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

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Date:	Mon, 06 May 2013 13:39:53 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Michael Wang <wangyun@...ux.vnet.ibm.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

On 05/06/2013 11:34 AM, Michael Wang wrote:
>> > @@ -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?


thanks for testing, Michael!

Maybe 2 fix worth to try.

1, change back the tg_weight in calc_tg_weight() to use tg_load_contrib not direct load.

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 6f4f14b..c770f8d 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -1037,8 +1037,8 @@ static inline long calc_tg_weight(struct task_group *tg, struct cfs_rq *cfs_rq)
 	 * update_cfs_rq_load_contribution().
 	 */
 	tg_weight = atomic64_read(&tg->load_avg);
-	tg_weight -= cfs_rq->tg_load_contrib;
-	tg_weight += cfs_rq->load.weight;
+	//tg_weight -= cfs_rq->tg_load_contrib;
+	//tg_weight += cfs_rq->load.weight;
 
 	return tg_weight;
 }

2, another try is follow the current calc_tg_weight, so remove the follow change.

>> > @@ -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;

Would you like to try them?


-- 
Thanks
    Alex
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