linux-kernel - [RFC PATCH 3/8] TEST: cpufreq/schedutil: Linear iowait boost step

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Message-Id: <20240905092645.2885200-4-christian.loehle@arm.com>
Date: Thu,  5 Sep 2024 10:26:40 +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 3/8] TEST: cpufreq/schedutil: Linear iowait boost step

In preparation for capping iowait boost make the steps linear as
opposed to doubling.

Signed-off-by: Christian Loehle <christian.loehle@....com>
---
 kernel/sched/cpufreq_schedutil.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index eece6244f9d2..7810374aaa5b 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -267,7 +267,8 @@ static void sugov_iowait_boost(struct sugov_cpu *sg_cpu, u64 time,
 	/* Double the boost at each request */
 	if (sg_cpu->iowait_boost) {
 		sg_cpu->iowait_boost =
-			min_t(unsigned int, sg_cpu->iowait_boost << 1, SCHED_CAPACITY_SCALE);
+			min_t(unsigned int,
+			      sg_cpu->iowait_boost + IOWAIT_BOOST_MIN, SCHED_CAPACITY_SCALE);
 		return;
 	}
 
@@ -308,11 +309,9 @@ static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
 		/*
 		 * No boost pending; reduce the boost value.
 		 */
-		sg_cpu->iowait_boost >>= 1;
-		if (sg_cpu->iowait_boost < IOWAIT_BOOST_MIN) {
-			sg_cpu->iowait_boost = 0;
+		sg_cpu->iowait_boost -= IOWAIT_BOOST_MIN;
+		if (!sg_cpu->iowait_boost)
 			return 0;
-		}
 	}
 
 	sg_cpu->iowait_boost_pending = false;
-- 
2.34.1