[PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance

From: Steve Sistare <steven.sistare@oracle.com>
To: mingo@redhat.com, peterz@infradead.org
Cc: subhra.mazumdar@oracle.com, dhaval.giani@oracle.com,
	daniel.m.jordan@oracle.com, pavel.tatashin@microsoft.com,
	matt@codeblueprint.co.uk, umgwanakikbuti@gmail.com,
	riel@redhat.com, jbacik@fb.com, juri.lelli@redhat.com,
	valentin.schneider@arm.com, vincent.guittot@linaro.org,
	quentin.perret@arm.com, steven.sistare@oracle.com,
	linux-kernel@vger.kernel.org
Subject: [PATCH v3 05/10] sched/fair: Hoist idle_stamp up from idle_balance
Date: Fri,  9 Nov 2018 04:50:35 -0800	[thread overview]
Message-ID: <1541767840-93588-6-git-send-email-steven.sistare@oracle.com> (raw)
In-Reply-To: <1541767840-93588-1-git-send-email-steven.sistare@oracle.com>

Move the update of idle_stamp from idle_balance to the call site in
pick_next_task_fair, to prepare for a future patch that adds work to
pick_next_task_fair which must be included in the idle_stamp interval.
No functional change.

Signed-off-by: Steve Sistare <steven.sistare@oracle.com>
---
 kernel/sched/fair.c | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 9031d39..da368ed 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -3725,6 +3725,8 @@ static inline void update_misfit_status(struct task_struct *p, struct rq *rq)
 	rq->misfit_task_load = task_h_load(p);
 }
 
+#define IF_SMP(statement)	statement
+
 static void overload_clear(struct rq *rq)
 {
 	struct sparsemask *overload_cpus;
@@ -3770,6 +3772,8 @@ static inline int idle_balance(struct rq *rq, struct rq_flags *rf)
 	return 0;
 }
 
+#define IF_SMP(statement)	/* empty */
+
 static inline void overload_clear(struct rq *rq) {}
 static inline void overload_set(struct rq *rq) {}
 
@@ -6764,8 +6768,18 @@ static void check_preempt_wakeup(struct rq *rq, struct task_struct *p, int wake_
 
 idle:
 	update_misfit_status(NULL, rq);
+
+	/*
+	 * We must set idle_stamp _before_ calling idle_balance(), such that we
+	 * measure the duration of idle_balance() as idle time.
+	 */
+	IF_SMP(rq->idle_stamp = rq_clock(rq);)
+
 	new_tasks = idle_balance(rq, rf);
 
+	if (new_tasks)
+		IF_SMP(rq->idle_stamp = 0;)
+
 	/*
 	 * Because idle_balance() releases (and re-acquires) rq->lock, it is
 	 * possible for any higher priority task to appear. In that case we
@@ -9611,12 +9625,6 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
 	u64 curr_cost = 0;
 
 	/*
-	 * We must set idle_stamp _before_ calling idle_balance(), such that we
-	 * measure the duration of idle_balance() as idle time.
-	 */
-	this_rq->idle_stamp = rq_clock(this_rq);
-
-	/*
 	 * Do not pull tasks towards !active CPUs...
 	 */
 	if (!cpu_active(this_cpu))
@@ -9707,9 +9715,6 @@ static int idle_balance(struct rq *this_rq, struct rq_flags *rf)
 	if (this_rq->nr_running != this_rq->cfs.h_nr_running)
 		pulled_task = -1;
 
-	if (pulled_task)
-		this_rq->idle_stamp = 0;
-
 	rq_repin_lock(this_rq, rf);
 
 	return pulled_task;
-- 
1.8.3.1

