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From: Josh Don <joshdon@google.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: "Michal Koutný" <mkoutny@suse.com>, "Tejun Heo" <tj@kernel.org>,
	"Joel Fernandes" <joel@joelfernandes.org>,
	"Hyser,Chris" <chris.hyser@oracle.com>,
	"Ingo Molnar" <mingo@kernel.org>,
	"Vincent Guittot" <vincent.guittot@linaro.org>,
	"Valentin Schneider" <valentin.schneider@arm.com>,
	"Mel Gorman" <mgorman@suse.de>,
	linux-kernel <linux-kernel@vger.kernel.org>,
	"Thomas Gleixner" <tglx@linutronix.de>,
	"Christian Brauner" <christian.brauner@ubuntu.com>,
	"Zefan Li" <lizefan.x@bytedance.com>
Subject: Re: [PATCH 0/9] sched: Core scheduling interfaces
Date: Thu, 8 Apr 2021 17:16:13 -0700	[thread overview]
Message-ID: <CABk29NtTScu2HO7V9Di+Fh2gv8zu5xiC5iNRwPFCLhpD+DKP0A@mail.gmail.com> (raw)
In-Reply-To: <YG8a/LbO4PXFLEix@hirez.programming.kicks-ass.net>

On Thu, Apr 8, 2021 at 9:47 AM Peter Zijlstra <peterz@infradead.org> wrote:
>
> On Thu, Apr 08, 2021 at 03:25:52PM +0200, Michal Koutný wrote:
>
> > I'm curious whether the cgroup API actually simplifies things that are
> > possible with the clone/prctl API or allows anything that wouldn't be
> > otherwise possible.
>
> With the cgroup API it is impossible for a task to escape the cgroup
> constraint. It can never share a core with anything not in the subtree.
>
> This is not possible with just the task interface.
>
> If this is actually needed I've no clue, IMO all of cgroups is not
> needed :-) Clearly other people feel differently about that.

The cgroup interface seems very nice from a management perspective;
moving arbitrary tasks around in the cgroup hierarchy will handle the
necessary cookie adjustments to ensure that nothing shares with an
unexpected task. It also makes auditing the core scheduling groups
very straightforward; anything in a cookie'd cgroup's tasks file will
be guaranteed isolated from the rest of the system, period.

Further, if a system management thread wants two arbitrary tasks A and
B to share a cookie, this seems more painful with the PRCTL interface.
The management thread would need to something like
- PR_SCHED_CORE_CREATE
- PR_SCHED_CORE_SHARE_TO A
- PR_SCHED_CORE_SHARE_TO B
- PR_SCHED_CORE_CLEAR

  reply	other threads:[~2021-04-09  0:16 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-04-01 13:10 Peter Zijlstra
2021-04-01 13:10 ` [PATCH 1/9] sched: Allow sched_core_put() from atomic context Peter Zijlstra
2021-04-01 13:10 ` [PATCH 2/9] sched: Implement core-sched assertions Peter Zijlstra
2021-04-01 13:10 ` [PATCH 3/9] sched: Trivial core scheduling cookie management Peter Zijlstra
2021-04-01 20:04   ` Josh Don
2021-04-02  7:13     ` Peter Zijlstra
2021-04-01 13:10 ` [PATCH 4/9] sched: Default core-sched policy Peter Zijlstra
2021-04-21 13:33   ` Peter Zijlstra
2021-04-21 14:31     ` Chris Hyser
2021-04-01 13:10 ` [PATCH 5/9] sched: prctl() core-scheduling interface Peter Zijlstra
2021-04-07 17:00   ` Peter Zijlstra
2021-04-18  3:52     ` Joel Fernandes
2021-04-01 13:10 ` [PATCH 6/9] kselftest: Add test for core sched prctl interface Peter Zijlstra
2021-04-01 13:10 ` [PATCH 7/9] sched: Cgroup core-scheduling interface Peter Zijlstra
2021-04-02  0:34   ` Josh Don
2021-04-01 13:10 ` [PATCH 8/9] rbtree: Remove const from the rb_find_add() comparator Peter Zijlstra
2021-04-01 13:10 ` [PATCH 9/9] sched: prctl() and cgroup interaction Peter Zijlstra
2021-04-03  1:30   ` Josh Don
2021-04-06 15:12     ` Peter Zijlstra
2021-04-04 23:39 ` [PATCH 0/9] sched: Core scheduling interfaces Tejun Heo
2021-04-05 18:46   ` Joel Fernandes
2021-04-06 14:16     ` Tejun Heo
2021-04-18  1:35       ` Joel Fernandes
2021-04-19  9:00         ` Peter Zijlstra
2021-04-21 13:35           ` Peter Zijlstra
2021-04-21 14:45             ` Chris Hyser
2021-04-06 15:32   ` Peter Zijlstra
2021-04-06 16:08     ` Tejun Heo
2021-04-07 18:39       ` Peter Zijlstra
2021-04-07 16:50   ` Michal Koutný
2021-04-07 18:34     ` Peter Zijlstra
2021-04-08 13:25       ` Michal Koutný
2021-04-08 15:02         ` Peter Zijlstra
2021-04-09  0:16           ` Josh Don [this message]
2021-04-19 11:30       ` Tejun Heo
2021-04-20  1:17         ` Josh Don

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