Messages in this thread | | | From | Vincent Guittot <> | Date | Wed, 8 Apr 2020 19:03:57 +0200 | Subject | Re: [PATCH 1/4] sched/topology: Store root domain CPU capacity sum |
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On Wed, 8 Apr 2020 at 18:31, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > On 08.04.20 14:29, Vincent Guittot wrote: > > On Wed, 8 Apr 2020 at 11:50, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote: > > [...] > > >> /** > >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c > >> index 8344757bba6e..74b0c0fa4b1b 100644 > >> --- a/kernel/sched/topology.c > >> +++ b/kernel/sched/topology.c > >> @@ -2052,12 +2052,17 @@ build_sched_domains(const struct cpumask *cpu_map, struct sched_domain_attr *att > >> /* Attach the domains */ > >> rcu_read_lock(); > >> for_each_cpu(i, cpu_map) { > >> + unsigned long cap = arch_scale_cpu_capacity(i); > > > > Why do you replace the use of rq->cpu_capacity_orig by > > arch_scale_cpu_capacity(i) ? > > There is nothing about this change in the commit message > > True. And I can change this back. > > It seems though that the solution is not sufficient because of the > 'rd->span &nsub cpu_active_mask' issue discussed under patch 2/4. > > But this remind me of another question I have. > > Currently we use arch_scale_cpu_capacity() more often (16 times) than > capacity_orig_of()/rq->cpu_capacity_orig . > > What's hindering us to remove rq->cpu_capacity_orig and the code around > it and solely rely on arch_scale_cpu_capacity()? I mean the arch > implementation should be fast.
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
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