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Date:   Wed, 6 Feb 2019 18:19:15 +0100
From:   Peter Zijlstra <peterz@infradead.org>
To:     ufo19890607@gmail.com
Cc:     mingo@redhat.com, yun.wang@linux.alibaba.com,
        yuzhoujian@didichuxing.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] sched/debug: Show intergroup and hierarchy sum wait time
 of a task group
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References: <1548236816-18712-1-git-send-email-ufo19890607@gmail.com>
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On Wed, Jan 23, 2019 at 05:46:56PM +0800, ufo19890607@gmail.com wrote:
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index e2ff4b6..35e89ca 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -858,6 +858,19 @@ static void update_curr_fair(struct rq *rq)
>  }
>  
>  static inline void
> +update_hierarchy_wait_sum(struct sched_entity *se,
> +			u64 delta_wait)
> +{
> +	for_each_sched_entity(se) {
> +		struct cfs_rq *cfs_rq = cfs_rq_of(se);
> +
> +		if (cfs_rq->tg != &root_task_group)
> +			__schedstat_add(cfs_rq->hierarchy_wait_sum,
> +					delta_wait);
> +	}
> +}
> +
> +static inline void
>  update_stats_wait_end(struct cfs_rq *cfs_rq, struct sched_entity *se)
>  {
>  	struct task_struct *p;
> @@ -880,6 +893,7 @@ static void update_curr_fair(struct rq *rq)
>  			return;
>  		}
>  		trace_sched_stat_wait(p, delta);
> +		update_hierarchy_wait_sum(se, delta);
>  	}
>  
>  	__schedstat_set(se->statistics.wait_max,

The problem I have with this is that it will make schedstats even more
expensive :/