Messages in this thread | | | Date | Wed, 8 Apr 2020 15:30:32 +0200 | From | luca abeni <> | Subject | Re: [PATCH 2/4] sched/deadline: Improve admission control for asymmetric CPU capacities |
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Hi Valentin,
On Wed, 08 Apr 2020 11:42:14 +0100 Valentin Schneider <valentin.schneider@arm.com> wrote:
> On 08/04/20 10:50, Dietmar Eggemann wrote: > > +++ b/kernel/sched/sched.h > > @@ -304,11 +304,14 @@ void __dl_add(struct dl_bw *dl_b, u64 tsk_bw, > > int cpus) __dl_update(dl_b, -((s32)tsk_bw / cpus)); > > } > > > > +static inline unsigned long rd_capacity(int cpu); > > + > > static inline > > -bool __dl_overflow(struct dl_bw *dl_b, int cpus, u64 old_bw, u64 > > new_bw) +bool __dl_overflow(struct dl_bw *dl_b, int cpu, u64 > > old_bw, u64 new_bw) { > > return dl_b->bw != -1 && > > - dl_b->bw * cpus < dl_b->total_bw - old_bw + new_bw; > > + cap_scale(dl_b->bw, rd_capacity(cpu)) < > > + dl_b->total_bw - old_bw + new_bw; > > } > > > > I don't think this is strictly equivalent to what we have now for the > SMP case. 'cpus' used to come from dl_bw_cpus(), which is an ugly way > of writing > > cpumask_weight(rd->span AND cpu_active_mask); > > The rd->cpu_capacity_orig field you added gets set once per domain > rebuild, so it also happens in sched_cpu_(de)activate() but is > separate from touching cpu_active_mask. AFAICT this mean we can > observe a CPU as !active but still see its capacity_orig accounted in > a root_domain.
Sorry, I suspect this is my fault, because the bug comes from my original patch. When I wrote the original code, I believed that when a CPU is deactivated it is also removed from its root domain.
I now see that I was wrong.
Luca
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