linux-kernel - Re: [PATCH RESEND v2] sched/deadline: do not try to push tasks if pinned task switches to dl

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Date:	Tue, 21 Oct 2014 20:14:08 +0800
From:	Wanpeng Li <kernellwp@...il.com>
To:	Juri Lelli <juri.lelli@....com>,
	Wanpeng Li <wanpeng.li@...ux.intel.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
CC:	Kirill V Tkhai <tkhai@...dex.ru>,
	Steven Rostedt <rostedt@...dmis.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH RESEND v2] sched/deadline: do not try to push tasks if
 pinned task switches to dl


于 10/21/14, 6:11 PM, Juri Lelli 写道:
> Hi,
>
> On 11/10/14 01:58, Wanpeng Li wrote:
>> As Kirill mentioned(https://lkml.org/lkml/2013/1/29/118):
>> | If rq has already had 2 or more pushable tasks and we try to add a
>> | pinned task then call of push_rt_task will just waste a time.
>>
>> Just switched pinned task is not able to be pushed. If the rq had had
>                                                                   ^
>                                                                  has
>> several dl tasks before they have already been considered as candidates
>> to be pushed (or pulled). This patch done the same behavior as rt class
>                                          ^
>                                      implements? aligns to...
>
>> which introduced by commit 10447917551e ("sched/rt: Do not try to push
>> tasks if pinned task switches to RT").
>>
>> Signed-off-by: Wanpeng Li <wanpeng.li@...ux.intel.com>
>> ---
>> v1 -> v2:
>>   * use 12 or more chars for the git commit ID
>>
>>   kernel/sched/deadline.c | 3 ++-
>>   1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
>> index abfaf3d..cf7c9b6 100644
>> --- a/kernel/sched/deadline.c
>> +++ b/kernel/sched/deadline.c
>> @@ -1603,7 +1603,8 @@ static void switched_to_dl(struct rq *rq, struct task_struct *p)
>>   
>>   	if (task_on_rq_queued(p) && rq->curr != p) {
>>   #ifdef CONFIG_SMP
>> -		if (rq->dl.overloaded && push_dl_task(rq) && rq != task_rq(p))
>> +		if (p->nr_cpus_allowed > 1 && rq->dl.overloaded
>> +				&& push_dl_task(rq) && rq != task_rq(p))
> I'd personally align this && to p->nr_cpus_allowed, but that's just my
> personal taste, though. :)

Ah, ok, I will send out a newer version tomorrow. ;-)

Regards,
Wanpeng Li

>
>>   			/* Only reschedule if pushing failed */
>>   			check_resched = 0;
>>   #endif /* CONFIG_SMP */
>>
> Anyway, the change looks good, thanks!
>
> Best,
>
> - Juri
>
> --
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