Re: So, what's the status on the recent patches here?

Rafael J. Wysocki
2006-09-03T20:57:49Z

On Sunday, 3 September 2006 18:25, David Singleton wrote:
> On 9/2/06, Rafael J. Wysocki <rjw@sisk.pl> wrote:
> > On Saturday 02 September 2006 20:05, David Singleton wrote:
> > > On 8/29/06, Matthew Locke <matthew.a.locke@comcast.net> wrote:
> > > >
> > > > On Aug 29, 2006, at 10:49 AM, Preece Scott-PREECE wrote:
> > > >
> > > > >
> > > > >> From: linux-pm-bounces@lists.osdl.org
> > > > >> [mailto:linux-pm-bounces@lists.osdl.org] On Behalf Of Pavel Machek
> > > > >> Sent: Tuesday, August 29, 2006 11:35 AM
> > > > >> To: David Singleton
> > > > >> Cc: linux-pm@lists.osdl.org
> > > > >> Subject: Re: [linux-pm] So, what's the status on the recent
> > > > >> patches here?
> > > > >>
> > > > >> Hi!
> > > > >>>>> point, by name. There is a new
> > > > >>>> /sys/power/operating_points directory
> > > > >>>>> that shows all the operating points the
> > > > >>>> system supports. An
> > > > >>>>> exampled from my centrino laptop shows:
> > > > >>>>>
> > > > >>>>> /sys/power/operating_points/high
> > > > >>>>> /sys/power/operating_points/highest
> > > > >>>>> /sys/power/operating_points/low
> > > > >>>>> /sys/power/operating_points/lowest
> > > > >>>>> /sys/power/operating_points/medium
> > > > >>>>> /sys/power/operating_points/mem
> > > > >>>>> /sys/power/operating_points/standby
> > > > >>>>
> > > > >>>> What makes you think that mixing operating and sleep
> > > > >> states is good
> > > > >>>> idea?
> > > > >>>
> > > > >>> They are all power states managed by the kernel and in the
> > > > >> operating
> > > > >>> point concept they are all operating points the system supports.
> > > > >>
> > > > >> That does not make mixing them right.
> > > > > ---
> > > > >
> > > > > Could you say why you think they shouldn't be mixed? Absent argument to
> > > > > the contrary,
> > > > > making it a single continuum seems appealing. Why have separate
> > > > > policies?
> > > >
> > > > I know this questions is directed at Pavel but I have similar concerns.
> > > > I agree that making sleep states into operating points is appealing.
> > > > However, if the implementation is just going to special case the sleep
> > > > state operating points then they should be handled separately. As
> > > > Pavel points out, you can see from Dave's implementation that the
> > > > operating point definition doesn't quite work for both. Voltage and
> > > > frequency don't have meaning for the sleep points.
> > >
> > > Actually what I was trying, unsuccessfully, to explain was that
> > > suspend states are valid, supported operating states the
> > > system can be in for power management. And that they are the
> > > same as an operating point for a processor frequency.
> >
> > That depends on the definition, but I think of suspend states as the ones
> > that require processes to be frozen before they can be entered. IMHO it is
> > quite clear that such states cannot be handled in the same way as those
> > that do not require the freezing of processes, so they are not the same.
>
> You are correct, processes do need to be frozen before a suspend.
> That's the prepare to suspend part of the suspend process, and
> the transtition is the suspending and finish is the un-freezing
> of the processes to resume execution.
>
> And those same steps are the same steps required to transition the
> system to a new operating point, whether it's suspend or change
> from 1.4GHz to 600MHz.

There are only a few states that require the processes to be frozen and I
think that's a good enough reason to handle them separately.

Greetings,
Rafael

--
You never change things by fighting the existing reality.
R. Buckminster Fuller