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Date:      Sun, 2 Dec 2001 14:45:47 -0500
From:      Bosko Milekic <bmilekic@technokratis.com>
To:        Matthew Dillon <dillon@apollo.backplane.com>
Cc:        Richard Sharpe <sharpe@ns.aus.com>, freebsd-hackers@FreeBSD.ORG
Subject:   Re: Patch #3 (TCP / Linux / Performance)
Message-ID:  <20011202144547.A58695@technokratis.com>
In-Reply-To: <200112021918.fB2JIg592414@apollo.backplane.com>; from dillon@apollo.backplane.com on Sun, Dec 02, 2001 at 11:18:42AM -0800
References:  <15364.38174.938500.946169@caddis.yogotech.com> <20011128104629.A43642@walton.maths.tcd.ie> <5.1.0.14.1.20011130181236.00a80160@postamt1.charite.de> <200111302047.fAUKlT811090@apollo.backplane.com> <200111302130.fAULUU324648@apollo.backplane.com> <3C08CF9D.2030109@ns.aus.com> <200112012138.fB1LcG837063@apollo.backplane.com> <200112020810.fB28Arr77757@apollo.backplane.com> <3C0A3204.3010009@ns.aus.com> <200112021918.fB2JIg592414@apollo.backplane.com>

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On Sun, Dec 02, 2001 at 11:18:42AM -0800, Matthew Dillon wrote:
[...]
> :Does the FreeBSD tcp stack do zero copy (page flip the data to 
> :userspace)? In the localhost case, it seems like there are two copies 
> :to/from userspace there.
> :
> :-- 
> :Richard Sharpe, rsharpe@ns.aus.com, LPIC-1
> 
>     There are zero-copy patches floating around but I haven't looked at
>     them to determine how messy they might be.

	http://people.freebsd.org/~ken/zero_copy/

	The main issues with the patch are, afaics:

  1. It's fairly large and difficult to maintain, especially in light of
     the large amount of SMPng-related changes.

  2. The receive code only works with certain network cards. [This is
     expected]. The performance may also vary based on the behavior of
     the application.

> 					-Matt
> 					Matthew Dillon 
> 					<dillon@backplane.com>

-- 
 Bosko Milekic
 bmilekic@technokratis.com


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