From owner-cvs-all  Wed Dec  1 16:18: 1 1999
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From: Archie Cobbs <archie@whistle.com>
Message-Id: <199912020016.QAA45269@bubba.whistle.com>
Subject: Re: cvs commit: src/sys/kern uipc_mbuf.c src/sys/sys mbuf.h
In-Reply-To: <199912012238.PAA09252@caspian.plutotech.com> from "Justin T. Gibbs" at "Dec 1, 1999 03:38:53 pm"
To: gibbs@FreeBSD.org (Justin T. Gibbs)
Date: Wed, 1 Dec 1999 16:16:22 -0800 (PST)
Cc: archie@whistle.com (Archie Cobbs), cvs-committers@FreeBSD.org,
	cvs-all@FreeBSD.org
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Justin T. Gibbs writes:
> >Not sure what a '0 copy system' is..
> >
> >Basically all it does is create a completely new mbuf chain containing
> >the same data as the original.  Definitely at least 1 copy :-)
> 
> There is support in the works for 0 copy transmission and receive
> for page sized/aligned packets on gig-E cards.  In this situation,
> the kernel doesn't own the data and copying the mbuf chain could
> be expensive.

Like Julian said, it's mainly for debugging and tracing.

On the other hand, if you want two versions of some data, where
modifying version doesn't modify the other, I don't know of any other
way to do that than copying the data.

-Archie

___________________________________________________________________________
Archie Cobbs   *   Whistle Communications, Inc.  *   http://www.whistle.com


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