linux-kernel - Re: [PATCH] sched_ext: Simplify cpumask computation in balance

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Message-ID: <Z8sXt5eRyga_ukql@slm.duckdns.org>
Date: Fri, 7 Mar 2025 05:58:47 -1000
From: Tejun Heo <tj@...nel.org>
To: lirongqing <lirongqing@...du.com>
Cc: void@...ifault.com, arighi@...dia.com, changwoo@...lia.com,
	mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
	vincent.guittot@...aro.org, dietmar.eggemann@....com,
	rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
	vschneid@...hat.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched_ext: Simplify cpumask computation in balance_scx

On Fri, Mar 07, 2025 at 02:45:33PM +0800, lirongqing wrote:
> From: Li RongQing <lirongqing@...du.com>
> 
> Compare SMT CPU against RQ CPU and skip balance it, to avoid calling
> for_each_cpu_andnot() and cpumask_of(), they are relatively expensive

How is cpumask_of() expensive? I have a hard time seeing how this would
actually improve anything. Do you have any measurements?

Thanks.

-- 
tejun