linux-kernel - Re: [PATCH 0/9] sched: Core scheduling interfaces

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Date:   Sat, 17 Apr 2021 21:35:07 -0400
From:   Joel Fernandes <joel@...lfernandes.org>
To:     Tejun Heo <tj@...nel.org>, Peter Zijlstra <peterz@...radead.org>
Cc:     Hao Luo <haoluo@...gle.com>,
        "Hyser,Chris" <chris.hyser@...cle.com>,
        Josh Don <joshdon@...gle.com>, Ingo Molnar <mingo@...nel.org>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Valentin Schneider <valentin.schneider@....com>,
        Mel Gorman <mgorman@...e.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Thomas Glexiner <tglx@...utronix.de>,
        Michal Koutný <mkoutny@...e.com>,
        Christian Brauner <christian.brauner@...ntu.com>,
        Zefan Li <lizefan.x@...edance.com>
Subject: Re: [PATCH 0/9] sched: Core scheduling interfaces

On Tue, Apr 06, 2021 at 10:16:12AM -0400, Tejun Heo wrote:
> Hello,
> 
> On Mon, Apr 05, 2021 at 02:46:09PM -0400, Joel Fernandes wrote:
> > Yeah, its at http://lore.kernel.org/r/20200822030155.GA414063@google.com
> > as mentioned above, let me know if you need any more details about
> > usecase.
> 
> Except for the unspecified reason in usecase 4, I don't see why cgroup is in
> the picture at all. This doesn't really have much to do with hierarchical
> resource distribution. Besides, yes, you can use cgroup for logical
> structuring and identificaiton purposes but in those cases the interactions
> and interface should be with the original subsystem while using cgroup IDs
> or paths as parameters - see tracing and bpf for examples.

Personally for ChromeOS, we need only the per-task interface. Considering
that the second argument of this prctl is a command, I don't see why we
cannot add a new command PR_SCHED_CORE_CGROUP_SHARE to do what Tejun is
saying (in the future).

In order to not block ChromeOS and other "per-task interface" usecases, I
suggest we keep the CGroup interface for a later time (whether that's
through prctl or the CGroups FS way which Tejun dislikes) and move forward
with per-task interface only initially.

Peter, any thoughts on this?

thanks,

- Joel