linux-kernel - Re: [PATCH] sched: sync with the cfs

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Message-ID: <20150812224145.GA2143@intel.com>
Date:	Thu, 13 Aug 2015 06:41:45 +0800
From:	Yuyang Du <yuyang.du@...el.com>
To:	byungchul.park@....com
Cc:	mingo@...nel.org, peterz@...radead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: sync with the cfs_rq when changing sched class

On Thu, Aug 13, 2015 at 02:55:55PM +0900, byungchul.park@....com wrote:
> 
> currently, a task load is synced with its cfs_rq, only when it
> leaves from fair class. we also need to sync it with cfs_rq when
> it returns back to fair class, too.
 
Syncing it at the time it is switched to fair is not necessary, because
since last_update_time if it has ever been updated, the load has become
random, IOW, useless. So we simply leave it unattended, and let itself
merge in the system.

>  
>  #ifdef CONFIG_SMP
>  	/* synchronize task with its prev cfs_rq */
> -	if (!queued)
> -		__update_load_avg(cfs_rq->avg.last_update_time, cpu_of(rq_of(cfs_rq)),
> -				&se->avg, se->on_rq * scale_load_down(se->load.weight),
> -				cfs_rq->curr == se, NULL);
> -
> -	/* remove our load when we leave */
> -	cfs_rq->avg.load_avg = max_t(long, cfs_rq->avg.load_avg - se->avg.load_avg, 0);
> -	cfs_rq->avg.load_sum = max_t(s64, cfs_rq->avg.load_sum - se->avg.load_sum, 0);
> -	cfs_rq->avg.util_avg = max_t(long, cfs_rq->avg.util_avg - se->avg.util_avg, 0);
> -	cfs_rq->avg.util_sum = max_t(s32, cfs_rq->avg.util_sum - se->avg.util_sum, 0);
> +	detach_entity_load_avg(cfs_rq, se);
>  #endif

You changed the logic.
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