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

[Evan T Mesterhazy]

Interesting, thanks Rik. I assumed that couldn't be correct, since it would
result in lower priority tasks receiving a slice less than the
sysctl_sched_min_granularity
- 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>
wrote:

> 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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.kernelnewbies.org/pipermail/kernelnewbies/attachments/20200407/e517ddd0/attachment.html>