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Message-Id: <20240312083431.3239989-4-beata.michalska@arm.com>
Date: Tue, 12 Mar 2024 08:34:31 +0000
From: Beata Michalska <beata.michalska@....com>
To: linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
ionela.voinescu@....com,
vanshikonda@...amperecomputing.com
Cc: sudeep.holla@....com,
will@...nel.org,
catalin.marinas@....com,
vincent.guittot@...aro.org,
sumitg@...dia.com,
yang@...amperecomputing.com,
lihuisong@...wei.com
Subject: [PATCH v3 3/3] arm64: Update AMU-based frequency scale factor on entering idle
Now that the frequency scale factor has been activated for retrieving
current frequency on a given CPU, trigger its update upon entering
idle. This will, to an extent, allow querying last known frequency
in a non-invasive way. It will also improve the frequency scale factor
accuracy when a CPU entering idle did not receive a tick for a while.
Suggested-by: Vanshidhar Konda <vanshikonda@...amperecomputing.com>
Signed-off-by: Beata Michalska <beata.michalska@....com>
---
arch/arm64/kernel/topology.c | 15 ++++++++++++++-
1 file changed, 14 insertions(+), 1 deletion(-)
diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 42cb19c31719..77c6ac577cef 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -215,6 +215,18 @@ static struct scale_freq_data amu_sfd = {
.set_freq_scale = amu_scale_freq_tick,
};
+void arch_cpu_idle_enter(void)
+{
+ unsigned int cpu = smp_processor_id();
+
+ if (!cpumask_test_cpu(cpu, amu_fie_cpus))
+ return;
+
+ /* Kick in AMU update but only if one has not happned already */
+ if (time_is_before_jiffies(per_cpu(cpu_amu_samples.last_update, cpu)))
+ amu_scale_freq_tick();
+}
+
#define AMU_SAMPLE_EXP_MS 20
unsigned int arch_freq_get_on_cpu(int cpu)
@@ -242,7 +254,8 @@ unsigned int arch_freq_get_on_cpu(int cpu)
* try an alternative source for the counters (and thus freq scale),
* if available for given policy
*/
- if (time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
+ if (!idle_cpu(cpu) &&
+ time_is_before_jiffies(last_update + msecs_to_jiffies(AMU_SAMPLE_EXP_MS))) {
struct cpufreq_policy *policy = cpufreq_cpu_get(cpu);
int ref_cpu = nr_cpu_ids;
--
2.25.1
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