Re: [Patch v6 3/7] Add infrastructure to store and update instantaneous thermal pressure

[Peter Zijlstra <peterz@infradead.org>]

On Wed, Dec 11, 2019 at 11:11:44PM -0500, Thara Gopinath wrote:
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index 8a0fae9..90b18c3 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -16,6 +16,9 @@
>  /* Enable topology flag updates */
>  #define arch_update_cpu_topology topology_update_cpu_topology
>  
> +/* Replace task scheduler's defalut thermal pressure retrieve API */
> +#define arch_scale_thermal_capacity topology_get_thermal_pressure

Witsness the previously observed confusion.

>  #else
>  
>  static inline void init_cpu_topology(void) { }
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index a4d945d..ccb277b 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -25,6 +25,9 @@ int pcibus_to_node(struct pci_bus *bus);
>  /* Enable topology flag updates */
>  #define arch_update_cpu_topology topology_update_cpu_topology
>  
> +/* Replace task scheduler's defalut thermal pressure retrieve API */
> +#define arch_scale_thermal_capacity topology_get_thermal_pressure
> +
>  #include <asm-generic/topology.h>
>  
>  #endif /* _ASM_ARM_TOPOLOGY_H */
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 1eb81f11..3a91379 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -42,6 +42,19 @@ void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity)
>  	per_cpu(cpu_scale, cpu) = capacity;
>  }
>  
> +DEFINE_PER_CPU(unsigned long, thermal_pressure);
> +
> +void arch_set_thermal_pressure(struct cpumask *cpus,
> +			       unsigned long capped_capacity)
> +{
> +	int cpu;
> +	unsigned long delta = arch_scale_cpu_capacity(cpumask_first(cpus)) -
> +					capped_capacity;
> +
> +	for_each_cpu(cpu, cpus)
> +		WRITE_ONCE(per_cpu(thermal_pressure, cpu), delta);
> +}

Not a capacity.

>  static ssize_t cpu_capacity_show(struct device *dev,
>  				 struct device_attribute *attr,
>  				 char *buf)
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index 3015ecb..7a04364 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -33,6 +33,17 @@ unsigned long topology_get_freq_scale(int cpu)
>  	return per_cpu(freq_scale, cpu);
>  }
>  
> +DECLARE_PER_CPU(unsigned long, thermal_pressure);
> +
> +static inline
> +unsigned long topology_get_thermal_pressure(int cpu)
> +{
> +	return per_cpu(thermal_pressure, cpu);
> +}