Messages in this thread | | | Date | Wed, 10 Aug 2022 15:57:54 +0300 | Subject | Re: [PATCH 1/2] sched/topology: Introduce sched_numa_hop_mask() | From | Tariq Toukan <> |
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On 8/10/2022 3:42 PM, Tariq Toukan wrote: > > > On 8/10/2022 1:51 PM, Valentin Schneider wrote: >> Tariq has pointed out that drivers allocating IRQ vectors would benefit >> from having smarter NUMA-awareness - cpumask_local_spread() only knows >> about the local node and everything outside is in the same bucket. >> >> sched_domains_numa_masks is pretty much what we want to hand out (a >> cpumask >> of CPUs reachable within a given distance budget), introduce >> sched_numa_hop_mask() to export those cpumasks. Add in an iteration >> helper >> to iterate over CPUs at an incremental distance from a given node. >> >> Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com >> Signed-off-by: Valentin Schneider <vschneid@redhat.com> >> --- >> include/linux/topology.h | 12 ++++++++++++ >> kernel/sched/topology.c | 28 ++++++++++++++++++++++++++++ >> 2 files changed, 40 insertions(+) >> >> diff --git a/include/linux/topology.h b/include/linux/topology.h >> index 4564faafd0e1..d66e3cf40823 100644 >> --- a/include/linux/topology.h >> +++ b/include/linux/topology.h >> @@ -245,5 +245,17 @@ static inline const struct cpumask >> *cpu_cpu_mask(int cpu) >> return cpumask_of_node(cpu_to_node(cpu)); >> } >> +#ifdef CONFIG_NUMA >> +extern const struct cpumask *sched_numa_hop_mask(int node, int hops); >> +#else >> +static inline const struct cpumask *sched_numa_hop_mask(int node, int >> hops) >> +{ >> + return -ENOTSUPP; > > missing ERR_PTR() > >> +} >> +#endif /* CONFIG_NUMA */ >> + >> +#define for_each_numa_hop_mask(node, hops, mask) \ >> + for (mask = sched_numa_hop_mask(node, hops); >> !IS_ERR_OR_NULL(mask); \ >> + mask = sched_numa_hop_mask(node, ++hops)) >> #endif /* _LINUX_TOPOLOGY_H */ >> diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c >> index 8739c2a5a54e..f0236a0ae65c 100644 >> --- a/kernel/sched/topology.c >> +++ b/kernel/sched/topology.c >> @@ -2067,6 +2067,34 @@ int sched_numa_find_closest(const struct >> cpumask *cpus, int cpu) >> return found; >> } >> +/** >> + * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops >> away. >> + * @node: The node to count hops from. >> + * @hops: Include CPUs up to that many hops away. 0 means local node.
AFAIU, here you work with a specific level/num of hops, description is not accurate.
>> + * >> + * Requires rcu_lock to be held. Returned cpumask is only valid >> within that >> + * read-side section, copy it if required beyond that. >> + * >> + * Note that not all hops are equal in size; see sched_init_numa() >> for how >> + * distances and masks are handled. >> + * >> + * Also note that this is a reflection of sched_domains_numa_masks, >> which may change >> + * during the lifetime of the system (offline nodes are taken out of >> the masks). >> + */ >> +const struct cpumask *sched_numa_hop_mask(int node, int hops) >> +{ >> + struct cpumask ***masks = rcu_dereference(sched_domains_numa_masks); >> + >> + if (node >= nr_node_ids || hops >= sched_domains_numa_levels) >> + return ERR_PTR(-EINVAL); >> + >> + if (!masks) >> + return NULL; >> + >> + return masks[hops][node]; >> +} >> +EXPORT_SYMBOL_GPL(sched_numa_hop_mask); >> + >> #endif /* CONFIG_NUMA */ >> static int __sdt_alloc(const struct cpumask *cpu_map)
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