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

[George Dunlap <George.Dunlap@xxxxxxxxxxxxx>]

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. :-)

I'm just doing a first pass, so just a few quick comments to begin with.

> diff --git a/xen/common/schedule.c b/xen/common/schedule.c
> index 55503e0..7d2c6d1 100644
> --- a/xen/common/schedule.c
> +++ b/xen/common/schedule.c
> @@ -69,6 +69,7 @@ static const struct scheduler *schedulers[] = {
>      &sched_credit_def,
>      &sched_credit2_def,
>      &sched_arinc653_def,
> +    &sched_rt_def,
>  };
>
>  static struct scheduler __read_mostly ops;
> @@ -1090,7 +1091,8 @@ long sched_adjust(struct domain *d, struct 
> xen_domctl_scheduler_op *op)
>
>      if ( (op->sched_id != DOM2OP(d)->sched_id) ||
>           ((op->cmd != XEN_DOMCTL_SCHEDOP_putinfo) &&
> -          (op->cmd != XEN_DOMCTL_SCHEDOP_getinfo)) )
> +          (op->cmd != XEN_DOMCTL_SCHEDOP_getinfo) &&
> +          (op->cmd != XEN_DOMCTL_SCHEDOP_getnumvcpus)) )

Why are you introducing this as a schedop?  Isn't this information
already exposed in getdomaininfo?

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