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Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732

From "Rafael J. Wysocki" <rafael@kernel.org>
Newsgroups linux.kernel
Subject Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732
Date 2016-04-10 05:50 +0200
Message-ID <rmexP-7mr-9@gated-at.bofh.it> (permalink)
References (3 earlier) <rlLFv-16v-7@gated-at.bofh.it> <rlUSu-SL-3@gated-at.bofh.it> <rm0lc-4YO-5@gated-at.bofh.it> <rm2Q2-74P-1@gated-at.bofh.it> <rm45r-7Ve-7@gated-at.bofh.it>
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On Sat, Apr 9, 2016 at 6:39 PM, Mike Galbraith <umgwanakikbuti@gmail.com> wrote:
>
> Hm, setting gov=performance, and taking the average of 3 30 second
> interval PkgWatt samples as pipe-test runs..
>
> 714KHz/28.03Ws = 25.46
> 877KHz/30.28Ws = 28.96
>
> ..for pipe-test, the tradeoff look a bit more like red than green.

Well, fair enough, but that's just pipe-test, and what about the
people who don't see the performance gain and see the energy loss,
like Doug?

Essentially, this trades performance gains in somewhat special
workloads for increased energy consumption in idle.  Those workloads
need not be run by everybody, but idle is.

That said I applied the patch you're complaining about mostly because
the commit that introduced the change in question in 4.5 claimed that
it wouldn't affect idle power on systems with reasonably fast C1, but
that didn't pass the reality test.  I'm not totally against restoring
that change, but it would need to be based on very solid evidence.

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Thread

[regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-08 07:30 +0200
  Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Peter Zijlstra <peterz@infradead.org> - 2016-04-08 08:50 +0200
    Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-08 09:00 +0200
      Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Rafael J. Wysocki" <rjw@rjwysocki.net> - 2016-04-08 23:00 +0200
        RE: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Doug Smythies" <dsmythies@telus.net> - 2016-04-09 00:20 +0200
          Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 08:50 +0200
          RE: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Doug Smythies" <dsmythies@telus.net> - 2016-04-09 09:20 +0200
            Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 09:30 +0200
          Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Peter Zijlstra <peterz@infradead.org> - 2016-04-09 13:10 +0200
        Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 08:50 +0200
          Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Rafael J. Wysocki" <rafael@kernel.org> - 2016-04-09 14:40 +0200
            Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 17:20 +0200
              Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-09 18:40 +0200
                Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Rafael J. Wysocki" <rafael@kernel.org> - 2016-04-10 05:50 +0200
                RE: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Doug Smythies" <dsmythies@telus.net> - 2016-04-10 09:20 +0200
                Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-10 11:40 +0200
                Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-10 17:00 +0200
        Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Peter Zijlstra <peterz@infradead.org> - 2016-04-09 13:10 +0200
          Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Rafael J. Wysocki" <rafael@kernel.org> - 2016-04-09 14:40 +0200
            Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-10 17:50 +0200
              Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Rik van Riel <riel@redhat.com> - 2016-04-10 22:30 +0200
                Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Mike Galbraith <umgwanakikbuti@gmail.com> - 2016-04-11 05:10 +0200
                Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Rik van Riel <riel@redhat.com> - 2016-04-11 14:40 +0200
                Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732 "Rafael J. Wysocki" <rafael@kernel.org> - 2016-04-11 15:30 +0200
                Re: [regression] cross core scheduling frequency drop bisected to  0c313cb20732 Rik van Riel <riel@redhat.com> - 2016-04-11 15:40 +0200

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