Message-ID: <43FF5DBE.1080905@atl.lmco.com>
Date: Fri, 24 Feb 2006 14:25:50 -0500
From: Gautam H Thaker <gthaker@atl.lmco.com>
Organization: Lockheed Martin -- Advanced Technology Laboratories
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To: "Theodore Ts'o" <tytso@mit.edu>
Cc: Gautam H Thaker <gautam.h.thaker@lmco.com>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@redhat.com>
Subject: Re: ~5x greater CPU load for a networked application when using 2.6.15-rt15-smp
 vs. 2.6.12-1.1390_FC4
References: <43FE134C.6070600@atl.lmco.com> <20060224165209.GC22097@thunk.org>
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Theodore Ts'o wrote:
> On Thu, Feb 23, 2006 at 02:55:56PM -0500, Gautam H Thaker wrote:
> 
>>The real-time patches at the URL below do a great job of endowing Linux with
>>real-time capabilities.
>>
>>http://people.redhat.com/mingo/realtime-preempt/
> 
> 
> Gautam,
> 
> #1) Can you publish the code you used in your tests?

This may not be easy for me but I will try to get corp. approval(s).
Basically, the process that is, at least according to "top", showing ~5x
increased CPU usage is receiving very short UDP packets over a gigabit
interface at the rate of about 38,000 per second. UDP packets are small and
according to "/sbin/ifconfig" there are no errors, drops, overruns, frame or
carrier errors or collisions. (it is an isolated network of 20 PC3000s (3 GH
Xeon processors) at www.emulab.net.

> 
> #2) Can you post your .config file?  In particular, did you have any
> of the latency measurement options or other debugging options?  

The config file I had used to build the "RT" kernel can be found at:

http://www.atl.external.lmco.com/projects/QoS/config.2.6.15-rt15-smp

I had tried to have all debug options off

> 
> Regards,
> 
> 					- Ted


Gautam

-- 

Gautam H. Thaker
Distributed Processing Lab; Lockheed Martin Adv. Tech. Labs
3 Executive Campus; Cherry Hill, NJ 08002
856-792-9754, fax 856-792-9925  email: gthaker@atl.lmco.com
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