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    Subject[PATCH 3/8] sched/cpufreq: new cfs capacity margin helpers
    Date
    Introduce helper functions that allow cpufreq governors to change the
    value of the capacity margin applied to the cfs_rq->avg.util_avg signal.
    This allows for run-time tuning of the margin.

    A follow-up patch will update the schedutil governor to use these
    helpers.

    Signed-off-by: Michael Turquette <mturquette+renesas@baylibre.com>
    ---
    include/linux/sched.h | 3 +++
    kernel/sched/cpufreq.c | 53 ++++++++++++++++++++++++++++++++++++++++++++++++++
    2 files changed, 56 insertions(+)

    diff --git a/include/linux/sched.h b/include/linux/sched.h
    index 1fa9b52..f18a99b 100644
    --- a/include/linux/sched.h
    +++ b/include/linux/sched.h
    @@ -2372,6 +2372,9 @@ void cpufreq_set_freq_update_hook(int cpu, struct freq_update_hook *hook,
    void (*func)(struct freq_update_hook *hook, u64 time,
    unsigned long util, unsigned long max));
    void cpufreq_clear_freq_update_hook(int cpu);
    +unsigned long cpufreq_get_cfs_capacity_margin(void);
    +void cpufreq_set_cfs_capacity_margin(unsigned long margin);
    +void cpufreq_reset_cfs_capacity_margin(void);
    #endif

    #ifdef CONFIG_SCHED_AUTOGROUP
    diff --git a/kernel/sched/cpufreq.c b/kernel/sched/cpufreq.c
    index bd012c2..a126b58 100644
    --- a/kernel/sched/cpufreq.c
    +++ b/kernel/sched/cpufreq.c
    @@ -61,6 +61,59 @@ void cpufreq_clear_freq_update_hook(int cpu)
    EXPORT_SYMBOL_GPL(cpufreq_clear_freq_update_hook);

    /**
    + * cpufreq_get_cfs_capacity_margin - Get global cfs enqueue capacity margin
    + *
    + * margin is a percentage of capacity that is applied to the current
    + * utilization when selecting a new capacity state or cpu frequency. The value
    + * should be normalized to the range of [0..SCHED_CAPACITY_SCALE], where
    + * SCHED_CAPACITY_SCALE is 100% of the normalized capacity, or equivalent to
    + * multiplying the utilization by one.
    + *
    + * This function returns the current global cfs enqueue capacity margin
    + */
    +unsigned long cpufreq_get_cfs_capacity_margin(void)
    +{
    + return cfs_capacity_margin;
    +}
    +EXPORT_SYMBOL_GPL(cpufreq_get_cfs_capacity_margin);
    +
    +/**
    + * cpufreq_set_cfs_capacity_margin - Set global cfs enqueue capacity margin
    + * @margin: new capacity margin
    + *
    + * margin is a percentage of capacity that is applied to the current
    + * utilization when selecting a new capacity state or cpu frequency. The value
    + * should be normalized to the range of [0..SCHED_CAPACITY_SCALE], where
    + * SCHED_CAPACITY_SCALE is 100% of the normalized capacity, or equivalent to
    + * multiplying the utilization by one.
    + *
    + * For instance, to add a 25% margin to a utilization, margin should be 1280,
    + * which is 1.25x 1024, the default for SCHED_CAPACITY_SCALE.
    + */
    +void cpufreq_set_cfs_capacity_margin(unsigned long margin)
    +{
    + cfs_capacity_margin = margin;
    +}
    +EXPORT_SYMBOL_GPL(cpufreq_set_cfs_capacity_margin);
    +
    +/**
    + * cpufreq_reset_cfs_capacity_margin - Reset global cfs enqueue cap margin
    + *
    + * margin is a percentage of capacity that is applied to the current
    + * utilization when selecting a new capacity state or cpu frequency. The value
    + * should be normalized to the range of [0..SCHED_CAPACITY_SCALE], where
    + * SCHED_CAPACITY_SCALE is 100% of the normalized capacity, or equivalent to
    + * multiplying the utilization by one.
    + *
    + * This function resets the global margin to its default value.
    + */
    +void cpufreq_reset_cfs_capacity_margin(void)
    +{
    + cfs_capacity_margin = CAPACITY_MARGIN_DEFAULT;
    +}
    +EXPORT_SYMBOL_GPL(cpufreq_reset_cfs_capacity_margin);
    +
    +/**
    * cpufreq_update_util - Take a note about CPU utilization changes.
    * @time: Current time.
    * @util: CPU utilization.
    --
    2.1.4
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