[RFC PATCH 4/4] sched/fair: call cpufreq hook for remote wakeups

From: Steve Muckle
Date: Tue Apr 19 2016 - 22:40:10 EST


Without calling the cpufreq hook for a remote wakeup it is possible
for such a wakeup to go unnoticed by cpufreq on the target CPU for up
to a full tick. This can occur if the target CPU is running a
CPU-bound task.

Signed-off-by: Steve Muckle <smuckle@xxxxxxxxxx>
---
kernel/sched/fair.c | 8 +++-----
kernel/sched/sched.h | 17 ++++++++++-------
2 files changed, 13 insertions(+), 12 deletions(-)

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index b06c1e938cb9..d21a80a44b6e 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -2826,15 +2826,13 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
struct rq *rq = rq_of(cfs_rq);
int cpu = cpu_of(rq);

- if (cpu == smp_processor_id() && &rq->cfs == cfs_rq) {
+ if (&rq->cfs == cfs_rq) {
unsigned long max = rq->cpu_capacity_orig;

/*
* There are a few boundary cases this might miss but it should
* get called often enough that that should (hopefully) not be
- * a real problem -- added to that it only calls on the local
- * CPU, so if we enqueue remotely we'll miss an update, but
- * the next tick/schedule should update.
+ * a real problem.
*
* It will not get called when we go idle, because the idle
* thread is a different class (!fair), nor will the utilization
@@ -2845,7 +2843,7 @@ static inline void cfs_rq_util_change(struct cfs_rq *cfs_rq)
*
* See cpu_util().
*/
- cpufreq_update_util(rq_clock(rq),
+ cpufreq_update_util(cpu, rq_clock(rq),
min(cfs_rq->avg.util_avg, max), max);
}
}
diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
index 921d6e5d33b7..a8a1eb603263 100644
--- a/kernel/sched/sched.h
+++ b/kernel/sched/sched.h
@@ -1799,6 +1799,7 @@ DECLARE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);

/**
* cpufreq_update_util - Take a note about CPU utilization changes.
+ * @cpu: Target CPU.
* @time: Current time.
* @util: Current utilization.
* @max: Utilization ceiling.
@@ -1808,13 +1809,14 @@ DECLARE_PER_CPU(struct update_util_data *, cpufreq_update_util_data);
*
* It can only be called from RCU-sched read-side critical sections.
*/
-static inline void cpufreq_update_util(u64 time, unsigned long util, unsigned long max)
+static inline void cpufreq_update_util(int cpu, u64 time, unsigned long util,
+ unsigned long max)
{
- struct update_util_data *data;
+ struct update_util_data *data;

- data = rcu_dereference_sched(*this_cpu_ptr(&cpufreq_update_util_data));
- if (data)
- data->func(data, time, util, max);
+ data = rcu_dereference_sched(per_cpu(cpufreq_update_util_data, cpu));
+ if (data)
+ data->func(data, time, util, max);
}

/**
@@ -1835,10 +1837,11 @@ static inline void cpufreq_update_util(u64 time, unsigned long util, unsigned lo
*/
static inline void cpufreq_trigger_update(u64 time)
{
- cpufreq_update_util(time, ULONG_MAX, 0);
+ cpufreq_update_util(smp_processor_id(), time, ULONG_MAX, 0);
}
#else
-static inline void cpufreq_update_util(u64 time, unsigned long util, unsigned long max) {}
+static inline void cpufreq_update_util(int cpu, u64 time, unsigned long util,
+ unsigned long max) {}
static inline void cpufreq_trigger_update(u64 time) {}
#endif /* CONFIG_CPU_FREQ */

--
2.4.10