On Sat, Jun 10, 2017 at 2:11 AM, Joel Fernandes <joe...@google.com> wrote: > On Fri, Jun 9, 2017 at 3:15 AM, Viresh Kumar <viresh.ku...@linaro.org> wrote: >> While reducing frequency if there are no frequencies available between >> "current" and "next" calculated frequency, then the core will never >> select the "next" frequency. >> >> For example, consider the possible range of frequencies as 900 MHz, 1 >> GHz, 1.1 GHz, and 1.2 GHz. If the current frequency is 1.1 GHz and the >> next frequency (based on current utilization) is 1 GHz, then the >> schedutil governor will try to set the average of these as the next >> frequency (i.e. 1.05 GHz). >> >> Because we always try to find the lowest frequency greater than equal to >> the target frequency, cpufreq_driver_resolve_freq() will end up >> returning 1.1 GHz only. And we will not be able to reduce the frequency >> eventually. The worst hit is the policy->min frequency as that will >> never get selected after the frequency is increased once. > > But once utilization goes to 0, it will select the min frequency > (because it selects lowest frequency >= target)?
Never mind my comment about util 0, I see the problem you mention. However I feel that this entire series adds complexity all to handle the case of a false cache-miss which I think might not be that bad, and the tradeoff with complexity/readability of the code kind of negates the benefit. That's just my opinion about it fwiw. Thanks, Joel
