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

From	Rik van Riel <riel@redhat.com>
Newsgroups	linux.kernel
Subject	Re: [regression] cross core scheduling frequency drop bisected to 0c313cb20732
Date	2016-04-10 22:30 +0200
Message-ID	<rmu9A-2e3-7@gated-at.bofh.it> (permalink)
References	(2 earlier) <rlyyC-8iG-19@gated-at.bofh.it> <rlLFv-16v-7@gated-at.bofh.it> <rlYW6-3XE-15@gated-at.bofh.it> <rm0lc-4YO-3@gated-at.bofh.it> <rmpMB-7eT-1@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Sun, 2016-04-10 at 17:39 +0200, Mike Galbraith wrote:
> On Sat, 2016-04-09 at 14:31 +0200, Rafael J. Wysocki wrote:
> > 
> > On Sat, Apr 9, 2016 at 1:07 PM, Peter Zijlstra <peterz@infradead.or
> > g>
> > wrote:
> > > 
> > > On Fri, Apr 08, 2016 at 10:59:59PM +0200, Rafael J. Wysocki
> > > wrote:
> > > > 
> > > > On Friday, April 08, 2016 08:50:54 AM Mike Galbraith wrote:
> > > > > 
> > > > > On Fri, 2016-04-08 at 08:45 +0200, Peter Zijlstra wrote:
> > > > > 
> > > > > > 
> > > > > > Cute, I thought you used governor=performance for your
> > > > > > runs?
> > > > > I do, and those numbers are with it thus set.
> > > > Well, this is a trade-off.
> > > > 
> > > > 4.5 introduced a power regression here so this one goes back to
> > > > the previous
> > > > state of things.
> > > Just for my elucidation; how can gov=performance have a 'power'
> > > regression?
> > Because of what is used as the "default" idle state most of the
> > time.
> > 
> > C1 was used before 4.5 and that changed to polling in 4.5.
> Should the default idle state not then be governor dependent?  When I
> set gov=performance, I'm expecting box to go just as fast as it can
> go
> without melting.  Does polling risk CPU -> lava conversion?

Current CPUs can only have some cores run at full speed
(turbo mode) if other cores are idling and/or running at
lower speeds.

It may be time to stop pretending that gov=performance
actually results in better performance on current CPUs,
since it may inhibit entire levels of turbo mode.

-- 
All Rights Reversed.

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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