linux-kernel - Re: [PATCH 06/16] sched: SCHED

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Date:	Wed, 11 Apr 2012 18:24:06 +0200
From:	Juri Lelli <juri.lelli@...il.com>
To:	Steven Rostedt <rostedt@...dmis.org>
CC:	peterz@...radead.org, tglx@...utronix.de, mingo@...hat.com,
	oleg@...hat.com, fweisbec@...il.com, darren@...art.com,
	johan.eker@...csson.com, p.faure@...tech.ch,
	linux-kernel@...r.kernel.org, claudio@...dence.eu.com,
	michael@...rulasolutions.com, fchecconi@...il.com,
	tommaso.cucinotta@...up.it, nicola.manica@...i.unitn.it,
	luca.abeni@...tn.it, dhaval.giani@...il.com, hgu1972@...il.com,
	paulmck@...ux.vnet.ibm.com, raistlin@...ux.it,
	insop.song@...csson.com, liming.wang@...driver.com
Subject: Re: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic

On 04/11/2012 06:21 PM, Steven Rostedt wrote:
> On Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:
>
>>   /*
>>    * Only called when both the current and waking task are -deadline
>>    * tasks.
>> @@ -487,8 +819,20 @@ static void yield_task_dl(struct rq *rq)
>>   static void check_preempt_curr_dl(struct rq *rq, struct task_struct *p,
>>   				  int flags)
>>   {
>> -	if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline))
>> +	if (dl_time_before(p->dl.deadline, rq->curr->dl.deadline)) {
>>   		resched_task(rq->curr);
>> +		return;
>> +	}
>> +
>> +#ifdef CONFIG_SMP
>> +	/*
>> +	 * In the unlikely case current and p have the same deadline
>> +	 * let us try to decide what's the best thing to do...
>> +	 */
>> +	if ((s64)(p->dl.deadline - rq->curr->dl.deadline) == 0&&
>> +	    !need_resched())
>
> OK, maybe I'm thick. But how is:
>
>    (s64)(p->dl.deadline - rq->curr->dl.deadline) == 0
>
> Better than:
>
>    p->dl.deadline == rq->curr->dl.deadline
>
> ?
>

I agree, will change.

>
>> +		check_preempt_equal_dl(rq, p);
>> +#endif /* CONFIG_SMP */
>>   }
>>
>
>


Thanks,

- Juri
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