[PATCH 04/11] sched/numa: Trace when no candidate CPU was found on the preferred node

[Mel Gorman]

sched:sched_stick_numa is meant to fire when a task is unable to migrate
to the preferred node. The case where no candidate CPU could be found is
not traced which is an important gap. The tracepoint is not fired when
the task is not allowed to run on any CPU on the preferred node or the
task is already running on the target CPU but neither are interesting
corner cases.

Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
 kernel/sched/fair.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d6b1d70e0b83..4ab18fba5b82 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1848,8 +1848,10 @@ static int task_numa_migrate(struct task_struct *p)
 	}
 
 	/* No better CPU than the current one was found. */
-	if (env.best_cpu == -1)
+	if (env.best_cpu == -1) {
+		trace_sched_stick_numa(p, env.src_cpu, -1);
 		return -EAGAIN;
+	}
 
 	best_rq = cpu_rq(env.best_cpu);
 	if (env.best_task == NULL) {
-- 
2.16.4