Re: [Xen-devel] VCPU migration overhead conpensation ?

[Sisu Xi <xisisu@xxxxxxxxx>]

Hi, Dario:

Thanks for your reply and tips for sending emails! Â:)

I am also performing some overhead measurement for the scheduler. If a VCPU is migrated from one core to another, the overhead is around 2 microseconds on my machine, which is much less than what is set in Credit2 (50 microseconds).Â

Thanks again for your help!

Sisu

On Mon, Apr 8, 2013 at 8:46 PM, Dario Faggioli <dario.faggioli@xxxxxxxxxx> wrote:

On ven, 2013-03-29 at 16:16 -0500, Sisu Xi wrote:
> Hi, all:
>
Hi again Sisu,

> I am studying the credit2 scheduler and found it would compensate VCPU
> migration with 50 microseconds.
> /* How much to "compensate" a vcpu for L2 migration */
> #define CSCHED_MIGRATE_COMPENSATION MICROSECS(50)
>
>
> Why 50us? Is this number based on some experiments?
>

This predates my joining of the Xen community, but yes, ISTR hearing
people talking about it coming from a mixture of common sense and
experience/measurements.

BTW, you may want to try, when sending e-mail to this list, adding in Cc
some of the people that are more involved with the code/feature you're
asking about. You can look at the MAINTAINERS file, in the source tree,
to have an idea of who to put there. For instance, for scheduling, the
absolute authority is George (which I added), and in fact MAINTAINERS
says:

SCHEDULING
M: Â Â ÂGeorge Dunlap <george.dunlap@xxxxxxxxxxxxx>
S: Â Â ÂSupported
F: Â Â Âxen/common/sched*

(however, feel free to Cc me as well... I do not master all the Xen
scheduler code yet, but am always curious about it. :-) )

Regards,
Dario

--
<<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)

--
Sisu Xi, PhD Candidate

http://www.cse.wustl.edu/~xis/
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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