[Ksummit-discuss] [TECH TOPIC] System-wide interface to specify the level of PM tuning
Rafael J. Wysocki
rjw at rjwysocki.net
Tue Jul 7 12:33:12 UTC 2015
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
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