A more readable version, with a few differences: - don't check against the root domain, but instead check SD_LOAD_BALANCE - don't re-iterate the cpus already iterated on the previous SD - use rcu_read_lock() around the sd iteration Signed-off-by: Peter Zijlstra Signed-off-by: Dinakar Guniguntala --- kernel/sched_fair.c | 45 +++++++++++++++++++++++++-------------------- 1 file changed, 25 insertions(+), 20 deletions(-) Index: linux-2.6.31.4-rt14-lb1/kernel/sched_fair.c =================================================================== --- linux-2.6.31.4-rt14-lb1.orig/kernel/sched_fair.c 2009-10-21 10:49:01.000000000 -0400 +++ linux-2.6.31.4-rt14-lb1/kernel/sched_fair.c 2009-10-21 10:49:02.000000000 -0400 @@ -1080,14 +1080,13 @@ * not idle and an idle cpu is available. The span of cpus to * search starts with cpus closest then further out as needed, * so we always favor a closer, idle cpu. - * Domains may include CPUs that are not usable for migration, - * hence we need to mask them out (cpu_active_mask) * * Returns the CPU we should wake onto. */ static int wake_idle(int cpu, struct task_struct *p) { - struct sched_domain *sd; + struct rq *task_rq = task_rq(p); + struct sched_domain *sd, *child = NULL; int i; i = wake_idle_power_save(cpu, p); @@ -1106,24 +1105,34 @@ if (idle_cpu(cpu) || cpu_rq(cpu)->cfs.nr_running > 1) return cpu; - for_each_domain(cpu, sd) { - if ((sd->flags & SD_WAKE_IDLE) - || ((sd->flags & SD_WAKE_IDLE_FAR) - && !task_hot(p, task_rq(p)->clock, sd))) { - for_each_cpu_and(i, sched_domain_span(sd), - &p->cpus_allowed) { - if (cpu_active(i) && idle_cpu(i)) { - if (i != task_cpu(p)) { - schedstat_inc(p, - se.nr_wakeups_idle); - } - return i; - } - } - } else { + rcu_read_lock(); + for_each_domain(cpu, sd) { + if (!(sd->flags & SD_LOAD_BALANCE)) + break; + + if (!(sd->flags & SD_WAKE_IDLE) && + (task_hot(p, task_rq->clock, sd) || !(sd->flags & SD_WAKE_IDLE_FAR))) break; - } - } + + for_each_cpu_and(i, sched_domain_span(sd), &p->cpus_allowed) { + if (child && cpumask_test_cpu(i, sched_domain_span(child))) + continue; + + if (!idle_cpu(i)) + continue; + + if (task_cpu(p) != i) + schedstat_inc(p, se.nr_wakeups_idle); + + cpu = i; + goto unlock; + } + + child = sd; + } +unlock: + rcu_read_unlock(); + return cpu; } #else /* !ARCH_HAS_SCHED_WAKE_IDLE*/ -- -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/