Re: [PATCH v3 for Xen 4.6 1/4] xen: enable per-VCPU parameter settings for RTDS scheduler

[Dario Faggioli <dario.faggioli@citrix.com>]

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On Tue, 2015-07-07 at 09:59 +0100, Jan Beulich wrote:
> >>> On 29.06.15 at 04:44, <lichong659@gmail.com> wrote:
> > --- a/xen/common/Makefile
> > +++ b/xen/common/Makefile
> > @@ -31,7 +31,6 @@ obj-y += rbtree.o
> >  obj-y += rcupdate.o
> >  obj-y += sched_credit.o
> >  obj-y += sched_credit2.o
> > -obj-y += sched_sedf.o
> >  obj-y += sched_arinc653.o
> >  obj-y += sched_rt.o
> >  obj-y += schedule.o
> 
> Stray change. Or perhaps the file doesn't build anymore, in which case
> you should instead have stated that the patch is dependent upon the
> series removing SEDF.
> 
This indeed does not belong in here. And of course, things should
build... So, Chong, either deal with SEDF as well, if basing your
patches on a tree where it is still there, or base on top of my patches,
ignore it, but state the dependency, as Jan is asking.

> > @@ -1157,8 +1158,75 @@ rt_dom_cntl(

> > +    case XEN_DOMCTL_SCHEDOP_putvcpuinfo:
> > +        spin_lock_irqsave(&prv->lock, flags);
> > +        for( index = 0; index < op->u.v.nr_vcpus; index++ )
> > +        {
> > +            if ( copy_from_guest_offset(&local_sched,
> > +                    op->u.v.vcpus, index, 1) )
> > +            {
> > +                rc = -EFAULT;
> > +                break;
> > +            }
> > +            if ( local_sched.vcpuid >= d->max_vcpus
> > +                    || d->vcpu[local_sched.vcpuid] == NULL )
> > +            {
> > +                rc = -EINVAL;
> > +                break;
> > +            }
> > +            svc = rt_vcpu(d->vcpu[local_sched.vcpuid]);
> > +            svc->period = MICROSECS(local_sched.s.rtds.period);
> > +            svc->budget = MICROSECS(local_sched.s.rtds.budget);
> 
> Are all input values valid here?
> 
That's a good point, actually. Right now, SEDF does some range
enforcement, by means of these values:

#define PERIOD_MAX MILLISECS(10000) /* 10s  */
#define PERIOD_MIN (MICROSECS(10))  /* 10us */
#define SLICE_MIN (MICROSECS(5))    /*  5us */

Chong, it probably makes sense to (in a separate patch), introduce
something like this in RTDS too (with SLICE_MIN-->BUDGET_MIN), and then
use them, in this patch, for sanity checking the input.

It also makes sense to check and enforce budget<=period, IMO.

About the specific values, I'm open to proposals. I think something like
the SEDF's one is fine. Meng?

Thanks and 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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