On Thu, 17 Jun 2010, Igor.Stoppa@xxxxxxxxx wrote: > i do understand that you are mostly targetting acpi based systems, > but even there, based on static leaks, it might not be always true > that lower frequencies are correlated to higher power savings > (or maybe i have misunderstood your draft - i am not so fluent in acpi) Right, my assertion is that ondemand deals only with P-states, where, by defintion, the deeper the P-state the lower the voltage, the higher the efficiency. I assume that ondemand is not used to enable T-states where the clock is throttled w/o lowering the voltage. I put a note to try to make that clear under max_powersave: "ondemand: min P-state (do not invoke T-states)" Of course it is also possible for a processor to do a poor job implementing P-states and a great job optimizing idle states such that race to idle were always a win. However, on such a processor it would make more sense to simply disable P-states. > > it is likely > > that some users would want to use "powersave" when on > > battery and perhaps shift to "performance" on A/C. > > if we consider also the thermal envelope and the fact that "performance" > might steal power from a charging battery, even ton A/C it might not be > possible to settle down in one state permanently. > > Or do you expect other mechanisms to intervene? Typical laptop BIOS commonly implement a scheme where they maximize performance on AC and bias towards saving energy on DC. That, of course, is just one example use-model. Here Linux user-space can choose whatever policy makes sense for them at run-time. cheers, -Len Brown, Intel Open Source Technology Center -- To unsubscribe from this list: send the line "unsubscribe linux-acpi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
