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

From: Peter Zijlstra
Date: Sat Oct 08 2016 - 04:00:41 EST

On Fri, Oct 07, 2016 at 03:38:23PM -0400, Joseph Salisbury wrote:
> Hello Peter,
> A kernel bug report was opened against Ubuntu [0]. After a kernel
> bisect, it was found that reverting the following commit resolved this bug:
> commit 3d30544f02120b884bba2a9466c87dba980e3be5
> Author: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
> Date: Tue Jun 21 14:27:50 2016 +0200
> sched/fair: Apply more PELT fixes

That commit doesn't revert cleanly, did you take out more?

> The regression was introduced as of v4.8-rc1. The bug can be reproduced
> on an X1 Carbon with the following:
> stress -c $your_total_cpu_cores
> I was hoping to get your feedback, since you are the patch author. Do
> you think gathering any additional data will help diagnose this issue,
> or would it be best to submit a revert request?

I'll try and have a look asap, but I'm traveling next week so it might a
tad slower than normal.

If you could provide a /proc/sched_debug dump while the thing is running
that'd might be useful.