On 06/07/2013 03:20 PM, Alex Shi wrote:
> We need initialize the se.avg.{decay_count, load_avg_contrib} for a
> new forked task.
> Otherwise random values of above variables cause mess when do new task
> enqueue:
> enqueue_task_fair
> enqueue_entity
> enqueue_entity_load_avg
>
> and make forking balancing imbalance since incorrect load_avg_contrib.
>
> Further more, Morten Rasmussen notice some tasks were not launched at
> once after created. So Paul and Peter suggest giving a start value for
> new task runnable avg time same as sched_slice().
>
> Signed-off-by: Alex Shi <alex....@intel.com>
Reviewed-by: Gu Zheng <guz.f...@cn.fujitsu.com>
> ---
> kernel/sched/core.c | 6 ++----
> kernel/sched/fair.c | 23 +++++++++++++++++++++++
> kernel/sched/sched.h | 2 ++
> 3 files changed, 27 insertions(+), 4 deletions(-)
>
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b9e7036..6f226c2 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1598,10 +1598,6 @@ static void __sched_fork(struct task_struct *p)
> p->se.vruntime = 0;
> INIT_LIST_HEAD(&p->se.group_node);
>
> -#ifdef CONFIG_SMP
> - p->se.avg.runnable_avg_period = 0;
> - p->se.avg.runnable_avg_sum = 0;
> -#endif
> #ifdef CONFIG_SCHEDSTATS
> memset(&p->se.statistics, 0, sizeof(p->se.statistics));
> #endif
> @@ -1745,6 +1741,8 @@ void wake_up_new_task(struct task_struct *p)
> set_task_cpu(p, select_task_rq(p, SD_BALANCE_FORK, 0));
> #endif
>
> + /* Give new task start runnable values */
> + set_task_runnable_avg(p);
> rq = __task_rq_lock(p);
> activate_task(rq, p, 0);
> p->on_rq = 1;
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index f404468..1fc30b9 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -680,6 +680,26 @@ static u64 sched_vslice(struct cfs_rq *cfs_rq, struct
> sched_entity *se)
> return calc_delta_fair(sched_slice(cfs_rq, se), se);
> }
>
> +#ifdef CONFIG_SMP
> +static inline void __update_task_entity_contrib(struct sched_entity *se);
> +
> +/* Give new task start runnable values to heavy its load in infant time */
> +void set_task_runnable_avg(struct task_struct *p)
> +{
> + u32 slice;
> +
> + p->se.avg.decay_count = 0;
> + slice = sched_slice(task_cfs_rq(p), &p->se) >> 10;
> + p->se.avg.runnable_avg_sum = slice;
> + p->se.avg.runnable_avg_period = slice;
> + __update_task_entity_contrib(&p->se);
> +}
> +#else
> +void set_task_runnable_avg(struct task_struct *p)
> +{
> +}
> +#endif
> +
> /*
> * Update the current task's runtime statistics. Skip current tasks that
> * are not in our scheduling class.
> @@ -1527,6 +1547,9 @@ static inline void enqueue_entity_load_avg(struct
> cfs_rq *cfs_rq,
> * We track migrations using entity decay_count <= 0, on a wake-up
> * migration we use a negative decay count to track the remote decays
> * accumulated while sleeping.
> + *
> + * When enqueue a new forked task, the se->avg.decay_count == 0, so
> + * we bypass update_entity_load_avg(), use avg.load_avg_contrib direct.
> */
> if (unlikely(se->avg.decay_count <= 0)) {
> se->avg.last_runnable_update = rq_clock_task(rq_of(cfs_rq));
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index 24b1503..8bc66c6 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -1058,6 +1058,8 @@ extern void init_rt_bandwidth(struct rt_bandwidth
> *rt_b, u64 period, u64 runtime
>
> extern void update_idle_cpu_load(struct rq *this_rq);
>
> +extern void set_task_runnable_avg(struct task_struct *p);
> +
> #ifdef CONFIG_PARAVIRT
> static inline u64 steal_ticks(u64 steal)
> {
--
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