Messages in this thread Patch in this message | | | From | Yuyang Du <> | Subject | [PATCH 2/2] sched/fair: Skip detach and attach load avgs for new group task | Date | Thu, 26 May 2016 09:14:24 +0800 |
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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@linaro.org> Signed-off-by: Yuyang Du <yuyang.du@intel.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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