Messages in this thread | | | From | Valentin Schneider <> | Subject | Re: [PATCH net-next V4 1/3] sched/topology: Add NUMA-based CPUs spread API | Date | Tue, 09 Aug 2022 18:36:59 +0100 |
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On 09/08/22 17:04, Tariq Toukan wrote: > 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(). >
So what I was thinking with this was to only have to export the sched_numa_level_mask() thing and the iterator, and then consumers would be free to use whatever storage form they want (cpumask, array, list...).
Right now I believe sched_domains_numa_masks has the right shape for the interface (for a given node, you a cpumask per distance level) and I don't want to impose an interface that uses just an array, but perhaps I'm being silly and the array isn't so bad and simpler to use - that said we could always build an array-based helper on top of the array of cpumasks thing.
Clearly I need to scratch my head a bit longer :-)
> LGTM. > How do you suggest to proceed? > You want to formalize it? Or should I take it from here? >
I need to have a think (feel free to ponder and share your thoughts as well) - I'm happy to push something if I get a brain-wave, but don't let that hold you back either.
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