Re: Run-time PM idea (was: Re: [linux-pm] [RFC][PATCH 0/2] PM:Rearrange core suspend code)

From: Ingo Molnar
Date: Mon Jun 08 2009 - 09:23:00 EST

* Matthew Garrett <mjg59@xxxxxxxxxxxxx> wrote:

> On Mon, Jun 08, 2009 at 03:05:09PM +0200, Ingo Molnar wrote:
> >
> > * Rafael J. Wysocki <rjw@xxxxxxx> wrote:
> > > Well, we've been discussing it for quite a while and since more
> > > and more people are interested, I'm giving it a high priority.
> >
> > Cool. I think that if within a few years we could achieve that every
> > default distro (both on desktops and on servers) triggers PM
> > functionality runtime on common hardware, we'd both have lower power
> > consumption in general, and we'd have more robust suspend-resume
> > code as well.
> The difficulty is in determining when it's viable to autosuspend a
> given device. There's a limit to how much we can determine purely
> from kernel state (for instance, we could suspend ahci when
> there's no pending disk access, but we'd lose hotplug
> notifications) so there's going to have to be some level of
> userspace policy determination. Having the infrastructure in the
> kernel is an important part of this, but there'll be some distance
> to go after that.

What will the 'user space policy' bit do what the kernel cannot?

If you mean the user has to configure something manually - that wont
really happen in practice. We are happy if they know where to put
those USB sticks in ;-)

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