From: Mel Gorman <mgorman@suse.de>
Date: Thu, 30 Jan 2020 11:18:33 +0000
Subject: [PATCH] sched/numa: Distinguish between the different
 task_numa_migrate() failure cases

References: bnc#1155798 (CPU scheduler functional and performance backports)
Patch-mainline: v5.7-rc1
Git-commit: b2b2042b204796190af7c20069ab790a614c36d0

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
Signed-off-by: Mel Gorman <mgorman@suse.de>
---
 include/trace/events/sched.h | 49 ++++++++++++++++++++++++--------------------
 kernel/sched/fair.c          |  6 +++---
 2 files changed, 30 insertions(+), 25 deletions(-)

diff --git a/include/trace/events/sched.h b/include/trace/events/sched.h
index 420e80e56e55..9c3ebb7c83a5 100644
--- a/include/trace/events/sched.h
+++ b/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.
  */
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index f524ce3cea82..5d9c23c134af 100644
--- a/kernel/sched/fair.c
+++ b/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;
 }
-- 
2.16.4