linux-kernel - [PATCH 06/18] sched: set initial load avg of new forked task as its load weight

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Date:	Mon, 10 Dec 2012 16:22:22 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	rob@...dley.net, mingo@...hat.com, peterz@...radead.org
Cc:	gregkh@...uxfoundation.org, andre.przywara@....com, rjw@...k.pl,
	paul.gortmaker@...driver.com, akpm@...ux-foundation.org,
	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	pjt@...gle.com, vincent.guittot@...aro.org
Subject: [PATCH 06/18] sched: set initial load avg of new forked task as its load weight

New task has no runnable sum at its first runnable time, that make
burst forking just select few idle cpus to put tasks.
Set initial load avg of new forked task as its load weight to resolve
this issue.

Signed-off-by: Alex Shi <alex.shi@...el.com>
---
 include/linux/sched.h |    1 +
 kernel/sched/core.c   |    2 +-
 kernel/sched/fair.c   |   13 +++++++++++--
 3 files changed, 13 insertions(+), 3 deletions(-)

diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5dafac3..093f9cd 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1058,6 +1058,7 @@ struct sched_domain;
 #else
 #define ENQUEUE_WAKING		0
 #endif
+#define ENQUEUE_NEWTASK		8
 
 #define DEQUEUE_SLEEP		1
 
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index e6533e1..96fa5f1 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1648,7 +1648,7 @@ void wake_up_new_task(struct task_struct *p)
 #endif
 
 	rq = __task_rq_lock(p);
-	activate_task(rq, p, 0);
+	activate_task(rq, p, ENQUEUE_NEWTASK);
 	p->on_rq = 1;
 	trace_sched_wakeup_new(p, true);
 	check_preempt_curr(rq, p, WF_FORK);
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 1faf89f..61c8d24 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1277,8 +1277,9 @@ static inline void update_rq_runnable_avg(struct rq *rq, int runnable)
 /* Add the load generated by se into cfs_rq's child load-average */
 static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
 						  struct sched_entity *se,
-						  int wakeup)
+						  int flags)
 {
+	int wakeup = flags & ENQUEUE_WAKEUP;
 	/*
 	 * We track migrations using entity decay_count <= 0, on a wake-up
 	 * migration we use a negative decay count to track the remote decays
@@ -1312,6 +1313,12 @@ static inline void enqueue_entity_load_avg(struct cfs_rq *cfs_rq,
 		update_entity_load_avg(se, 0);
 	}
 
+	/*
+	 * set the initial load avg of new task same as its load
+	 * in order to avoid brust fork make few cpu too heavier
+	 */
+	if (flags & ENQUEUE_NEWTASK)
+		se->avg.load_avg_contrib = se->load.weight;
 	cfs_rq->runnable_load_avg += se->avg.load_avg_contrib;
 	/* we force update consideration on load-balancer moves */
 	update_cfs_rq_blocked_load(cfs_rq, !wakeup);
@@ -1476,7 +1483,8 @@ enqueue_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int flags)
 	 */
 	update_curr(cfs_rq);
 	account_entity_enqueue(cfs_rq, se);
-	enqueue_entity_load_avg(cfs_rq, se, flags & ENQUEUE_WAKEUP);
+	enqueue_entity_load_avg(cfs_rq, se, flags &
+				(ENQUEUE_WAKEUP | ENQUEUE_NEWTASK));
 
 	if (flags & ENQUEUE_WAKEUP) {
 		place_entity(cfs_rq, se, 0);
@@ -2586,6 +2594,7 @@ enqueue_task_fair(struct rq *rq, struct task_struct *p, int flags)
 		cfs_rq->h_nr_running++;
 
 		flags = ENQUEUE_WAKEUP;
+		flags &= ~ENQUEUE_NEWTASK;
 	}
 
 	for_each_sched_entity(se) {
-- 
1.7.5.1

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