[PATCH 0/2] Some improvements to the cpuidle menu governor

[Arjan van de Ven <arjan@infradead.org>]

Hi,

two patches to the menu governor that, together, boost the quality of
the decisions it makes significantly (results below).
The first patch is basically a bugfix, while the second patch adds some
smarts to the algorithm.

Both patches only impact the idle-duration predictor (for those
unfamiliar with the menu governor, the menu governor first tries to
predict the idle duration, and then uses a set of heuristics to pick
a suitable idle state based on this prediction. The better the
prediction the better the decision ends up being)

To show the quality of the predictor, I added some instrumentation
where I had perf report out the result of the current, after patch 1
and after patch 2 prediction value as well as the actual idle duration
as measured at the end of the idle period. The test run I give below had
69854 samples (other runs had pretty much the same result).

The quality indicator I use is the percentage of samples for which the
prediction is within a certain factor of the actual duration.

Factor         before patches       patch 1          patch 1+2
1.5x            29.1%               30.4%            34.1%
2x              33.6%               49.3%            52.9%
4x              43.6%               73.6%            75.2%
10x             56.9%               86.1%            86.5%
100x            78.4%               97.0%            97.2%



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
For development, discussion and tips for power savings, 
visit http://www.lesswatts.org