diff mbox series

[RFC,v3,6/6] arm64/amu: use capacity_ref_freq to set AMU ratio

Message ID 20231018162540.667646-7-vincent.guittot@linaro.org (mailing list archive)
State New, archived
Headers show
Series consolidate and cleanup CPU capacity | expand

Commit Message

Vincent Guittot Oct. 18, 2023, 4:25 p.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 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  | 18 ++++++++++--------
 drivers/base/arch_topology.c  | 14 ++++++++++++--
 include/linux/arch_topology.h |  1 +
 3 files changed, 23 insertions(+), 10 deletions(-)

Comments

Ionela Voinescu Oct. 23, 2023, 8:58 p.m. UTC | #1
Hi,

On Wednesday 18 Oct 2023 at 18:25:40 (+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 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  | 18 ++++++++++--------
>  drivers/base/arch_topology.c  | 14 ++++++++++++--
>  include/linux/arch_topology.h |  1 +
>  3 files changed, 23 insertions(+), 10 deletions(-)
> 
> diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> index 817d788cd866..0f8f6e90c46d 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_SHIFT until
> + * the CPU capacity and its assosciated frequency have been correctly
> + * initialized.

s/SCHED_CAPACITY_SHIFT/SCHED_CAPACITY_SCALE

> + */
> +static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = (2 * SCHED_CAPACITY_SHIFT);

It should be 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;
> @@ -112,9 +117,9 @@ 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)
> +int 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",
> @@ -142,7 +147,7 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
>  		return -EINVAL;
>  	}

The return value is no longer used so it might be worth declaring it to
return void and WARN_ONCE for unlikely(!max_rate || !ref_rate).

>  
> -	per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
> +	WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
>  
>  	return 0;
>  }
> @@ -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 2372ce791bb4..3a604b77b12d 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -344,6 +344,11 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
>  	return !ret;
>  }
>  
> +int __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
> +{
> +	return 0;
> +}
> +
>  #ifdef CONFIG_ACPI_CPPC_LIB
>  #include <acpi/cppc_acpi.h>
>  
> @@ -369,7 +374,6 @@ void topology_init_cpu_capacity_cppc(void)
>  			capacity_scale = max_t(u64, capacity_scale, raw_capacity[cpu]);
>  
>  			per_cpu(capacity_ref_freq, cpu) = cppc_perf_to_khz(&perf_caps, raw_capacity[cpu]);
> -
>  			pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
>  				 cpu, raw_capacity[cpu]);
>  			continue;
> @@ -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));
> +
>  		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));

capacity_ref_freq is in KHz while arch_timer_get_rate() is in Hz. One or
the other needs to be scaled.

The same in topology_init_cpu_capacity_cppc().

Thanks,
Ionela.

> +	}
>  
>  	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..b6e95d763279 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);
> +int freq_inv_set_max_ratio(int cpu, u64 max_rate);
>  #endif
>  
>  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> -- 
> 2.34.1
>
Vincent Guittot Oct. 24, 2023, 9:58 a.m. UTC | #2
On Mon, 23 Oct 2023 at 22:58, Ionela Voinescu <ionela.voinescu@arm.com> wrote:
>
> Hi,
>
> On Wednesday 18 Oct 2023 at 18:25:40 (+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 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  | 18 ++++++++++--------
> >  drivers/base/arch_topology.c  | 14 ++++++++++++--
> >  include/linux/arch_topology.h |  1 +
> >  3 files changed, 23 insertions(+), 10 deletions(-)
> >
> > diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
> > index 817d788cd866..0f8f6e90c46d 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_SHIFT until
> > + * the CPU capacity and its assosciated frequency have been correctly
> > + * initialized.
>
> s/SCHED_CAPACITY_SHIFT/SCHED_CAPACITY_SCALE
>
> > + */
> > +static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = (2 * SCHED_CAPACITY_SHIFT);
>
> It should be 1UL << (2 * SCHED_CAPACITY_SHIFT).

yes

>
> >  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;
> > @@ -112,9 +117,9 @@ 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)
> > +int 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",
> > @@ -142,7 +147,7 @@ static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
> >               return -EINVAL;
> >       }
>
> The return value is no longer used so it might be worth declaring it to
> return void and WARN_ONCE for unlikely(!max_rate || !ref_rate).
>
> >
> > -     per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
> > +     WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
> >
> >       return 0;
> >  }
> > @@ -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 2372ce791bb4..3a604b77b12d 100644
> > --- a/drivers/base/arch_topology.c
> > +++ b/drivers/base/arch_topology.c
> > @@ -344,6 +344,11 @@ bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
> >       return !ret;
> >  }
> >
> > +int __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
> > +{
> > +     return 0;
> > +}
> > +
> >  #ifdef CONFIG_ACPI_CPPC_LIB
> >  #include <acpi/cppc_acpi.h>
> >
> > @@ -369,7 +374,6 @@ void topology_init_cpu_capacity_cppc(void)
> >                       capacity_scale = max_t(u64, capacity_scale, raw_capacity[cpu]);
> >
> >                       per_cpu(capacity_ref_freq, cpu) = cppc_perf_to_khz(&perf_caps, raw_capacity[cpu]);
> > -
> >                       pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
> >                                cpu, raw_capacity[cpu]);
> >                       continue;
> > @@ -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));
> > +
> >               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));
>
> capacity_ref_freq is in KHz while arch_timer_get_rate() is in Hz. One or
> the other needs to be scaled.
>
> The same in topology_init_cpu_capacity_cppc().
>
> Thanks,
> Ionela.
>
> > +     }
> >
> >       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..b6e95d763279 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);
> > +int freq_inv_set_max_ratio(int cpu, u64 max_rate);
> >  #endif
> >
> >  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
> > --
> > 2.34.1
> >
Dietmar Eggemann Oct. 26, 2023, 11:19 a.m. UTC | #3
On 24/10/2023 11:58, Vincent Guittot wrote:
> On Mon, 23 Oct 2023 at 22:58, Ionela Voinescu <ionela.voinescu@arm.com> wrote:
>>
>> Hi,
>>
>> On Wednesday 18 Oct 2023 at 18:25:40 (+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 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.

Nitpick: Could you mention that arch_max_freq_scale is the default value
for this ratio? Took me a while to recreate the (not so simple) story
for this change, i.e. make the connection between ratio and
arch_max_freq_scale.

init_cpu_capacity_callback()

  freq_inv_set_max_ratio()

    u64 ratio
    ...
    per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio
            ^^^^^^^^^^^^^^^^^^^


static struct scale_freq_data amu_sfd = {
        .set_freq_scale = amu_scale_freq_tick,
}

#define arch_scale_freq_tick topology_scale_freq_tick

topology_scale_freq_tick()

  sfd->set_freq_scale()


amu_scale_freq_tick()

  ...
  scale *= this_cpu_read(arch_max_freq_scale)
                         ^^^^^^^^^^^^^^^^^^^
  ...
  this_cpu_write(arch_freq_scale, (unsigned long)scale);


#define arch_scale_freq_capacity topology_get_freq_scale

topology_get_freq_scale(cpu)

  return per_cpu(arch_freq_scale, cpu)

[...]
Vincent Guittot Oct. 26, 2023, 2:30 p.m. UTC | #4
On Thu, 26 Oct 2023 at 13:19, Dietmar Eggemann <dietmar.eggemann@arm.com> wrote:
>
> On 24/10/2023 11:58, Vincent Guittot wrote:
> > On Mon, 23 Oct 2023 at 22:58, Ionela Voinescu <ionela.voinescu@arm.com> wrote:
> >>
> >> Hi,
> >>
> >> On Wednesday 18 Oct 2023 at 18:25:40 (+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 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.
>
> Nitpick: Could you mention that arch_max_freq_scale is the default value
> for this ratio? Took me a while to recreate the (not so simple) story
> for this change, i.e. make the connection between ratio and
> arch_max_freq_scale.

something like :
"
The default value of the ratio (saved 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.
"

Or I can rename the variable per_cpu(arch_max_freq_ratio)

>
> init_cpu_capacity_callback()
>
>   freq_inv_set_max_ratio()
>
>     u64 ratio
>     ...
>     per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio
>             ^^^^^^^^^^^^^^^^^^^
>
>
> static struct scale_freq_data amu_sfd = {
>         .set_freq_scale = amu_scale_freq_tick,
> }
>
> #define arch_scale_freq_tick topology_scale_freq_tick
>
> topology_scale_freq_tick()
>
>   sfd->set_freq_scale()
>
>
> amu_scale_freq_tick()
>
>   ...
>   scale *= this_cpu_read(arch_max_freq_scale)
>                          ^^^^^^^^^^^^^^^^^^^
>   ...
>   this_cpu_write(arch_freq_scale, (unsigned long)scale);
>
>
> #define arch_scale_freq_capacity topology_get_freq_scale
>
> topology_get_freq_scale(cpu)
>
>   return per_cpu(arch_freq_scale, cpu)
>
> [...]
>
diff mbox series

Patch

diff --git a/arch/arm64/kernel/topology.c b/arch/arm64/kernel/topology.c
index 817d788cd866..0f8f6e90c46d 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_SHIFT until
+ * the CPU capacity and its assosciated frequency have been correctly
+ * initialized.
+ */
+static DEFINE_PER_CPU_READ_MOSTLY(unsigned long, arch_max_freq_scale) = (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;
@@ -112,9 +117,9 @@  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)
+int 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",
@@ -142,7 +147,7 @@  static int freq_inv_set_max_ratio(int cpu, u64 max_rate, u64 ref_rate)
 		return -EINVAL;
 	}
 
-	per_cpu(arch_max_freq_scale, cpu) = (unsigned long)ratio;
+	WRITE_ONCE(per_cpu(arch_max_freq_scale, cpu), (unsigned long)ratio);
 
 	return 0;
 }
@@ -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 2372ce791bb4..3a604b77b12d 100644
--- a/drivers/base/arch_topology.c
+++ b/drivers/base/arch_topology.c
@@ -344,6 +344,11 @@  bool __init topology_parse_cpu_capacity(struct device_node *cpu_node, int cpu)
 	return !ret;
 }
 
+int __weak freq_inv_set_max_ratio(int cpu, u64 max_rate)
+{
+	return 0;
+}
+
 #ifdef CONFIG_ACPI_CPPC_LIB
 #include <acpi/cppc_acpi.h>
 
@@ -369,7 +374,6 @@  void topology_init_cpu_capacity_cppc(void)
 			capacity_scale = max_t(u64, capacity_scale, raw_capacity[cpu]);
 
 			per_cpu(capacity_ref_freq, cpu) = cppc_perf_to_khz(&perf_caps, raw_capacity[cpu]);
-
 			pr_debug("cpu_capacity: CPU%d cpu_capacity=%u (raw).\n",
 				 cpu, raw_capacity[cpu]);
 			continue;
@@ -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));
+
 		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));
+	}
 
 	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..b6e95d763279 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);
+int freq_inv_set_max_ratio(int cpu, u64 max_rate);
 #endif
 
 #endif /* _LINUX_ARCH_TOPOLOGY_H_ */