linux-kernel - Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

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Message-ID: <4fde8f26a9aeaeafda15b81bbb17b0ffc96941f0.camel@gmx.de>
Date: Wed, 11 Sep 2024 11:10:26 +0200
From: Mike Galbraith <efault@....de>
To: Peter Zijlstra <peterz@...radead.org>, Luis Machado
 <luis.machado@....com>
Cc: Dietmar Eggemann <dietmar.eggemann@....com>, Vincent Guittot
 <vincent.guittot@...aro.org>, Hongyan Xia <hongyan.xia2@....com>, 
 mingo@...hat.com, juri.lelli@...hat.com, rostedt@...dmis.org,
 bsegall@...gle.com,  mgorman@...e.de, vschneid@...hat.com,
 linux-kernel@...r.kernel.org,  kprateek.nayak@....com,
 wuyun.abel@...edance.com, youssefesmat@...omium.org,  tglx@...utronix.de
Subject: Re: [PATCH 10/24] sched/uclamg: Handle delayed dequeue

On Wed, 2024-09-11 at 10:45 +0200, Peter Zijlstra wrote:
> On Wed, Sep 11, 2024 at 09:35:16AM +0100, Luis Machado wrote:
> > > 
> > > I'm assuming that removing the usage sites restores function?
> > 
> > It does restore function if we remove the usage.
> > 
> > From an initial look:
> > 
> > cat /sys/kernel/debug/sched/debug | grep -i delay                                                                                                                                                                                                                             
> >   .h_nr_delayed                  : -4
> >   .h_nr_delayed                  : -6
> >   .h_nr_delayed                  : -1
> >   .h_nr_delayed                  : -6
> >   .h_nr_delayed                  : -1
> >   .h_nr_delayed                  : -1
> >   .h_nr_delayed                  : -5
> >   .h_nr_delayed                  : -6
> > 
> > So probably an unexpected decrement or lack of an increment somewhere.
> 
> Yeah, that's buggered. Ok, I'll go rebase sched/core and take this patch
> out. I'll see if I can reproduce that.

Hm, would be interesting to know how the heck he's triggering that.

My x86_64 box refuses to produce any such artifacts with anything I've
tossed at it, including full LTP with enterprise RT and !RT configs,
both in master and my local SLE15-SP7 branch.  Hohum.

	-Mike