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Re: TxDescriptors -> 1024 default. Please not for every NIC!

To: Marc Herbert <marc.herbert@xxxxxxx>
Subject: Re: TxDescriptors -> 1024 default. Please not for every NIC!
From: Andi Kleen <ak@xxxxxx>
Date: Wed, 19 May 2004 13:54:53 +0200
Cc: netdev@xxxxxxxxxxx
In-reply-to: <Pine.LNX.4.58.0405190256010.30653@fcat> (Marc Herbert's message of "Wed, 19 May 2004 11:30:28 +0200 (CEST)")
References: <OF72607111.CD0234C8-ON85256DA1.0068861B-86256DA1.0068FF60@xxxxxxxxxx> <Pine.LNX.4.58.0405151354220.9894@fcat> <Pine.LNX.4.58.0405190256010.30653@fcat>
Sender: netdev-bounce@xxxxxxxxxxx
User-agent: Gnus/5.110003 (No Gnus v0.3) Emacs/21.2 (gnu/linux)
Marc Herbert <marc.herbert@xxxxxxx> writes:
>
> PS: several people seem to think TCP "drops" packets when the qdisc is
> full. My analysis of the code _and_ my experiments makes me think they
> are wrong: TCP rather "blocks" when the qdisc is full. See explanation
> here: <http://oss.sgi.com/archives/netdev/2004-05/msg00151.html>
> (Subject: Re: TcpOutSegs way too optimistic (netstat -s))

This behaviour was only added relatively recently (in late 2.3.x timeframe)
I believe all the default queue lengths tunings were done before that.
So it would probably make sense to reevaluate/rebenchmark the default 
queue lengths for various devices with the newer code.

-Andi



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