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Re: [RFC] sched: unused cpu in affine workload

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [RFC] sched: unused cpu in affine workload
Date 2016-04-04 23:40 +0200
Message-ID <rkko3-VB-23@gated-at.bofh.it> (permalink)
References (1 earlier) <rk8wx-tQ-1@gated-at.bofh.it> <rk8ZA-Wy-23@gated-at.bofh.it> <rk99g-118-21@gated-at.bofh.it> <rkcJP-3AF-3@gated-at.bofh.it> <rkiFA-89A-5@gated-at.bofh.it>
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On Mon, Apr 04, 2016 at 03:45:16PM -0400, Rik van Riel wrote:
> An optimal solution is NP hard.
> 
> Heuristics that "move tasks with pressure" may be
> much more doable, and lead to perfectly satisfactory
> results, especially if most migrations happen within
> a socket (and the same shared L3 cache).

Right; trick will be finding something that mostly works without making
the regular balance paths increase in complexity.

As per the argument in kernel/sched/fair.c:5694 the current
load-balancing averages out to O(n), and I would very much like to keep
it that way.

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Thread

[RFC] sched: unused cpu in affine workload Jiri Olsa <jolsa@redhat.com> - 2016-04-04 10:30 +0200
  Re: [RFC] sched: unused cpu in affine workload Peter Zijlstra <peterz@infradead.org> - 2016-04-04 10:50 +0200
  Re: [RFC] sched: unused cpu in affine workload Ingo Molnar <mingo@kernel.org> - 2016-04-04 11:00 +0200
    Re: [RFC] sched: unused cpu in affine workload Ingo Molnar <mingo@kernel.org> - 2016-04-04 11:30 +0200
      Re: [RFC] sched: unused cpu in affine workload Ingo Molnar <mingo@kernel.org> - 2016-04-04 11:40 +0200
        Re: [RFC] sched: unused cpu in affine workload Peter Zijlstra <peterz@infradead.org> - 2016-04-04 15:30 +0200
          Re: [RFC] sched: unused cpu in affine workload Rik van Riel <riel@redhat.com> - 2016-04-04 21:50 +0200
            Re: [RFC] sched: unused cpu in affine workload Peter Zijlstra <peterz@infradead.org> - 2016-04-04 23:40 +0200
              Re: [RFC] sched: unused cpu in affine workload Jiri Olsa <jolsa@redhat.com> - 2016-04-05 11:00 +0200

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