Received-SPF: pass (google.com: domain of linux-kernel+bounces-165429-linux.lists.archive=gmail.com@vger.kernel.org designates 147.75.199.223 as permitted sender) client-ip=147.75.199.223;
Sender: Tejun Heo <htejun@gmail.com>
From: Tejun Heo <tj@kernel.org>
To: torvalds@linux-foundation.org,
	mingo@redhat.com,
	peterz@infradead.org,
	juri.lelli@redhat.com,
	vincent.guittot@linaro.org,
	dietmar.eggemann@arm.com,
	rostedt@goodmis.org,
	bsegall@google.com,
	mgorman@suse.de,
	bristot@redhat.com,
	vschneid@redhat.com,
	ast@kernel.org,
	daniel@iogearbox.net,
	andrii@kernel.org,
	martin.lau@kernel.org,
	joshdon@google.com,
	brho@google.com,
	pjt@google.com,
	derkling@google.com,
	haoluo@google.com,
	dvernet@meta.com,
	dschatzberg@meta.com,
	dskarlat@cs.cmu.edu,
	riel@surriel.com,
	changwoo@igalia.com,
	himadrics@inria.fr,
	memxor@gmail.com,
	andrea.righi@canonical.com,
	joel@joelfernandes.org
Cc: linux-kernel@vger.kernel.org,
	bpf@vger.kernel.org,
	kernel-team@meta.com,
	Tejun Heo <tj@kernel.org>,
	"Rafael J . Wysocki" <rafael.j.wysocki@intel.com>
Subject: [PATCH 11/39] cpufreq_schedutil: Refactor sugov_cpu_is_busy()
Date: Wed,  1 May 2024 05:09:46 -1000
Message-ID: <20240501151312.635565-12-tj@kernel.org>
In-Reply-To: <20240501151312.635565-1-tj@kernel.org>
References: <20240501151312.635565-1-tj@kernel.org>
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

sugov_cpu_is_busy() is used to avoid decreasing performance level while the
CPU is busy and called by sugov_update_single_freq() and
sugov_update_single_perf(). Both callers repeat the same pattern to first
test for uclamp and then the business. Let's refactor so that the tests
aren't repeated.

The new helper is named sugov_hold_freq() and tests both the uclamp
exception and CPU business. No functional changes. This will make adding
more exception conditions easier.

Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: David Vernet <dvernet@meta.com>
Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
---
 kernel/sched/cpufreq_schedutil.c | 38 +++++++++++++++-----------------
 1 file changed, 18 insertions(+), 20 deletions(-)

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index eece6244f9d2..972b7dd65af2 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -325,16 +325,27 @@ static unsigned long sugov_iowait_apply(struct sugov_cpu *sg_cpu, u64 time,
 }
 
 #ifdef CONFIG_NO_HZ_COMMON
-static bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu)
+static bool sugov_hold_freq(struct sugov_cpu *sg_cpu)
 {
-	unsigned long idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
-	bool ret = idle_calls == sg_cpu->saved_idle_calls;
+	unsigned long idle_calls;
+	bool ret;
+
+	/* if capped by uclamp_max, always update to be in compliance */
+	if (uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)))
+		return false;
+
+	/*
+	 * Maintain the frequency if the CPU has not been idle recently, as
+	 * reduction is likely to be premature.
+	 */
+	idle_calls = tick_nohz_get_idle_calls_cpu(sg_cpu->cpu);
+	ret = idle_calls == sg_cpu->saved_idle_calls;
 
 	sg_cpu->saved_idle_calls = idle_calls;
 	return ret;
 }
 #else
-static inline bool sugov_cpu_is_busy(struct sugov_cpu *sg_cpu) { return false; }
+static inline bool sugov_hold_freq(struct sugov_cpu *sg_cpu) { return false; }
 #endif /* CONFIG_NO_HZ_COMMON */
 
 /*
@@ -382,14 +393,8 @@ static void sugov_update_single_freq(struct update_util_data *hook, u64 time,
 		return;
 
 	next_f = get_next_freq(sg_policy, sg_cpu->util, max_cap);
-	/*
-	 * Do not reduce the frequency if the CPU has not been idle
-	 * recently, as the reduction is likely to be premature then.
-	 *
-	 * Except when the rq is capped by uclamp_max.
-	 */
-	if (!uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)) &&
-	    sugov_cpu_is_busy(sg_cpu) && next_f < sg_policy->next_freq &&
+
+	if (sugov_hold_freq(sg_cpu) && next_f < sg_policy->next_freq &&
 	    !sg_policy->need_freq_update) {
 		next_f = sg_policy->next_freq;
 
@@ -436,14 +441,7 @@ static void sugov_update_single_perf(struct update_util_data *hook, u64 time,
 	if (!sugov_update_single_common(sg_cpu, time, max_cap, flags))
 		return;
 
-	/*
-	 * Do not reduce the target performance level if the CPU has not been
-	 * idle recently, as the reduction is likely to be premature then.
-	 *
-	 * Except when the rq is capped by uclamp_max.
-	 */
-	if (!uclamp_rq_is_capped(cpu_rq(sg_cpu->cpu)) &&
-	    sugov_cpu_is_busy(sg_cpu) && sg_cpu->util < prev_util)
+	if (sugov_hold_freq(sg_cpu) && sg_cpu->util < prev_util)
 		sg_cpu->util = prev_util;
 
 	cpufreq_driver_adjust_perf(sg_cpu->cpu, sg_cpu->bw_min,
-- 
2.44.0