Hi Chen Yu and ACPI experts,
On Sat, May 05, 2018 at 07:53:22PM +0800, Chen Yu wrote:
> According to current implementation of acpi_pad driver,
> it does not make sense to spawn any power saving threads
> on the cpus which are already idle - it might bring
> unnecessary overhead on these idle cpus and causes power
> waste. So verify the condition that if the number of 'busy'
> cpus exceeds the amount of the 'forced idle' cpus is met.
> This is applicable due to round-robin attribute of the
> power saving threads, otherwise ignore the setting/ACPI
> notification.
>
> Suggested-by: Lenny Szubowicz <lszubowi@xxxxxxxxxx>
> Suggested-by: Len Brown <lenb@xxxxxxxxxx>
> Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
> Cc: Lenny Szubowicz <lszubowi@xxxxxxxxxx>
> Cc: Len Brown <lenb@xxxxxxxxxx>
> Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
> Cc: Rui Zhang <rui.zhang@xxxxxxxxx>
> Cc: linux-acpi@xxxxxxxxxxxxxxx
> Signed-off-by: Chen Yu <yu.c.chen@xxxxxxxxx>
Do you have any news for this patch? Why it did not merged by kernel
maineline?
Thanks a lot!
Joey Lee
> ---
> drivers/acpi/acpi_pad.c | 52 ++++++++++++++++++++++++++++++++++++++++++++++++-
> 1 file changed, 51 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/acpi/acpi_pad.c b/drivers/acpi/acpi_pad.c
> index 552c1f7..515e60e 100644
> --- a/drivers/acpi/acpi_pad.c
> +++ b/drivers/acpi/acpi_pad.c
> @@ -254,12 +254,62 @@ static void set_power_saving_task_num(unsigned int num)
> }
> }
>
> +/*
> + * Extra acpi_pad threads should not be created until
> + * the requested idle count is less than/equals to the
> + * number of the busy cpus - it does not make sense to
> + * throttle the idle cpus.
> + */
> +#define SAMPLE_INTERVAL_JIF 20
> +
> +static u64 get_idle_time(int cpu)
> +{
> + u64 idle, idle_usecs = -1ULL;
> +
> + idle_usecs = get_cpu_idle_time_us(cpu, NULL);
> +
> + if (idle_usecs == -1ULL)
> + idle = kcpustat_cpu(cpu).cpustat[CPUTIME_IDLE];
> + else
> + idle = idle_usecs * NSEC_PER_USEC;
> +
> + return idle;
> +}
> +
> +static bool idle_nr_valid(unsigned int num_cpus)
> +{
> + int busy_nr = 0, i = 0, load_thresh = 100 - idle_pct;
> +
> + if (!num_cpus)
> + return true;
> +
> + for_each_online_cpu(i) {
> + u64 wall_time, idle_time;
> + unsigned int elapsed_delta, idle_delta, load;
> +
> + wall_time = jiffies64_to_nsecs(get_jiffies_64());
> + idle_time = get_idle_time(i);
> + /* Wait and see... */
> + schedule_timeout_uninterruptible(SAMPLE_INTERVAL_JIF);
> +
> + idle_delta = get_idle_time(i) - idle_time;
> + elapsed_delta = jiffies64_to_nsecs(get_jiffies_64()) - wall_time;
> + idle_delta = (idle_delta > elapsed_delta) ? elapsed_delta : idle_delta;
> + load = 100 * (elapsed_delta - idle_delta) / elapsed_delta;
> + if (load >= load_thresh)
> + busy_nr++;
> + }
> +
> + return (busy_nr >= num_cpus) ? true : false;
> +}
> +
> static void acpi_pad_idle_cpus(unsigned int num_cpus)
> {
> get_online_cpus();
>
> num_cpus = min_t(unsigned int, num_cpus, num_online_cpus());
> - set_power_saving_task_num(num_cpus);
> + if (idle_nr_valid(num_cpus))
> + set_power_saving_task_num(num_cpus);
>
> put_online_cpus();
> }
> --
> 2.7.4
>
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