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Subject: Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes
To: Linus Torvalds <torvalds@linux-foundation.org>
References: <57F7F9AF.2010609@canonical.com>
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Cc: Peter Zijlstra <peterz@infradead.org>, Mike Galbraith <efault@gmx.de>,
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From: Joseph Salisbury <joseph.salisbury@canonical.com>
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Date: Fri, 7 Oct 2016 16:22:24 -0400
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On 10/07/2016 03:57 PM, Linus Torvalds wrote:
> On Fri, Oct 7, 2016 at 12:38 PM, Joseph Salisbury
> <joseph.salisbury@canonical.com> wrote:
>> A kernel bug report was opened against Ubuntu [0].  After a kernel
>> bisect, it was found that reverting the following commit resolved this bug:
> Hmm. Interesting, and it sounds like we should revert that unless
> somebody figures out *why* following the rules wrt cfq updates causes
> problems. But I also wonder what the Ubuntu kernel config is. Does
> Ubuntu enable CONFIG_SCHED_AUTOGROUP=y, for example? Because
> regardless of any other scheduler issues, autogrouping *should* mean
> that when you run some CPU hogger in one session, that should still
> balance all CPU time with other sessions..
>
> I'm not seeing anything odd on my xps13, which should have a similar
> CPU to the X1 Carbon.
>
>                Linus
Hi Linus,

Yes, CONFIG_SCHED_AUTOGROUP is enabled in the Ubuntu kernel.  However,
that config was also enable in the Ubuntu 4.4 kerrnels without seeing
this issue.   I can try disabling the config in the 4.8 based kernel and
see if that changes things.

Thanks,

Joe