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Re: [Xen-devel] [PATCH 15/16] xen: sched: scratch space for cpumasks on Credit2

On Thu, 2016-03-24 at 12:44 +0000, George Dunlap wrote:
> On 18/03/16 19:27, Andrew Cooper wrote:
> > This avoids all this opencoded allocation/refcounting, the chance
> > that
> > starting a scheduler would fail for memory reasons, and one extra
> > cpumask in the per-cpu data area won't break the bank.
> Going a bit further, since (according to the changelog) both credit1
> and
> rtds also do this, would it make sense to have schedule.c define
> these,
> and allow any of the schedulers to use them?
Yeah, well, I guess it could.

> (Assuming that both credit1 and rtds allocate exactly one mask per
> cpu.)
They do.

The only difference between credit1 and the other two is that credit1
already has a per-cpu private scheduler structure (csched_pcpu, where
also the runqueue is), and the mask has been put there, so it's handled
a little bit differently.

But it should be no problem turning it into using a mask from
schedule.c, in the same way that RTDS and Credit2 will do.

I like the idea, and I'm up for it for v2.

Thanks and Regards,
<<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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