Re: [patch] x86, mm: pass in 'total' to __copy_from_user_*nocache()

From: H. Peter Anvin
Date: Sun Mar 01 2009 - 23:50:50 EST


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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