Hi Guys,
This work in inspired by some of the concerns raised by Steve in one of his patchset.
Currently, the cpufreq drivers aren't required to provide a sorted list of frequencies to the cpufreq-core and so traversing that list match a target frequency is very inefficient.
This is not bearable by, for example, the fast-switch path of schedutil governor and so we have moved the traversing logic local to the acpi-cpufreq driver for now. That is better handled in the core, but it has to be efficient first.
OTOH, even for traditional governors without a fast-switch path, it would be much better to be able to traverse this table quickly.
The ideal solution would be to keep a single *sorted* freq-table in struct cpufreq_policy. But there are few dependencies due to which it can't be done today (Hint: cpufreq drivers are abusing the 'index' passed to them, to refer to multiple arrays).
And so for now, lets create a separate table local to the cpufreq-core *only*.
This modifies the existing API cpufreq_frequency_table_target() to use the sorted table.
Lightly tested on Exynos board, frequencies were getting selected as expected.
V1->V2: - This optimizes cpufreq_frequency_table_target() instead of new APIs. - Is rebased over bleeding-edge + following cleanup series. [PATCH 0/8] cpufreq: cleanups and reorganization
-- viresh
Viresh Kumar (2): cpufreq: Store sorted frequency table cpufreq: Optimize cpufreq_frequency_table_target()
drivers/cpufreq/acpi-cpufreq.c | 15 +-- drivers/cpufreq/cpufreq.c | 23 ++-- drivers/cpufreq/freq_table.c | 247 ++++++++++++++++++++++++++------------ drivers/cpufreq/s3c24xx-cpufreq.c | 13 +- include/linux/cpufreq.h | 23 +++- 5 files changed, 220 insertions(+), 101 deletions(-)