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Maybe I'm too late on this, but I have some concerns. >>> >>> On 10/17/24 05:39, Dhananjay Ugwekar wrote: >>>> In other systems, power consumption has increased but so has the >>>> throughput/watt. >>> >>> I just want to bring up the fact that this change affects all >>> governors. It sounds good for the performance governor, but not so >>> much for the powersave governor. >>> >>> So the question is: don't we want the lowest power consumption >>> possible in the powersave mode? Even if it means decreased efficiency. >>> Powersave by definition supposed to make battery last as long as >>> possible no matter what, isn't it? >>> >> >> No, the powersave governor isn't a one stop shop to bring everything to >> longest battery. >> >> By your argument we should set the EPP to "power" by default and "boost" >> to off by default when the powersave governor is enacted? >> >> All of those are far too aggressive for a default behavior.  Setting the >> lowest nonlinear frequency as the default lowest scaling frequency is >> about having a good default that balances responsiveness, battery life >> and performance. >> >> Like all knobs anyone that doesn't agree with it can of course modify it >> from sysfs. >> > > If the documentation is correct, the lowest_nonlinear_frequency *does* > result in the lowest battery consumption unless you are running one or > more threads at 100% utilization until the battery dies. In that case, > lowest nonlinear frequency should result in greatest number of > instructions retired when the battery dies. I say instructions retired > rather than work completed, because "100% until the battery dies" is > only stress tests, malware, and damn-the-torpedos concurrency frameworks > that use spinwaits. > > If that is not true, then either the documentation is wrong, or the > CPU's reporting of its lowest nonlinear frequency is wrong. > > I am puzzled why the CPU even exposes frequencies below > lowest-nonlinear. They should always be worse than PWM-ing between C0 at > lowest nonlinear freq and some deeper C-state. I dont think we can assume that idling at lowest frequency would *always* be worse than going to the shallowest C-state (considering the c-state entry-exit latency), in terms of power, performance or tail latencies. This might vary between different systems and scenarios. Testing software that has > to run on much slower CPUs, I guess?