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Re: [Xen-devel] [PATCH v2] Modified RTDS scheduler to use an event-driven model instead of polling.

On Sun, 2015-06-28 at 13:45 -0700, Meng Xu wrote:
> 2015-06-28 13:17 GMT-07:00 Dagaen Golomb <dgolomb@xxxxxxxxxxxxxx>:

> > > The scenario in my mind that will potentially invoke one more rt_schedule 
> > >  is:
> > > VCPU j currently runs out of budget and will have top priority once it
> > > get budget replenishment.
> > > If replenishment runs first, rt_schedule will be invoked for only once.
> > > If rt_schedule runs first and schedule a VCPU to run, rt_schedule will
> > > be invoked again when replenishment is invoked.
> >
> > This is a good point here. The ordering in this case doesn't seem to cause
> > any functional/behavior problems, but it will cause rt_schedule to run twice
> > when it could have been ran once. So, even as a corner case, it would seem
> > that its a performance corner case and not a behavior one.
> Right.
> Let's look forward to the reply from others, especially Dario's.  :-)
I concur. There might be situation where more scheduler invocations than
in the ideal (theoretical?) case will be involved, but that's a problem
(in different ways) with any actual implementation (we discussed this at
length already :-) ).

But really, from a correctness point of view, I see no issues.

<<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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