Messages in this thread | | | Subject | Re: [PATCH v5 2/3] sched/topology: Rework CPU capacity asymmetry detection | From | Dietmar Eggemann <> | Date | Tue, 25 May 2021 13:59:30 +0200 |
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On 25/05/2021 11:30, Beata Michalska wrote: > On Tue, May 25, 2021 at 10:25:36AM +0200, Dietmar Eggemann wrote: >> On 24/05/2021 12:16, Beata Michalska wrote:
[...]
>>> @@ -1266,6 +1266,112 @@ static void init_sched_groups_capacity(int cpu, struct sched_domain *sd) >>> update_group_capacity(sd, cpu); >>> } >>> >>> +/** >>> + * Asymmetric CPU capacity bits >>> + */ >>> +struct asym_cap_data { >>> + struct list_head link; >>> + unsigned long capacity; >>> + struct cpumask *cpu_mask; >> >> Not sure if this has been discussed already but shouldn't the flexible >> array members` approach known from struct sched_group, struct >> sched_domain or struct em_perf_domain be used here? >> IIRC the last time this has been discussed in this thread: >> https://lkml.kernel.org/r/20200910054203.525420-2-aubrey.li@intel.com >> > If I got right the discussion you have pointed to, it was about using > cpumask_var_t which is not the case here. I do not mind moving the code > to use the array but I am not sure if this changes much. Looking at the > code changes to support that (to_cpumask namely) it was introduced for > cases where cpumask_var_t was not appropriate, which again isn't the case > here.
Yeah, it was more about using `flexible array members` or allocating the cpumask separately.
Looks like you're using some kind of a mixed approach:
(1) struct asym_cap_data { ... struct cpumask *cpu_mask;
(2) entry = kzalloc(sizeof(*entry) + cpumask_size(), GFP_KERNEL);
(3) entry->cpu_mask = (struct cpumask *)((char *)entry + sizeof(*entry));
(4) cpumask_intersects(foo, entry->cpu_mask)
E.g. struct em_perf_domain has
(1) struct em_perf_domain { ... unsigned long cpus[];
(2) like yours
(3) is not needed.
(4) cpumask_copy(em_span_cpus(pd), foo)
with #define em_span_cpus(em) (to_cpumask((em)->cpus))
IMHO, it's better to keep this approach aligned between the different data structures.
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