linux-kernel - Re: [PATCH v3 05/10] drivers base/arch_topology: provide frequency-invariant accounting support

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Date:   Fri, 28 Jul 2017 13:56:42 +0530
From:   Viresh Kumar <viresh.kumar@...aro.org>
To:     Dietmar Eggemann <dietmar.eggemann@....com>
Cc:     linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
        linux@....linux.org.uk,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Russell King <rmk+kernel@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Juri Lelli <juri.lelli@....com>,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Morten Rasmussen <morten.rasmussen@....com>,
        "Rafael J . Wysocki" <rjw@...ysocki.net>,
        Sudeep Holla <sudeep.holla@....com>
Subject: Re: [PATCH v3 05/10] drivers base/arch_topology: provide
 frequency-invariant accounting support

On 27-07-17, 20:33, Dietmar Eggemann wrote:
> Implements the arch-specific (arm and arm64) frequency-invariance setter
> function arch_set_freq_scale() which provides the following frequency
> scaling factor:
> 
>   current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)
> 
> One possible consumer of the frequency-invariance getter function
> topology_get_freq_scale() is the Per-Entity Load Tracking (PELT)
> mechanism of the task scheduler.
> 
> Allow inlining of topology_get_freq_scale() into the task scheduler
> fast path (e.g. __update_load_avg_se()) by coding it as a static inline
> function in the arch topology header file.
> 
> Cc: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
> Cc: Juri Lelli <juri.lelli@....com>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@....com>
> ---
>  drivers/base/arch_topology.c  | 14 ++++++++++++++
>  include/linux/arch_topology.h | 10 ++++++++++
>  2 files changed, 24 insertions(+)
> 
> diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
> index 562e0c93ae52..af9ab98a233e 100644
> --- a/drivers/base/arch_topology.c
> +++ b/drivers/base/arch_topology.c
> @@ -22,6 +22,20 @@
>  #include <linux/string.h>
>  #include <linux/sched/topology.h>
>  
> +DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
> +
> +void arch_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
> +			 unsigned long max_freq)
> +{
> +	unsigned long scale;
> +	int i;
> +
> +	scale = (cur_freq << SCHED_CAPACITY_SHIFT) / max_freq;
> +
> +	for_each_cpu(i, cpus)
> +		per_cpu(freq_scale, i) = scale;
> +}
> +
>  static DEFINE_MUTEX(cpu_scale_mutex);
>  static DEFINE_PER_CPU(unsigned long, cpu_scale) = SCHED_CAPACITY_SCALE;
>  
> diff --git a/include/linux/arch_topology.h b/include/linux/arch_topology.h
> index 9af3c174c03a..3e3c2657c9a1 100644
> --- a/include/linux/arch_topology.h
> +++ b/include/linux/arch_topology.h
> @@ -4,6 +4,8 @@
>  #ifndef _LINUX_ARCH_TOPOLOGY_H_
>  #define _LINUX_ARCH_TOPOLOGY_H_
>  
> +#include <linux/percpu.h>
> +
>  void topology_normalize_cpu_scale(void);
>  
>  struct device_node;
> @@ -14,4 +16,12 @@ unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);
>  
>  void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);
>  
> +DECLARE_PER_CPU(unsigned long, freq_scale);
> +
> +static inline
> +unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
> +{
> +	return per_cpu(freq_scale, cpu);
> +}
> +
>  #endif /* _LINUX_ARCH_TOPOLOGY_H_ */

Acked-by: Viresh Kumar <viresh.kumar@...aro.org>

-- 
viresh