[PATCH] sched/numa: Fix NUMA_DIRECT topology identification

From: Aravind Gopalakrishnan
Date: Mon Aug 10 2015 - 21:03:12 EST

Systems which have all nodes at a distance of at most
1 hop should be identified as 'NUMA_DIRECT'.

However, the scheduler incorrectly identifies it as
'NUMA_BACKPLANE'. This is because 'n' is assigned to
sched_max_numa_distance but the code (mis)interprets it
to mean 'number of hops'.

Rik had actually used sched_domains_numa_levels for detecting
a 'NUMA_DIRECT' topology-

But that was changed when he removed the hops table in the
subsequent version-

Fixing the issue here.

Signed-off-by: Aravind Gopalakrishnan <Aravind.Gopalakrishnan@xxxxxxx>
kernel/sched/core.c | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 655557d..e51739e 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -6442,8 +6442,10 @@ static void init_numa_topology_type(void)

n = sched_max_numa_distance;

- if (n <= 1)
+ if (sched_domains_numa_levels <= 1) {
sched_numa_topology_type = NUMA_DIRECT;
+ return;
+ }

for_each_online_node(a) {
for_each_online_node(b) {

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