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

[Meng Xu <xumengpanda@xxxxxxxxx>]

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

On Mon, 2014-09-15 at 21:11 -0400, Meng Xu wrote:

>Â Â Â Â Â> +Â Â if (scinfo->period !=
>Â Â Â Â ÂLIBXL_DOMAIN_SCHED_PARAM_PERIOD_DEFAULT) {
>Â Â Â Â Â> +Â Â Â Â if (scinfo->period < 1) {
>Â Â Â Â Â> +Â Â Â Â Â Â LOG(ERROR, "VCPU period is not set or out of
>Â Â Â Â Ârange, "
>Â Â Â Â Â> +Â Â Â Â Â Â Â Â Â Â Â Â"valid values are larger than 1");
>
>Â Â Â Â ÂThere's no upper limit? Likewise for the budget further down?
>
>
> âYes. 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.â

Â

âMengâ

--

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

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