Re: [Ksummit-discuss] [TECH TOPIC] System-wide interface to specify the level of PM tuning

["Rafael J. Wysocki" <rjw@rjwysocki.net>]

On Tuesday, July 07, 2015 09:53:44 AM Jiri Kosina wrote:
> On Mon, 6 Jul 2015, Rafael J. Wysocki wrote:
> 
> > For one example, the default for most of the device/.../power/control 
> > files in sysfs is "on" (meaning no runtime PM) while it might be "auto" 
> > (use runtime PM if you can).  Making that change for everybody in one go 
> > may lead to various issues (that may be regarded as regressions then), 
> 
> I don't believe that the current default settings are set the way they are 
> set because we intentionally want to prefer performance to power efficiency.

No, this is not the intent, but having those defaults favors performance as
a consequence (and increasingly so as the integration of systems increases).

> The real problem is that it's really the only "safe" default, 
> because turning power-management features on is likely to cause 
> unpredictable issues (being it either real bugs in code, or just bad user 
> experience stemming from unexpected system behavior).
> 
> Such as suspended keyboard losing first keypress during wakeup (very 
> common). Or wireless power management not working properly between the 
> client and AP. Etc etc.

Agreed.

On the other hand, though, there are systems without those problems and their
users should be able to choose a more power-oriented behavior relatively
easily.

Thanks,
Rafael