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Date: Wed, 30 Jan 2002 12:22:00 +0300
From: Andrey Panin <pazke@orbita1.ru>
To: linux-kernel@vger.kernel.org
Subject: Re: [ACPI] ACPI mentioned on lwn.net/kernel
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In-Reply-To: <Pine.LNX.4.33.0201261339220.17628-100000@penguin.transmeta.com>; from torvalds@transmeta.com on Sat, Jan 26, 2002 at 01:42:52PM -0800
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On Sat, Jan 26, 2002 at 01:42:52PM -0800, Linus Torvalds wrote:
>=20
> On Sat, 26 Jan 2002, Martin Eriksson wrote:
> >
> > Hmm.. I tried to compile the kernel with -Os (gcc 2.96-98) and I just g=
ot a
> > ~1% smaller vmlinux and a ~3% smaller bzImage.
>=20
> Note that while "-Os" exists and is documented, as far as I know gcc
> doesn't actually do much with it. It really acts mostly as a "disable
> certain optimizations" than anything else.
>=20

Stupid questions:
	- what stop us from using -mregparm=3D3 gcc switch ?
	- same with -Os -malign-loops=3D1 -malign-jumps=3D1 ?
	- any tool to measure perfomance gain/penalty of above ?

> In the 3.0.x tree, it seems to change some of the weights of some
> instructions, and it might make more of a difference there. But at the
> same time it is quite telling that "-Os" doesn't even change any of the
> alignments etc - because gcc developers do not seem to really support it
> as a real option. It's an after-thought, not a big performance push.
>=20
> 		Linus
>=20

--=20
Andrey Panin            | Embedded systems software engineer
pazke@orbita1.ru        | PGP key: wwwkeys.eu.pgp.net
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