diff mbox series

[v4,7/7] arm64/amu: use capacity_ref_freq to set AMU ratio

Message ID 20231027080400.56703-8-vincent.guittot@linaro.org
State Superseded
Headers show
Series consolidate and cleanup CPU capacity | expand

Commit Message

Vincent Guittot Oct. 27, 2023, 8:04 a.m. UTC 
Use the new capacity_ref_freq to set the ratio that is used by AMU for
computing the arch_scale_freq_capacity().
This helps to keep everything aligned using the same reference for
computing CPUs capacity.

The default value of the ratio (stored in per_cpu(arch_max_freq_scale)
ensures that arch_scale_freq_capacity() returns max capacity until it is
set to its correct value with the cpu capacity and capacity_ref_freq.

Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
---
 arch/arm64/kernel/topology.c  | 26 ++++++++++++++------------
 drivers/base/arch_topology.c  | 12 +++++++++++-
 include/linux/arch_topology.h |  1 +
 3 files changed, 26 insertions(+), 13 deletions(-)

Comments

Beata Michalska Oct. 31, 2023, 11:58 p.m. UTC | #1 
On Fri, Oct 27, 2023 at 10:04:00AM +0200, Vincent Guittot wrote:
> Use the new capacity_ref_freq to set the ratio that is used by AMU for
> computing the arch_scale_freq_capacity().
> This helps to keep everything aligned using the same reference for
> computing CPUs capacity.
> 
> The default value of the ratio (stored in per_cpu(arch_max_freq_scale)
> ensures that arch_scale_freq_capacity() returns max capacity until it is
> set to its correct value with the cpu capacity and capacity_ref_freq.
> 
> Signed-off-by: Vincent Guittot <vincent.guittot@linaro.org>
> ---
>  arch/arm64/kernel/topology.c  | 26 ++++++++++++++------------
>  drivers/base/arch_topology.c  | 12 +++++++++++-
>  include/linux/arch_topology.h |  1 +
>  3 files changed, 26 insertions(+), 13 deletions(-)
> 
> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> index 817d788cd866..626031076b75 100644
> --- a/arch/arm64/kernel/topology.c
> +++ b/arch/arm64/kernel/topology.c
> @@ -82,7 +82,12 @@ int __init parse_acpi_topology(void)
>  #undef pr_fmt
>  #define pr_fmt(fmt) "AMU: " fmt
>  
> -static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale);
> +/*
> + * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SCALE until
> + * the CPU capacity and its assosciated frequency have been correctly
> + * initialized.
> + */
> +static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) =  1UL << (2 * SCHED_CAPACITY_SHIFT);
>  static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
>  static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
>  static cpumask_var_t amu_fie_cpus;
> @@ -112,14 +117,14 @@ static inline bool freq_counters_valid(int cpu)
>  	return true;
>  }
>  
> -static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
> +void freq_inv_set_max_ratio(int cpu, u64 max_rate)
>  {
> -	u64 ratio;
> +	u64 ratio, ref_rate = arch_timer_get_rate();
>  
>  	if (unlikely(!max_rate || !ref_rate)) {
> -		pr_debug("CPU%d: invalid maximum or reference frequency.\n",
> +		WARN_ONCE(1, "CPU%d: invalid maximum or reference frequency.\n",
>  			 cpu);
> -		return -EINVAL;
> +		return;
>  	}
>  
>  	/*
> @@ -139,12 +144,12 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
>  	ratio = div64_u64(ratio, max_rate);
>  	if (!ratio) {
>  		WARN_ONCE(1, "Reference frequency too low.\n");
> -		return -EINVAL;
> +		return;
>  	}
>  
> -	per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
> +	WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
>  
> -	return 0;
> +	return;
>  }
>  
>  static void amu_scale_freq_tick(void)
> @@ -195,10 +200,7 @@ static void amu_fie_setup(const struct cpumask *cpus)
>  		return;
>  
>  	for_each_cpu(cpu, cpus) {
> -		if (!freq_counters_valid(cpu) ||
> -		    freq_inv_set_max_ratio(cpu,
> -					   cpufreq_get_hw_max_freq(cpu) * 1000ULL,
> -					   arch_timer_get_rate()))
> +		if (!freq_counters_valid(cpu))
>  			return;
>  	}
>  
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index d4bef370feb3..3cba7dc753b3 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -344,6 +344,10 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
>  	return !ret;
>  }
>  
> +void __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
> +{
> +}
> +
>  #ifdef CONFIG_ACPI_CPPC_LIB
>  #include <acpi/cppc_acpi.h>
>  
> @@ -381,6 +385,9 @@ void topology_init_cpu_capacity_cppc(void)
>  	}
>  
>  	for_each_possible_cpu(cpu) {
> +		freq_inv_set_max_ratio(cpu,
> +				       per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> +
The capacity_ref_freq set earlier will still lead to units mismatch,
as at the point of calling topology_init_cpu_capacity_cppc the lowest & nominal
frequencies will be provided in MHz (unless I have missed smth).
This means that use of both, the capacity_ref_freq and the arch_freq_scale
will generate unexpected results, so I guess this should get amended in the
preceding patch (?) [1]

---
BR
B.

[1] https://lore.kernel.org/linux-arm-kernel/20231027080400.56703-4-vincent.guittot@linaro.org/T/#m42daa167097edc190b1cfc05382c385ed801d909

>  		capacity = raw_capacity[cpu];
>  		capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
>  				     capacity_scale);
> @@ -422,8 +429,11 @@ init_cpu_capacity_callback(struct notifier_block *nb,
>  
>  	cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
>  
> -	for_each_cpu(cpu, policy->related_cpus)
> +	for_each_cpu(cpu, policy->related_cpus) {
>  		per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
> +		freq_inv_set_max_ratio(cpu,
> +				       per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> +	}
>  
>  	if (cpumask_empty(cpus_to_visit)) {
>  		topology_normalize_cpu_scale();
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index 38ca6c76af56..ffdf0b7c55fa 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -99,6 +99,7 @@ void update_siblings_masks(unsigned int cpu);
>  void remove_cpu_topology(unsigned int cpuid);
>  void reset_cpu_topology(void);
>  int parse_acpi_topology(void);
> +void freq_inv_set_max_ratio(int cpu, u64 max_rate);
>  #endif
>  
>  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> -- 
> 2.34.1
>
Beata Michalska Nov. 2, 2023, 10:30 a.m. UTC | #2 
Hi Vincent,

On Wed, Nov 01, 2023 at 10:04:27AM +0100, Vincent Guittot wrote:
> Hi Beata,
> 
> On Wed, 1 Nov 2023 at 00:59, Beata Michalska <beata.michalska@arm.com> wrote:
> >
> > On Fri, Oct 27, 2023 at 10:04:00AM +0200, Vincent Guittot wrote:
> > > Use the new capacity_ref_freq to set the ratio that is used by AMU for
> > > computing the arch_scale_freq_capacity().
> > > This helps to keep everything aligned using the same reference for
> > > computing CPUs capacity.
> > >
> 
> [..]
> 
> > > @@ -381,6 +385,9 @@ void topology_init_cpu_capacity_cppc(void)
> > >       }
> > >
> > >       for_each_possible_cpu(cpu) {
> > > +             freq_inv_set_max_ratio(cpu,
> > > +                                    per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> > > +
> > The capacity_ref_freq set earlier will still lead to units mismatch,
> > as at the point of calling topology_init_cpu_capacity_cppc the lowest & nominal
> > frequencies will be provided in MHz (unless I have missed smth).
> 
> I don't get your point:
> the unit of per_cpu(capacity_freq_ref, cpu) is Khz
> 
> For cppc, we have
> per_cpu(capacity_freq_ref, cpu) = cppc_perf_to_khz(&perf_caps,
> raw_capacity[cpu]);
> 
> freq_inv_set_max_ratio() uses
> arch_timer_get_rate() which returns a freq in Hz
> and
> per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ. to get a freq in Hz too.
> 
Apologies, I should have been more verbose here.
Before the change made in [1] the cppc_perf_to_khz was indeed operating on
lowest & nominal frequency values expressed in kHZ, as those were appropriately
amended:
cppc_cpufreq_cpu_init
	|__> cppc_cpufreq_get_cpu_data:
		|__> 	...
			/* Convert the lowest and nominal freq from MHz to KHz */
			cpu_data->perf_caps.lowest_freq *= 1000;
			cpu_data->perf_caps.nominal_freq *= 1000;

So far cppc_perf_to_khz (previously cppc_cpufreq_perf_to_khz) was being called
with the post-processed CPC data (through cppc_cpufreq_get_cpu_data) and thus
guaranteed to be operating on values in kHz.
With the new changes the cppc_perf_to_khz will operate on raw CPC data,
which are expressed in MHz.(as per acpi spec)

---
Best Regards
B.
> > This means that use of both, the capacity_ref_freq and the arch_freq_scale
> > will generate unexpected results, so I guess this should get amended in the
> > preceding patch (?) [1]
> >
> > ---
> > BR
> > B.
> >
> > [1] https://lore.kernel.org/linux-arm-kernel/20231027080400.56703-4-vincent.guittot@linaro.org/T/#m42daa167097edc190b1cfc05382c385ed801d909
> >
> > >               capacity = raw_capacity[cpu];
> > >               capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
> > >                                    capacity_scale);
> > > @@ -422,8 +429,11 @@ init_cpu_capacity_callback(struct notifier_block *nb,
> > >
> > >       cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
> > >
> > > -     for_each_cpu(cpu, policy->related_cpus)
> > > +     for_each_cpu(cpu, policy->related_cpus) {
> > >               per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
> > > +             freq_inv_set_max_ratio(cpu,
> > > +                                    per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> > > +     }
> > >
> > >       if (cpumask_empty(cpus_to_visit)) {
> > >               topology_normalize_cpu_scale();
> > > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> > > index 38ca6c76af56..ffdf0b7c55fa 100644
> > > --- a/include/linux/arch_topology.h
> > > +++ b/include/linux/arch_topology.h
> > > @@ -99,6 +99,7 @@ void update_siblings_masks(unsigned int cpu);
> > >  void remove_cpu_topology(unsigned int cpuid);
> > >  void reset_cpu_topology(void);
> > >  int parse_acpi_topology(void);
> > > +void freq_inv_set_max_ratio(int cpu, u64 max_rate);
> > >  #endif
> > >
> > >  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> > > --
> > > 2.34.1
> > >
Vincent Guittot Nov. 2, 2023, 10:40 a.m. UTC | #3 
On Thu, 2 Nov 2023 at 11:31, Beata Michalska <beata.michalska@arm.com> wrote:
>
> Hi Vincent,
>
> On Wed, Nov 01, 2023 at 10:04:27AM +0100, Vincent Guittot wrote:
> > Hi Beata,
> >
> > On Wed, 1 Nov 2023 at 00:59, Beata Michalska <beata.michalska@arm.com> wrote:
> > >
> > > On Fri, Oct 27, 2023 at 10:04:00AM +0200, Vincent Guittot wrote:
> > > > Use the new capacity_ref_freq to set the ratio that is used by AMU for
> > > > computing the arch_scale_freq_capacity().
> > > > This helps to keep everything aligned using the same reference for
> > > > computing CPUs capacity.
> > > >
> >
> > [..]
> >
> > > > @@ -381,6 +385,9 @@ void topology_init_cpu_capacity_cppc(void)
> > > >       }
> > > >
> > > >       for_each_possible_cpu(cpu) {
> > > > +             freq_inv_set_max_ratio(cpu,
> > > > +                                    per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> > > > +
> > > The capacity_ref_freq set earlier will still lead to units mismatch,
> > > as at the point of calling topology_init_cpu_capacity_cppc the lowest & nominal
> > > frequencies will be provided in MHz (unless I have missed smth).
> >
> > I don't get your point:
> > the unit of per_cpu(capacity_freq_ref, cpu) is Khz
> >
> > For cppc, we have
> > per_cpu(capacity_freq_ref, cpu) = cppc_perf_to_khz(&perf_caps,
> > raw_capacity[cpu]);
> >
> > freq_inv_set_max_ratio() uses
> > arch_timer_get_rate() which returns a freq in Hz
> > and
> > per_cpu(capacity_freq_ref, cpu) * HZ_PER_KHZ. to get a freq in Hz too.
> >
> Apologies, I should have been more verbose here.
> Before the change made in [1] the cppc_perf_to_khz was indeed operating on
> lowest & nominal frequency values expressed in kHZ, as those were appropriately
> amended:
> cppc_cpufreq_cpu_init
>         |__> cppc_cpufreq_get_cpu_data:
>                 |__>    ...
>                         /* Convert the lowest and nominal freq from MHz to KHz */
>                         cpu_data->perf_caps.lowest_freq *= 1000;
>                         cpu_data->perf_caps.nominal_freq *= 1000;
>
> So far cppc_perf_to_khz (previously cppc_cpufreq_perf_to_khz) was being called
> with the post-processed CPC data (through cppc_cpufreq_get_cpu_data) and thus
> guaranteed to be operating on values in kHz.
> With the new changes the cppc_perf_to_khz will operate on raw CPC data,
> which are expressed in MHz.(as per acpi spec)

Ok, thanks for the explanation. I haven't noticed that cppc_cpufreq
was processing the raw CPC data  (*1000) before using them. I'm going
to fix that.


>
> ---
> Best Regards
> B.
> > > This means that use of both, the capacity_ref_freq and the arch_freq_scale
> > > will generate unexpected results, so I guess this should get amended in the
> > > preceding patch (?) [1]
> > >
> > > ---
> > > BR
> > > B.
> > >
> > > [1] https://lore.kernel.org/linux-arm-kernel/20231027080400.56703-4-vincent.guittot@linaro.org/T/#m42daa167097edc190b1cfc05382c385ed801d909
> > >
> > > >               capacity = raw_capacity[cpu];
> > > >               capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
> > > >                                    capacity_scale);
> > > > @@ -422,8 +429,11 @@ init_cpu_capacity_callback(struct notifier_block *nb,
> > > >
> > > >       cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
> > > >
> > > > -     for_each_cpu(cpu, policy->related_cpus)
> > > > +     for_each_cpu(cpu, policy->related_cpus) {
> > > >               per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
> > > > +             freq_inv_set_max_ratio(cpu,
> > > > +                                    per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
> > > > +     }
> > > >
> > > >       if (cpumask_empty(cpus_to_visit)) {
> > > >               topology_normalize_cpu_scale();
> > > > diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> > > > index 38ca6c76af56..ffdf0b7c55fa 100644
> > > > --- a/include/linux/arch_topology.h
> > > > +++ b/include/linux/arch_topology.h
> > > > @@ -99,6 +99,7 @@ void update_siblings_masks(unsigned int cpu);
> > > >  void remove_cpu_topology(unsigned int cpuid);
> > > >  void reset_cpu_topology(void);
> > > >  int parse_acpi_topology(void);
> > > > +void freq_inv_set_max_ratio(int cpu, u64 max_rate);
> > > >  #endif
> > > >
> > > >  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> > > > --
> > > > 2.34.1
> > > >
diff mbox series

Patch

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 817d788cd866..626031076b75 100644
--- a/arch/arm64/kernel/topology.c
+++ b/arch/arm64/kernel/topology.c
@@ -82,7 +82,12 @@  int __init parse_acpi_topology(void)
 #undef pr_fmt
 #define pr_fmt(fmt) "AMU: " fmt
 
-static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale);
+/*
+ * Ensure that amu_scale_freq_tick() will return SCHED_CAPACITY_SCALE until
+ * the CPU capacity and its assosciated frequency have been correctly
+ * initialized.
+ */
+static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) =  1UL << (2 * SCHED_CAPACITY_SHIFT);
 static DEFINE_PER_CPU(u64, arch_const_cycles_prev);
 static DEFINE_PER_CPU(u64, arch_core_cycles_prev);
 static cpumask_var_t amu_fie_cpus;
@@ -112,14 +117,14 @@  static inline bool freq_counters_valid(int cpu)
 	return true;
 }
 
-static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
+void freq_inv_set_max_ratio(int cpu, u64 max_rate)
 {
-	u64 ratio;
+	u64 ratio, ref_rate = arch_timer_get_rate();
 
 	if (unlikely(!max_rate || !ref_rate)) {
-		pr_debug("CPU%d: invalid maximum or reference frequency.\n",
+		WARN_ONCE(1, "CPU%d: invalid maximum or reference frequency.\n",
 			 cpu);
-		return -EINVAL;
+		return;
 	}
 
 	/*
@@ -139,12 +144,12 @@  static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
 	ratio = div64_u64(ratio, max_rate);
 	if (!ratio) {
 		WARN_ONCE(1, "Reference frequency too low.\n");
-		return -EINVAL;
+		return;
 	}
 
-	per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
+	WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
 
-	return 0;
+	return;
 }
 
 static void amu_scale_freq_tick(void)
@@ -195,10 +200,7 @@  static void amu_fie_setup(const struct cpumask *cpus)
 		return;
 
 	for_each_cpu(cpu, cpus) {
-		if (!freq_counters_valid(cpu) ||
-		    freq_inv_set_max_ratio(cpu,
-					   cpufreq_get_hw_max_freq(cpu) * 1000ULL,
-					   arch_timer_get_rate()))
+		if (!freq_counters_valid(cpu))
 			return;
 	}
 
diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
index d4bef370feb3..3cba7dc753b3 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -344,6 +344,10 @@  bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
 	return !ret;
 }
 
+void __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
+{
+}
+
 #ifdef CONFIG_ACPI_CPPC_LIB
 #include <acpi/cppc_acpi.h>
 
@@ -381,6 +385,9 @@  void topology_init_cpu_capacity_cppc(void)
 	}
 
 	for_each_possible_cpu(cpu) {
+		freq_inv_set_max_ratio(cpu,
+				       per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
+
 		capacity = raw_capacity[cpu];
 		capacity = div64_u64(capacity << SCHED_CAPACITY_SHIFT,
 				     capacity_scale);
@@ -422,8 +429,11 @@  init_cpu_capacity_callback(struct notifier_block *nb,
 
 	cpumask_andnot(cpus_to_visit, cpus_to_visit, policy->related_cpus);
 
-	for_each_cpu(cpu, policy->related_cpus)
+	for_each_cpu(cpu, policy->related_cpus) {
 		per_cpu(capacity_ref_freq, cpu) = policy->cpuinfo.max_freq;
+		freq_inv_set_max_ratio(cpu,
+				       per_cpu(capacity_ref_freq, cpu) * HZ_PER_KHZ);
+	}
 
 	if (cpumask_empty(cpus_to_visit)) {
 		topology_normalize_cpu_scale();
diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
index 38ca6c76af56..ffdf0b7c55fa 100644
--- a/include/linux/arch_topology.h
+++ b/include/linux/arch_topology.h
@@ -99,6 +99,7 @@  void update_siblings_masks(unsigned int cpu);
 void remove_cpu_topology(unsigned int cpuid);
 void reset_cpu_topology(void);
 int parse_acpi_topology(void);
+void freq_inv_set_max_ratio(int cpu, u64 max_rate);
 #endif
 
 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */