From: Dietmar Eggemann <dietmar.eggemann@arm.com>
To: Josh Don <joshdon@google.com>,
Vincent Guittot <vincent.guittot@linaro.org>
Cc: Ingo Molnar <mingo@redhat.com>,
Peter Zijlstra <peterz@infradead.org>,
Juri Lelli <juri.lelli@redhat.com>,
Steven Rostedt <rostedt@goodmis.org>,
Ben Segall <bsegall@google.com>, Mel Gorman <mgorman@suse.de>,
linux-kernel <linux-kernel@vger.kernel.org>,
Paul Turner <pjt@google.com>
Subject: Re: [PATCH v2] sched/fair: Do not set skip buddy up the sched hierarchy
Date: Mon, 9 Dec 2019 10:18:59 +0100 [thread overview]
Message-ID: <edc9f4aa-a6ab-3bab-0a9e-73a155b8a48a@arm.com> (raw)
In-Reply-To: <CABk29NsCjgMVf-xrhpyzFBTpyTvyWxZc4RJSarnHVzdOXyVPMw@mail.gmail.com>
On 06.12.19 23:13, Josh Don wrote:
[...]
> On Thu, Dec 5, 2019 at 11:57 PM Vincent Guittot
> <vincent.guittot@linaro.org> wrote:
>>
>> Hi Josh,
>>
>> On Wed, 4 Dec 2019 at 21:06, Josh Don <joshdon@google.com> wrote:
>>>
>>> From: Venkatesh Pallipadi <venki@google.com>
>>>
>>> Setting skip buddy all the way up the hierarchy does not play well
>>> with intra-cgroup yield. One typical usecase of yield is when a
>>> thread in a cgroup wants to yield CPU to another thread within the
>>> same cgroup. For such a case, setting the skip buddy all the way up
But with yield_task{_fair}() you have no way to control which other task
gets accelerated. The other task in the taskgroup (cgroup) could be even
on another CPU.
It's not like yield_to_task_fair() which uses next buddy to accelerate
another task p.
What's this typical usecase?
>>> the hierarchy is counter-productive, as that results in CPU being
>>> yielded to a task in some other cgroup.
>>>
>>> So, limit the skip effect only to the task requesting it.
[...]
next prev parent reply other threads:[~2019-12-09 9:19 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-04 20:06 [PATCH v2] sched/fair: Do not set skip buddy up the sched hierarchy Josh Don
2019-12-06 7:57 ` Vincent Guittot
2019-12-06 22:13 ` Josh Don
2019-12-09 9:18 ` Dietmar Eggemann [this message]
2019-12-12 22:19 ` Josh Don
2019-12-18 11:36 ` Dietmar Eggemann
2019-12-18 20:02 ` Josh Don
2019-12-19 0:14 ` [PATCH v3] " Josh Don
2019-12-26 15:05 ` Vincent Guittot
2020-02-25 1:50 ` Josh Don
2019-12-12 8:05 ` [PATCH v2] " Vincent Guittot
2019-12-17 19:58 ` Josh Don
2019-12-17 20:42 ` Peter Zijlstra
2019-12-17 21:00 ` Greg Kroah-Hartman
-- strict thread matches above, loose matches on Subject: below --
2019-11-04 14:54 [PATCH] " Vincent Guittot
2019-11-06 22:14 ` [PATCH v2] " Josh Don
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