linux-kernel - Re: -Os versus -O2

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Message-Id: <1182733127.6819.13.camel@laptopd505.fenrus.org>
Date:	Sun, 24 Jun 2007 17:58:46 -0700
From:	Arjan van de Ven <arjan@...radead.org>
To:	Adrian Bunk <bunk@...sta.de>
Cc:	Benjamin LaHaise <bcrl@...ck.org>,
	Oleg Verych <olecom@...wer.upol.cz>, rae l <crquan@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: -Os versus -O2

> I wouldn't care if CONFIG_CC_OPTIMIZE_FOR_SIZE was hidden behind
> CONFIG_EMBEDDED, but as long as it's available as a general purpose
> option we have to consider it's performance.

I think you are missing the point. You tell the kernel to
OPTIMIZE_FOR_SIZE. *over performance*. Sure. Performance shouldn't be
EXTREMELY pathetic, but it's not; and if it were, it's a problem with
the gcc version you have (and if you are a distro, you can surely fix
that)

> 
> The interesting questions are:
> Does -Os still sometimes generate faster code with gcc 4.2?
> If yes, why?

on a system level, size can help performance because you have more
memory available for other things.  It also reduces download size and
gives you more space on the live CD....

if you want to make things bigger again, please do this OUTSIDE the
"optimize for size" option. Because that TELLS you to go for size.

-- 
if you want to mail me at work (you don't), use arjan (at) linux.intel.com
Test the interaction between Linux and your BIOS via http://www.linuxfirmwarekit.org

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