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Re: [Xen-devel] trace IDLE VCPU using xenalyze --scatterplot-pcpu?

On mar, 2013-03-26 at 14:12 -0500, Sisu Xi wrote:
> Hi, All:
Hi Sisu!

> I was following the article here to plot the scheduler execution trace.
> http://blog.xen.org/index.php/2012/09/27/tracing-with-xentrace-and-xenalyze/
> I was able to get the trace and plot it, 
EhEh, glad it was helpful! :-P

> however, the trace for IDLE
> VCPU is skipped. This makes it harder to understand the scheduler
> behavior (For example, cap in credit).
Mmmm... I think I see what you mean.

> Does anyone know how to get the data for the IDLE VCPU when using
> xenalyze --scatterplot-pcpu?
Well, I double-checked and it is true that, at least here,
--scatterplot-pcpu does not show the vCPUs of the idle domain. One could
probably try to understand when they're scheduled by looking at when
_no_other_ vCPU of any other domain runs on a particular pCPU (and
considering that the idle domain has one vCPU pinned to each pCPU), but
that would be quite unpractical I guess...

Perhaps you can achieve something similar to what you need by looking
for/plotting the runstate changes for the vCPUs of the idle domain
(i.e., 32767vXX from `xenalyze --scatterplot-runstate') ?

George, any other ideas?


<<This happens because I choose it to happen!>> (Raistlin Majere)
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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