linux-kernel - Re: [PATCH] sched/fair: Fix util_est UTIL_AVG

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Date:   Fri, 28 May 2021 14:25:29 +0800
From:   Xuewen Yan <xuewen.yan94@...il.com>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     Vincent Donnefort <vincent.donnefort@....com>,
        Ingo Molnar <mingo@...hat.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Patrick Bellasi <patrick.bellasi@...bug.net>,
        Quentin Perret <qperret@...gle.com>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: Fix util_est UTIL_AVG_UNCHANGED handling

On Fri, May 28, 2021 at 6:38 AM Dietmar Eggemann
<dietmar.eggemann@....com> wrote:
>
> On 27/05/2021 07:41, Xuewen Yan wrote:
> > Hi
> >
> > On Wed, May 26, 2021 at 10:59 PM Dietmar Eggemann
> > <dietmar.eggemann@....com> wrote:
> >>
> >> On 19/05/2021 18:06, Vincent Donnefort wrote:
> >>> On Fri, May 14, 2021 at 12:37:48PM +0200, Dietmar Eggemann wrote:
>
> [...]
>
> >> diff --git a/include/linux/sched.h b/include/linux/sched.h
> >> index c7e7d50e2fdc..0a0bca694536 100644
> >> --- a/include/linux/sched.h
> >> +++ b/include/linux/sched.h
> >> @@ -357,6 +357,16 @@ struct util_est {
> >>  #define UTIL_EST_WEIGHT_SHIFT          2
> >>  } __attribute__((__aligned__(sizeof(u64))));
> >>
> >> +/*
> >> + * This flag is used to synchronize util_est with util_avg updates.
> >> + * When a task is dequeued, its util_est should not be updated if its util_avg
> >> + * has not been updated in the meantime.
> >> + * This information is mapped into the MSB bit of util_est.enqueued at dequeue
> >> + * time. Since max value of util_est.enqueued for a task is 1024 (PELT util_avg
> >> + * for a task) it is safe to use MSB.
> >> + */
> >> +#define UTIL_AVG_UNCHANGED 0x80000000
> >> +
> >
> > IMHO, Maybe it would be better to put it in the util_est structure
> > just like UTIL_EST_WEIGHT_SHIFT?
>
> Yeah, can do.
>
> I just realized that 'kernel/sched/pelt.h' does not include
> <linux/sched.h> directly (or indirectly via "sched.h". But I can easily
> move cfs_se_util_change() (which uses UTIL_AVG_UNCHANGED) from pelt.h to
> pelt.c, its only consumer anyway.

Since there are so many questions, why not add ( #include "pelt.h" )
directly into (kernel/sched/debug.c)?

diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
index 9c882f20803e..dde91171d4ae 100644
--- a/kernel/sched/debug.c
+++ b/kernel/sched/debug.c
@@ -7,6 +7,7 @@
  * Copyright(C) 2007, Red Hat, Inc., Ingo Molnar
  */
 #include "sched.h"
+#include "pelt.h"

 /*
  * This allows printing both to /proc/sched_debug and