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

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

On Saturday, July 25, 2015 05:16:00 PM Josh Triplett wrote:
> On Sun, Jul 26, 2015 at 02:03:55AM +0200, Rafael J. Wysocki wrote:
> > On Saturday, July 25, 2015 12:50:16 PM Josh Triplett wrote:

[cut]

> > 
> > Say the user has a new machine and doesn't know which tunables can be safely
> > enabled on it.  The only way to check is to toggle all of them and see if
> > anything breaks.  The difficulty here is that the user actually needs to
> > know about all of them which takes quite a bit of research and if nothing
> > breaks really that's a fair amount of work pretty much in vain.  A global
> > switch would make it somewhat easier for the lucky users whose systems
> > don't break after toggling it.
> 
> Odds are at least one thing will break, though, and if the user doesn't
> know about all of the tunables they just changed, they won't necessarily
> know how to diagnose the reason, especially if the failure is more
> subtle and doesn't completely break the system.
> 
> Perhaps, as a start towards this, we could document all the "might or
> might not work" power management tunables in one place, and document
> what might go wrong if they don't work on your system.  That could then
> easily become an /etc/sysctl.d file to toggle them all.  And even if we
> offer a single global "dangerous PM tunables" switch, that document
> would help identify what might go wrong and help re-disable the things
> that don't work.

That sounds like a good idea to me.

Thanks,
Rafael