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

Hi, Dario and George:

Thanks for your quick reply and help!

I comments out the line and got the trace for IDLE Domain.  :)


On Wed, Mar 27, 2013 at 5:23 AM, George Dunlap
<george.dunlap@xxxxxxxxxxxxx> wrote:
> On 27/03/13 02:15, Dario Faggioli wrote:
>> 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?
> Well, I always intendended xenalyze to be a tool you could modify to add
> functionality as-needed; more like a library of useful analytical functions
> than a finished product.  --scatterplot-pcpu doesn't show vcpus of the idle
> domain because I found it extraneous and confusing, so I excluded it:
>     if ( opt.scatterplot_pcpu
>          && next->d->did != IDLE_DOMAIN
>          && next->d->did != DEFAULT_DOMAIN )
>     {
> If you just want to make the change locally, you can just take out the one
> line about the IDLE_DOMAIN.  I'd be happy to take a patch to xenalyze to add
> an option to show the idle domain as well.  (Maybe "--with-idle-domain" as a
> general way to say, 'don't exclude the idle domain from the output'?)
>  -George

Sisu Xi, PhD Candidate

Department of Computer Science and Engineering
Campus Box 1045
Washington University in St. Louis
One Brookings Drive
St. Louis, MO 63130

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