On Tuesday, 5 September 2006 18:03, Scott E. Preece wrote: > > | From: "Rafael J. Wysocki" <rjw at sisk.pl> > | > | On Monday, 4 September 2006 01:00, Scott E. Preece wrote: > | > policy decision to suspend is based on factors that are wholly different > | > than the factors that drive frequency/voltage changes. If that were the > | > case, then there would be no point to making the decisions in the same > | > place. Honestly, I'm not sure of the answer to that... > | > | I think the decision to suspend is made > | a) by the user, > | b) by a policy manager in case when, for example, the battery is running > | critical (ie. on emergency). > | and the decision to change a frequency/voltage is usually based on some > | efficiency factors. > | > | Also, the suspend "transitions" are never transparent to the user and the > | changes of frequency/voltage usually are, at least as far as CPUs are > | concerned. > --- > > Your scope is too narrow. In our domain (mobile phones) the user has no > control at all over power management and decisions to suspend are always > transparent. > > In our own implementation, the user-space policy manager initiates > frequency and voltage changes and enabled suspends, but doesn't actually > initiate them. That is, the policy manager says "based on current user > activity, it would be OK to suspend now", and a kernel component then > looks for a good time to do it, based on the system being idle. Okay, but it's not like that on a PC. IMHO there are architectures on which suspend states are distinct and therefore they should be treated as such in general. > We have thought about merging the decisions into a single range of > operating points, but the added plumbing to get idle information back to > the policy manager seemed unappealing. > > We don't use cpufreq, so Pavel's arguments about not changing the kernel > interface weren't a concern, for us. We're using a kernel interface that > is all our own (and unappealingly ioctl-based). Fine, as far as I'm concerned. ;-) Greetings, Rafael -- You never change things by fighting the existing reality. R. Buckminster Fuller
