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Re: [PATCH RFC] select_idle_sibling experiments

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On Wed, Apr 06, 2016 at 09:27:24AM +0200, Mike Galbraith wrote:
> > On Tue, 2016-04-05 at 14:08 -0400, Chris Mason wrote:
> 
> > Now, on to the patch.  I pushed some code around and narrowed the
> > problem down to select_idle_sibling()   We have cores going into and out
> > of idle fast enough that even this cut our latencies in half:
> 
> Are you using NO_HZ?  If so, you may want to try the attached.

[ nohz throttling patch ]

I tested the nohz throttle two different ways, first with schbench's
pipe simulation, it's easily 8% faster with messages bouncing between
cpus.

In production it's hard to pick a single number because the benchmarks
produce latency curves as the workload scales up in RPS.  The benefits
range from 2-9% depending on the metric.  It's a nice win, and I'd love to
see it go in.

-chris

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Thread

[PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-05 20:20 +0200
  Re: [PATCH RFC] select_idle_sibling experiments Bastien Bastien Philbert <bastienphilbert@gmail.com> - 2016-04-05 20:50 +0200
    Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-05 21:30 +0200
  Re: [PATCH RFC] select_idle_sibling experiments Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-05 22:10 +0200
    Re: [PATCH RFC] select_idle_sibling experiments Bastien Philbert <bastienphilbert@gmail.com> - 2016-04-05 23:10 +0200
    Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-06 02:50 +0200
  Re: [PATCH RFC] select_idle_sibling experiments Mike Galbraith <mgalbraith@suse.de> - 2016-04-06 09:30 +0200
    Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-06 15:40 +0200
    Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-09 19:40 +0200
      Re: [PATCH RFC] select_idle_sibling experiments Matt Fleming <matt@codeblueprint.co.uk> - 2016-04-12 23:50 +0200
        Re: [PATCH RFC] select_idle_sibling experiments Mike Galbraith <mgalbraith@suse.de> - 2016-04-13 05:50 +0200
          Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-13 18:00 +0200
  Re: [PATCH RFC] select_idle_sibling experiments Chris Mason <clm@fb.com> - 2016-04-07 17:20 +0200
  sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-09 21:10 +0200
    Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-10 12:10 +0200
      Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-10 14:40 +0200
        Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-10 14:50 +0200
      Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-10 22:00 +0200
        Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-11 07:00 +0200
          Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-12 02:40 +0200
            Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-12 06:50 +0200
              Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-12 15:30 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-12 20:20 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-12 22:10 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-13 05:20 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-13 15:50 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-13 16:30 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Chris Mason <clm@fb.com> - 2016-04-13 16:40 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-13 17:10 +0200
                Re: sched: tweak select_idle_sibling to look for idle threads Mike Galbraith <mgalbraith@suse.de> - 2016-04-13 17:40 +0200

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