Messages in this thread | | | Date | Wed, 29 Aug 2012 16:41:17 -0400 | From | Rik van Riel <> | Subject | Re: KS/Plumbers: c-state governor BOF |
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On 08/24/2012 01:01 PM, Rik van Riel wrote:
> Since a good number of us will be in San Diego next week, at > Kernel Summit / Plumbers / etc, I will organize a c-state > governor BOF for those who are interested.
Here are the note from today's c-state governor BOF session:
- idle time estimator can be improved to return more conservative values - have a trace point to verify how well idle time estimation works, returning expected idle time for the current algorithm, expected idle time for a test algorithm, and actually measured idle time - we can objectively measure whether one idle time estimation algorithm is better than another - example: last 8 idle times are 180 200 30 210 1000 150 10000 190 - average idle time around 1500, but not typical - typical idle time just under 200 - almost all idle time spent in one interval - scheduler and cpufreq people also want idle time statistics, idea is to move the idle time statistics to the scheduler - having idle time statistics in the scheduler allows the stats to be migrated when the scheduler migrates a task - interface: expected idle time, demotion time - if we sleep much more than the expected idle time, put CPU into a deeper c-state - on x86 timed mwait could be used - generic timer code would be usable too - take into account both the idle statistics and power break-even
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