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Re: [Xen-devel] [PATCH v1 0/4] Enabling XL to set per-VCPU parameters of a domain for RTDS scheduler

On Mon, May 11, 2015 at 4:56 AM, Dario Faggioli <dario.faggioli@xxxxxxxxxx> wrote:
On Thu, 2015-05-07 at 12:05 -0500, Chong Li wrote:
> [Goal]
> The current xl sched-rtds tool can only set the VCPUs of a domain to the same parameter
> although the scheduler supports VCPUs with different parameters. This patchset is to
> enable xl sched-rtds tool to configure the VCPUs of a domain with different parameters.
> This per-VCPU settings can be used in many scenarios. For example, based on Dario's statement in our pervious discussion(http://lists.xen.org/archives/html/xen-devel/2014-09/msg00423.html), if there are two real-time applications, which have different timing requirements, running in a multi-VCPU guest domain, it is beneficial to pin these two applications to two seperate VCPUs with different scheduling parameters.
Right. And in fact, I'm glad to see this is happening, thanks for doing
this work! :-)

> 1) show the budget and period of each VCPU of each domain, by using "xl sched-rtds" command. An example would be like:
> [..]
> 2) show the budget and period of each VCPU of a specific domain, by using,
> e.g., "xl sched-rtds -d vm1" command. The output would be like:
> [..]
> 3) set the budget and period of each VCPU of a specific domain, by using,
> e.g., "xl sched-rtds -d vm1 -v 0 -p 100 -b 50" command (where "-v 0" specifies
> the VCPU with ID=0). The parameters would be like:
> [..]
> 4) Users can still set the per-domain parameters (previous xl rtds tool already supported this).
> e.g., "xl sched-rtds -d vm1 -p 500 -b 250". The parameters would be like:
The CLI looks nice to me. I'm wondering, what happens if the user tries
to only alter the budget or the period of a vcpu (or of a domain)? I
think that is not possible right now, is it?
You're right. The current design requires both budget and period in a 'set' command.

Would it make sense to allow that? I think it would, but this can well
happen later, once we will have this in.

Yes, we can definitely implement that, after all the other issues in this patch are well solved.


Chong Li
Department of Computer Science and Engineering
Washington University in St.louis
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