[PATCH 8/8] use avg_vruntime for task placement

[Peter Zijlstra]

Allow to use the avg_vruntime for task placement.

The pro: its the 'fair' place to insert tasks.
The con: its an extra division.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
 kernel/sched.c          |    9 +++++++--
 kernel/sched_fair.c     |    7 ++++++-
 kernel/sched_features.h |    1 +
 3 files changed, 14 insertions(+), 3 deletions(-)

Index: linux-2.6/kernel/sched.c
===================================================================
--- linux-2.6.orig/kernel/sched.c
+++ linux-2.6/kernel/sched.c
@@ -1847,8 +1847,13 @@ void set_task_cpu(struct task_struct *p,
 			schedstat_inc(p, se.nr_forced2_migrations);
 	}
 #endif
-	p->se.vruntime -= old_cfsrq->min_vruntime -
-					 new_cfsrq->min_vruntime;
+	if (sched_feat(AVG_VRUNTIME)) {
+		p->se.vruntime -=
+			avg_vruntime(old_cfsrq) - avg_vruntime(new_cfsrq);
+	} else {
+		p->se.vruntime -=
+			old_cfsrq->min_vruntime - new_cfsrq->min_vruntime;
+	}
 
 	__set_task_cpu(p, new_cpu);
 }
Index: linux-2.6/kernel/sched_fair.c
===================================================================
--- linux-2.6.orig/kernel/sched_fair.c
+++ linux-2.6/kernel/sched_fair.c
@@ -719,7 +719,12 @@ static void check_spread(struct cfs_rq *
 static void
 place_entity(struct cfs_rq *cfs_rq, struct sched_entity *se, int initial)
 {
-	u64 vruntime = cfs_rq->min_vruntime;
+	u64 vruntime;
+
+	if (sched_feat(AVG_VRUNTIME))
+		vruntime = avg_vruntime(cfs_rq);
+	else
+		vruntime = cfs_rq->min_vruntime;
 
 	/*
 	 * The 'current' period is already promised to the current tasks,
Index: linux-2.6/kernel/sched_features.h
===================================================================
--- linux-2.6.orig/kernel/sched_features.h
+++ linux-2.6/kernel/sched_features.h
@@ -11,4 +11,5 @@ SCHED_FEAT(ASYM_GRAN, 1)
 SCHED_FEAT(LB_BIAS, 1)
 SCHED_FEAT(LB_WAKEUP_UPDATE, 1)
 SCHED_FEAT(ASYM_EFF_LOAD, 1)
+SCHED_FEAT(AVG_VRUNTIME, 0)
 SCHED_FEAT(WAKEUP_OVERLAP, 0)

-- 

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