diff mbox series

[SRU,J/K,V2,1/1] cpufreq: ACPI: Defer setting boost MSRs

Message ID 20230405194820.13770-2-michael.reed@canonical.com
State New
Headers show
Series Performance per Watt (DAPC) enabled in the BIOS | expand

Commit Message

Michael Reed April 5, 2023, 7:48 p.m. UTC 
From: Stuart Hayes <stuart.w.hayes@gmail.com>

When acpi-cpufreq is loaded, boost is enabled on every CPU (by setting an
MSR) before the driver is registered with cpufreq.  This can be very time
consuming, because it is done with a CPU hotplug startup callback, and
cpuhp_setup_state() schedules the callback (cpufreq_boost_online()) to run
on each CPU one at a time, waiting for each to run before calling the next.

If cpufreq_register_driver() fails--if, for example, there are no ACPI
P-states present--this is wasted time.

Since cpufreq already sets up a CPU hotplug startup callback if and when
acpi-cpufreq is registered, set the boost MSRs in acpi_cpufreq_cpu_init(),
which is called by the cpufreq cpuhp callback.  This allows acpi-cpufreq to
exit quickly if it is loaded but not needed.

On one system with 192 CPUs, this patch speeds up boot by about 30 seconds.

BugLink: https://bugs.launchpad.net/bugs/2008527

Signed-off-by: Stuart Hayes <stuart.w.hayes@gmail.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
(cherry picked from commit 13fdbc8b8da6a2325cad3359c9a70504b0ff2f93)
Signed-off-by: Michael Reed <Michael.Reed@canonical.com>
---
 drivers/cpufreq/acpi-cpufreq.c | 31 +++----------------------------
 1 file changed, 3 insertions(+), 28 deletions(-)
diff mbox series

Patch

diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
index 28467d83c745..8b5c84c9dc1e 100644
--- a/drivers/cpufreq/acpi-cpufreq.c
+++ b/drivers/cpufreq/acpi-cpufreq.c
@@ -530,15 +530,6 @@  static void free_acpi_perf_data(void)
 	free_percpu(acpi_perf_data);
 }
 
-static int cpufreq_boost_online(unsigned int cpu)
-{
-	/*
-	 * On the CPU_UP path we simply keep the boost-disable flag
-	 * in sync with the current global state.
-	 */
-	return boost_set_msr(acpi_cpufreq_driver.boost_enabled);
-}
-
 static int cpufreq_boost_down_prep(unsigned int cpu)
 {
 	/*
@@ -892,6 +883,8 @@  static int acpi_cpufreq_cpu_init(struct cpufreq_policy *policy)
 	if (perf->states[0].core_frequency * 1000 != freq_table[0].frequency)
 		pr_warn(FW_WARN "P-state 0 is not max freq\n");
 
+	set_boost(policy, acpi_cpufreq_driver.boost_enabled);
+
 	return result;
 
 err_unreg:
@@ -911,6 +904,7 @@  static int acpi_cpufreq_cpu_exit(struct cpufreq_policy *policy)
 
 	pr_debug("%s\n", __func__);
 
+	cpufreq_boost_down_prep(policy->cpu);
 	policy->fast_switch_possible = false;
 	policy->driver_data = NULL;
 	acpi_processor_unregister_performance(data->acpi_perf_cpu);
@@ -967,25 +961,9 @@  static void __init acpi_cpufreq_boost_init(void)
 	acpi_cpufreq_driver.set_boost = set_boost;
 	acpi_cpufreq_driver.boost_enabled = boost_state(0);
 
-	/*
-	 * This calls the online callback on all online cpu and forces all
-	 * MSRs to the same value.
-	 */
-	ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "cpufreq/acpi:online",
-				cpufreq_boost_online, cpufreq_boost_down_prep);
-	if (ret < 0) {
-		pr_err("acpi_cpufreq: failed to register hotplug callbacks\n");
-		return;
-	}
 	acpi_cpufreq_online = ret;
 }
 
-static void acpi_cpufreq_boost_exit(void)
-{
-	if (acpi_cpufreq_online > 0)
-		cpuhp_remove_state_nocalls(acpi_cpufreq_online);
-}
-
 static int __init acpi_cpufreq_init(void)
 {
 	int ret;
@@ -1027,7 +1005,6 @@  static int __init acpi_cpufreq_init(void)
 	ret = cpufreq_register_driver(&acpi_cpufreq_driver);
 	if (ret) {
 		free_acpi_perf_data();
-		acpi_cpufreq_boost_exit();
 	}
 	return ret;
 }
@@ -1036,8 +1013,6 @@  static void __exit acpi_cpufreq_exit(void)
 {
 	pr_debug("%s\n", __func__);
 
-	acpi_cpufreq_boost_exit();
-
 	cpufreq_unregister_driver(&acpi_cpufreq_driver);
 
 	free_acpi_perf_data();