linux-kernel - Re: [PATCH v4 3/4] sched/isolation: Consolidate housekeeping cpumasks that are always identical

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Message-ID: <ZvV98RseDnagMpnh@localhost.localdomain>
Date: Thu, 26 Sep 2024 17:29:53 +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 v4 3/4] sched/isolation: Consolidate housekeeping
 cpumasks that are always identical

Le Sat, Sep 21, 2024 at 03:07:19PM -0400, Waiman Long a écrit :
> The housekeeping cpumasks are only set by two boot commandline
> parameters: "nohz_full" and "isolcpus". When there is more than one of
> "nohz_full" or "isolcpus", the extra ones must have the same CPU list
> or the setup will fail partially.
> 
> The HK_TYPE_DOMAIN and HK_TYPE_MANAGED_IRQ types are settable by
> "isolcpus" only and their settings can be independent of the other
> types. The other housekeeping types are all set by "nohz_full" or
> "isolcpus=nohz" without a way to set them individually. So they all
> have identical cpumasks.
> 
> There is actually no point in having different cpumasks for these
> "nohz_full" only housekeeping types. Consolidate these types to use the
> same cpumask by aliasing them to the same value. If there is a need to
> set any of them independently in the future, we can break them out to
> their own cpumasks again.
> 
> With this change, the number of cpumasks in the housekeeping structure
> drops from 9 to 3. Other than that, there should be no other functional
> change.
> 
> Signed-off-by: Waiman Long <longman@...hat.com>

Acked-by: Frederic Weisbecker <frederic@...nel.org>