Messages in this thread | | | Subject | Re: [PATCH v2] sched/fair: Do not set skip buddy up the sched hierarchy | From | Dietmar Eggemann <> | Date | Mon, 9 Dec 2019 10:18:59 +0100 |
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On 06.12.19 23:13, Josh Don wrote:
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> 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.
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