linux-kernel - Re: [PATCH] sched/fair: Remove rq->load

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Message-ID: <c76a9ece-bfc9-c9dc-a0e0-a41698f56f78@arm.com>
Date:   Mon, 6 May 2019 12:46:00 +0200
From:   Dietmar Eggemann <dietmar.eggemann@....com>
To:     Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched/fair: Remove rq->load

Hi,

On 4/24/19 10:45 AM, Dietmar Eggemann wrote:
> The CFS class is the only one maintaining and using the CPU wide load
> (rq->load(.weight)). The last use case of the CPU wide load in CFS's
> set_next_entity() can be replaced by using the load of the CFS class
> (rq->cfs.load(.weight)) instead.
> 
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> ---
>   kernel/sched/debug.c | 2 --
>   kernel/sched/fair.c  | 7 ++-----
>   kernel/sched/sched.h | 2 --
>   3 files changed, 2 insertions(+), 9 deletions(-)
> 
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c
> index 8039d62ae36e..1148f43dbd42 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -656,8 +656,6 @@ do {									\
>   	SEQ_printf(m, "  .%-30s: %Ld.%06ld\n", #x, SPLIT_NS(rq->x))
>   
>   	P(nr_running);
> -	SEQ_printf(m, "  .%-30s: %lu\n", "load",
> -		   rq->load.weight);
>   	P(nr_switches);
>   	P(nr_load_updates);
>   	P(nr_uninterruptible);
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index a4d9e14bf138..73a6718f29cc 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -2682,8 +2682,6 @@ 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);
> @@ -2699,8 +2697,6 @@ static void
>   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);
>   #ifdef CONFIG_SMP
>   	if (entity_is_task(se)) {
>   		account_numa_dequeue(rq_of(cfs_rq), task_of(se));
> @@ -4096,7 +4092,8 @@ set_next_entity(struct cfs_rq *cfs_rq, struct sched_entity *se)
>   	 * least twice that of our own weight (i.e. dont track it
>   	 * when there are only lesser-weight tasks around):
>   	 */
> -	if (schedstat_enabled() && rq_of(cfs_rq)->load.weight >= 2*se->load.weight) {
> +	if (schedstat_enabled() &&
> +	    rq_of(cfs_rq)->cfs.load.weight >= 2*se->load.weight) {
>   		schedstat_set(se->statistics.slice_max,
>   			max((u64)schedstat_val(se->statistics.slice_max),
>   			    se->sum_exec_runtime - se->prev_sum_exec_runtime));
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index efa686eeff26..e4059e81e99c 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -830,8 +830,6 @@ struct rq {
>   	atomic_t nohz_flags;
>   #endif /* CONFIG_NO_HZ_COMMON */
>   
> -	/* capture load from *all* tasks on this CPU: */
> -	struct load_weight	load;
>   	unsigned long		nr_load_updates;
>   	u64			nr_switches;

Is there anything else I should do for this patch ?

Thanks,

-- Dietmar