linux-kernel - Re: [patch] x86, mm: pass in 'total' to __copy_from_user

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Message-ID: <20090228103958.41fce55b@infradead.org>
Date:	Sat, 28 Feb 2009 10:39:58 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	Nick Piggin <nickpiggin@...oo.com.au>,
	Salman Qazi <sqazi@...gle.com>, davem@...emloft.net,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, Andi Kleen <andi@...stfloor.org>
Subject: Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()

On Sat, 28 Feb 2009 19:27:59 +0100
Ingo Molnar <mingo@...e.hu> wrote:

> 
> OTOH, given how draconian non-temporal stores are, i'm leaning 
> towards removing them from the x86 code altogether. If it matter 
> to performance somewhere it can be reintroduced, based on really 
> well backed up numbers.

I think that is mostly the right approach; O_DIRECT could be the
exception to that (because there we don't only wipe it from the cpu
cache due to DMA, it even gets wiped from the pagecache!).
But I can see that being too special of a case to care about in the
grand scheme of things (although the database people will now get upset
with me ;-)

-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org
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