netdev - Re: cat /proc/net/tcp takes 0.5 seconds on x86

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Message-ID: <48B51AE9.5080709@hhs.nl>
Date:	Wed, 27 Aug 2008 11:14:17 +0200
From:	Hans de Goede <j.w.r.degoede@....nl>
To:	Eric Dumazet <dada1@...mosbay.com>
CC:	Dave Jones <davej@...hat.com>, netdev@...r.kernel.org
Subject: Re: cat /proc/net/tcp takes 0.5 seconds on x86_64

Eric Dumazet wrote:
> 
> I dont know, you tell us 50x, but nowhere I saw your numbers on i386,
> nor the amount of memory of your test machine.
> 

My machine has 2 Gb of memory, but that is not really relevant as I'm not the 
reporter of the problem (but I can reproduce it) I'm only in the loop because I 
maintain the gkrellm package in Fedora which exhibits this problem. Also I gave 
you no i386 numbers on the same machine because I don't have an i386 install 
readily available on this machine.

Now you can spin this anyway you want, but lets cut to the chase, gkrellmd 
which is a system monitoring daemon reads /proc/net/tcp and /proc/net/tcp6 3 
times a second, with slightly older kernel this used to give a CPU load of
2-3% on x86_64 now it gives a load of 50-70% (on my test machine with a whole 8 
tcp connections open).

Now you can wing it any way you want, but this is a serious regression. I don't 
want to go to lkml and start shouting regression REGRESSION regression, but 
given the treating and enormous amount of help I've received sofar (and 
remember I'm only the messenger I didn't write nor use gkrellmd) I'm tending 
towards starting shouting regression on lkml, as atleast there this seems to 
get some attention.

Regards,

Hans
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