linux-kernel - Re: [PATCH v5 7/7] sched: consider runnable load average in effective

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Message-ID: <518724D1.9040006@linux.vnet.ibm.com>
Date:	Mon, 06 May 2013 11:34:41 +0800
From:	Michael Wang <wangyun@...ux.vnet.ibm.com>
To:	Alex Shi <alex.shi@...el.com>
CC:	mingo@...hat.com, peterz@...radead.org, tglx@...utronix.de,
	akpm@...ux-foundation.org, bp@...en8.de, pjt@...gle.com,
	namhyung@...nel.org, efault@....de, morten.rasmussen@....com,
	vincent.guittot@...aro.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org,
	mgorman@...e.de, riel@...hat.com
Subject: Re: [PATCH v5 7/7] sched: consider runnable load average in effective_load

Hi, Alex

On 05/06/2013 09:45 AM, Alex Shi wrote:
> effective_load calculates the load change as seen from the
> root_task_group. It needs to engage the runnable average
> of changed task.
[snip]
>   */
> @@ -3045,7 +3045,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
>  		/*
>  		 * w = rw_i + @wl
>  		 */
> -		w = se->my_q->load.weight + wl;
> +		w = se->my_q->tg_load_contrib + wl;

I've tested the patch set, seems like the last patch caused big
regression on pgbench:

			base	patch 1~6	patch 1~7
| db_size | clients |  tps  |   |  tps  |	|  tps  |
+---------+---------+-------+	+-------+	+-------+
| 22 MB   |      32 | 43420 |	| 53387 |	| 41625 |

I guess some magic thing happened in effective_load() while calculating
group decay combined with load decay, what's your opinion?

Regards,
Michael Wang

> 
>  		/*
>  		 * wl = S * s'_i; see (2)
> @@ -3066,7 +3066,7 @@ static long effective_load(struct task_group *tg, int cpu, long wl, long wg)
>  		/*
>  		 * wl = dw_i = S * (s'_i - s_i); see (3)
>  		 */
> -		wl -= se->load.weight;
> +		wl -= se->avg.load_avg_contrib;
> 
>  		/*
>  		 * Recursively apply this logic to all parent groups to compute
> @@ -3112,14 +3112,14 @@ static int wake_affine(struct sched_domain *sd, struct task_struct *p, int sync)
>  	 */
>  	if (sync) {
>  		tg = task_group(current);
> -		weight = current->se.load.weight;
> +		weight = current->se.avg.load_avg_contrib;
> 
>  		this_load += effective_load(tg, this_cpu, -weight, -weight);
>  		load += effective_load(tg, prev_cpu, 0, -weight);
>  	}
> 
>  	tg = task_group(p);
> -	weight = p->se.load.weight;
> +	weight = p->se.avg.load_avg_contrib;
> 
>  	/*
>  	 * In low-load situations, where prev_cpu is idle and this_cpu is idle
> 

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