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RE: [Xen-users] decreasing Xenmon overhead

To: "Mark Williamson" <mark.williamson@xxxxxxxxxxxx>, xen-users@xxxxxxxxxxxxxxxxxxx
Subject: RE: [Xen-users] decreasing Xenmon overhead
From: "Petersson, Mats" <Mats.Petersson@xxxxxxx>
Date: Wed, 30 May 2007 14:19:28 +0200
Cc: Ashish Gupta <ashishgup@xxxxxxxxx>
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Thread-topic: [Xen-users] decreasing Xenmon overhead

> -----Original Message-----
> From: M.A. Williamson [mailto:maw48@xxxxxxxxxxxxxxxx] On 
> Behalf Of Mark Williamson
> Sent: 30 May 2007 13:11
> To: xen-users@xxxxxxxxxxxxxxxxxxx
> Cc: Petersson, Mats; Ashish Gupta
> Subject: Re: [Xen-users] decreasing Xenmon overhead
> > > Are there ways I can drastically reduce this overhead ? I
> > > read somwhere about event overhead, using event masks and
> > > python overhead,  but am not really sure how to use this
> > > information to reduce the overhead.
> >
> > Perhaps write a C-program rather than using Python to 
> fetch/format the
> > information? That shouls improve it, but I guess you'll still see a
> > noticable overhead if you sample the information every 100ms.
> xentrace (for instance) just logs out data to a file, and 
> does the formatting 
> offline using a python script.  This is also a useful 
> approach if you're 
> getting data out at a high bandwidth.

Very good point. Just "storing" the data in a trivial format is much
less CPU-intensive than doing a lot of processing for each process step.
And hopefully, when you've finished the testing/logging, you don't care
as much about how big the load is on the system. 

> Cheers,
> Mark
> -- 
> Dave: Just a question. What use is a unicyle with no seat?  
> And no pedals!
> Mark: To answer a question with a question: What use is a skateboard?
> Dave: Skateboards have wheels.
> Mark: My wheel has a wheel!

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