linux-kernel - Re: [PATCH v4] sched: fix wrong rq's runnable

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Date:	Tue, 9 Apr 2013 11:06:15 +0200
From:	Vincent Guittot <vincent.guittot@...aro.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	linux-kernel <linux-kernel@...r.kernel.org>,
	"linaro-kernel@...ts.linaro.org" <linaro-kernel@...ts.linaro.org>,
	Ingo Molnar <mingo@...nel.org>, Paul Turner <pjt@...gle.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Frédéric Weisbecker <fweisbec@...il.com>,
	Mike Galbraith <efault@....de>
Subject: Re: [PATCH v4] sched: fix wrong rq's runnable_avg update with rt tasks

On 9 April 2013 10:50, Peter Zijlstra <peterz@...radead.org> wrote:
> On Thu, 2013-04-04 at 16:15 +0200, Vincent Guittot wrote:
>> Signed-off-by: Vincent Guittot <vincent.guittot@...aro.org>
>> ---
>>  kernel/sched/fair.c      |   23 +++++++++++++++++++++--
>>  kernel/sched/idle_task.c |   10 ++++++++++
>>  kernel/sched/sched.h     |   12 ++++++++++++
>>  3 files changed, 43 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 0fcdbff..1851ca8 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -1562,6 +1562,27 @@ static inline void
>> dequeue_entity_load_avg(struct cfs_rq *cfs_rq,
>>                 se->avg.decay_count =
>> atomic64_read(&cfs_rq->decay_counter);
>>         } /* migrations, e.g. sleep=0 leave decay_count == 0 */
>>  }
>> +
>> +/*
>> + * Update the rq's load with the elapsed running time before entering
>> + * idle. if the last scheduled task is not a CFS task, idle_enter
>> will
>> + * be the only way to update the runnable statistic.
>> + */
>> +void idle_enter(struct rq *this_rq)
>> +{
>> +       update_rq_runnable_avg(this_rq, 1);
>> +}
>> +
>> +/*
>> + * Update the rq's load with the elapsed idle time before a task is
>> + * scheduled. if the newly scheduled task is not a CFS task,
>> idle_exit will
>> + * be the only way to update the runnable statistic.
>> + */
>> +void idle_exit(struct rq *this_rq)
>> +{
>> +       update_rq_runnable_avg(this_rq, 0);
>> +}
>
> These seem like fairly unfortunate names to expose to the global
> namespace, why not expose update_rq_runnable_avg() instead?

Just to gather in one place all cfs actions that should be done when
exiting idle even if we only have update_rq_runnable_avg right now. I
have distinguished that from idle_balance because this sequence can't
generate extra context switch like idle_balance and they would finally
not be called in the same time

>
>
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