linux-kernel - Re: [PATCH 13/22] x86: smp: move cpumask_weight() out of for-loop in remove

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Date:   Wed, 11 May 2022 11:47:57 +0200
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Yury Norov <yury.norov@...il.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        David Laight <David.Laight@...LAB.COM>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Joe Perches <joe@...ches.com>,
        Julia Lawall <Julia.Lawall@...ia.fr>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Nicholas Piggin <npiggin@...il.com>,
        Nicolas Palix <nicolas.palix@...g.fr>,
        Peter Zijlstra <peterz@...radead.org>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Matti Vaittinen <Matti.Vaittinen@...rohmeurope.com>,
        linux-kernel@...r.kernel.org
Cc:     Yury Norov <yury.norov@...il.com>,
        Balbir Singh <sblbir@...zon.com>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Borislav Petkov <bp@...en8.de>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        "H . Peter Anvin" <hpa@...or.com>, Huang Rui <ray.huang@....com>,
        Ingo Molnar <mingo@...hat.com>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@...el.com>,
        Sean Christopherson <seanjc@...gle.com>,
        Tim Chen <tim.c.chen@...ux.intel.com>, x86@...nel.org
Subject: Re: [PATCH 13/22] x86: smp: move cpumask_weight() out of for-loop
 in remove_siblinginfo

On Tue, May 10 2022 at 08:47, Yury Norov wrote:

Subject: x86: smp: move cpumask_weight() out of for-loop in remove_siblinginfo

Can you please format this according to

https://www.kernel.org/doc/html/latest/process/maintainer-tip.html#patch-submission-notes

> Because argument of the function is constant inside for_each_cpu()
> loop, the cpumask_weight() does the same work O(NR_CPUS) times, while
> it may be calculated only once.
>
> This patch moves cpumask_weight() out of the loop and replaces it

Ditto.

Thanks,

        tglx