Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers

[Posted January 3, 2006 by corbet]

From:		Ingo Molnar <mingo-AT-elte.hu>
To:		Andi Kleen <ak-AT-suse.de>
Subject:		Re: [patch 00/2] improve .text size on gcc 4.0 and newer compilers
Date:		Fri, 30 Dec 2005 11:14:43 +0100
Cc:		Jakub Jelinek <jakub-AT-redhat.com>, Arjan van de Ven <arjan-AT-infradead.org>, Christoph Hellwig <hch-AT-infradead.org>, Linus Torvalds <torvalds-AT-osdl.org>, lkml <linux-kernel-AT-vger.kernel.org>, Andrew Morton <akpm-AT-osdl.org>, Matt Mackall <mpm-AT-selenic.com>

* Ingo Molnar <mingo@elte.hu> wrote:

> > I'm not quite sure I buy Ingo's original argument also.  If he's only 
> > looking at text size then with the above fixed then he ideally would 
> > like to not inline anything (because except these exceptions above 
> > .text usually near always shrinks when not inlining). But that's not 
> > necessarily best for performance.
> 
> well, i think the numbers talk for themselves. Here are my latest 
> results:

i now have x86 allyesconfig numbers too:

    text     data     bss      dec  filename
 24190215 6737902 1775592 32703709  vmlinux-allyes-speed-orig
 20096423 6758758 1775592 28630773  vmlinux-allyes-orig
 19223511 6844002 1775656 27843169  vmlinux-allyes-inline+units+fixes+capable

i.e. enabling CONFIG_CC_OPTIMIZE_FOR_SIZE gives a 20.4% size reduction, 
and adding my latest debloating-queue ontop of gives an additional 4.5% 
of reduction. The queue is at:

  http://redhat.com/~mingo/debloating-patches/

note: my focus is still mostly on CC_OPTIMIZE_FOR_SIZE (which is only 
offered if CONFIG_EMBEDDED is enabled) - if you want a larger kernel 
optimized for speed, do not enable it.

	Ingo