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

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Message-ID: <1334160884.23924.260.camel@gandalf.stny.rr.com>
Date:	Wed, 11 Apr 2012 12:14:44 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Juri Lelli <juri.lelli@...il.com>
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 Fri, 2012-04-06 at 09:14 +0200, Juri Lelli wrote:

> +static int latest_cpu_find(struct cpumask *span,
> +			   struct task_struct *task,
> +			   struct cpumask *later_mask)
>  {
> +	const struct sched_dl_entity *dl_se = &task->dl;
> +	int cpu, found = -1, best = 0;
> +	u64 max_dl = 0;
> +
> +	for_each_cpu(cpu, span) {
> +		struct rq *rq = cpu_rq(cpu);
> +		struct dl_rq *dl_rq = &rq->dl;
> +
> +		if (cpumask_test_cpu(cpu, &task->cpus_allowed) &&
> +		    (!dl_rq->dl_nr_running || dl_time_before(dl_se->deadline,
> +		     dl_rq->earliest_dl.curr))) {
> +			if (later_mask)
> +				cpumask_set_cpu(cpu, later_mask);
> +			if (!best && !dl_rq->dl_nr_running) {

I hate to say this (and I also have yet to look at the patches after
this) but we should really take into account the RT tasks. It would suck
to preempt a normal RT task when a non RT task is running on another
CPU.

-- Steve

> +				best = 1;
> +				found = cpu;
> +			} else if (!best &&
> +				   dl_time_before(max_dl,
> +						  dl_rq->earliest_dl.curr)) {
> +				max_dl = dl_rq->earliest_dl.curr;
> +				found = cpu;
> +			}
> +		} else if (later_mask)
> +			cpumask_clear_cpu(cpu, later_mask);
> +	}
> +
> +	return found;
> +}


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