linux-kernel - Re: [patch 1/2] i386: use asm() like the other atomic operations already do.

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Message-ID: <20070815234434.GC28775@gondor.apana.org.au>
Date:	Thu, 16 Aug 2007 07:44:34 +0800
From:	Herbert Xu <herbert.xu@...hat.com>
To:	Chris Snook <csnook@...hat.com>
Cc:	Andi Kleen <ak@...e.de>, sebastian@...akpoint.cc,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 1/2] i386: use asm() like the other atomic operations already do.

On Wed, Aug 15, 2007 at 01:02:23PM -0400, Chris Snook wrote:
> Herbert Xu wrote:
> >Andi Kleen <ak@...e.de> wrote:
> >>>My config with march=pentium-m and gcc (GCC) 4.1.2 (Gentoo 4.1.2):
> >>>  text    data     bss     dec     hex filename
> >>>3434150  249176  176128 3859454  3ae3fe atomic_normal/vmlinux
> >>>3435308  249176  176128 3860612  3ae884 atomic_inlineasm/vmlinux
> >>What is the difference between atomic_normal and atomic_inlineasm? 
> >
> >The inline asm stops certain optimisations from occuring.
> >
> >I'm still unconvinced why we need this because nobody has
> >brought up any examples of kernel code that legitimately
> >need this.
> 
> There's plenty of kernel code that *wants* this though.  If we can 

You keep saying this yet everytime I ask for an example I
get nothing.

> reduce the need for register-clobbering barriers, shrink our binaries, 
> shrink our code, improve performance, and avoid heisenbugs, I think it's 
> a win, whether or not we *need* it.

Hmm, you're increasing our binary size and probably killing
performance.

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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