linux-kernel - Re: [patch v4 07/18] sched: set initial load avg of new forked task

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Date:	Thu, 14 Feb 2013 21:07:55 +0800
From:	Alex Shi <alex.shi@...el.com>
To:	Paul Turner <pjt@...gle.com>
CC:	Peter Zijlstra <peterz@...radead.org>,
	torvalds@...ux-foundation.org, mingo@...hat.com,
	tglx@...utronix.de, akpm@...ux-foundation.org,
	arjan@...ux.intel.com, bp@...en8.de, namhyung@...nel.org,
	efault@....de, vincent.guittot@...aro.org,
	gregkh@...uxfoundation.org, preeti@...ux.vnet.ibm.com,
	viresh.kumar@...aro.org, linux-kernel@...r.kernel.org
Subject: Re: [patch v4 07/18] sched: set initial load avg of new forked task


> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index 1dff78a..9d1c193 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -1557,8 +1557,8 @@ static void __sched_fork(struct task_struct *p)
>   * load-balance).
>   */
>  #if defined(CONFIG_SMP) && defined(CONFIG_FAIR_GROUP_SCHED)
> -       p->se.avg.runnable_avg_period = 0;
> -       p->se.avg.runnable_avg_sum = 0;
> +       p->se.avg.runnable_avg_period = 1024;
> +       p->se.avg.runnable_avg_sum = 1024;

It can't work.
avg.decay_count needs to be set to 0 before enqueue_entity_load_avg(), then
update_entity_load_avg() can't be called, so, runnable_avg_period/sum
are unusable.

Even we has chance to call __update_entity_runnable_avg(),
avg.last_runnable_update needs be set before that, usually, it needs to
be set as 'now', that cause __update_entity_runnable_avg() function
return 0, then update_entity_load_avg() still can not reach to
__update_entity_load_avg_contrib().

If we embed a simple new task load initialization to many functions,
that is too hard for future reader.

>  #endif
>  #ifdef CONFIG_SCHEDSTATS
>         memset(&p->se.statistics, 0, sizeof(p->se.statistics));
> 
> 
> 
>>
>>
>> --
>> Thanks
>>     Alex


-- 
Thanks
    Alex
--
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