FROMLIST: sched: Make iowait_boost optional in schedutil

We should apply the iowait boost only if cpufreq policy has iowait boost
enabled. Also make it a schedutil configuration from sysfs so it can be
turned on/off if needed (by default initialize it to the policy value).

For systems that don't need/want it enabled, such as those on arm64
based mobile devices that are battery operated, it saves energy when the
cpufreq driver policy doesn't have it enabled (details below):

Here are some results for energy measurements collected running a
YouTube video for 30 seconds:
Before: 8.042533 mWh
After: 7.948377 mWh
Energy savings is ~1.2%

Bug: 38010527
Link: https://lkml.org/lkml/2017/5/19/42
Change-Id: If124076ad0c16ade369253840dedfbf870aff927
Signed-off-by: Joel Fernandes <joelaf@google.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 6c84b4d28914..6effb44aeb30 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -33,6 +33,7 @@ struct sugov_tunables {
 	struct gov_attr_set attr_set;
 	unsigned int up_rate_limit_us;
 	unsigned int down_rate_limit_us;
+	bool iowait_boost_enable;
 };
 
 struct sugov_policy {
@@ -228,6 +229,11 @@ static void sugov_get_util(unsigned long *util, unsigned long *max, u64 time)
 static void sugov_set_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
 				   unsigned int flags)
 {
+	struct sugov_policy *sg_policy = sg_cpu->sg_policy;
+
+	if (!sg_policy->tunables->iowait_boost_enable)
+		return;
+
 	if (flags & SCHED_CPUFREQ_IOWAIT) {
 		if (sg_cpu->iowait_boost_pending)
 			return;
@@ -510,12 +516,36 @@ static ssize_t down_rate_limit_us_store(struct gov_attr_set *attr_set,
 	return count;
 }
 
+static ssize_t iowait_boost_enable_show(struct gov_attr_set *attr_set,
+					char *buf)
+{
+	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
+
+	return sprintf(buf, "%u\n", tunables->iowait_boost_enable);
+}
+
+static ssize_t iowait_boost_enable_store(struct gov_attr_set *attr_set,
+					 const char *buf, size_t count)
+{
+	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
+	bool enable;
+
+	if (kstrtobool(buf, &enable))
+		return -EINVAL;
+
+	tunables->iowait_boost_enable = enable;
+
+	return count;
+}
+
 static struct governor_attr up_rate_limit_us = __ATTR_RW(up_rate_limit_us);
 static struct governor_attr down_rate_limit_us = __ATTR_RW(down_rate_limit_us);
+static struct governor_attr iowait_boost_enable = __ATTR_RW(iowait_boost_enable);
 
 static struct attribute *sugov_attributes[] = {
 	&up_rate_limit_us.attr,
 	&down_rate_limit_us.attr,
+	&iowait_boost_enable.attr,
 	NULL
 };
 
@@ -675,6 +705,8 @@ static int sugov_init(struct cpufreq_policy *policy)
                 }
 	}
 
+	tunables->iowait_boost_enable = policy->iowait_boost_enable;
+
 	policy->governor_data = sg_policy;
 	sg_policy->tunables = tunables;