linux-kernel - Re: [RFC 00/15] x86_64: Optimize percpu accesses

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Message-Id: <200807111659.19704.rusty@rustcorp.com.au>
Date:	Fri, 11 Jul 2008 16:59:19 +1000
From:	Rusty Russell <rusty@...tcorp.com.au>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	Mike Travis <travis@....com>, "H. Peter Anvin" <hpa@...or.com>,
	Arjan van de Ven <arjan@...radead.org>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Christoph Lameter <cl@...ux-foundation.org>,
	Jack Steiner <steiner@....com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC 00/15] x86_64: Optimize percpu accesses

On Friday 11 July 2008 06:22:52 Eric W. Biederman wrote:
> Jeremy Fitzhardinge <jeremy@...p.org> writes:
> > No, that sounds like a bad idea.  For one, how would you enforce it?  How
> > would you check for it?  It's one of those things that would mostly work
> > and then fail very rarely.
>
> Well the easiest way would be to avoid the letting people take the address
> of per cpu memory, and just provide macros to read/write it.  We are 90% of
> the way there already so it isn't a big jump.

Hi Eric,

    I decided against that originally, but we can revisit that decision.  But 
it would *not* be easy.  Try it on kernel/sched.c which uses per-cpu "struct 
rq".

Perhaps we could limit dynamically allocated per-cpu mem this way though...

Rusty.
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