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Re: [Xen-devel] [PATCH v1 1/4] xen: add real time scheduler rt

2014-09-03 13:18 GMT-04:00 George Dunlap <George.Dunlap@xxxxxxxxxxxxx>:
On Wed, Sep 3, 2014 at 5:57 PM, Dario Faggioli
<dario.faggioli@xxxxxxxxxx> wrote:
>> Re the per-vcpu settings, though: Is it really that common for RT
>> domains to want different parameters for different vcpus?
> Whether it's common it is hard to say, but yes, it has to be possible.
> For instance, I can put, in an SMP guest, two real-time applications
> with different timing requirements, and pin each one to a different
> (v)cpu (I mean pin *inside* the guest). At this point, I'd like for each
> vcpu to have a set of RT scheduling parameters, at the Xen level, that
> matches the timing requirements of what's running inside.
> This may not look so typical in a server/cloud environment, but can
> happen (at least in my experience) in a mobile/embedded env.

But to play devil's advocate for a minute here: couldn't you just put
them in two different single-vcpu VMs then?

âNot really. What if these two applications (or threads) want to communicate with each other. For example, One thread is sensing some data and send to the other thread to do some control-algorithm's computation.Â

Well, they can still share info. between VMs, but the overhead should be larger than the sharing in the same domain. â

Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania
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