linux-kernel - Re: [PATCH v3 2/2] sched/isolation: Consolidate housekeeping cpumasks that are always identical

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Message-ID: <Ztr_SIwkOK1MXTIW@pavilion.home>
Date: Fri, 6 Sep 2024 15:10:32 +0200
From: Frederic Weisbecker <frederic@...nel.org>
To: Waiman Long <longman@...hat.com>
Cc: Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
	Juri Lelli <juri.lelli@...hat.com>,
	Vincent Guittot <vincent.guittot@...aro.org>,
	Dietmar Eggemann <dietmar.eggemann@....com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Ben Segall <bsegall@...gle.com>, Mel Gorman <mgorman@...e.de>,
	Valentin Schneider <vschneid@...hat.com>,
	linux-kernel@...r.kernel.org, Phil Auld <pauld@...hat.com>
Subject: Re: [PATCH v3 2/2] sched/isolation: Consolidate housekeeping
 cpumasks that are always identical

Le Wed, Sep 04, 2024 at 07:57:13PM -0400, Waiman Long a écrit :
> > > diff --git a/include/linux/sched/isolation.h b/include/linux/sched/isolation.h
> > > index 499d5e480882..e2c42172de82 100644
> > > --- a/include/linux/sched/isolation.h
> > > +++ b/include/linux/sched/isolation.h
> > > @@ -7,15 +7,21 @@
> > >   #include <linux/tick.h>
> > >   enum hk_type {
> > > -	HK_TYPE_TIMER,
> > > -	HK_TYPE_RCU,
> > > -	HK_TYPE_MISC,
> > >   	HK_TYPE_TICK,
> > >   	HK_TYPE_DOMAIN,
> > > -	HK_TYPE_WQ,
> > >   	HK_TYPE_MANAGED_IRQ,
> > > -	HK_TYPE_KTHREAD,
> > > -	HK_TYPE_MAX
> > > +	HK_TYPE_KERNEL_NOISE,
> > > +	HK_TYPE_MAX,
> > > +
> > > +	/*
> > > +	 * The following housekeeping types are only set by the nohz_full
> > > +	 * boot commandline option. So they can share the same value.
> > > +	 */
> > > +	HK_TYPE_TIMER   = HK_TYPE_KERNEL_NOISE,
> > > +	HK_TYPE_RCU     = HK_TYPE_KERNEL_NOISE,
> > > +	HK_TYPE_MISC    = HK_TYPE_KERNEL_NOISE,
> > > +	HK_TYPE_WQ      = HK_TYPE_KERNEL_NOISE,
> > > +	HK_TYPE_KTHREAD = HK_TYPE_KERNEL_NOISE
> > Why not removing them entirely and only keep HK_TYPE_KERNEL_NOISE ?
> 
> All these HK_TYPE_* types are still used in other parts of kernel. We need
> to clean them all up before we can remove them, but that is outside the
> scope of this series.

If that can help, I posted this a while ago:

https://lore.kernel.org/lkml/20230203232409.163847-2-frederic@kernel.org/

I think it is very much needed. People keep getting confused about these individual
bits.

> Cheers,
> Longman
> 
>