linux-kernel - Re: [RFC] sched: make update_cpu_load

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Message-ID: <20150817233927.GB24261@byungchulpark-X58A-UD3R>
Date:	Tue, 18 Aug 2015 08:39:27 +0900
From:	Byungchul Park <byungchul.park@....com>
To:	mingo@...nel.org, peterz@...radead.org
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [RFC] sched: make update_cpu_load_active care more than one tick

On Thu, Aug 13, 2015 at 06:35:24PM +0900, byungchul.park@....com wrote:
> From: Byungchul Park <byungchul.park@....com>
> 
> i found do_timer accounts other than one tick, so i made
> update_cpu_load_active care that.
> 
> is it intended because of its overhead?

hello,

is there anyone who can tell me any opinion about this concern?

> 
> Signed-off-by: Byungchul Park <byungchul.park@....com>
> ---
>  kernel/sched/fair.c |    7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
> index ffa70dc..cd3d98f 100644
> --- a/kernel/sched/fair.c
> +++ b/kernel/sched/fair.c
> @@ -4506,12 +4506,15 @@ void update_cpu_load_nohz(void)
>   */
>  void update_cpu_load_active(struct rq *this_rq)
>  {
> +	unsigned long curr_jiffies = READ_ONCE(jiffies);
> +	unsigned long pending_updates;
>  	unsigned long load = this_rq->cfs.runnable_load_avg;
>  	/*
>  	 * See the mess around update_idle_cpu_load() / update_cpu_load_nohz().
>  	 */
> -	this_rq->last_load_update_tick = jiffies;
> -	__update_cpu_load(this_rq, load, 1);
> +	pending_updates = curr_jiffies - this_rq->last_load_update_tick;
> +	this_rq->last_load_update_tick = curr_jiffies;
> +	__update_cpu_load(this_rq, load, pending_updates);
>  }
>  
>  /* Used instead of source_load when we know the type == 0 */
> -- 
> 1.7.9.5
> 
> --
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