linux-kernel - [PATCH 2/2] sched/fair: Update task group's load

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Date:	Tue, 13 Oct 2015 09:18:23 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	peterz@...radead.org, mingo@...nel.org,
	linux-kernel@...r.kernel.org
Cc:	umgwanakikbuti@...il.com, Yuyang Du <yuyang.du@...el.com>
Subject: [PATCH 2/2] sched/fair: Update task group's load_avg after task migrate

When cfs_rq has removed_load_avg (when task migrates from this cfs_rq),
we need to update its contribution to the group's load_avg. This should
not increase tg's update too much, because in most of the cases, the
cfs_rq has already decayed load_avg.

Signed-off-by: Yuyang Du <yuyang.du@...el.com>
---
 kernel/sched/fair.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 601a253..824aa9f 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2686,12 +2686,13 @@ static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq);
 static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 {
 	struct sched_avg *sa = &cfs_rq->avg;
-	int decayed;
+	int decayed, removed = 0;
 
 	if (atomic_long_read(&cfs_rq->removed_load_avg)) {
 		long r = atomic_long_xchg(&cfs_rq->removed_load_avg, 0);
 		sa->load_avg = max_t(long, sa->load_avg - r, 0);
 		sa->load_sum = max_t(s64, sa->load_sum - r * LOAD_AVG_MAX, 0);
+		removed = 1;
 	}
 
 	if (atomic_long_read(&cfs_rq->removed_util_avg)) {
@@ -2708,7 +2709,7 @@ static inline int update_cfs_rq_load_avg(u64 now, struct cfs_rq *cfs_rq)
 	cfs_rq->load_last_update_time_copy = sa->last_update_time;
 #endif
 
-	return decayed;
+	return decayed || removed;
 }
 
 /* Update task and its cfs_rq load average */
-- 
2.1.4

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