linux-kernel - Re: [PATCH 10/54] net: ethernet: replace bitmap_weight with bitmap

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Date:   Mon, 24 Jan 2022 14:28:00 +0200
From:   Andy Shevchenko <andriy.shevchenko@...ux.intel.com>
To:     Yury Norov <yury.norov@...il.com>
Cc:     Rasmus Villemoes <linux@...musvillemoes.dk>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michał Mirosław <mirq-linux@...e.qmqm.pl>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Laight <David.Laight@...lab.com>,
        Joe Perches <joe@...ches.com>, Dennis Zhou <dennis@...nel.org>,
        Emil Renner Berthing <kernel@...il.dk>,
        Nicholas Piggin <npiggin@...il.com>,
        Matti Vaittinen <matti.vaittinen@...rohmeurope.com>,
        Alexey Klimov <aklimov@...hat.com>,
        linux-kernel@...r.kernel.org, Ariel Elior <aelior@...vell.com>,
        Manish Chopra <manishc@...vell.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>, netdev@...r.kernel.org
Subject: Re: [PATCH 10/54] net: ethernet: replace bitmap_weight with
 bitmap_empty for qlogic

On Sun, Jan 23, 2022 at 10:38:41AM -0800, Yury Norov wrote:
> qlogic/qed code calls bitmap_weight() to check if any bit of a given
> bitmap is set. It's better to use bitmap_empty() in that case because
> bitmap_empty() stops traversing the bitmap as soon as it finds first
> set bit, while bitmap_weight() counts all bits unconditionally.

> -		if (bitmap_weight((unsigned long *)&pmap[item], 64 * 8))
> +		if (!bitmap_empty((unsigned long *)&pmap[item], 64 * 8))

> -	    (bitmap_weight((unsigned long *)&pmap[item],
> +	    (!bitmap_empty((unsigned long *)&pmap[item],

Side note, these castings reminds me previous discussion and I'm wondering
if you have this kind of potentially problematic places in your TODO as
subject to fix.


-- 
With Best Regards,
Andy Shevchenko