Re: [PATCH v3 3/4] libxl: add rtds scheduler

[Meng Xu <xumengpanda@gmail.com>]

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2014-09-15 21:49 GMT-04:00 Ian Campbell <ian.campbell@citrix.com>:

> On Mon, 2014-09-15 at 21:11 -0400, Meng Xu wrote:
>
> >         > +    if (scinfo->period !=
> >         LIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT) {
> >         > +        if (scinfo->period < 1) {
> >         > +            LOG(ERROR, "VCPU period is not set or out of
> >         range, "
> >         > +                       "valid values are larger than 1");
> >
> >         There's no upper limit? Likewise for the budget further down?
> >
> >
> > ​Yes. In the previous version, I used the UINT_MAX as the upper bound.
> > Because period is int, so it will never reach the UINT_MAX. Even if I
> > change the UINT_MAX to INT_MAX as the upper bound, period may still
> > not able to reach it. So George suggests to remove the upper bound
> > check if it uses the range of type of period.
> >
> >
> > Since period is int, the largest period we support should be 2^31-1us
> > = 0.5965 hours. That's why we don't have the upper bound check. Of
> > course, I can add the upper bound as INT_MAX (2^31-1) and reports
> > error when users try to assign a large value to period and budget.
> >
> >
> > What do you think?
>
> If the upper limit is the same as the maximum value of the field then
> there is no need for a check.
>
> Is a 0.5hr maximum period considered to be larger than any practically
> useful value?
>

I think so. If the period is larger than 0.5hr, they can scale it down to a
smaller value with the same bandwidth. The guest domain should be more
repsonsive.​


​Meng​

-- 


-----------
Meng Xu
PhD Student in Computer and Information Science
University of Pennsylvania

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