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Subject: Re: [PATCH v2 1/3] arch_topology, sched/core: Cleanup thermal
 pressure definition
To:     Valentin Schneider <valentin.schneider@arm.com>,
        linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-pm@vger.kernel.org
Cc:     Russell King <linux@armlinux.org.uk>,
        Sudeep Holla <sudeep.holla@arm.com>,
        Amit Daniel Kachhap <amit.kachhap@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Ingo Molnar <mingo@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>
References: <20200712165917.9168-1-valentin.schneider@arm.com>
 <20200712165917.9168-2-valentin.schneider@arm.com>
From:   Thara Gopinath <thara.gopinath@linaro.org>
Message-ID: <88488b17-fd01-76e6-ae53-027c1016340b@linaro.org>
Date:   Mon, 13 Jul 2020 10:32:42 -0400
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On 7/12/20 12:59 PM, Valentin Schneider wrote:
> The following commit:
> 
>    14533a16c46d ("thermal/cpu-cooling, sched/core: Move the arch_set_thermal_pressure() API to generic scheduler code")
> 
> moved the definition of arch_set_thermal_pressure() to sched/core.c, but
> kept its declaration in linux/arch_topology.h. When building e.g. an x86
> kernel with CONFIG_SCHED_THERMAL_PRESSURE=y, cpufreq_cooling.c ends up
> getting the declaration of arch_set_thermal_pressure() from
> include/linux/arch_topology.h, which is somewhat awkward.
> 
> On top of this, sched/core.c unconditionally defines
> o The thermal_pressure percpu variable
> o arch_set_thermal_pressure()
> 
> while arch_scale_thermal_pressure() does nothing unless redefined by the
> architecture.
> 
> arch_*() functions are meant to be defined by architectures, so revert the
> aforementioned commit and re-implement it in a way that keeps
> arch_set_thermal_pressure() architecture-definable, and doesn't define the
> thermal pressure percpu variable for kernels that don't need
> it (CONFIG_SCHED_THERMAL_PRESSURE=n).
> 
> Signed-off-by: Valentin Schneider <valentin.schneider@arm.com>
> ---

Reviewed-by: Thara Gopinath <thara.gopinath@linaro.org>

>   arch/arm/include/asm/topology.h   |  3 ++-
>   arch/arm64/include/asm/topology.h |  3 ++-
>   drivers/base/arch_topology.c      | 11 +++++++++++
>   include/linux/arch_topology.h     |  4 ++--
>   include/linux/sched/topology.h    |  7 +++++++
>   kernel/sched/core.c               | 11 -----------
>   6 files changed, 24 insertions(+), 15 deletions(-)
> 
> diff --git a/arch/arm/include/asm/topology.h b/arch/arm/include/asm/topology.h
> index 435aba289fc5..e0593cf095d0 100644
> --- a/arch/arm/include/asm/topology.h
> +++ b/arch/arm/include/asm/topology.h
> @@ -16,8 +16,9 @@
>   /* Enable topology flag updates */
>   #define arch_update_cpu_topology topology_update_cpu_topology
>   
> -/* Replace task scheduler's default thermal pressure retrieve API */
> +/* Replace task scheduler's default thermal pressure API */
>   #define arch_scale_thermal_pressure topology_get_thermal_pressure
> +#define arch_set_thermal_pressure   topology_set_thermal_pressure
>   
>   #else
>   
> diff --git a/arch/arm64/include/asm/topology.h b/arch/arm64/include/asm/topology.h
> index 0cc835ddfcd1..e042f6527981 100644
> --- a/arch/arm64/include/asm/topology.h
> +++ b/arch/arm64/include/asm/topology.h
> @@ -34,8 +34,9 @@ void topology_scale_freq_tick(void);
>   /* Enable topology flag updates */
>   #define arch_update_cpu_topology topology_update_cpu_topology
>   
> -/* Replace task scheduler's default thermal pressure retrieve API */
> +/* Replace task scheduler's default thermal pressure API */
>   #define arch_scale_thermal_pressure topology_get_thermal_pressure
> +#define arch_set_thermal_pressure   topology_set_thermal_pressure
>   
>   #include <asm-generic/topology.h>
>   
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 4d0a0038b476..d14cab7dfa3c 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -54,6 +54,17 @@ 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(const struct cpumask *cpus,
> +			       unsigned long th_pressure)
> +{
> +	int cpu;
> +
> +	for_each_cpu(cpu, cpus)
> +		WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure);
> +}
> +
>   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 0566cb3314ef..69b1dabe39dc 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -39,8 +39,8 @@ static inline unsigned long topology_get_thermal_pressure(int cpu)
>   	return per_cpu(thermal_pressure, cpu);
>   }
>   
> -void arch_set_thermal_pressure(struct cpumask *cpus,
> -			       unsigned long th_pressure);
> +void topology_set_thermal_pressure(const struct cpumask *cpus,
> +				   unsigned long th_pressure);
>   
>   struct cpu_topology {
>   	int thread_id;
> diff --git a/include/linux/sched/topology.h b/include/linux/sched/topology.h
> index fb11091129b3..764222d637b7 100644
> --- a/include/linux/sched/topology.h
> +++ b/include/linux/sched/topology.h
> @@ -232,6 +232,13 @@ unsigned long arch_scale_thermal_pressure(int cpu)
>   }
>   #endif
>   
> +#ifndef arch_set_thermal_pressure
> +static __always_inline
> +void arch_set_thermal_pressure(const struct cpumask *cpus,
> +			       unsigned long th_pressure)
> +{ }
> +#endif
> +
>   static inline int task_node(const struct task_struct *p)
>   {
>   	return cpu_to_node(task_cpu(p));
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index ff0519551188..90b44f3840e4 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3731,17 +3731,6 @@ unsigned long long task_sched_runtime(struct task_struct *p)
>   	return ns;
>   }
>   
> -DEFINE_PER_CPU(unsigned long, thermal_pressure);
> -
> -void arch_set_thermal_pressure(struct cpumask *cpus,
> -			       unsigned long th_pressure)
> -{
> -	int cpu;
> -
> -	for_each_cpu(cpu, cpus)
> -		WRITE_ONCE(per_cpu(thermal_pressure, cpu), th_pressure);
> -}
> -
>   /*
>    * This function gets called by the timer code, with HZ frequency.
>    * We call it with interrupts disabled.
> 

-- 
Warm Regards
Thara