Re: [Xen-devel] confusions on monitoring VM cpu usage in Xen hypervisor

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On gio, 2014-02-20 at 16:09 +0800, Charles wrote:
> Hi everyone, Iâm trying to monitor the VM CPU usage in xen hypervisor and use 
> the VM CPU usage 
> information in Xen's Credit Scheduler. 
>
Monitoring how? More important, "use the usage information in Credit"
how and for what purpose?

Providing as much info as possible on the final goal is often very
important for us to be able to help you.

> I googled it, and find that most references about this topic is monitoring 
> the VM CPU usage information in Domain-0 while not in the Xen hypervisor.
>
Provided that I really would like you to define better what you mean
with "VM CPU usage", what I can say is that credit does not have any
load tracking mechanism. Credit2 has, and it would be possible (and
nice!) to abstract that from there and make it available for all
schedulers.

Basically, that means moving some of the code in schedule.c, as well as
add some callbacks, to be implemente by the various scheduler (Credit,
Credit2, etc).

This is something I have on my TODO list since a while, but did not
manage to get to it yet. If you think this would be helpful for you too,
and you're up for helping, I'll be share to discuss/share more.

> I'm now blocking at how to determine the state of vCPU, My understanding is 
> that vCPU running on a physical CPU doesn't mean it really consumes CPU 
> cycles, so I could determine the whether vCPU is consuming CPU cycles or not? 
> So could you please give me some advice.
>
Mmm... if a vCPU is _running_ on a pCPU, I would say it is consuming
pCPU cycles... But perhaps I am not understanding what you really mean
here. So, again, please try to describe your final goal, I'm sure it
will help figuring out things better.

Regards,
Dario

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

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