On 13-07-16, 13:25, Steve Muckle wrote: > Invoking the cpufreq driver to set a frequency can be expensive. On platforms > with a cpufreq driver that does not support fast switching a thread must be > woken to complete the operation. IPIs will also occur if and when support to > process remote task wakeups is added in schedutil. > > Currently schedutil calculates a raw frequency request from scheduler > utilization data. This raw frequency request does not correlate to supported > cpufreq driver frequencies aside from being capped by the CPU's maximum > frequency. Consequently, there may be many consecutive requests for different > raw frequency values which all translate to the same driver-supported > frequency. For example on a platform with 3 supported frequencies 200MHz, > 400MHz, and 600MHz, raw requests for 257MHz, 389MHz, and 307MHz all map to a > driver-supported frequency of 400MHz in schedutil. Assuming these requests > were > consecutive and there were no changes in policy limits (min/max), there is no > need to issue the second or third request. > > In order to resolve a raw frequency request to a driver-supported one a new > cpufreq API is added, cpufreq_driver_resolve_freq(). This API relies on a new > cpufreq driver callback in the case of ->target() style drivers. Otherwise it > uses the existing frequency table operations. > > Lookups are cached both in cpufreq_driver_resolve_freq() (for the benefit of > the > driver) and in schedutil. > > Changes since v2: > - incorporated feedback from Viresh to use resolve_freq driver callbacks > only for ->target() style drivers, to use cpufreq's freq table operations, > and move freq mapping caching into cpufreq policy
Sorry for the delay buddy :( I have some concerns for the first patch. The second and third patch look fine. Feel free to add my Reviewed-by: Viresh Kumar <viresh.ku...@linaro.org> for them. -- viresh
