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Subject: Re: [PATCH] zerocopy NFS for 2.5.36
From: Alan Cox <alan@lxorguk.ukuu.org.uk>
To: "David S. Miller" <davem@redhat.com>
Cc: taka@valinux.co.jp, neilb@cse.unsw.edu.au, linux-kernel@vger.kernel.org,
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Date: 19 Sep 2002 00:54:37 +0100
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On Thu, 2002-09-19 at 00:00, David S. Miller wrote:
> It was discussed long ago that csum_and_copy_from_user() performs
> better than plain copy_from_user() on x86.  I do not remember all

The better was a freak of PPro/PII scheduling I think

> details, but I do know that using copy_from_user() is not a real
> improvement at least on x86 architecture.

The same as bit is easy to explain. Its totally memory bandwidth limited
on current x86-32 processors. (Although I'd welcome demonstrations to
the contrary on newer toys)

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