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Date:      Sun, 02 May 1999 12:55:48 -0700
From:      David Greenman <dg@root.com>
To:        Robert Watson <robert+freebsd@cyrus.watson.org>
Cc:        advocacy@freebsd.org
Subject:   Re: new picture of wcarchive 
Message-ID:  <199905021955.MAA29773@implode.root.com>
In-Reply-To: Your message of "Sun, 02 May 1999 11:25:09 EDT." <Pine.BSF.3.96.990502112355.5183G-100000@fledge.watson.org> 

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>So I'd hate to see how it would shine if we ran it with the IOlite code
>that allows transfers with a single copy, and uses the same copy for the
>socket buffers while the date is queued.  Has there been any discussion of
>bringing that into the source code base?  The work was on 2.2, but would
>certainly be worthwhile for the big server stuff.  I don't know what the
>license was (someone gave a talk on it at CMU a few weeks ago and I was
>extremely impressed).

   Wcarchive uses "dg-ftpd", which uses the zero-copy sendfile() for sending
files. The data is still touched during the checksum, however. The current
machine has enough CPU to handle >200Mbps, and a lot more if I can get the
hardware checksum working with the gigabit ether card. The bottleneck is
the network connection and going to something faster is the only solution.
   IOlite, while interesting in principle, was nothing more than a proof of
concept and unfortunately isn't something that we would want to include in
FreeBSD. I spoke with the researcher at length about it. For this particular
application, sendfile() is the most efficient way to get the zero-copy job
done.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project - http://www.freebsd.org
Creator of high-performance Internet servers - http://www.terasolutions.com


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