AM Valdis Klētnieks <valdis.kletnieks at vt.edu>

> On Thu, 02 Apr 2020 22:10:11 -0400, Evan T Mesterhazy said:
> > I ran a test by starting five busy processes with a nice level of -10.
> > Next, I launched ~40 busy processes with a nice level of 0 (all procs
> were
> > set to use the same CPU). I expected CFS to expand the period and assign
> > each process a slice equal to the min granularity. However, the 5
> processes
> > with nice = -10 still used considerably more CPU than the other
> processes.
> Well, it's *expected* that if you set nice = -10 they'll get more CPU.
> Do you have any evidence that CFS *didn't* give the nice==0 processes a
> min_granularity slide once in a while?

Evan Mesterhazy
etm2131 at columbia.edu
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