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Groups > linux.kernel > #1238747

Re: 4.2.2: NR_CPUS effectively being 1 bug

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: 4.2.2: NR_CPUS effectively being 1 bug
Date 2015-10-03 09:00 +0200
Message-ID <qfoXw-2Gd-15@gated-at.bofh.it> (permalink)
References <qffrc-5YK-7@gated-at.bofh.it> <qffKy-6Av-23@gated-at.bofh.it>
Organization linux.* mail to news gateway

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On Fri, Oct 02, 2015 at 02:00:33PM -0700, Andrew Morton wrote:
> On Fri, 2 Oct 2015 23:46:59 +0300 Alexey Dobriyan <adobriyan@gmail.com> wrote:
> 
> > FYI, I've upgraded from 4.1.7 to 4.2.1 (and retested with 4.2.2) and
> > everything is scheduled on 1 CPU out of 4 (i5 760).
> > 
> > 	$ sudo cat /proc/1/status | grep cpu -i
> > 	Cpus_allowed:   1
> > 	Cpus_allowed_list:      0
> > 
> > Every process inherits this tiny cpumask.
> 
> Sell the other CPUs on ebay?
> 
> I haven't seen such a report before - maybe it rings a bell with Peter
> & Ingo?

I think this is related to some NO_HZ_FULL quackery. People seem to have
enabled stuff they've really no sane reason for.
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Thread

Re: 4.2.2: NR_CPUS effectively being 1 bug Andrew Morton <akpm@linux-foundation.org> - 2015-10-02 23:10 +0200
  Re: 4.2.2: NR_CPUS effectively being 1 bug Peter Zijlstra <peterz@infradead.org> - 2015-10-03 09:00 +0200
    Re: 4.2.2: NR_CPUS effectively being 1 bug Ingo Molnar <mingo@kernel.org> - 2015-10-03 09:40 +0200
      Re: 4.2.2: NR_CPUS effectively being 1 bug Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-10-03 10:20 +0200
        Re: 4.2.2: NR_CPUS effectively being 1 bug Ingo Molnar <mingo@kernel.org> - 2015-10-03 10:20 +0200
          Re: 4.2.2: NR_CPUS effectively being 1 bug Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-10-03 10:30 +0200
            Re: 4.2.2: NR_CPUS effectively being 1 bug Ingo Molnar <mingo@kernel.org> - 2015-10-03 11:00 +0200
              Re: 4.2.2: NR_CPUS effectively being 1 bug Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-10-03 14:10 +0200
                Re: 4.2.2: NR_CPUS effectively being 1 bug Frederic Weisbecker <fweisbec@gmail.com> - 2015-10-03 14:40 +0200
                Re: 4.2.2: NR_CPUS effectively being 1 bug Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-10-03 14:50 +0200
        Re: 4.2.2: NR_CPUS effectively being 1 bug Alexey Dobriyan <adobriyan@gmail.com> - 2015-10-03 14:20 +0200
          Re: 4.2.2: NR_CPUS effectively being 1 bug Mike Galbraith <umgwanakikbuti@gmail.com> - 2015-10-03 14:30 +0200

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