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* [PATCH V2 0/2] cpufreq: Use sorted frequency tables
@ 2016-06-01 10:39 Viresh Kumar
  2016-06-01 10:39 ` [PATCH V2 1/2] cpufreq: Store sorted frequency table Viresh Kumar
  2016-06-01 10:39 ` [PATCH V2 2/2] cpufreq: Optimize cpufreq_frequency_table_target() Viresh Kumar
  0 siblings, 2 replies; 7+ messages in thread
From: Viresh Kumar @ 2016-06-01 10:39 UTC (permalink / raw)
  To: Rafael Wysocki; +Cc: linaro-kernel, linux-pm, smuckle, Viresh Kumar

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(-)

-- 
2.7.1.410.g6faf27b


^ permalink raw reply	[flat|nested] 7+ messages in thread

end of thread, other threads:[~2016-06-03  3:16 UTC | newest]

Thread overview: 7+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2016-06-01 10:39 [PATCH V2 0/2] cpufreq: Use sorted frequency tables Viresh Kumar
2016-06-01 10:39 ` [PATCH V2 1/2] cpufreq: Store sorted frequency table Viresh Kumar
2016-06-01 10:39 ` [PATCH V2 2/2] cpufreq: Optimize cpufreq_frequency_table_target() Viresh Kumar
2016-06-01 19:46   ` Steve Muckle
2016-06-02  1:29     ` Viresh Kumar
2016-06-02 18:28       ` Steve Muckle
2016-06-03  3:16         ` Viresh Kumar

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