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Subject[PATCH] sched/fair: Rearrange select_task_rq_fair() to optimize it
Date
Rearrange select_task_rq_fair() a bit to avoid executing some
conditional statements in few specific code-paths. That gets rid of the
goto as well.

This shouldn't result in any functional changes.

Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
kernel/sched/fair.c | 24 +++++++++---------------
1 file changed, 9 insertions(+), 15 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 54dc31e7ab9b..cacee15076a4 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -6636,6 +6636,7 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
*/
if (want_affine && (tmp->flags & SD_WAKE_AFFINE) &&
cpumask_test_cpu(prev_cpu, sched_domain_span(tmp))) {
+ sd = NULL; /* Prefer wake_affine over balance flags */
affine_sd = tmp;
break;
}
@@ -6646,33 +6647,26 @@ select_task_rq_fair(struct task_struct *p, int prev_cpu, int sd_flag, int wake_f
break;
}

- if (affine_sd) {
- sd = NULL; /* Prefer wake_affine over balance flags */
- if (cpu == prev_cpu)
- goto pick_cpu;
-
- new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);
- }
-
- if (sd && !(sd_flag & SD_BALANCE_FORK)) {
+ if (sd) {
/*
* We're going to need the task's util for capacity_spare_wake
* in find_idlest_group. Sync it up to prev_cpu's
* last_update_time.
*/
- sync_entity_load_avg(&p->se);
- }
+ if (!(sd_flag & SD_BALANCE_FORK))
+ sync_entity_load_avg(&p->se);
+
+ new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
+ } else {
+ if (affine_sd && cpu != prev_cpu)
+ new_cpu = wake_affine(affine_sd, p, cpu, prev_cpu, sync);

- if (!sd) {
-pick_cpu:
if (sd_flag & SD_BALANCE_WAKE) { /* XXX always ? */
new_cpu = select_idle_sibling(p, prev_cpu, new_cpu);

if (want_affine)
current->recent_used_cpu = cpu;
}
- } else {
- new_cpu = find_idlest_cpu(sd, p, cpu, prev_cpu, sd_flag);
}
rcu_read_unlock();

--
2.15.0.194.g9af6a3dea062
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