linux-kernel - Re: [PATCH 01/22] x86: add methods for writing of an MSR on several CPUs

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Message-ID: <20090522143918.GA22850@aftab>
Date:	Fri, 22 May 2009 16:39:18 +0200
From:	Borislav Petkov <borislav.petkov@....com>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	akpm@...ux-foundation.org, greg@...ah.com, mingo@...e.hu,
	norsk5@...oo.com, tglx@...utronix.de, mchehab@...hat.com,
	aris@...hat.com, edt@....ca, linux-kernel@...r.kernel.org,
	Andreas Herrmann <andreas.herrmann3@....com>
Subject: Re: [PATCH 01/22] x86: add methods for writing of an MSR on
	several CPUs

On Thu, May 21, 2009 at 10:38:01AM -0700, H. Peter Anvin wrote:
> Borislav Petkov wrote:
> > 
> > Well, let's do the nonserializing thing and have it done right from the
> > beginning. We might not care now but who knows..?
> > 
> 
> If nothing else it might matter for boot time.  Serializing *anything*
> across a large number of CPUs can be very expensive.

well, upon a closer look, smp_call_function_many() skips over the CPU
it is executing on and there's currently work in that area to extend
that API: http://marc.info/?l=linux-kernel&m=123979231511594&w=2.

However, according to Linus' comments, it looks like this would need a
bit of work so I guess we should wait with the concurrency stuff a bit,
no?

-- 
Regards/Gruss,
Boris.

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