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SubjectRe: [PATCH 06/16] sched: SCHED_DEADLINE push and pull logic
On 04/11/2012 06:14 PM, Steven Rostedt wrote:
> 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.

Well, this changes in 15/16, but your point remains, and I see it :-).
We are currently reworking the push/pull mechanism (15/16 will most probably
change as well) to speed it up. I agree that it would be nice to take into
accont RT tasks as well, so we'll surely think about it.

>> + 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;
>> +}
>
>

Thanks,

- Juri


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