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From:   Joel Fernandes <joel@joelfernandes.org>
Date:   Sat, 27 Jun 2020 12:21:36 -0400
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Subject: Re: [RFC PATCH 00/13] Core scheduling v5
To:     Vineeth Remanan Pillai <vpillai@digitalocean.com>
Cc:     Nishanth Aravamudan <naravamudan@digitalocean.com>,
        Julien Desfossez <jdesfossez@digitalocean.com>,
        Peter Zijlstra <peterz@infradead.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Linux List Kernel Mailing <linux-kernel@vger.kernel.org>,
        =?UTF-8?B?RnLDqWTDqXJpYyBXZWlzYmVja2Vy?= <fweisbec@gmail.com>,
        Ingo Molnar <mingo@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        Greg Kerr <kerrnel@google.com>, Phil Auld <pauld@redhat.com>,
        Aaron Lu <aaron.lwe@gmail.com>,
        Aubrey Li <aubrey.intel@gmail.com>,
        "Li, Aubrey" <aubrey.li@linux.intel.com>,
        Valentin Schneider <valentin.schneider@arm.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Pawan Gupta <pawan.kumar.gupta@linux.intel.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Paul Turner <pjt@google.com>
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On Fri, Jun 26, 2020 at 11:10 AM Joel Fernandes <joel@joelfernandes.org> wrote:
> [..]
> > What do you think about having a separate cgroup for coresched?
> > Both coresched cgroup and prctl() could co-exist where prctl could
> > be used to isolate individual process or task and coresched cgroup
> > to group trusted processes.
>
> This sounds like a fine idea to me. I wonder how Tejun and Peter feel about
> having a new attribute-less CGroup controller for core-scheduling and just
> use that for tagging. (No need to even have a tag file, just adding/removing
> to/from CGroup will tag).

Unless there are any major objections to this idea, or better ideas
for CGroup users, we will consider proposing a new CGroup controller
for this. The issue with CPU controller CGroups being they may be
configured in a way that is incompatible with tagging.

And I was also thinking of a new clone flag CLONE_CORE (which allows a
child to share a parent's core). This is because the fork-semantics
are not clear and it may be better to leave the behavior of fork to
userspace IMHO than hard-coding policy in the kernel.

Perhaps we can also discuss this at the scheduler MC at Plumbers.

Any other thoughts?

 - Joel