linux-kernel - Re: [PATCH v4 00/49] bitmap: optimize bitmap

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Message-Id: <164493593823.3069697.15308947342224952378.b4-ty@kernel.org>
Date:   Tue, 15 Feb 2022 23:18:33 +0000
From:   Will Deacon <will@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        David Laight <David.Laight@...lab.com>,
        Andy Shevchenko <andriy.shevchenko@...ux.intel.com>,
        Alexey Klimov <aklimov@...hat.com>,
        Yury Norov <yury.norov@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Dennis Zhou <dennis@...nel.org>, Joe Perches <joe@...ches.com>,
        linux-kernel@...r.kernel.org,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>
Cc:     catalin.marinas@....com, kernel-team@...roid.com,
        Will Deacon <will@...nel.org>
Subject: Re: [PATCH v4 00/49] bitmap: optimize bitmap_weight() usage

On Thu, 10 Feb 2022 14:48:44 -0800, Yury Norov wrote:
> In many cases people use bitmap_weight()-based functions to compare
> the result against a number of expression:
> 
>         if (cpumask_weight(mask) > 1)
>                 do_something();
> 
> This may take considerable amount of time on many-cpus machines because
> cpumask_weight() will traverse every word of underlying cpumask
> unconditionally.
> 
> [...]

Applied to will (for-next/perf), thanks!

[12/49] perf: replace bitmap_weight with bitmap_empty where appropriate
        https://git.kernel.org/will/c/95ed57c73bbc

Cheers,
-- 
Will

https://fixes.arm64.dev
https://next.arm64.dev
https://will.arm64.dev