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    Subject[PATCH v2 03/10] drivers base/arch_topology: frequency-invariant load-tracking support
    Date
    Implements an arch-specific frequency-scaling function
    topology_get_freq_scale() which provides the following frequency
    scaling factor:

    current_freq(cpu) << SCHED_CAPACITY_SHIFT / max_supported_freq(cpu)

    One possible consumer of this is the Per-Entity Load Tracking (PELT)
    mechanism of the task scheduler.

    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 | 20 ++++++++++++++++++++
    include/linux/arch_topology.h | 7 +++++++
    2 files changed, 27 insertions(+)

    diff --git a/drivers/base/arch_topology.c b/drivers/base/arch_topology.c
    index f4832c662762..63fb3f945d21 100644
    --- a/drivers/base/arch_topology.c
    +++ b/drivers/base/arch_topology.c
    @@ -22,6 +22,26 @@
    #include <linux/string.h>
    #include <linux/sched/topology.h>

    +static DEFINE_PER_CPU(unsigned long, freq_scale) = SCHED_CAPACITY_SCALE;
    +
    +unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu)
    +{
    + return per_cpu(freq_scale, cpu);
    +}
    +
    +void topology_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..168104d2d2cf 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/cpumask.h>
    +
    void topology_normalize_cpu_scale(void);

    struct device_node;
    @@ -14,4 +16,9 @@ unsigned long topology_get_cpu_scale(struct sched_domain *sd, int cpu);

    void topology_set_cpu_scale(unsigned int cpu, unsigned long capacity);

    +unsigned long topology_get_freq_scale(struct sched_domain *sd, int cpu);
    +
    +void topology_set_freq_scale(struct cpumask *cpus, unsigned long cur_freq,
    + unsigned long max_freq);
    +
    #endif /* _LINUX_ARCH_TOPOLOGY_H_ */
    --
    2.11.0
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