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

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On mer, 2014-09-03 at 14:40 +0100, George Dunlap wrote:
> On Sun, Aug 24, 2014 at 11:58 PM, Meng Xu <mengxu@xxxxxxxxxxxxx> wrote:
> > This scheduler follows the pre-emptive Global EDF theory in real-time field.
> > Each VCPU can have a dedicated period and budget.
> > While scheduled, a VCPU burns its budget.
> > A VCPU has its budget replenished at the beginning of each of its periods;
> > The VCPU discards its unused budget at the end of each of its periods.
> > If a VCPU runs out of budget in a period, it has to wait until next period.
> > The mechanism of how to burn a VCPU's budget depends on the server mechanism
> > implemented for each VCPU.
> >
> > Server mechanism: a VCPU is implemented as a deferable server.
> > When a VCPU is scheduled to execute on a PCPU, its budget is continuously
> > burned.
> >
> > Priority scheme: Preemptive Global Earliest Deadline First (gEDF).
> > At any scheduling point, the VCPU with earliest deadline has highest
> > priority.
> >
> > Queue scheme: A global Runqueue for each CPU pool.
> > The Runqueue holds all runnable VCPUs.
> > VCPUs in the Runqueue are divided into two parts: with and without budget.
> > At each part, VCPUs are sorted based on gEDF priority scheme.
> >
> > Scheduling quantum: 1 ms;
> >
> > Note: cpumask and cpupool is supported.
> >
> > This is still in the development phase.
> 
> You should probably take this out now that you've removed the RFC. :-)
> 
Should him?

I mean, AFAIUI, we are accepting (well, at least, that's the plan :-) )
the scheduler in an 'experimental' status.

When we merged ARM support for the first time, I remember there were
some similar claims around the code and docs (it was API/ABI/something
stability at the time, I think), and the same, IIRC, for PVH.

Credit2 still warns his users like this, on boot:

    printk("Initializing Credit2 scheduler\n" \
           " WARNING: This is experimental software in development.\n" \
           " Use at your own risk.\n");

So, probably "still in the development phase" may be a bit strong, but
I'd be inclined have something like that somewhere.

Thoughts?

Regards,
Dario

-- 
<<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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