Re: [RFCv5 PATCH 40/46] sched/cpufreq_sched: compute freq_new based on capacity_orig_of()

Steve Muckle
2015-10-13T19:47:58Z

On 08/17/2015 05:19 AM, Juri Lelli wrote:
>> Nah, just maybe: (capacity << SCHED_CAPACITY_SHIFT) / capacity_orig_of()
>> > such that you don't have to export that knowledge to this thing.
>> >
> Oh, right. I guess we can just go with something like:
>
> req_cap = get_cpu_usage(cpu) * capacity_margin / capacity_orig_of(cpu);
>
> on fair.c side and switch back to
>
> freq_new = capacity * policy->max >> SCHED_CAPACITY_SHIFT;
>
> on cpufreq_sched.c side. That saves us exporting capacity_orig_of().

Another good reason to make this change - I believe the current code
will not support a cpufreq policy covering CPUs of different types (such
as a b.L system in a single frequency domain).

The max requested capacity is calculated using the absolute/global
capacity values requested from each CPU. A small CPU needing a higher
OPP may get ignored because of a request from a big CPU for a lower OPP,
because the big CPU @ lower OPP shows up as the max capacity request.