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Date: Fri, 11 Nov 2016 15:52:22 +0530
From: Viresh Kumar <viresh.kumar@...aro.org>
To: Rafael Wysocki <rjw@...ysocki.net>, Ingo Molnar <mingo@...hat.com>,
Peter Zijlstra <peterz@...radead.org>
Cc: linaro-kernel@...ts.linaro.org, linux-pm@...r.kernel.org,
linux-kernel@...r.kernel.org,
Vincent Guittot <vincent.guittot@...aro.org>,
Juri Lelli <Juri.Lelli@....com>,
Robin Randhawa <robin.randhawa@....com>,
Viresh Kumar <viresh.kumar@...aro.org>,
Steve Muckle <smuckle.linux@...il.com>
Subject: [PATCH 2/3] cpufreq: schedutil: move slow path from workqueue to SCHED_FIFO task
If slow path frequency changes are conducted in a SCHED_OTHER context
then they may be delayed for some amount of time, including
indefinitely, when real time or deadline activity is taking place.
Move the slow path to a real time kernel thread. In the future the
thread should be made SCHED_DEADLINE. The RT priority is arbitrarily set
to 50 for now.
Hackbench results on ARM Exynos, dual core A15 platform for 10
iterations:
$ hackbench -s 100 -l 100 -g 10 -f 20
Before After
---------------------------------
1.808 1.603
1.847 1.251
2.229 1.590
1.952 1.600
1.947 1.257
1.925 1.627
2.694 1.620
1.258 1.621
1.919 1.632
1.250 1.240
Average:
1.8829 1.5041
Based on initial work by Steve Muckle.
Signed-off-by: Steve Muckle <smuckle.linux@...il.com>
Signed-off-by: Viresh Kumar <viresh.kumar@...aro.org>
---
kernel/sched/cpufreq_schedutil.c | 62 ++++++++++++++++++++++++++++++++--------
1 file changed, 50 insertions(+), 12 deletions(-)
diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index ccb2ab89affb..045ce0a4e6d1 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -12,6 +12,7 @@
#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
#include <linux/cpufreq.h>
+#include <linux/kthread.h>
#include <linux/slab.h>
#include <trace/events/power.h>
@@ -35,8 +36,10 @@ struct sugov_policy {
/* The next fields are only needed if fast switch cannot be used. */
struct irq_work irq_work;
- struct work_struct work;
+ struct kthread_work work;
struct mutex work_lock;
+ struct kthread_worker worker;
+ struct task_struct *thread;
bool work_in_progress;
bool need_freq_update;
@@ -291,9 +294,10 @@ static void sugov_update_shared(struct update_util_data *hook, u64 time,
raw_spin_unlock(&sg_policy->update_lock);
}
-static void sugov_work(struct work_struct *work)
+static void sugov_work(struct kthread_work *work)
{
- struct sugov_policy *sg_policy = container_of(work, struct sugov_policy, work);
+ struct sugov_policy *sg_policy =
+ container_of(work, struct sugov_policy, work);
mutex_lock(&sg_policy->work_lock);
__cpufreq_driver_target(sg_policy->policy, sg_policy->next_freq,
@@ -308,7 +312,7 @@ static void sugov_irq_work(struct irq_work *irq_work)
struct sugov_policy *sg_policy;
sg_policy = container_of(irq_work, struct sugov_policy, irq_work);
- schedule_work_on(smp_processor_id(), &sg_policy->work);
+ kthread_queue_work(&sg_policy->worker, &sg_policy->work);
}
/************************** sysfs interface ************************/
@@ -362,9 +366,23 @@ static struct kobj_type sugov_tunables_ktype = {
static struct cpufreq_governor schedutil_gov;
+static void sugov_policy_free(struct sugov_policy *sg_policy)
+{
+ if (!sg_policy->policy->fast_switch_enabled) {
+ kthread_flush_worker(&sg_policy->worker);
+ kthread_stop(sg_policy->thread);
+ }
+
+ mutex_destroy(&sg_policy->work_lock);
+ kfree(sg_policy);
+}
+
static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
{
struct sugov_policy *sg_policy;
+ struct task_struct *thread;
+ struct sched_param param = { .sched_priority = 50 };
+ int ret;
sg_policy = kzalloc(sizeof(*sg_policy), GFP_KERNEL);
if (!sg_policy)
@@ -372,16 +390,36 @@ static struct sugov_policy *sugov_policy_alloc(struct cpufreq_policy *policy)
sg_policy->policy = policy;
init_irq_work(&sg_policy->irq_work, sugov_irq_work);
- INIT_WORK(&sg_policy->work, sugov_work);
mutex_init(&sg_policy->work_lock);
raw_spin_lock_init(&sg_policy->update_lock);
- return sg_policy;
-}
-static void sugov_policy_free(struct sugov_policy *sg_policy)
-{
- mutex_destroy(&sg_policy->work_lock);
- kfree(sg_policy);
+ /* kthread only required for slow path */
+ if (policy->fast_switch_enabled)
+ return sg_policy;
+
+ kthread_init_work(&sg_policy->work, sugov_work);
+ kthread_init_worker(&sg_policy->worker);
+ thread = kthread_create(kthread_worker_fn, &sg_policy->worker,
+ "sugov:%d", cpumask_first(policy->related_cpus));
+ if (IS_ERR(thread)) {
+ mutex_destroy(&sg_policy->work_lock);
+ kfree(sg_policy);
+ pr_err("failed to create sugov thread: %ld\n", PTR_ERR(thread));
+ return NULL;
+ }
+ sg_policy->thread = thread;
+
+ ret = sched_setscheduler_nocheck(thread, SCHED_FIFO, ¶m);
+ if (ret) {
+ sugov_policy_free(sg_policy);
+ pr_warn("%s: failed to set SCHED_FIFO\n", __func__);
+ return NULL;
+ }
+
+ kthread_bind_mask(thread, policy->related_cpus);
+ wake_up_process(thread);
+
+ return sg_policy;
}
static struct sugov_tunables *sugov_tunables_alloc(struct sugov_policy *sg_policy)
@@ -541,7 +579,7 @@ static void sugov_stop(struct cpufreq_policy *policy)
synchronize_sched();
irq_work_sync(&sg_policy->irq_work);
- cancel_work_sync(&sg_policy->work);
+ kthread_cancel_work_sync(&sg_policy->work);
}
static void sugov_limits(struct cpufreq_policy *policy)
--
2.7.1.410.g6faf27b
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