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Message-ID: <5a3342ef-f14f-173c-630f-6b474bded257@linux.dev>
Date: Mon, 9 Oct 2023 19:13:18 +0800
From: Yajun Deng <yajun.deng@...ux.dev>
To: Ingo Molnar <mingo@...nel.org>
Cc: mingo@...hat.com, peterz@...radead.org, juri.lelli@...hat.com,
vincent.guittot@...aro.org, dietmar.eggemann@....com,
rostedt@...dmis.org, bsegall@...gle.com, mgorman@...e.de,
bristot@...hat.com, vschneid@...hat.com,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] sched/rt: Move sched_rt_entity::back to under the
CONFIG_RT_GROUP_SCHED block
On 2023/10/9 18:16, Ingo Molnar wrote:
> * Yajun Deng <yajun.deng@...ux.dev> wrote:
>
>> The member back in struct sched_rt_entity only related to RT_GROUP_SCHED,
>> So move sched_rt_entity::back to under the CONFIG_RT_GROUP_SCHED block. It
>> will save a few bytes.
>>
>> Also, init child when parent isn't NULL in init_tg_rt_entry().
>>
>> Signed-off-by: Yajun Deng <yajun.deng@...ux.dev>
>> ---
>> include/linux/sched.h | 2 +-
>> kernel/sched/rt.c | 18 +++++++++---------
>> 2 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 292c31697248..d0fe56603e60 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -597,8 +597,8 @@ struct sched_rt_entity {
>> unsigned short on_rq;
>> unsigned short on_list;
>>
>> - struct sched_rt_entity *back;
>> #ifdef CONFIG_RT_GROUP_SCHED
>> + struct sched_rt_entity *back;
>> struct sched_rt_entity *parent;
>> /* rq on which this entity is (to be) queued: */
>> struct rt_rq *rt_rq;
> Title claims this change - the rest of the changes should be in a separate
> patch:
Okay. I will send v2.
>> diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
>> index 642edbd24ffb..7b3105b875f1 100644
>> --- a/kernel/sched/rt.c
>> +++ b/kernel/sched/rt.c
>> @@ -233,8 +233,10 @@ void init_tg_rt_entry(struct task_group *tg, struct rt_rq *rt_rq,
>>
>> if (!parent)
>> rt_se->rt_rq = &rq->rt;
>> - else
>> + else {
>> rt_se->rt_rq = parent->my_q;
>> + parent->back = rt_se;
>> + }
>>
>> rt_se->my_q = rt_rq;
>> rt_se->parent = parent;
>> @@ -1441,23 +1443,21 @@ static void __dequeue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flag
>> */
>> static void dequeue_rt_stack(struct sched_rt_entity *rt_se, unsigned int flags)
>> {
>> - struct sched_rt_entity *back = NULL;
>> + struct sched_rt_entity *root = NULL;
>> unsigned int rt_nr_running;
>>
>> - for_each_sched_rt_entity(rt_se) {
>> - rt_se->back = back;
>> - back = rt_se;
>> - }
>> + for_each_sched_rt_entity(rt_se)
>> + root = rt_se;
>>
>> - rt_nr_running = rt_rq_of_se(back)->rt_nr_running;
>> + rt_nr_running = rt_rq_of_se(root)->rt_nr_running;
>>
>> - rt_se = back;
>> + rt_se = root;
>> for_each_sched_rt_entity_back(rt_se) {
>> if (on_rt_rq(rt_se))
>> __dequeue_rt_entity(rt_se, flags);
>> }
>>
>> - dequeue_top_rt_rq(rt_rq_of_se(back), rt_nr_running);
>> + dequeue_top_rt_rq(rt_rq_of_se(root), rt_nr_running);
>> }
>>
>> static void enqueue_rt_entity(struct sched_rt_entity *rt_se, unsigned int flags)
>> --
>> 2.25.1
> Thanks,
>
> Ingo
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