linux-kernel - Re: [PATCH v4 1/5] sched/fair: Clean up attach_entity_load

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Date:	Mon, 6 Jun 2016 15:40:18 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Matt Fleming <matt@...eblueprint.co.uk>
Cc:	Yuyang Du <yuyang.du@...el.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...nel.org>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Benjamin Segall <bsegall@...gle.com>,
	Paul Turner <pjt@...gle.com>,
	Morten Rasmussen <morten.rasmussen@....com>,
	Dietmar Eggemann <dietmar.eggemann@....com>
Subject: Re: [PATCH v4 1/5] sched/fair: Clean up attach_entity_load_avg()

Hi Matt,

On 6 June 2016 at 15:30, Matt Fleming <matt@...eblueprint.co.uk> wrote:
> On Mon, 06 Jun, at 08:20:37AM, Yuyang Du wrote:
>> attach_entity_load_avg() is called (indirectly) from:
>>
>>  - switched_to_fair(): switch between classes to fair
>>  - task_move_group_fair(): move between task groups
>>  - enqueue_entity_load_avg(): enqueue entity
>>
>> Only in switched_to_fair() is it possible that the task's last_update_time
>> is not 0 and therefore the task needs sched avgs update, so move the task
>> sched avgs update to switched_to_fair() only. In addition, the code is
>> refactored and code comments are updated.
>>
>> No functionality change.
>>
>> Signed-off-by: Yuyang Du <yuyang.du@...el.com>
>> ---
>>  kernel/sched/fair.c |   43 ++++++++++++++++++++-----------------------
>>  1 file changed, 20 insertions(+), 23 deletions(-)
>
> What about when tasks are moved between groups on CONFIG_SMP=n ?
> Doesn't this change fail to age the load in that case?

The load average stuff is only enable for SMP system but it's not used
for UP system.
To be honest, I don't know why

Vincent