sched/topology: Introduce for_each_node_numadist() iterator
Introduce the new helper for_each_node_numadist() to iterate over node
IDs in order of increasing NUMA distance from a given starting node.
This iterator is somehow similar to for_each_numa_hop_mask(), but
instead of providing a cpumask at each iteration, it provides a node ID.
Example usage:
nodemask_t unvisited = NODE_MASK_ALL;
int node, start = cpu_to_node(smp_processor_id());
node = start;
for_each_node_numadist(node, unvisited)
pr_info("node (%d, %d) -> %d\n",
start, node, node_distance(start, node));
On a system with equidistant nodes:
$ numactl -H
...
node distances:
node 0 1 2 3
0: 10 20 20 20
1: 20 10 20 20
2: 20 20 10 20
3: 20 20 20 10
Output of the example above (on node 0):
[ 7.367022] node (0, 0) -> 10
[ 7.367151] node (0, 1) -> 20
[ 7.367186] node (0, 2) -> 20
[ 7.367247] node (0, 3) -> 20
On a system with non-equidistant nodes (simulated using virtme-ng):
$ numactl -H
...
node distances:
node 0 1 2 3
0: 10 51 31 41
1: 51 10 21 61
2: 31 21 10 11
3: 41 61 11 10
Output of the example above (on node 0):
[ 8.953644] node (0, 0) -> 10
[ 8.953712] node (0, 2) -> 31
[ 8.953764] node (0, 3) -> 41
[ 8.953817] node (0, 1) -> 51
Suggested-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: Andrea Righi <arighi@nvidia.com>
Acked-by: Yury Norov [NVIDIA] <yury.norov@gmail.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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