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Date: Wed, 2 Apr 2003 15:58:55 -0500
From: Jeff Garzik <jgarzik@pobox.com>
To: Dennis Cook <cook@sandgate.com>
Cc: linux-kernel@vger.kernel.org, kernelnewbies@nl.linux.org
Subject: Re: Deactivating TCP checksumming
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On Wed, Apr 02, 2003 at 03:47:35PM -0500, Dennis Cook wrote:
> What I was looking for is a general capability to keep the SW transport
> stack from
> computing outgoing TCP/UDP/IP checksums so that the HW can be allowed to do
> it,
> similar to Windows checksum offload capability.

If you are not using sendfile(2), it is _more expensive_ to offload
checksums, because we already checksum and copy at the same time.

Hardware checksum offload is only a win when a copy is eliminated.

Therefore, _always_ offloading checksum is actually slower in some
cases, because of the unneeded additional HW csum setup that would be
performed.

	Jeff