linux-kernel - [RFC PATCH 4/8] TEST: cpufreq/schedutil: iowait boost cap sysfs

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Message-Id: <20240905092645.2885200-5-christian.loehle@arm.com>
Date: Thu,  5 Sep 2024 10:26:41 +0100
From: Christian Loehle <christian.loehle@....com>
To: linux-pm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	rafael@...nel.org,
	peterz@...radead.org
Cc: juri.lelli@...hat.com,
	mingo@...hat.com,
	dietmar.eggemann@....com,
	vschneid@...hat.com,
	vincent.guittot@...aro.org,
	Johannes.Thumshirn@....com,
	adrian.hunter@...el.com,
	ulf.hansson@...aro.org,
	bvanassche@....org,
	andres@...razel.de,
	asml.silence@...il.com,
	linux-block@...r.kernel.org,
	io-uring@...r.kernel.org,
	qyousef@...alina.io,
	dsmythies@...us.net,
	axboe@...nel.dk,
	Christian Loehle <christian.loehle@....com>
Subject: [RFC PATCH 4/8] TEST: cpufreq/schedutil: iowait boost cap sysfs

Add a knob to cap applied iowait_boost per sysfs.
This is to test for potential regressions.

Signed-off-by: Christian Loehle <christian.loehle@....com>
---
 kernel/sched/cpufreq_schedutil.c | 38 ++++++++++++++++++++++++++++++++
 1 file changed, 38 insertions(+)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 7810374aaa5b..5324f07fc93a 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -11,6 +11,7 @@
 struct sugov_tunables {
 	struct gov_attr_set	attr_set;
 	unsigned int		rate_limit_us;
+	unsigned int		iowait_boost_cap;
 };
 
 struct sugov_policy {
@@ -35,6 +36,8 @@ struct sugov_policy {
 
 	bool			limits_changed;
 	bool			need_freq_update;
+
+	unsigned int		iowait_boost_cap;
 };
 
 struct sugov_cpu {
@@ -316,6 +319,9 @@ static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
 
 	sg_cpu->iowait_boost_pending = false;
 
+	if (sg_cpu->iowait_boost > sg_cpu->sg_policy->iowait_boost_cap)
+		sg_cpu->iowait_boost = sg_cpu->sg_policy->iowait_boost_cap;
+
 	/*
 	 * sg_cpu->util is already in capacity scale; convert iowait_boost
 	 * into the same scale so we can compare.
@@ -554,6 +560,14 @@ static ssize_t rate_limit_us_show(struct gov_attr_set *attr_set, char *buf)
 	return sprintf(buf, "%u\n", tunables->rate_limit_us);
 }
 
+
+static ssize_t iowait_boost_cap_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_cap);
+}
+
 static ssize_t
 rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf, size_t count)
 {
@@ -572,10 +586,30 @@ rate_limit_us_store(struct gov_attr_set *attr_set, const char *buf, size_t count
 	return count;
 }
 
+static ssize_t
+iowait_boost_cap_store(struct gov_attr_set *attr_set, const char *buf, size_t count)
+{
+	struct sugov_tunables *tunables = to_sugov_tunables(attr_set);
+	struct sugov_policy *sg_policy;
+	unsigned int iowait_boost_cap;
+
+	if (kstrtouint(buf, 10, &iowait_boost_cap))
+		return -EINVAL;
+
+	tunables->iowait_boost_cap = iowait_boost_cap;
+
+	list_for_each_entry(sg_policy, &attr_set->policy_list, tunables_hook)
+		sg_policy->iowait_boost_cap = iowait_boost_cap;
+
+	return count;
+}
+
 static struct governor_attr rate_limit_us = __ATTR_RW(rate_limit_us);
+static struct governor_attr iowait_boost_cap = __ATTR_RW(iowait_boost_cap);
 
 static struct attribute *sugov_attrs[] = {
 	&rate_limit_us.attr,
+	&iowait_boost_cap.attr,
 	NULL
 };
 ATTRIBUTE_GROUPS(sugov);
@@ -765,6 +799,8 @@ static int sugov_init(struct cpufreq_policy *policy)
 
 	tunables->rate_limit_us = cpufreq_policy_transition_delay_us(policy);
 
+	tunables->iowait_boost_cap = SCHED_CAPACITY_SCALE;
+
 	policy->governor_data = sg_policy;
 	sg_policy->tunables = tunables;
 
@@ -834,6 +870,8 @@ static int sugov_start(struct cpufreq_policy *policy)
 	sg_policy->limits_changed		= false;
 	sg_policy->cached_raw_freq		= 0;
 
+	sg_policy->iowait_boost_cap		= SCHED_CAPACITY_SCALE;
+
 	sg_policy->need_freq_update = cpufreq_driver_test_flags(CPUFREQ_NEED_UPDATE_LIMITS);
 
 	if (policy_is_shared(policy))
-- 
2.34.1