linux-kernel - Re: [PATCH v7 11/15] sched/core: uclamp: Extend CPU's cgroup controller

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Message-ID: <20190214154817.GN50184@devbig004.ftw2.facebook.com>
Date:   Thu, 14 Feb 2019 07:48:17 -0800
From:   Tejun Heo <tj@...nel.org>
To:     Patrick Bellasi <patrick.bellasi@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-api@...r.kernel.org, Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Viresh Kumar <viresh.kumar@...aro.org>,
        Paul Turner <pjt@...gle.com>,
        Quentin Perret <quentin.perret@....com>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Morten Rasmussen <morten.rasmussen@....com>,
        Juri Lelli <juri.lelli@...hat.com>,
        Todd Kjos <tkjos@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Steve Muckle <smuckle@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Subject: Re: [PATCH v7 11/15] sched/core: uclamp: Extend CPU's cgroup
 controller

Hello,

On Fri, Feb 08, 2019 at 10:05:50AM +0000, Patrick Bellasi wrote:
> a) are available only for non-root nodes, both on default and legacy
>    hierarchies, while system wide clamps are defined by a generic
>    interface which does not depends on cgroups
> 
> b) do not enforce any constraints and/or dependencies between the parent
>    and its child nodes, thus relying:
>    - on permission settings defined by the system management software,
>      to define if subgroups can configure their clamp values
>    - on the delegation model, to ensure that effective clamps are
>      updated to consider both subgroup requests and parent group
>      constraints

I'm not sure about this hierarchical behavior.

> c) have higher priority than task-specific clamps, defined via
>    sched_setattr(), thus allowing to control and restrict task requests

and I have some other concerns about the interface, but let's discuss
them once the !cgroup portion is settled.

Thanks.

-- 
tejun