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SubjectRe: [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@linuxfoundation.org>
> Cc: Juri Lelli <juri.lelli@arm.com>
> Signed-off-by: Dietmar Eggemann <dietmar.eggemann@arm.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@linaro.org>

--
viresh

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