Re: [ACPI] ACPI mentioned on lwn.net/kernel

[Andrey Panin <pazke@orbita1.ru>]

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On Sat, Jan 26, 2002 at 01:42:52PM -0800, Linus Torvalds wrote:
> 
> On Sat, 26 Jan 2002, Martin Eriksson wrote:
> >
> > Hmm.. I tried to compile the kernel with -Os (gcc 2.96-98) and I just got a
> > ~1% smaller vmlinux and a ~3% smaller bzImage.
> 
> 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.
> 

Stupid questions:
	- what stop us from using -mregparm=3 gcc switch ?
	- same with -Os -malign-loops=1 -malign-jumps=1 ?
	- 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.
> 
> 		Linus
> 

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

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