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Commit a50bde51 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

sched: Cleanup select_task_rq_fair() 



Clean up the new affine to idle sibling bits while trying to
grok them. Should not have any function differences.

Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20091112145610.832503781@chello.nl>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 761b1d26

kernel/sched_fair.c

+51 −22
Original line number Diff line number Diff line
@@ -1318,6 +1318,41 @@ find_idlest_cpu(struct sched_group *group, struct task_struct *p, int this_cpu) 
	return idlest;

}



/*

 * Try and locate an idle CPU in the sched_domain.

 */

static int

select_idle_sibling(struct task_struct *p, struct sched_domain *sd, int target)

{

	int cpu = smp_processor_id();

	int prev_cpu = task_cpu(p);

	int i;



	/*

	 * If this domain spans both cpu and prev_cpu (see the SD_WAKE_AFFINE

	 * test in select_task_rq_fair) and the prev_cpu is idle then that's

	 * always a better target than the current cpu.

	 */

	if (target == cpu) {

		if (!cpu_rq(prev_cpu)->cfs.nr_running)

			target = prev_cpu;

	}



	/*

	 * Otherwise, iterate the domain and find an elegible idle cpu.

	 */

	if (target == -1 || target == cpu) {

		for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) {

			if (!cpu_rq(i)->cfs.nr_running) {

				target = i;

				break;

			}

		}

	}



	return target;

}



/*

 * sched_balance_self: balance the current task (running on cpu) in domains

 * that have the 'flag' flag set. In practice, this is SD_BALANCE_FORK and
@@ -1373,36 +1408,30 @@ static int select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flag 
		}



		if (want_affine && (tmp->flags & SD_WAKE_AFFINE)) {

			int candidate = -1, i;

			int target = -1;



			/*

			 * If both cpu and prev_cpu are part of this domain,

			 * cpu is a valid SD_WAKE_AFFINE target.

			 */

			if (cpumask_test_cpu(prev_cpu, sched_domain_span(tmp)))

				candidate = cpu;

				target = cpu;



			/*

			 * Check for an idle shared cache.

			 * If there's an idle sibling in this domain, make that

			 * the wake_affine target instead of the current cpu.

			 *

			 * XXX: should we possibly do this outside of

			 * WAKE_AFFINE, in case the shared cache domain is

			 * smaller than the WAKE_AFFINE domain?

			 */

			if (tmp->flags & SD_PREFER_SIBLING) {

				if (candidate == cpu) {

					if (!cpu_rq(prev_cpu)->cfs.nr_running)

						candidate = prev_cpu;

				}



				if (candidate == -1 || candidate == cpu) {

					for_each_cpu(i, sched_domain_span(tmp)) {

						if (!cpumask_test_cpu(i, &p->cpus_allowed))

							continue;

						if (!cpu_rq(i)->cfs.nr_running) {

							candidate = i;

							break;

						}

					}

				}

			}

			if (tmp->flags & SD_PREFER_SIBLING)

				target = select_idle_sibling(p, tmp, target);



			if (candidate >= 0) {

			if (target >= 0) {

				affine_sd = tmp;

				want_affine = 0;

				cpu = candidate;

				cpu = target;

			}

		}