From:	"David S. Miller" <davem@redhat.com>
Date:	Tue, 6 Feb 2001 23:43:40 -0800 (PST)
To:	linux-kernel@vger.kernel.org
Subject: [UPDATE] New zerocopy patch.


Against 2.4.2-pre1:

ftp://ftp.kernel.org/pub/linux/kernel/people/davem/zerocopy-2.4.2p1-2.diff.gz

Only one notable change since the last installment, but
an important one:

1) When doing paged SKB sendmsg(), use csum_and_copy_from_user
   instead of copy_from_user.

   The problem is that there appears to be some performance bug
   with some x86 processors when doing non-8-byte aligned memcpy
   operations via rep/movsl (P-II Mendocino is one known chip with
   the problem).

   So this change aims to remove this x86 anomaly from the zerocopy
   performance characteristics so we can see if there are some real
   implementation issues compared to running without the zerocopy
   patch applied.

   This is not to say that the x86 memcpy performance thing is being
   ignored, Linus and others are working on what to do about that
   seperately.

Please test, thanks.

Later,
David S. Miller
davem@redhat.com
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