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Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds

From Peter Zijlstra <peterz@infradead.org>
Newsgroups linux.kernel
Subject Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds
Date 2016-01-28 18:50 +0100
Message-ID <qVYRI-6R2-33@gated-at.bofh.it> (permalink)
References <qVzJE-4Zj-9@gated-at.bofh.it> <qVX9g-5Ao-13@gated-at.bofh.it>
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On Thu, Jan 28, 2016 at 04:55:02PM +0100, Jan Stancek wrote:
> On 01/27/2016 03:52 PM, Jan Stancek wrote:
> > Hello,
> > 
> > pthread_cond_wait_1/2 [1] is rarely failing for me on 4.5.0-rc1,
> > on x86_64 KVM guest with 2 CPUs.
> > 
> > This test [1]:
> > - spawns 2 SCHED_RR threads
> > - first thread with higher priority sets alarm for 2 seconds and blocks on condition
> > - second thread with lower priority is busy looping for 5 seconds
> > - after 2 seconds alarm signal arrives and handler signals condition
> > - high priority thread should resume running
> 
> I have slightly modified testcase, so it will finish immediately when high prio
> thread is done. And also to allow it to compile outside of openposix testsuite.

Yeah, I 'fixed' the testcase too.

So I've had it run for almost 2 hours without a single fail. I've
hot-plugged my cpu count down to 2.

How long should I have to wait for a fail?

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Thread

Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds Jan Stancek <jstancek@redhat.com> - 2016-01-28 17:00 +0100
  Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds Peter Zijlstra <peterz@infradead.org> - 2016-01-28 18:50 +0100
    Re: [BUG] scheduler doesn't balance thread to idle cpu for 3  seconds Jan Stancek <jstancek@redhat.com> - 2016-01-28 20:00 +0100
      Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds Peter Zijlstra <peterz@infradead.org> - 2016-01-29 11:20 +0100
        Re: [BUG] scheduler doesn't balance thread to idle cpu for 3  seconds Jan Stancek <jstancek@redhat.com> - 2016-01-29 11:40 +0100
          Re: [BUG] scheduler doesn't balance thread to idle cpu for 3 seconds Jan Stancek <jstancek@redhat.com> - 2016-02-08 14:50 +0100

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