diff mbox series

[v2,4/6] cpufreq/schedutil: use a fixed reference frequency

Message ID 20231009103621.374412-5-vincent.guittot@linaro.org (mailing list archive)
State Superseded, archived
Headers show
Series consolidate and cleanup CPU capacity | expand

Commit Message

Vincent Guittot Oct. 9, 2023, 10:36 a.m. UTC
cpuinfo.max_freq can change at runtime because of boost as an example. This
implies that the value could be different than the one that has been
used when computing the capacity of a CPU.

The new arch_scale_freq_ref() returns a fixed and coherent reference
frequency that can be used when computing a frequency based on utilization.

Use this arch_scale_freq_ref() when available and fallback to
policy otherwise.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 kernel/sched/cpufreq_schedutil.c | 26 ++++++++++++++++++++++++--
 1 file changed, 24 insertions(+), 2 deletions(-)

Comments

Lukasz Luba Oct. 18, 2023, 11:21 a.m. UTC | #1
On 10/9/23 11:36, Vincent Guittot wrote:
> cpuinfo.max_freq can change at runtime because of boost as an example. This
> implies that the value could be different than the one that has been
> used when computing the capacity of a CPU.
> 
> The new arch_scale_freq_ref() returns a fixed and coherent reference
> frequency that can be used when computing a frequency based on utilization.
> 
> Use this arch_scale_freq_ref() when available and fallback to
> policy otherwise.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>   kernel/sched/cpufreq_schedutil.c | 26 ++++++++++++++++++++++++--
>   1 file changed, 24 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
> index 4492608b7d7f..1fa7e74add8f 100644
> --- a/kernel/sched/cpufreq_schedutil.c
> +++ b/kernel/sched/cpufreq_schedutil.c
> @@ -114,6 +114,28 @@ static void sugov_deferred_update(struct sugov_policy *sg_policy)
>   	}
>   }
>   
> +/**
> + * cpufreq_get_capacity_ref_freq - get the reference frequency of a given CPU that
> + * has been used to correlate frequency and compute capacity.
> + * @policy: the cpufreq policy of the CPU in question.
> + * @use_current: Fallback to current freq instead of policy->cpuinfo.max_freq.
> + *
> + * Return: the reference CPU frequency to compute a capacity.
> + */
> +static __always_inline
> +unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
> +{
> +	unsigned int freq = arch_scale_freq_ref(policy->cpu);
> +
> +	if (freq)
> +		return freq;

Looks good, for the platforms having this inline function returning 0,
this will be optimized out.

> +
> +	if (arch_scale_freq_invariant())
> +		return policy->cpuinfo.max_freq;
> +
> +	return policy->cur;
> +}
> +
>   /**
>    * get_next_freq - Compute a new frequency for a given cpufreq policy.
>    * @sg_policy: schedutil policy object to compute the new frequency for.
> @@ -140,10 +162,10 @@ static unsigned int get_next_freq(struct sugov_policy *sg_policy,
>   				  unsigned long util, unsigned long max)
>   {
>   	struct cpufreq_policy *policy = sg_policy->policy;
> -	unsigned int freq = arch_scale_freq_invariant() ?
> -				policy->cpuinfo.max_freq : policy->cur;
> +	unsigned int freq;
>   
>   	util = map_util_perf(util);
> +	freq = get_capacity_ref_freq(policy);
>   	freq = map_util_freq(util, freq, max);
>   
>   	if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)


Reviewed-by: Lukasz Luba <lukasz.luba@arm.com>
diff mbox series

Patch

diff --git a/kernel/sched/cpufreq_schedutil.c b/kernel/sched/cpufreq_schedutil.c
index 4492608b7d7f..1fa7e74add8f 100644
--- a/kernel/sched/cpufreq_schedutil.c
+++ b/kernel/sched/cpufreq_schedutil.c
@@ -114,6 +114,28 @@  static void sugov_deferred_update(struct sugov_policy *sg_policy)
 	}
 }
 
+/**
+ * cpufreq_get_capacity_ref_freq - get the reference frequency of a given CPU that
+ * has been used to correlate frequency and compute capacity.
+ * @policy: the cpufreq policy of the CPU in question.
+ * @use_current: Fallback to current freq instead of policy->cpuinfo.max_freq.
+ *
+ * Return: the reference CPU frequency to compute a capacity.
+ */
+static __always_inline
+unsigned long get_capacity_ref_freq(struct cpufreq_policy *policy)
+{
+	unsigned int freq = arch_scale_freq_ref(policy->cpu);
+
+	if (freq)
+		return freq;
+
+	if (arch_scale_freq_invariant())
+		return policy->cpuinfo.max_freq;
+
+	return policy->cur;
+}
+
 /**
  * get_next_freq - Compute a new frequency for a given cpufreq policy.
  * @sg_policy: schedutil policy object to compute the new frequency for.
@@ -140,10 +162,10 @@  static unsigned int get_next_freq(struct sugov_policy *sg_policy,
 				  unsigned long util, unsigned long max)
 {
 	struct cpufreq_policy *policy = sg_policy->policy;
-	unsigned int freq = arch_scale_freq_invariant() ?
-				policy->cpuinfo.max_freq : policy->cur;
+	unsigned int freq;
 
 	util = map_util_perf(util);
+	freq = get_capacity_ref_freq(policy);
 	freq = map_util_freq(util, freq, max);
 
 	if (freq == sg_policy->cached_raw_freq && !sg_policy->need_freq_update)