[PATCH v4 17/19] sched: Add migrate_disable() tracepoints

From: Peter Zijlstra <peterz@infradead.org>
To: tglx@linutronix.de, mingo@kernel.org
Cc: linux-kernel@vger.kernel.org, bigeasy@linutronix.de,
	qais.yousef@arm.com, swood@redhat.com, peterz@infradead.org,
	valentin.schneider@arm.com, juri.lelli@redhat.com,
	vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
	rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
	bristot@redhat.com, vincent.donnefort@arm.com, tj@kernel.org,
	ouwen210@hotmail.com
Subject: [PATCH v4 17/19] sched: Add migrate_disable() tracepoints
Date: Fri, 23 Oct 2020 12:12:15 +0200	[thread overview]
Message-ID: <20201023102347.697960969@infradead.org> (raw)
In-Reply-To: 20201023101158.088940906@infradead.org

XXX write a tracer:

 - 'migirate_disable() -> migrate_enable()' time in task_sched_runtime()
 - 'migrate_pull -> sched-in' time in task_sched_runtime()

The first will give worst case for the second, which is the actual
interference experienced by the task to due migration constraints of
migrate_disable().

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
---
 include/trace/events/sched.h |   12 ++++++++++++
 kernel/sched/core.c          |    4 ++++
 kernel/sched/deadline.c      |    1 +
 kernel/sched/rt.c            |    8 +++++++-
 4 files changed, 24 insertions(+), 1 deletion(-)

--- a/include/trace/events/sched.h
+++ b/include/trace/events/sched.h
@@ -646,6 +646,18 @@ DECLARE_TRACE(sched_update_nr_running_tp
 	TP_PROTO(struct rq *rq, int change),
 	TP_ARGS(rq, change));
 
+DECLARE_TRACE(sched_migrate_disable_tp,
+	      TP_PROTO(struct task_struct *p),
+	      TP_ARGS(p));
+
+DECLARE_TRACE(sched_migrate_enable_tp,
+	      TP_PROTO(struct task_struct *p),
+	      TP_ARGS(p));
+
+DECLARE_TRACE(sched_migrate_pull_tp,
+	      TP_PROTO(struct task_struct *p),
+	      TP_ARGS(p));
+
 #endif /* _TRACE_SCHED_H */
 
 /* This part must be outside protection */
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1732,6 +1732,8 @@ void migrate_disable(void)
 		return;
 	}
 
+	trace_sched_migrate_disable_tp(p);
+
 	preempt_disable();
 	this_rq()->nr_pinned++;
 	p->migration_disabled = 1;
@@ -1764,6 +1766,8 @@ void migrate_enable(void)
 	p->migration_disabled = 0;
 	this_rq()->nr_pinned--;
 	preempt_enable();
+
+	trace_sched_migrate_enable_tp(p);
 }
 EXPORT_SYMBOL_GPL(migrate_enable);
 
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -2245,6 +2245,7 @@ static void pull_dl_task(struct rq *this
 				goto skip;
 
 			if (is_migration_disabled(p)) {
+				trace_sched_migrate_pull_tp(p);
 				push_task = get_push_task(src_rq);
 			} else {
 				deactivate_task(src_rq, p, 0);
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -1877,7 +1877,12 @@ static int push_rt_task(struct rq *rq, b
 		struct task_struct *push_task = NULL;
 		int cpu;
 
-		if (!pull || rq->push_busy)
+		if (!pull)
+			return 0;
+
+		trace_sched_migrate_pull_tp(next_task);
+
+		if (rq->push_busy)
 			return 0;
 
 		cpu = find_lowest_rq(rq->curr);
@@ -2223,6 +2228,7 @@ static void pull_rt_task(struct rq *this
 				goto skip;
 
 			if (is_migration_disabled(p)) {
+				trace_sched_migrate_pull_tp(p);
 				push_task = get_push_task(src_rq);
 			} else {
 				deactivate_task(src_rq, p, 0);


