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Message-ID: <FA4A95BE-596A-4550-BB28-959938D19729@tencent.com>
Date: Tue, 11 Aug 2020 23:18:21 +0000
From: benbjiang(蒋彪)
<benbjiang@...cent.com>
To: Dietmar Eggemann <dietmar.eggemann@....com>
CC: Jiang Biao <benbjiang@...il.com>,
"mingo@...hat.com" <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>,
"juri.lelli@...hat.com" <juri.lelli@...hat.com>,
"vincent.guittot@...aro.org" <vincent.guittot@...aro.org>,
"rostedt@...dmis.org" <rostedt@...dmis.org>,
"bsegall@...gle.com" <bsegall@...gle.com>,
"mgorman@...e.de" <mgorman@...e.de>,
LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] sched/fair: Optimize dequeue_task_fair()(Internet mail)
Hi,
> On Aug 12, 2020, at 12:55 AM, Dietmar Eggemann <dietmar.eggemann@....com> wrote:
>
> On 11/08/2020 10:43, Jiang Biao wrote:
>> Similar optimization as what has been done in commit,
>> 7d148be69e3a(sched/fair: Optimize enqueue_task_fair())
>>
>> dequeue_task_fair jumps to dequeue_throttle label when cfs_rq_of(se) is
>> throttled which means that se can't be NULL. We can move the label after
>> the if (!se) statement and remove the if(!se) statment as se is always
>> NULL when reaching this point.
>>
>> Besides, trying to keep the same pattern with enqueue_task_fair can make
>> it more readable.
>>
>> Signed-off-by: Jiang Biao <benbjiang@...cent.com>
>> ---
>> kernel/sched/fair.c | 6 +++---
>> 1 file changed, 3 insertions(+), 3 deletions(-)
>>
>> diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
>> index 04fa8dbcfa4d..cbbeafdfa8b7 100644
>> --- a/kernel/sched/fair.c
>> +++ b/kernel/sched/fair.c
>> @@ -5618,10 +5618,10 @@ static void dequeue_task_fair(struct rq *rq, struct task_struct *p, int flags)
>>
>> }
>>
>> -dequeue_throttle:
>> - if (!se)
>> - sub_nr_running(rq, 1);
>> + /* At this point se is NULL and we are at root level*/
>> + sub_nr_running(rq, 1);
>>
>> +dequeue_throttle:
>> /* balance early to pull high priority tasks */
>> if (unlikely(!was_sched_idle && sched_idle_rq(rq)))
>> rq->next_balance = jiffies;
>
> There is already a similar patch in master.
>
> 423d02e1463b - sched/fair: Optimize dequeue_task_fair() (2020-06-25 Peng
> Wang)
Indeed, my local repo has been outdated, sorry for the interruption. :)
Thx.
Regards,
Jiang
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