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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>
This commit is contained in:
Valentin Schneider 2023-01-20 20:24:33 -08:00 committed by Jakub Kicinski
parent b1beed72b8
commit 9feae65845
2 changed files with 40 additions and 0 deletions
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7
include/linux/topology.h
View File

@ -247,11 +247,18 @@ static inline const struct cpumask *cpu_cpu_mask(int cpu)
#ifdef CONFIG_NUMA
int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node);
extern const struct cpumask *sched_numa_hop_mask(unsigned int node, unsigned int hops);
#else
static __always_inline int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node)
{
return cpumask_nth(cpu, cpus);
}
static inline const struct cpumask *
sched_numa_hop_mask(unsigned int node, unsigned int hops)
{
return ERR_PTR(-EOPNOTSUPP);
}
#endif /* CONFIG_NUMA */
#endif /* _LINUX_TOPOLOGY_H */

33
kernel/sched/topology.c
View File

@ -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)