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Message-Id: <1464225264-32760-3-git-send-email-yuyang.du@intel.com>
Date: Thu, 26 May 2016 09:14:24 +0800
From: Yuyang Du <yuyang.du@...el.com>
To: peterz@...radead.org, mingo@...nel.org,
linux-kernel@...r.kernel.org
Cc: bsegall@...gle.com, pjt@...gle.com, morten.rasmussen@....com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
byungchul.park@....com, Yuyang Du <yuyang.du@...el.com>
Subject: [PATCH 2/2] sched/fair: Skip detach and attach load avgs for new group task
Vincent reported that the first task to a new task group's cfs_rq will
be attached in attach_task_cfs_rq() and once more when it is enqueued
(see https://lkml.org/lkml/2016/5/25/388).
Actually, it is worse, attach_task_cfs_rq() is called for new task even
way before init_entity_runnable_average().
Solve this by avoiding attach as well as detach new task's sched avgs
in task_move_group_fair(). To do it, we need to know whether the task
is forked or not, so we pass this info all the way from sched_move_task()
to attach_task_cfs_rq().
Reported-by: Vincent Guittot <vincent.guittot@...aro.org>
Signed-off-by: Yuyang Du <yuyang.du@...el.com>
---
kernel/sched/auto_group.c | 2 +-
kernel/sched/core.c | 8 ++++----
kernel/sched/fair.c | 23 ++++++++++++-----------
kernel/sched/sched.h | 4 ++--
4 files changed, 19 insertions(+), 18 deletions(-)
diff --git a/kernel/sched/auto_group.c b/kernel/sched/auto_group.c
index a5d966c..e5f0be2 100644
--- a/kernel/sched/auto_group.c
+++ b/kernel/sched/auto_group.c
@@ -143,7 +143,7 @@ autogroup_move_group(struct task_struct *p, struct autogroup *ag)
goto out;
for_each_thread(p, t)
- sched_move_task(t);
+ sched_move_task(t, 0);
out:
unlock_task_sighand(p, &flags);
autogroup_kref_put(prev);
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index 7f2cae4..8585032 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -7724,7 +7724,7 @@ void sched_offline_group(struct task_group *tg)
* by now. This function just updates tsk->se.cfs_rq and tsk->se.parent to
* reflect its new group.
*/
-void sched_move_task(struct task_struct *tsk)
+void sched_move_task(struct task_struct *tsk, int fork)
{
struct task_group *tg;
int queued, running;
@@ -7753,7 +7753,7 @@ void sched_move_task(struct task_struct *tsk)
#ifdef CONFIG_FAIR_GROUP_SCHED
if (tsk->sched_class->task_move_group)
- tsk->sched_class->task_move_group(tsk);
+ tsk->sched_class->task_move_group(tsk, fork);
else
#endif
set_task_rq(tsk, task_cpu(tsk));
@@ -8186,7 +8186,7 @@ static void cpu_cgroup_css_free(struct cgroup_subsys_state *css)
static void cpu_cgroup_fork(struct task_struct *task)
{
- sched_move_task(task);
+ sched_move_task(task, 1);
}
static int cpu_cgroup_can_attach(struct cgroup_taskset *tset)
@@ -8213,7 +8213,7 @@ static void cpu_cgroup_attach(struct cgroup_taskset *tset)
struct cgroup_subsys_state *css;
cgroup_taskset_for_each(task, css, tset)
- sched_move_task(task);
+ sched_move_task(task, 0);
}
#ifdef CONFIG_FAIR_GROUP_SCHED
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index e89c39b..e5a61b1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2970,6 +2970,7 @@ static void attach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *s
cfs_rq_util_change(cfs_rq);
}
+/* Catch up with the cfs_rq and then remove our sched avgs from it */
static void detach_entity_load_avg(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
@@ -8368,9 +8369,6 @@ static void detach_task_cfs_rq(struct task_struct *p)
place_entity(cfs_rq, se, 0);
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);
}
static void attach_task_cfs_rq(struct task_struct *p)
@@ -8386,9 +8384,6 @@ static void attach_task_cfs_rq(struct task_struct *p)
se->depth = se->parent ? se->parent->depth + 1 : 0;
#endif
- /* Synchronize task with its cfs_rq */
- attach_entity_load_avg(cfs_rq, se);
-
if (!vruntime_normalized(p))
se->vruntime += cfs_rq->min_vruntime;
}
@@ -8396,6 +8391,7 @@ static void attach_task_cfs_rq(struct task_struct *p)
static void switched_from_fair(struct rq *rq, struct task_struct *p)
{
detach_task_cfs_rq(p);
+ detach_entity_load_avg(cfs_rq_of(&p->se), &p->se);
}
static void switched_to_fair(struct rq *rq, struct task_struct *p)
@@ -8422,6 +8418,7 @@ static void switched_to_fair(struct rq *rq, struct task_struct *p)
skip_aging:
#endif
attach_task_cfs_rq(p);
+ attach_entity_load_avg(cfs_rq_of(se), se);
if (task_on_rq_queued(p)) {
/*
@@ -8468,16 +8465,20 @@ void init_cfs_rq(struct cfs_rq *cfs_rq)
}
#ifdef CONFIG_FAIR_GROUP_SCHED
-static void task_move_group_fair(struct task_struct *p)
+static void task_move_group_fair(struct task_struct *p, int fork)
{
detach_task_cfs_rq(p);
+ /*
+ * New task does not need detach or attach load (see below)
+ */
+ if (!fork)
+ detach_entity_load_avg(cfs_rq_of(&p->se), &p->se);
+
set_task_rq(p, task_cpu(p));
-#ifdef CONFIG_SMP
- /* Tell se's cfs_rq has been changed -- migrated */
- p->se.avg.last_update_time = 0;
-#endif
attach_task_cfs_rq(p);
+ if (!fork)
+ attach_entity_load_avg(cfs_rq_of(&p->se), &p->se);
}
void free_fair_sched_group(struct task_group *tg)
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 72f1f30..58b1259 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -343,7 +343,7 @@ extern void sched_online_group(struct task_group *tg,
extern void sched_destroy_group(struct task_group *tg);
extern void sched_offline_group(struct task_group *tg);
-extern void sched_move_task(struct task_struct *tsk);
+extern void sched_move_task(struct task_struct *tsk, int fork);
#ifdef CONFIG_FAIR_GROUP_SCHED
extern int sched_group_set_shares(struct task_group *tg, unsigned long shares);
@@ -1247,7 +1247,7 @@ struct sched_class {
void (*update_curr) (struct rq *rq);
#ifdef CONFIG_FAIR_GROUP_SCHED
- void (*task_move_group) (struct task_struct *p);
+ void (*task_move_group) (struct task_struct *p, int fork);
#endif
};
--
1.7.9.5
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