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authorValentin Schneider <vschneid@redhat.com>2023-01-20 20:24:33 -0800
committerJakub Kicinski <kuba@kernel.org>2023-02-07 18:20:00 -0800
commit9feae65845f7b16376716fe70b7d4b9bf8721848 (patch)
tree10c9cf542cad95b89564fbdf5617fc6b5b8857f9 /kernel/sched
parentb1beed72b8b75d365fdbc925da856c212195051b (diff)
downloadlwn-9feae65845f7b16376716fe70b7d4b9bf8721848.tar.gz
lwn-9feae65845f7b16376716fe70b7d4b9bf8721848.zip
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. Link: http://lore.kernel.org/r/20220728191203.4055-1-tariqt@nvidia.com Signed-off-by: Valentin Schneider <vschneid@redhat.com> Reviewed-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Yury Norov <yury.norov@gmail.com> Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'kernel/sched')
-rw-r--r--kernel/sched/topology.c33
1 files changed, 33 insertions, 0 deletions
diff --git a/kernel/sched/topology.c b/kernel/sched/topology.c
index 2bf89186a10f..1233affc106c 100644
--- a/kernel/sched/topology.c
+++ b/kernel/sched/topology.c
@@ -2124,6 +2124,39 @@ unlock:
return ret;
}
EXPORT_SYMBOL_GPL(sched_numa_find_nth_cpu);
+
+/**
+ * sched_numa_hop_mask() - Get the cpumask of CPUs at most @hops hops away from
+ * @node
+ * @node: The node to count hops from.
+ * @hops: Include CPUs up to that many hops away. 0 means local node.
+ *
+ * Return: On success, a pointer to a cpumask of CPUs at most @hops away from
+ * @node, an error value otherwise.
+ *
+ * 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 distance; 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(unsigned int node, unsigned int hops)
+{
+ struct cpumask ***masks;
+
+ if (node >= nr_node_ids || hops >= sched_domains_numa_levels)
+ return ERR_PTR(-EINVAL);
+
+ masks = rcu_dereference(sched_domains_numa_masks);
+ if (!masks)
+ return ERR_PTR(-EBUSY);
+
+ return masks[hops][node];
+}
+EXPORT_SYMBOL_GPL(sched_numa_hop_mask);
+
#endif /* CONFIG_NUMA */
static int __sdt_alloc(const struct cpumask *cpu_map)