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From: "Rafael J. Wysocki" <rjw@rjwysocki.net>
To: Daniel Vetter <daniel.vetter@ffwll.ch>
Date: Thu, 16 Jul 2015 00:44:01 +0200
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Cc: "Brown, Len" <len.brown@intel.com>,
	"ksummit-discuss@lists.linuxfoundation.org"
	<ksummit-discuss@lists.linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Kristen Carlson Accardi <kristen@linux.intel.com>,
	Grant Likely <grant.likely@linaro.org>
Subject: Re: [Ksummit-discuss] [TECH TOPIC] System-wide interface to specify
	the level of PM tuning
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On Tuesday, July 14, 2015 06:51:31 PM Daniel Vetter wrote:
> On Tue, Jul 14, 2015 at 1:07 AM, Rafael J. Wysocki <rjw@rjwysocki.net> wrote:
> > However, there are places in the kernel where there is a real tradeoff between
> > power and performance (or power and capacity in general) and there are places
> > that tend to keep conservative settings for fear of exposing latent bugs to
> > a wide community of users.
> >
> > Those might benefit from allowing the users to relax the settings globally
> > if they want to.
> 
> Well that's the approach I don't like personally. Essentially we
> should be the experts on what works and what doesn't. But then kernel
> developers chicken out and dump this problem onto users, which happily
> enable all kinds of options they hear about. And then when it eats
> their data or crashes machines everyone shrugs and says "oh well you
> probably have one of the broken machines, don't enable this" and moves
> on.
> 
> There's certainly the case that some tuning stuff in core kernel has
> real downsides to either perf or power, but generally (for device
> drivers) I feel like simply not enabling the all the power features is
> a cheap way to chicken out of bugs reports and responsibility. I'm
> somewhat opionated on this ;-)

But that's what's happening.  Many PM features are not enabled by default for
this reason or another.

The point here is whether or not we want to have a way to make all of them be
enabled by default instead and see what happens, for example.

Thanks,
Rafael