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Re: [Xen-devel] Xenoprof and the hypervisor

To: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] Xenoprof and the hypervisor
From: "Ray Bryant" <raybry@xxxxxxxxxxxxxxxxx>
Date: Wed, 24 May 2006 14:46:12 -0500
Cc: David Carr <dc@xxxxxxxxx>, "Santos, Jose Renato G" <joserenato.santos@xxxxxx>
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On Tuesday 23 May 2006 17:13, Santos, Jose Renato G wrote:
> The sample is delivered to the VCPU (and associated domain) that is
> currently running on the CPU when the sample is taken,
> as computed by the Xen macro "current". That means that samples
> taken when a harware interrupt is running are associated
> with the VCPU/domain that was interrupted by the HW interrupt.
> Renato

So let's suppose what we are trying to do is to optimize or measure the 
performace of the hypervisor itself?   What we would like to happen in that 
case would be that we would to collect all of the samples that found that the 
hypervisor was running when the nmi occurred and ship these samples off to, 
say, dom0 for later collection.

At the moment, if a fully virtualized guest is taking most of the cycles (say 
> 97.5% of the cpu), and without passive domain support in xenoprof, then 
what happens is that 97.5% of the samples are discarded, because the fully 
virtualized domain is not being profiled (is_profiled(vcpu->domain) is false 
in xenoprof_log_event()).

So, I'd just like those samples handed to dom0, if possible.   I've tried to 
do this, but it appears oprofile then throws away the samples (needs to be 
looked at some more to be sure).

So what's the easiest way to get those samples collected and out to dom0?
Ray Bryant
AMD Performance Labs                   Austin, Tx
512-602-0038 (o)                 512-507-7807 (c)

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