This is a note to let you know that I've just added the patch titled
ACPI: processor: perflib: Avoid updating frequency QoS unnecessarily
to the 5.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
acpi-processor-perflib-avoid-updating-frequency-qos-unnecessarily.patch
and it can be found in the queue-5.4 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 99387b016022c29234c4ebf9abd34358c6e56532 Mon Sep 17 00:00:00 2001
From: "Rafael J. Wysocki" <rafael.j.wysocki@xxxxxxxxx>
Date: Wed, 28 Dec 2022 22:24:10 +0100
Subject: ACPI: processor: perflib: Avoid updating frequency QoS unnecessarily
From: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
commit 99387b016022c29234c4ebf9abd34358c6e56532 upstream.
Modify acpi_processor_get_platform_limit() to avoid updating its
frequency QoS request when the _PPC return value has not changed
by comparing that value to the previous _PPC return value stored in
the performance_platform_limit field of the struct acpi_processor
corresponding to the given CPU.
While at it, do the _PPC return value check against the state count
earlier, to avoid setting performance_platform_limit to an invalid
value, and make acpi_processor_ppc_init() use FREQ_QOS_MAX_DEFAULT_VALUE
as the "no limit" frequency QoS for consistency.
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@xxxxxxxxx>
Tested-by: Hagar Hemdan <hagarhem@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/acpi/processor_perflib.c | 18 ++++++++++++++----
1 file changed, 14 insertions(+), 4 deletions(-)
--- a/drivers/acpi/processor_perflib.c
+++ b/drivers/acpi/processor_perflib.c
@@ -79,13 +79,16 @@ static int acpi_processor_get_platform_l
index = ppc;
+ if (pr->performance_platform_limit == index ||
+ ppc >= pr->performance->state_count)
+ return 0;
+
pr_debug("CPU %d: _PPC is %d - frequency %s limited\n", pr->id,
index, index ? "is" : "is not");
pr->performance_platform_limit = index;
- if (ppc >= pr->performance->state_count ||
- unlikely(!freq_qos_request_active(&pr->perflib_req)))
+ if (unlikely(!freq_qos_request_active(&pr->perflib_req)))
return 0;
/*
@@ -180,9 +183,16 @@ void acpi_processor_ppc_init(struct cpuf
if (!pr)
continue;
+ /*
+ * Reset performance_platform_limit in case there is a stale
+ * value in it, so as to make it match the "no limit" QoS value
+ * below.
+ */
+ pr->performance_platform_limit = 0;
+
ret = freq_qos_add_request(&policy->constraints,
- &pr->perflib_req,
- FREQ_QOS_MAX, INT_MAX);
+ &pr->perflib_req, FREQ_QOS_MAX,
+ FREQ_QOS_MAX_DEFAULT_VALUE);
if (ret < 0)
pr_err("Failed to add freq constraint for CPU%d (%d)\n",
cpu, ret);
Patches currently in stable-queue which might be from rafael.j.wysocki@xxxxxxxxx are
queue-5.4/acpi-processor-perflib-use-the-no-limit-frequency-qos.patch
queue-5.4/cpufreq-intel_pstate-drop-acpi-_pss-states-table-patching.patch
queue-5.4/acpi-processor-perflib-avoid-updating-frequency-qos-unnecessarily.patch
