From mboxrd@z Thu Jan  1 00:00:00 1970
From: Michal =?iso-8859-1?Q?Koutn=FD?= <mkoutny-IBi9RG/b67k@public.gmane.org>
Subject: Re: Short process stall after assigning it to a cgroup
Date: Wed, 23 Jun 2021 19:28:11 +0200
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References: <CAMJ=MEegYBi_G=_nk1jaJh-dtJj59EFs6ehCwP5qSBqEKseQ-Q@mail.gmail.com>
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To: Ronny Meeus <ronny.meeus-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
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Hello Ronny.

On Mon, Jun 14, 2021 at 05:29:35PM +0200, Ronny Meeus <ronny.meeus-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:
> All apps are running in the realtime domain and I'm using kernel 4.9
> and cgroup v1. [...]  when it enters a full load condition [...]
> I start to gradually reduce the budget of the cgroup until the system
> is idle enough.

Has your application some RT requirements or is there other reason why
you use group RT allocations? (When your app seems to require all CPU
time, you decide to curb it. And it still fullfills RT requirements?)


> But sometimes, immediately after the process assignment, it stops for
> a short period (something like 1 or 2s) and then starts to consume 40%
> again.

What if you reduce cpu.rt_period_us (and cpu.rt_runtime_us
proportionally)? (Are the pauses shorter?) Is there any useful info in
/proc/$PID/stack during these periods?

> Is that expected behavior?

Someone with RT group schedulling knowledge may tell :-)

HTH,
Michal

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