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Date: Wed, 10 Aug 2022 11:51:18 +0100 From: Valentin Schneider <vschneid@...hat.com> To: netdev@...r.kernel.org, linux-kernel@...r.kernel.org Cc: Tariq Toukan <ttoukan.linux@...il.com>, Tariq Toukan <tariqt@...dia.com>, "David S. Miller" <davem@...emloft.net>, Saeed Mahameed <saeedm@...dia.com>, Jakub Kicinski <kuba@...nel.org>, Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>, Juri Lelli <juri.lelli@...hat.com>, Eric Dumazet <edumazet@...gle.com>, Paolo Abeni <pabeni@...hat.com>, Gal Pressman <gal@...dia.com>, Vincent Guittot <vincent.guittot@...aro.org> Subject: [PATCH 1/2] sched/topology: Introduce sched_numa_hop_mask() 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@...hat.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; +} +#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. + * + * 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) -- 2.31.1
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