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Date:      Tue, 3 Apr 2001 01:18:42 +0200 (CEST)
From:      Bert Driehuis <driehuis@playbeing.org>
To:        "Jason T. Luttgens" <lucky@lansters.com>
Cc:        freebsd-stable@FreeBSD.ORG
Subject:   RE: Network performance question
Message-ID:  <Pine.BSI.4.21.0104030111410.5679-100000@c1111.nl.compuware.com>
In-Reply-To: <000001c0bbc9$cc97b990$0200010a@lucky>

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On Mon, 2 Apr 2001, Jason T. Luttgens wrote:

> However - I noticed something while testing. Linux 2.4.3 did not access the
> drive as much as FreeBSD was. I guess Linux is caching the file more or
> something...who knows. So I re-performed the tests with output going to
> /dev/null and looking at the tcpdump and interface counters (I know, it's
> not the best way, but at this point I was thinking it's the disk I/O that's
> causing the drops/loss).

You could try enabling softupdates if you haven't done so yet. For
benchmarking purposes, you could also try async mount (but note that
async can screw up your disk real bad in case of a system crash).

I would not expect either to have much effect if the machine is
otherwise quiescent, but if you are being hit because of any synchronous
activity going on it would be nice if this could be eliminated from the
equation.

Note that you really are entering a grey area here -- it may well be
that the respective kernels have different priorities or strategies that
have little to do with Ethernet performance, e.g. FreeBSD's insistence
(by default) that file systems remain consistent in case of a system
crash might cause some packets to be lost in this flat out. worst case
scenario. It is unlikely that you will prove what happens unless you
stumble upon something that eliminates the difference.

Cheers,

			-- Bert

-- 
Bert Driehuis -- driehuis@playbeing.org -- +31-20-3116119
If the only tool you've got is an axe, every problem looks like fun!


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