Re: [PATCH V2 2/2] cpufreq: Optimize cpufreq_frequency_table_target()

From: Steve Muckle
Date: Wed Jun 01 2016 - 15:46:27 EST


On Wed, Jun 01, 2016 at 04:09:55PM +0530, Viresh Kumar wrote:
> cpufreq core keeps another table of sorted frequencies now and that can
> be used to find a match quickly, instead of traversing the unsorted list
> in an inefficient way.
>
> Create helper routines for separate relation types to optimize it
> further.
>
> Ideally the new routine cpufreq_find_target_index() is required to be
> exported, but s3c24xx was abusing the earlier API and have to be
> supported for now. Added a FIXME for it.
>
> Tested on Exynos board with both ondemand and schedutil governor and
> confirmed with help of various print messages that we are eventually
> switching to the desired frequency based on a target frequency.
>
> Signed-off-by: Viresh Kumar <viresh.kumar@xxxxxxxxxx>
> ---
> drivers/cpufreq/acpi-cpufreq.c | 15 ++--
> drivers/cpufreq/freq_table.c | 180 ++++++++++++++++++++++----------------
> drivers/cpufreq/s3c24xx-cpufreq.c | 13 ++-
> include/linux/cpufreq.h | 20 ++++-
> 4 files changed, 134 insertions(+), 94 deletions(-)
>
> diff --git a/drivers/cpufreq/acpi-cpufreq.c b/drivers/cpufreq/acpi-cpufreq.c
> index 32a15052f363..4f9f7504a17c 100644
> --- a/drivers/cpufreq/acpi-cpufreq.c
> +++ b/drivers/cpufreq/acpi-cpufreq.c
> @@ -468,20 +468,15 @@ unsigned int acpi_cpufreq_fast_switch(struct cpufreq_policy *policy,
> struct acpi_cpufreq_data *data = policy->driver_data;
> struct acpi_processor_performance *perf;
> struct cpufreq_frequency_table *entry;
> - unsigned int next_perf_state, next_freq, freq;
> + unsigned int next_perf_state, next_freq, index;
>
> /*
> * Find the closest frequency above target_freq.
> - *
> - * The table is sorted in the reverse order with respect to the
> - * frequency and all of the entries are valid (see the initialization).
> */
> - entry = policy->freq_table;
> - do {
> - entry++;
> - freq = entry->frequency;
> - } while (freq >= target_freq && freq != CPUFREQ_TABLE_END);
> - entry--;
> + index = cpufreq_frequency_table_target(policy, target_freq,
> + CPUFREQ_RELATION_L);

This adds a function call to the fast path...