[RFC PATCH 2/4] sched: Consolidate nohz cpu load prelude code

[Frederic Weisbecker]

Gather the common code that computes the pending idle cpu load
to decay.

Signed-off-by: Frederic Weisbecker <fweisbec@xxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Li Zhong <zhong@xxxxxxxxxxxxxxxxxx>
Cc: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Steven Rostedt <rostedt@xxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Borislav Petkov <bp@xxxxxxxxx>
Cc: Alex Shi <alex.shi@xxxxxxxxx>
Cc: Paul Turner <pjt@xxxxxxxxxx>
Cc: Mike Galbraith <efault@xxxxxx>
Cc: Vincent Guittot <vincent.guittot@xxxxxxxxxx>
---
 kernel/sched/proc.c |   40 ++++++++++++++--------------------------
 1 files changed, 14 insertions(+), 26 deletions(-)

diff --git a/kernel/sched/proc.c b/kernel/sched/proc.c
index bb3a6a0..030528a 100644
--- a/kernel/sched/proc.c
+++ b/kernel/sched/proc.c
@@ -470,11 +470,14 @@ decay_load_missed(unsigned long load, unsigned long missed_updates, int idx)
  * scheduler tick (TICK_NSEC). With tickless idle this will not be called
  * every tick. We fix it up based on jiffies.
  */
-static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
-			      unsigned long pending_updates)
+static void __update_cpu_load(struct rq *this_rq, unsigned long this_load)
 {
+	unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
+	unsigned long pending_updates;
 	int i, scale;
 
+	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
+	this_rq->last_load_update_tick = curr_jiffies;
 	this_rq->nr_load_updates++;
 
 	/* Update our load: */
@@ -521,20 +524,15 @@ static void __update_cpu_load(struct rq *this_rq, unsigned long this_load,
  */
 void update_idle_cpu_load(struct rq *this_rq)
 {
-	unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
 	unsigned long load = this_rq->load.weight;
-	unsigned long pending_updates;
 
 	/*
 	 * bail if there's load or we're actually up-to-date.
 	 */
-	if (load || curr_jiffies == this_rq->last_load_update_tick)
+	if (load || jiffies == this_rq->last_load_update_tick)
 		return;
 
-	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
-	this_rq->last_load_update_tick = curr_jiffies;
-
-	__update_cpu_load(this_rq, load, pending_updates);
+	__update_cpu_load(this_rq, load);
 }
 
 /*
@@ -543,22 +541,16 @@ void update_idle_cpu_load(struct rq *this_rq)
 void update_cpu_load_nohz(void)
 {
 	struct rq *this_rq = this_rq();
-	unsigned long curr_jiffies = ACCESS_ONCE(jiffies);
-	unsigned long pending_updates;
 
-	if (curr_jiffies == this_rq->last_load_update_tick)
+	if (jiffies == this_rq->last_load_update_tick)
 		return;
 
 	raw_spin_lock(&this_rq->lock);
-	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
-	if (pending_updates) {
-		this_rq->last_load_update_tick = curr_jiffies;
-		/*
-		 * We were idle, this means load 0, the current load might be
-		 * !0 due to remote wakeups and the sort.
-		 */
-		__update_cpu_load(this_rq, 0, pending_updates);
-	}
+	/*
+	 * We were idle, this means load 0, the current load might be
+	 * !0 due to remote wakeups and the sort.
+	 */
+	__update_cpu_load(this_rq, 0);
 	raw_spin_unlock(&this_rq->lock);
 }
 #endif /* CONFIG_NO_HZ */
@@ -568,11 +560,7 @@ void update_cpu_load_nohz(void)
  */
 void update_cpu_load_active(struct rq *this_rq)
 {
-	/*
-	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
-	 */
-	this_rq->last_load_update_tick = jiffies;
-	__update_cpu_load(this_rq, this_rq->load.weight, 1);
+	__update_cpu_load(this_rq, this_rq->load.weight);
 
 	calc_load_account_active(this_rq);
 }
-- 
1.7.5.4

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