sched/numa: Distinguish between the different task_numa_migrate() failure cases

sched:sched_stick_numa is meant to fire when a task is unable to migrate
to the preferred node but from the trace, it's possibile to tell the
difference between "no CPU found", "migration to idle CPU failed" and
"tasks could not be swapped". Extend the tracepoint accordingly.

Signed-off-by: Mel Gorman <mgorman@techsingularity.net>
[ Minor edits. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Vincent Guittot <vincent.guittot@linaro.org>
Cc: Juri Lelli <juri.lelli@redhat.com>
Cc: Dietmar Eggemann <dietmar.eggemann@arm.com>
Cc: Valentin Schneider <valentin.schneider@arm.com>
Cc: Phil Auld <pauld@redhat.com>
Cc: Hillf Danton <hdanton@sina.com>
Link: https://lore.kernel.org/r/20200224095223.13361-4-mgorman@techsingularity.net

include/trace/events/sched.h

@@ -487,7 +487,11 @@ TRACE_EVENT(sched_process_hang,
 );
 #endif /* CONFIG_DETECT_HUNG_TASK */
 
-DECLARE_EVENT_CLASS(sched_move_task_template,
+/*
+ * Tracks migration of tasks from one runqueue to another. Can be used to
+ * detect if automatic NUMA balancing is bouncing between nodes.
+ */
+TRACE_EVENT(sched_move_numa,
 
 	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
 
@@ -519,23 +523,7 @@ DECLARE_EVENT_CLASS(sched_move_task_template,
 			__entry->dst_cpu, __entry->dst_nid)
 );
 
-/*
- * Tracks migration of tasks from one runqueue to another. Can be used to
- * detect if automatic NUMA balancing is bouncing between nodes
- */
-DEFINE_EVENT(sched_move_task_template, sched_move_numa,
-	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
-
-	TP_ARGS(tsk, src_cpu, dst_cpu)
-);
-
-DEFINE_EVENT(sched_move_task_template, sched_stick_numa,
-	TP_PROTO(struct task_struct *tsk, int src_cpu, int dst_cpu),
-
-	TP_ARGS(tsk, src_cpu, dst_cpu)
-);
-
-TRACE_EVENT(sched_swap_numa,
+DECLARE_EVENT_CLASS(sched_numa_pair_template,
 
 	TP_PROTO(struct task_struct *src_tsk, int src_cpu,
 		 struct task_struct *dst_tsk, int dst_cpu),
@@ -561,11 +549,11 @@ TRACE_EVENT(sched_swap_numa,
 		__entry->src_ngid	= task_numa_group_id(src_tsk);
 		__entry->src_cpu	= src_cpu;
 		__entry->src_nid	= cpu_to_node(src_cpu);
-		__entry->dst_pid	= task_pid_nr(dst_tsk);
-		__entry->dst_tgid	= task_tgid_nr(dst_tsk);
-		__entry->dst_ngid	= task_numa_group_id(dst_tsk);
+		__entry->dst_pid	= dst_tsk ? task_pid_nr(dst_tsk) : 0;
+		__entry->dst_tgid	= dst_tsk ? task_tgid_nr(dst_tsk) : 0;
+		__entry->dst_ngid	= dst_tsk ? task_numa_group_id(dst_tsk) : 0;
 		__entry->dst_cpu	= dst_cpu;
-		__entry->dst_nid	= cpu_to_node(dst_cpu);
+		__entry->dst_nid	= dst_cpu >= 0 ? cpu_to_node(dst_cpu) : -1;
 	),
 
 	TP_printk("src_pid=%d src_tgid=%d src_ngid=%d src_cpu=%d src_nid=%d dst_pid=%d dst_tgid=%d dst_ngid=%d dst_cpu=%d dst_nid=%d",
@@ -575,6 +563,23 @@ TRACE_EVENT(sched_swap_numa,
 			__entry->dst_cpu, __entry->dst_nid)
 );
 
+DEFINE_EVENT(sched_numa_pair_template, sched_stick_numa,
+
+	TP_PROTO(struct task_struct *src_tsk, int src_cpu,
+		 struct task_struct *dst_tsk, int dst_cpu),
+
+	TP_ARGS(src_tsk, src_cpu, dst_tsk, dst_cpu)
+);
+
+DEFINE_EVENT(sched_numa_pair_template, sched_swap_numa,
+
+	TP_PROTO(struct task_struct *src_tsk, int src_cpu,
+		 struct task_struct *dst_tsk, int dst_cpu),
+
+	TP_ARGS(src_tsk, src_cpu, dst_tsk, dst_cpu)
+);
+
+
 /*
  * Tracepoint for waking a polling cpu without an IPI.
  */

kernel/sched/fair.c

@@ -1849,7 +1849,7 @@ static int task_numa_migrate(struct task_struct *p)
 
 	/* No better CPU than the current one was found. */
 	if (env.best_cpu == -1) {
-		trace_sched_stick_numa(p, env.src_cpu, -1);
+		trace_sched_stick_numa(p, env.src_cpu, NULL, -1);
 		return -EAGAIN;
 	}
 
@@ -1858,7 +1858,7 @@ static int task_numa_migrate(struct task_struct *p)
 		ret = migrate_task_to(p, env.best_cpu);
 		WRITE_ONCE(best_rq->numa_migrate_on, 0);
 		if (ret != 0)
-			trace_sched_stick_numa(p, env.src_cpu, env.best_cpu);
+			trace_sched_stick_numa(p, env.src_cpu, NULL, env.best_cpu);
 		return ret;
 	}
 
@@ -1866,7 +1866,7 @@ static int task_numa_migrate(struct task_struct *p)
 	WRITE_ONCE(best_rq->numa_migrate_on, 0);
 
 	if (ret != 0)
-		trace_sched_stick_numa(p, env.src_cpu, task_cpu(env.best_task));
+		trace_sched_stick_numa(p, env.src_cpu, env.best_task, env.best_cpu);
 	put_task_struct(env.best_task);
 	return ret;
 }