Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

From: Joseph Salisbury
Date: Fri Oct 07 2016 - 16:22:38 EST

On 10/07/2016 03:57 PM, Linus Torvalds wrote:
> On Fri, Oct 7, 2016 at 12:38 PM, Joseph Salisbury
> <joseph.salisbury@xxxxxxxxxxxxx> 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.