Commit 9feae658 authored by Valentin Schneider's avatar Valentin Schneider Committed by Jakub Kicinski
Browse files

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: default avatarValentin Schneider <vschneid@redhat.com>
Reviewed-by: default avatarYury Norov <yury.norov@gmail.com>
Signed-off-by: default avatarYury Norov <yury.norov@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent b1beed72

include/linux/topology.h

+7 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/sched/topology.c

+33 −0
Original line number Diff line number Diff line
@@ -2124,6 +2124,39 @@ int sched_numa_find_nth_cpu(const struct cpumask *cpus, int cpu, int node) 
	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)