linux-kernel - Re: [External] Re: [PATCH v2] sched: RT bandwidth interface for cgroup unified hierarchy

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Date:   Thu, 23 Jun 2022 09:51:02 +0200
From:   Michal Koutný <mkoutny@...e.com>
To:     Chengming Zhou <zhouchengming@...edance.com>
Cc:     rdunlap@...radead.org, mingo@...hat.com, peterz@...radead.org,
        juri.lelli@...hat.com, vincent.guittot@...aro.org,
        dietmar.eggemann@....com, rostedt@...dmis.org, bsegall@...gle.com,
        tj@...nel.org, lizefan.x@...edance.com, hannes@...xchg.org,
        corbet@....net, cgroups@...r.kernel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [External] Re: [PATCH v2] sched: RT bandwidth interface for
 cgroup unified hierarchy

On Thu, Jun 23, 2022 at 10:23:26AM +0800, Chengming Zhou <zhouchengming@...edance.com> wrote:
> I don't know why v2 differ from v1 in the RT bandwidth control.. Is there
> some links of explanation? (CFS bandwidth control can work on v2 now.)

You can see some ideas in [1] (the v1 API allows configurations that are
not implemented).
And I'd also say more generally, that applying throttling to an RT task
is already a lost game (either it's a runaway meaning there's a bug
elsewhere or the RT task won't have sufficient runtime which defeats its
RTness).

> If the problem can't be solved, we have to unset CONFIG_RT_GROUP_SCHED.

AFAICT, this was enough so far (but RT group scheduling can still be
(re)worked).

HTH,
Michal

[1] https://www.kernel.org/doc/html/latest/scheduler/sched-rt-group.html