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Re: TCP performance drop 2.6.6->2.6.7

To: Baruch Even <baruch@xxxxxxxxx>
Subject: Re: TCP performance drop 2.6.6->2.6.7
From: Stephen Hemminger <shemminger@xxxxxxxx>
Date: Tue, 12 Apr 2005 16:07:52 -0700
Cc: netdev@xxxxxxxxxxx, "David S. Miller" <davem@xxxxxxxxxxxxx>
In-reply-to: <425C493B.5040206@ev-en.org>
Organization: Open Source Development Lab
References: <425C493B.5040206@ev-en.org>
Sender: netdev-bounce@xxxxxxxxxxx
On Tue, 12 Apr 2005 23:18:35 +0100
Baruch Even <baruch@xxxxxxxxx> wrote:

> Hello,
> 
> I'm trying to port my H-TCP and SACK improvements to 2.6.11, but I seem 
> to hit performance problems that are unrelated to what I worked on so far.
> 
> My tests show that between 2.6.6 and 2.6.7 the TCP performance dropped 
> considerably.

Remember 2.6.6 had the old hyper aggressive and over correcting version
of BIC.

> The setup for the tests, vanilla kernels, dummynet with 100 Mbit/s and 
> 40ms rtt using the BIC protocol. No patches applied whatsoever.
> 
> iperf tests for 2.6.6 get about 90Mbit/s while 2.6.7 gets 30Mbit/s.

Haven't measured old kernels recently. But haven't seen that with the
newest stuff I tested last night. At 40ms delay  with netem
over 1G to 100M bridge.
        Reno    99.6
        Vegas   61.6
        BIC       97.8
        Hstcp    99.4
        Westwood 99.4

What are your sysctl settings. 

> I was wondering if someone can think of a reason why this happens?
> 
> Is there a way to get the different network related patches between 
> these two versions? I don't have access to bk to get it myself.
> 
> Baruch

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