[PATCH 2/5] sched/deadline: Remove cpu_active_mask from cpudl_find()

Xunlei Pang
2015-01-19T04:51:58Z

cpu_active_mask is rarely changeable, so remove this operation
to gain a little performance.

If there is a change in cpu_active_mask, rq_online_dl() and
rq_offline_dl() should take care of it normally, so cpudl::
free_cpus carries enough information for us.

For the rare case(causing a task put onto a dying cpu) which
rq_offline_dl() can't handle timely, then it can be handled
through _cpu_down()->...->multi_cpu_stop()->migration_call()
->migrate_tasks(), preventing the task from hanging on the
dead cpu.

Signed-off-by: Xunlei Pang <pang.xunlei@linaro.org>
---
kernel/sched/cpudeadline.c | 3 +--
1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/kernel/sched/cpudeadline.c b/kernel/sched/cpudeadline.c
index fd9d3fb..c6acb07 100644
--- a/kernel/sched/cpudeadline.c
+++ b/kernel/sched/cpudeadline.c
@@ -108,8 +108,7 @@ int cpudl_find(struct cpudl *cp, struct task_struct *p,
const struct sched_dl_entity *dl_se = &p->dl;

if (later_mask &&
- cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed) &&
- cpumask_and(later_mask, later_mask, cpu_active_mask)) {
+ cpumask_and(later_mask, cp->free_cpus, &p->cpus_allowed)) {
best_cpu = cpumask_any(later_mask);
goto out;
} else if (cpumask_test_cpu(cpudl_maximum(cp), &p->cpus_allowed) &&
--
1.9.1