linux-kernel - Re: [PATCH] lib/memweight.c: optimize by inlining bitmap

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Message-Id: <20190821182507.b0dea16f57360cf0ac40deb6@linux-foundation.org>
Date:   Wed, 21 Aug 2019 18:25:07 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Denis Efremov <efremov@...ras.ru>
Cc:     Akinobu Mita <akinobu.mita@...il.com>, Jan Kara <jack@...e.cz>,
        Matthew Wilcox <matthew@....cx>, linux-kernel@...r.kernel.org,
        dm-devel@...hat.com, linux-fsdevel@...r.kernel.org,
        linux-media@...r.kernel.org, Erdem Tumurov <erdemus@...il.com>,
        Vladimir Shelekhov <vshel@....nsk.su>
Subject: Re: [PATCH] lib/memweight.c: optimize by inlining bitmap_weight()

On Wed, 21 Aug 2019 10:42:00 +0300 Denis Efremov <efremov@...ras.ru> wrote:

> This patch inlines bitmap_weight() call.

It is better to say the patch "open codes" the bitmap_weight() call.

> Thus, removing the BUG_ON,

Why is that OK to do?

I expect all the code size improvements are from doing this?

> and 'longs to bits -> bits to longs' conversion by directly calling
> hweight_long().
> 
> ./scripts/bloat-o-meter lib/memweight.o.old lib/memweight.o.new
> add/remove: 0/0 grow/shrink: 0/1 up/down: 0/-10 (-10)
> Function                                     old     new   delta
> memweight                                    162     152     -10
>