Messages in this thread | | | Date | Tue, 9 Aug 2022 17:04:07 +0300 | Subject | Re: [PATCH net-next V4 1/3] sched/topology: Add NUMA-based CPUs spread API | From | Tariq Toukan <> |
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On 8/9/2022 3:52 PM, Valentin Schneider wrote: > On 09/08/22 13:18, Tariq Toukan wrote: >> On 8/9/2022 1:02 PM, Valentin Schneider wrote: >>> >>> Are there cases where we can't figure this out in advance? From what I grok >>> out of the two callsites you patched, all vectors will be used unless some >>> error happens, so compressing the CPUs in a single cpumask seemed >>> sufficient. >>> >> >> All vectors will be initialized to support the maximum number of traffic >> rings. However, the actual number of traffic rings can be controlled and >> set to a lower number N_actual < N. In this case, we'll be using only >> N_actual instances and we want them to be the first/closest. > > Ok, that makes sense, thank you. > > In that case I wonder if we'd want a public-facing iterator for > sched_domains_numa_masks[%i][node], rather than copy a portion of > it. Something like the below (naming and implementation haven't been > thought about too much). > > const struct cpumask *sched_numa_level_mask(int node, int level) > { > struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); > > if (node >= nr_node_ids || level >= sched_domains_numa_levels) > return NULL; > > if (!masks) > return NULL; > > return masks[level][node]; > } > EXPORT_SYMBOL_GPL(sched_numa_level_mask); >
The above can be kept static, and expose only the foo() function below, similar to my sched_cpus_set_spread().
LGTM. How do you suggest to proceed? You want to formalize it? Or should I take it from here?
> #define for_each_numa_level_mask(node, lvl, mask) \ > for (mask = sched_numa_level_mask(node, lvl); mask; \ > mask = sched_numa_level_mask(node, ++lvl)) > > void foo(int node, int cpus[], int ncpus) > { > const struct cpumask *mask; > int lvl = 0; > int i = 0; > int cpu; > > rcu_read_lock(); > for_each_numa_level_mask(node, lvl, mask) { > for_each_cpu(cpu, mask) { > cpus[i] = cpu; > if (++i == ncpus) > goto done; > } > } > done: > rcu_read_unlock(); > } >
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