linux-kernel - Re: [PATCH v2] sched: separate operations only for SMP from account_entity

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Date:	Tue, 7 Jul 2015 15:28:18 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	mingo@...nel.org, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched: separate operations only for SMP from
 account_entity_en(de)queue

On Tue, Jul 07, 2015 at 10:07:03AM +0900, byungchul.park@....com wrote:
> From: Byungchul Park <byungchul.park@....com>
> 
> manipulating rq->cfs_tasks and numa-accounting are not meaningless on !SMP.
> separate the operations from account_entity_en(de)queue.
> 
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>  kernel/sched/fair.c |   40 +++++++++++++++++++++++++++-------------
>  1 file changed, 27 insertions(+), 13 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index 09456fc..a22f255 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2314,20 +2314,36 @@ static inline void account_numa_dequeue(struct rq *rq, struct task_struct *p)
>  }
>  #endif /* CONFIG_NUMA_BALANCING */
>  
> +#ifdef CONFIG_SMP
> +static void account_task_enqueue(struct rq *rq, struct sched_entity *se)
> +{
> +	account_numa_enqueue(rq, task_of(se));

i put this code within #ifdef CONFIG_SMP as original code. see below.

> +	list_add(&se->group_node, &rq->cfs_tasks);

se->group_node can be used for other purposes, so i didn't touch the structure.
but manipulating rq->cfs_tasks list is only for CONFIG_SMP.
so i just touched the code manipulating the list.

> +}
> +
> +static void account_task_dequeue(struct rq *rq, struct sched_entity *se)
> +{
> +	account_numa_dequeue(rq, task_of(se));
> +	list_del_init(&se->group_node);
> +}
> +#else
> +static inline void account_task_enqueue(struct rq *rq, struct sched_entity *se)
> +{
> +}
> +
> +static inline void account_task_dequeue(struct rq *rq, struct sched_entity *se)
> +{
> +}
> +#endif /* CONFIG_SMP */
> +
>  static void
>  account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  {
>  	update_load_add(&cfs_rq->load, se->load.weight);
>  	if (!parent_entity(se))
>  		update_load_add(&rq_of(cfs_rq)->load, se->load.weight);
> -#ifdef CONFIG_SMP
> -	if (entity_is_task(se)) {
> -		struct rq *rq = rq_of(cfs_rq);
> -
> -		account_numa_enqueue(rq, task_of(se));
> -		list_add(&se->group_node, &rq->cfs_tasks);
> -	}
> -#endif

this is the original code i mentioned.

> +	if (entity_is_task(se))
> +		account_task_enqueue(rq_of(cfs_rq), se);
>  	cfs_rq->nr_running++;
>  }
>  
> @@ -2337,15 +2353,13 @@ account_entity_dequeue(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  	update_load_sub(&cfs_rq->load, se->load.weight);
>  	if (!parent_entity(se))
>  		update_load_sub(&rq_of(cfs_rq)->load, se->load.weight);
> -	if (entity_is_task(se)) {
> -		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
> -		list_del_init(&se->group_node);
> -	}
> +	if (entity_is_task(se))
> +		account_task_dequeue(rq_of(cfs_rq), se);
>  	cfs_rq->nr_running--;
>  }
>  
>  #ifdef CONFIG_FAIR_GROUP_SCHED
> -# ifdef CONFIG_SMP
> +#ifdef CONFIG_SMP
>  static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
>  {
>  	long tg_weight;
> -- 
> 1.7.9.5
> 
> --
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