Re: [RFC] More efficient RTDS scheduler for Xen 4.6

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Sun, 2015-02-22 at 00:31 -0500, Dagaen Golomb wrote:
> Hello everyone,
>
Hello,

> I'd like to solicit comments on improvements to the RTDS scheduler for
> Xen 4.6.
>
My first comment is that I'm happy that you guys are working on
this! :-)


> [Motivation]
> 
> This change will increase the efficiency of the scheduler by
> eliminating invocations when no scheduling decision will be made. The
> scheduler is currently ran every 1 millisecond. If no tasks have
> terminated or budgets been depleted/replenished since the last
> scheduling, no changes will be made. Due to this, the scheduler is
> currently called at times when no new action will be taken, wasting
> processing resources. With the vital role that the scheduler plays and
> the frequency at which it is invoked, this design shift is a
> relatively important improvement.
>
I don't have much to say about this: I'm the one that suggested to go
for this approach, and I still think it is a goog idea... Looking
forward to see it implemented.

The only possible problem that comes to my mind is the need for a lot of
timers. How many, it will depend on the actual implementation. Using
fewer timer(s) would mean less overhead, but more issues on the event
queue(s).

The only way, I think, we have is just to get down and implement one
solution and see how fast it runs, and whether there are
overhead/scalability issue s(and address them at that time, if it will
be the case).

Regards,
Dario


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