Re: [Xen-devel] [PATCH RFC v1 3/4] libxl for rt scheduler

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On ven, 2014-07-11 at 00:49 -0400, Meng Xu wrote:

> --- a/tools/libxl/libxl.c
> +++ b/tools/libxl/libxl.c

> +static int sched_rt_domain_get(libxl__gc *gc, uint32_t domid,
> +                               libxl_domain_sched_params *scinfo)
> +{
> +    struct xen_domctl_sched_rt_params sdom;
> +    int rc, i;
> +
> +    rc = xc_sched_rt_domain_get(CTX->xch, domid, &sdom);
> +    if (rc != 0) {
> +        LOGE(ERROR, "getting domain sched rt");
> +        return ERROR_FAIL;
> +    }
> +
> +    libxl_domain_sched_params_init(scinfo);
> +    scinfo->sched = LIBXL_SCHEDULER_RT;
> +    scinfo->rt.max_vcpus = LIBXL_XEN_LEGACY_MAX_VCPUS;
> +    /*TODO: alloc array with exact num of dom's vcpus; and use 
> GCNEW_ARRAY()*/
>
Indeed. That, or just do an hypercall for each VCPU, at least as a first
step.

> +    scinfo->rt.vcpus = (libxl_vcpu *)
> +                    malloc( sizeof(libxl_vcpu) * scinfo->rt.max_vcpus );
>
Yes, you said it yourself, I see: GCNEW_ARRAY() and no malloc() in
libxl.

> +    if ( !scinfo->rt.vcpus ){
> +        LOGE(ERROR, "Allocate lib_vcpu array fails\n");
> +        return ERROR_INVAL;
> +    }
> +    scinfo->rt.num_vcpus = sdom.num_vcpus;
> +    for( i = 0; i < sdom.num_vcpus; ++i)
> +    {
> +        scinfo->rt.vcpus[i].period = sdom.vcpus[i].period;
> +        scinfo->rt.vcpus[i].budget = sdom.vcpus[i].budget;
> +    }
> +
> +    return 0;
> +}
> +
> +#define SCHED_RT_VCPU_PARAMS_MAX    4294967295 /* 2^32-1 */
> +
I don't like the name. I'd go for something like
SCHED_RT_VCPU_PERIOD_MAX and SCHED_RT_VCPU_BUDGET_MAX.

You well can define both to the same value, of course.

As per the value, yes, even if we turn the interface in usecs, 2^32
usecs is still ~4000 secs, which ought to be enough as a period or
budget for everyone! :-)

For the rest of this file, I think I'll wait for v2, as the interface is
subject to be changed.

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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