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[PATCH v5 0/5] sched/fair: Fix attach and detach sched avgs for task group change and sched class change

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  [PATCH v5 0/5] sched/fair: Fix attach and detach sched avgs for task group change and sched class change Yuyang Du <yuyang.du@intel.com> - 2016-06-09 09:20 +0200
    [PATCH v5 3/5] sched/fair: Move load and util avgs from wake_up_new_task() to sched_fork() Yuyang Du <yuyang.du@intel.com> - 2016-06-09 09:20 +0200
    [PATCH v5 5/5] sched/fair: Add inline to detach_entity_load_evg() Yuyang Du <yuyang.du@intel.com> - 2016-06-09 09:20 +0200

#1418118 — [PATCH v5 0/5] sched/fair: Fix attach and detach sched avgs for task group change and sched class change

Hi Peter,

The attach/detach twice problem is worse than Vincent reported.

The attach twice issue can happen not only as Vincent raised when task moves
between groups, but also when switching to fair class. In addition, for newly
forked task, the detach also has a problem. This patchset attempts to address
all of those problems.

Thanks a lot to Vincent and Peter. This new version addresses their comments to
reword the changelog and comments. Also thanks to Matt for the suggestion to
fix the newly forked task's detach problem easier.

Thanks,
Yuyang

--

Yuyang Du (5):
  sched/fair: Clean up attach_entity_load_avg()
  sched/fair: Fix attaching task sched avgs twice when switching to
    fair or changing task group
  sched/fair: Move load and util avgs from wake_up_new_task() to
    sched_fork()
  sched/fair: Skip detach sched avgs for new task when changing task
    groups
  sched/fair: Add inline to detach_entity_load_evg()

 kernel/sched/core.c  |    5 +--
 kernel/sched/fair.c  |   96 ++++++++++++++++++++++++++++++--------------------
 kernel/sched/sched.h |    2 +-
 3 files changed, 61 insertions(+), 42 deletions(-)

-- 
1.7.9.5

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#1418119 — [PATCH v5 3/5] sched/fair: Move load and util avgs from wake_up_new_task() to sched_fork()

Move new task initialization to sched_fork(). For initial non-fair class
task, the first switched_to_fair() will do the attach correctly.

Suggested-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: Yuyang Du <yuyang.du@intel.com>
---
 kernel/sched/core.c  |    5 +++--
 kernel/sched/fair.c  |   14 +++++---------
 kernel/sched/sched.h |    2 +-
 3 files changed, 9 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f2cae4..5d72567 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2370,6 +2370,9 @@ int sched_fork(unsigned long clone_flags, struct task_struct *p)
 	if (p->sched_class->task_fork)
 		p->sched_class->task_fork(p);
 
+	/* Initialize new task's sched averages */
+	init_entity_sched_avg(&p->se);
+
 	/*
 	 * The child is not yet in the pid-hash so no cgroup attach races,
 	 * and the cgroup is pinned to this child due to cgroup_fork()
@@ -2510,8 +2513,6 @@ void wake_up_new_task(struct task_struct *p)
 	struct rq_flags rf;
 	struct rq *rq;
 
-	/* Initialize new task's runnable average */
-	init_entity_runnable_average(&p->se);
 	raw_spin_lock_irqsave(&p->pi_lock, rf.flags);
 #ifdef CONFIG_SMP
 	/*
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 68fcd2e..6e870c6 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -668,8 +668,8 @@ static unsigned long task_h_load(struct task_struct *p);
 #define LOAD_AVG_MAX 47742 /* maximum possible load avg */
 #define LOAD_AVG_MAX_N 345 /* number of full periods to produce LOAD_AVG_MAX */
 
-/* Give new sched_entity start runnable values to heavy its load in infant time */
-void init_entity_runnable_average(struct sched_entity *se)
+/* Give new sched_entity start load values to heavy its load in infant time */
+void init_entity_sched_avg(struct sched_entity *se)
 {
 	struct sched_avg *sa = &se->avg;
 
@@ -738,12 +738,8 @@ void post_init_entity_util_avg(struct sched_entity *se)
 static inline unsigned long cfs_rq_runnable_load_avg(struct cfs_rq *cfs_rq);
 static inline unsigned long cfs_rq_load_avg(struct cfs_rq *cfs_rq);
 #else
-void init_entity_runnable_average(struct sched_entity *se)
-{
-}
-void post_init_entity_util_avg(struct sched_entity *se)
-{
-}
+void init_entity_sched_avg(struct sched_entity *se) { }
+void post_init_entity_util_avg(struct sched_entity *se) { }
 #endif
 
 /*
@@ -8514,7 +8510,7 @@ int alloc_fair_sched_group(struct task_group *tg, struct task_group *parent)
 
 		init_cfs_rq(cfs_rq);
 		init_tg_cfs_entry(tg, cfs_rq, se, i, parent->se[i]);
-		init_entity_runnable_average(se);
+		init_entity_sched_avg(se);
 		post_init_entity_util_avg(se);
 	}
 
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 72f1f30..6087950 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1321,7 +1321,7 @@ extern void init_dl_task_timer(struct sched_dl_entity *dl_se);
 
 unsigned long to_ratio(u64 period, u64 runtime);
 
-extern void init_entity_runnable_average(struct sched_entity *se);
+extern void init_entity_sched_avg(struct sched_entity *se);
 extern void post_init_entity_util_avg(struct sched_entity *se);
 
 #ifdef CONFIG_NO_HZ_FULL
-- 
1.7.9.5

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#1418121 — [PATCH v5 5/5] sched/fair: Add inline to detach_entity_load_evg()

detach_entity_load_evg() is only called by detach_task_cfs_rq(), so
explicitly add inline attribute to it.

Signed-off-by: Yuyang Du <yuyang.du@intel.com>
---
 kernel/sched/fair.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e0f219b..2bbda0d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2941,7 +2941,8 @@ static inline void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_en
 	cfs_rq_util_change(cfs_rq);
 }
 
-static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
+/* Catch up with the cfs_rq and remove our load when we leave */
+static inline void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
 {
 	/* Newly forked tasks are not attached yet. */
 	if (!se->avg.last_update_time)
@@ -8346,7 +8347,6 @@ static void detach_task_cfs_rq(struct task_struct *p)
 		se->vruntime -= cfs_rq->min_vruntime;
 	}
 
-	/* Catch up with the cfs_rq and remove our load when we leave */
 	detach_entity_load_avg(cfs_rq, se);
 }
 
-- 
1.7.9.5

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