Re: [Xen-devel] [PATCH for 4.5 v4 1/4] xen: add real time scheduler rtds

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On sab, 2014-09-20 at 18:13 -0400, Meng Xu wrote:
> This scheduler follows the Preemptive Global Earliest Deadline First
> (EDF) theory in real-time field.
> At any scheduling point, the VCPU with earlier deadline has higher
> priority. The scheduler always picks the highest priority VCPU to run on a
> feasible PCPU.
> A PCPU is feasible if the VCPU can run on this PCPU and (the PCPU is
> idle or has a lower-priority VCPU running on it.)
> 
> Each VCPU has a dedicated period and budget.
> The deadline of a VCPU is at the end of each period;
> A VCPU has its budget replenished at the beginning of each period;
> While scheduled, a VCPU burns its budget.
> The VCPU needs to finish its budget before its deadline in each period;
> The VCPU discards its unused budget at the end of each period.
> If a VCPU runs out of budget in a period, it has to wait until next period.
> 
> Each VCPU is implemented as a deferable server.
> When a VCPU has a task running on it, its budget is continuously burned;
> When a VCPU has no task but with budget left, its budget is preserved.
> 
> Queue scheme:
> A global runqueue and a global depletedq for each CPU pool.
> The runqueue holds all runnable VCPUs with budget and sorted by deadline;
> The depletedq holds all VCPUs without budget and unsorted.
> 
> Note: cpumask and cpupool is supported.
> 
> This is an experimental scheduler.
> 
> Signed-off-by: Meng Xu <mengxu@xxxxxxxxxxxxx>
> Signed-off-by: Sisu Xi <xisisu@xxxxxxxxx>
> Acked-by: Jan Beulich <jbeulich@xxxxxxxx>
>
Reviewed-and-Tested-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

Thanks and Regards,
Dario

-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
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Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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