linux-kernel - Re: [PATCH] include: kernel.h: rewrite min3, max3 and clamp using min and max

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Message-Id: <20140616161804.bb06ed842f59371c031d1252@linux-foundation.org>
Date:	Mon, 16 Jun 2014 16:18:04 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Steven Rostedt <rostedt@...dmis.org>,
	Hagen Paul Pfeifer <hagen@...u.net>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] include: kernel.h: rewrite min3, max3 and clamp using
 min and max

On Mon, 16 Jun 2014 23:07:22 +0200 Michal Nazarewicz <mina86@...a86.com> wrote:

> It appears that gcc is better at optimising a double call to min
> and max rather than open coded min3 and max3.  This can be observed
> here:
> 
> ...
>
> Furthermore, after ___make allmodconfig && make bzImage modules___ this is the
> comparison of image and modules sizes:
> 
>     # Without this patch applied
>     $ ls -l arch/x86/boot/bzImage **/*.ko |awk '{size += $5} END {print size}'
>     350715800
> 
>     # With this patch applied
>     $ ls -l arch/x86/boot/bzImage **/*.ko |awk '{size += $5} END {print size}'
>     349856528

We saved nearly a megabyte by optimising min3(), max3() and clamp()? 

I'm counting a grand total of 182 callsites for those macros.  So the
saving is 4700 bytes per invokation?  I don't believe it...


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