[RFCv5 PATCH 46/46] sched/fair: cpufreq_sched triggers for load balancing

Morten Rasmussen
2015-07-07T18:50:07Z

From: Juri Lelli <juri.lelli@arm.com>

As we don't trigger freq changes from {en,de}queue_task_fair() during load
balancing, we need to do explicitly so on load balancing paths.

cc: Ingo Molnar <mingo@redhat.com>
cc: Peter Zijlstra <peterz@infradead.org>

Signed-off-by: Juri Lelli <juri.lelli@arm.com>
---
kernel/sched/fair.c | 64 +++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 62 insertions(+), 2 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index c2d6de4..c513b19 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -7741,6 +7741,20 @@ static int load_balance(int this_cpu, struct rq *this_rq,
* ld_moved - cumulative load moved across iterations
*/
cur_ld_moved = detach_tasks(&env);
+ /*
+ * We want to potentially update env.src_cpu's OPP.
+ *
+ * Add a margin (same ~20% used for the tipping point)
+ * to our request to provide some head room for the remaining
+ * tasks.
+ */
+ if (sched_energy_freq() && cur_ld_moved) {
+ unsigned long req_cap = get_cpu_usage(env.src_cpu);
+
+ req_cap = req_cap * capacity_margin
+ >> SCHED_CAPACITY_SHIFT;
+ cpufreq_sched_set_cap(env.src_cpu, req_cap);
+ }

/*
* We've detached some tasks from busiest_rq. Every
@@ -7755,6 +7769,21 @@ static int load_balance(int this_cpu, struct rq *this_rq,
if (cur_ld_moved) {
attach_tasks(&env);
ld_moved += cur_ld_moved;
+ /*
+ * We want to potentially update env.dst_cpu's OPP.
+ *
+ * Add a margin (same ~20% used for the tipping point)
+ * to our request to provide some head room if p's
+ * utilization further increases.
+ */
+ if (sched_energy_freq()) {
+ unsigned long req_cap =
+ get_cpu_usage(env.dst_cpu);
+
+ req_cap = req_cap * capacity_margin
+ >> SCHED_CAPACITY_SHIFT;
+ cpufreq_sched_set_cap(env.dst_cpu, req_cap);
+ }
}

local_irq_restore(flags);
@@ -8114,8 +8143,24 @@ static int active_load_balance_cpu_stop(void *data)
schedstat_inc(sd, alb_count);

p = detach_one_task(&env);
- if (p)
+ if (p) {
schedstat_inc(sd, alb_pushed);
+ /*
+ * We want to potentially update env.src_cpu's OPP.
+ *
+ * Add a margin (same ~20% used for the tipping point)
+ * to our request to provide some head room for the
+ * remaining task.
+ */
+ if (sched_energy_freq()) {
+ unsigned long req_cap =
+ get_cpu_usage(env.src_cpu);
+
+ req_cap = req_cap * capacity_margin
+ >> SCHED_CAPACITY_SHIFT;
+ cpufreq_sched_set_cap(env.src_cpu, req_cap);
+ }
+ }
else
schedstat_inc(sd, alb_failed);
}
@@ -8124,8 +8169,23 @@ static int active_load_balance_cpu_stop(void *data)
busiest_rq->active_balance = 0;
raw_spin_unlock(&busiest_rq->lock);

- if (p)
+ if (p) {
attach_one_task(target_rq, p);
+ /*
+ * We want to potentially update target_cpu's OPP.
+ *
+ * Add a margin (same ~20% used for the tipping point)
+ * to our request to provide some head room if p's utilization
+ * further increases.
+ */
+ if (sched_energy_freq()) {
+ unsigned long req_cap = get_cpu_usage(target_cpu);
+
+ req_cap = req_cap * capacity_margin
+ >> SCHED_CAPACITY_SHIFT;
+ cpufreq_sched_set_cap(target_cpu, req_cap);
+ }
+ }

local_irq_enable();

--
1.9.1