Message-ID: <49AB648B.5090302@zytor.com>
Date: Sun, 01 Mar 2009 20:46:03 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Nick Piggin <nickpiggin@yahoo.com.au>
CC: Arjan van de Ven <arjan@infradead.org>, Andi Kleen <andi@firstfloor.org>,
       David Miller <davem@davemloft.net>, torvalds@linux-foundation.org,
       mingo@elte.hu, sqazi@google.com, linux-kernel@vger.kernel.org,
       tglx@linutronix.de
Subject: Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()
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Nick Piggin wrote:
> 
> I would expect any high performance CPU these days to combine entries
> in the store queue, even for normal store instructions (especially for
> linear memcpy patterns). Isn't this likely to be the case?
> 

Actually, that is often not the case simply because it doesn't buy that
much.  The big win comes when you don't read a whole cache line in from
memory, but that is a property of the cache, not the store queue.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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