Re: [Xen-devel] Interested in taking up a project

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Sat, 2015-07-25 at 18:04 +0530, Abhinav Gupta wrote:
> Hii everyone :) , 
>
Hi,

>    I'm quite familiar with the linux powerclamp driver now. 
>
Nice to hear. Is there anything about that you think it would be
useful/interesting about to share here? 
> 
> I have also started looking into xen's code as Dario suggested, but am
> not able to find proper documentation for xen.
>
He, I think I see what you mean... Consider that, when you reach a
certain point, e.g., wanting to understand the code of a complex project
like Xen, the best documentation for the source code is the source code
itself.

> 1. Looking for a brief explanation of different fields in scheduler
> data structure in sched-if.h
>
> 2. From where do the different fields of scheduler structure gets
> called.
>
As said above, something like that does not exist for any reasonably big
and reasonably complex piece of software. There are many reasons. One,
for instance, is that it would take a great effort to be put together,
and it will get out of date in a matter of a few months, at most (but
even a few weeks, or a few days, if you're unlucky).

All that being said, you can have a look here:
 http://wiki.xen.org/wiki/Credit2_Scheduler_Development

It's not exactly what you're asking, but it's probably the closest
existing thing.

Also, as a proof that I was speaking the truth just above:
 1. it's incomplete
 2. it's (slightly) out of dated already

 :-(

> 3. The driver i'll be writing will it be running at host machine level
> or guest OS level ?. 
>
Definitely host.

Actually, at the guest level, it's already there... it's powerclamp
itself, isn't it (at lease in case of Linux) ? :-D

> As far as my understanding goes we should have it at host level to
> optimize the performance of all the guests, 
>
Yes, exactly. Also, it's only the host that have a big enough picture,
and the access to all the information and the data you need.

> since VMs deal with the abstract interface (VCPU) so they wont be
> having the exact notion of the various parameters of cpu at runtime.
>
Indeed. They won't have the exact notion of a bunch of stuff. :-)

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)

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