linux-kernel - [RFCv4 PATCH 12/34] sched: Initialize CFS task load and usage before placing task on rq

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Message-Id: <1431459549-18343-13-git-send-email-morten.rasmussen@arm.com>
Date:	Tue, 12 May 2015 20:38:47 +0100
From:	Morten Rasmussen <morten.rasmussen@....com>
To:	peterz@...radead.org, mingo@...hat.com
Cc:	vincent.guittot@...aro.org,
	Dietmar Eggemann <Dietmar.Eggemann@....com>,
	yuyang.du@...el.com, preeti@...ux.vnet.ibm.com,
	mturquette@...aro.org, rjw@...ysocki.net,
	Juri Lelli <Juri.Lelli@....com>, sgurrappadi@...dia.com,
	pang.xunlei@....com.cn, linux-kernel@...r.kernel.org,
	linux-pm@...r.kernel.org, morten.rasmussen@....com
Subject: [RFCv4 PATCH 12/34] sched: Initialize CFS task load and usage before placing task on rq

Task load or usage is not currently considered in select_task_rq_fair(),
but if we want that in the future we should make sure it is not zero for
new tasks.

The load-tracking sums are currently initialized using sched_slice(),
that won't work before the task has been assigned a rq. Initialization
is therefore changed to another semi-arbitrary value, sched_latency,
instead.

cc: Ingo Molnar <mingo@...hat.com>
cc: Peter Zijlstra <peterz@...radead.org>

Signed-off-by: Morten Rasmussen <morten.rasmussen@....com>
---
 kernel/sched/core.c | 4 ++--
 kernel/sched/fair.c | 7 +++----
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 355f953..bceb3a8 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2126,6 +2126,8 @@ void wake_up_new_task(struct task_struct *p)
 	struct rq *rq;
 
 	raw_spin_lock_irqsave(&p->pi_lock, flags);
+	/* Initialize new task's runnable average */
+	init_task_runnable_average(p);
 #ifdef CONFIG_SMP
 	/*
 	 * Fork balancing, do it here and not earlier because:
@@ -2135,8 +2137,6 @@ void wake_up_new_task(struct task_struct *p)
 	set_task_cpu(p, select_task_rq(p, task_cpu(p), SD_BALANCE_FORK, 0));
 #endif
 
-	/* Initialize new task's runnable average */
-	init_task_runnable_average(p);
 	rq = __task_rq_lock(p);
 	activate_task(rq, p, 0);
 	p->on_rq = TASK_ON_RQ_QUEUED;
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index d045404..f20fae9 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -675,11 +675,10 @@ static inline void __update_task_entity_utilization(struct sched_entity *se);
 /* Give new task start runnable values to heavy its load in infant time */
 void init_task_runnable_average(struct task_struct *p)
 {
-	u32 slice;
+	u32 start_load = sysctl_sched_latency >> 10;
 
-	slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
-	p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = slice;
-	p->se.avg.avg_period = slice;
+	p->se.avg.runnable_avg_sum = p->se.avg.running_avg_sum = start_load;
+	p->se.avg.avg_period = start_load;
 	__update_task_entity_contrib(&p->se);
 	__update_task_entity_utilization(&p->se);
 }
-- 
1.9.1

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