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

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Message-ID: <CA+55aFw5DTubaqgszpZW44gnt_k-_1ENjgrtWo6M9hexbbJsBw@mail.gmail.com>
Date:   Fri, 7 Oct 2016 12:57:47 -0700
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Joseph Salisbury <joseph.salisbury@...onical.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        Mike Galbraith <efault@....de>,
        Thomas Gleixner <tglx@...utronix.de>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>
Subject: Re: [v4.8-rc1 Regression] sched/fair: Apply more PELT fixes

On Fri, Oct 7, 2016 at 12:38 PM, Joseph Salisbury
<joseph.salisbury@...onical.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