Messages in this thread | | | Subject | Re: [PATCH 1/4] sched/topology: Store root domain CPU capacity sum | From | Dietmar Eggemann <> | Date | Tue, 14 Apr 2020 17:27:21 +0200 |
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On 14.04.20 14:45, Quentin Perret wrote: > On Wednesday 08 Apr 2020 at 19:03:57 (+0200), Vincent Guittot wrote: >> Or we can do the opposite and only use capacity_orig_of()/rq->cpu_capacity_orig. >> >> Is there a case where the max cpu capacity changes over time ? So I >> would prefer to use cpu_capacity_orig which is a field of scheduler >> instead of always calling an external arch specific function > > Note however that using arch_scale_cpu_capacity() would be more > efficient, especially on non-arm/arm64 systems where it is a > compile-time constant.
or essentially all ARCHs not defining it.
> > It's probably a matter of personal taste, but I find rq->cpu_capacity_orig > superfluous. It wastes space without actually giving you anything no? > Anybody remembers why it was introduced in the first place?
v3.18 arm providing arch_scale_cpu_capacity() v4.1 introduction of rq->cpu_capacity_orig v4.10 arm64 providing arch_scale_cpu_capacity() ...
So it's down to the question of 'minimizing the scheduler calls to an external arch function' vs 'efficiency'.
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