Re: [PATCH v2 1/3] sched: don't repeat the initialization in sched_init()

From: Michael Wang
Date: Wed Jun 05 2013 - 22:19:29 EST


On 06/05/2013 07:06 PM, Peter Zijlstra wrote:
> On Wed, Jun 05, 2013 at 10:24:18AM +0800, Michael Wang wrote:
>> v2:
>> Move comments back before init_tg_cfs_entry(). (Thanks for the notify from pjt)
>>
>> In sched_init(), there is no need to initialize 'root_task_group.shares' and
>> 'root_task_group.cfs_bandwidth' repeatedly.
>>
>> CC: Paul Tuner <pjt@xxxxxxxxxx>
>> CC: Ingo Molnar <mingo@xxxxxxxxxx>
>> CC: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
>> Signed-off-by: Michael Wang <wangyun@xxxxxxxxxxxxxxxxxx>
>> ---
>> kernel/sched/core.c | 7 +++++--
>> 1 files changed, 5 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
>> index 58453b8..96f69da 100644
>> --- a/kernel/sched/core.c
>> +++ b/kernel/sched/core.c
>> @@ -6955,6 +6955,11 @@ void __init sched_init(void)
>>
>> #endif /* CONFIG_CGROUP_SCHED */
>>
>> +#ifdef CONFIG_FAIR_GROUP_SCHED
>> + root_task_group.shares = ROOT_TASK_GROUP_LOAD;
>> + init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
>> +#endif
>> +
>> for_each_possible_cpu(i) {
>> struct rq *rq;
>>
>> @@ -6966,7 +6971,6 @@ void __init sched_init(void)
>> init_cfs_rq(&rq->cfs);
>> init_rt_rq(&rq->rt, rq);
>> #ifdef CONFIG_FAIR_GROUP_SCHED
>> - root_task_group.shares = ROOT_TASK_GROUP_LOAD;
>> INIT_LIST_HEAD(&rq->leaf_cfs_rq_list);
>> /*
>> * How much cpu bandwidth does root_task_group get?
>> @@ -6987,7 +6991,6 @@ void __init sched_init(void)
>> * We achieve this by letting root_task_group's tasks sit
>> * directly in rq->cfs (i.e root_task_group->se[] = NULL).
>> */
>> - init_cfs_bandwidth(&root_task_group.cfs_bandwidth);
>> init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL);
>> #endif /* CONFIG_FAIR_GROUP_SCHED */
>
> I would actually like a patch reducing the #ifdef forest there, not
> adding to it.

I see :)

>
> There's no actual harm in doing the initialization mutliple times,
> right?

Yeah, it's safe to redo the init, cost some cycles but not so expensive.

Regards,
Michael Wang

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