netdev - Re: O(n^2) or worse ? cat /proc/net/tcp

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Message-ID: <20080327105123.GS3700@mea-ext.zmailer.org>
Date:	Thu, 27 Mar 2008 12:51:23 +0200
From:	Matti Aarnio <matti.aarnio@...iler.org>
To:	Andi Kleen <andi@...stfloor.org>
Cc:	netdev@...r.kernel.org
Subject: Re: O(n^2) or worse ?   cat /proc/net/tcp

On Mon, Mar 24, 2008 at 05:06:28AM +0100, Andi Kleen wrote:
> Matti Aarnio <matti.aarnio@...iler.org> writes:
> > 
> > I did observe odd slowness at first with  "lsof -p .."  program, 
> 
> You could oprofile it.

Ah, I forgot to start learning of oprofile..

> > then at
> > "netstat -na".  Same slowdown happens with:  cat /proc/net/tcp
> > (that 'cat' took 25 seconds...)
> 
> /proc/net/tcp should be only O(n^2) if the application does a lot of 
> open()/seek()/read()/close() for very small chunks, but at least netstat
> doesn't do that. Not sure about lsof though.

Or  cat  -- which definitely does not seek around..

> -Andi

  /Matti Aarnio
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