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

Scott E. Preece
2006-09-03T22:12:22Z

| From: Pavel Machek<pavel@ucw.cz>
|
| Hi!
|
| > | > > 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.
| >
| > ---
| >
| > But, surely that distinction can be handled in the implementation behind
| > the interface, rather than exsposed in the interface. Does that
| > distinction matter to the policy manager? I would argue that it
| > increases the latency, which would be important to the policy manager,
| > but that the nature of the latency isn't important to making a policy
| > decision, and the proposed interface already exposes the latency as
| > something that can be used in making transition decisions.
|
| Are we talking about the same thing?
|
| If policy manager decides to suspend-to-RAM, it will freeze
| itself. Puff, it is not running any more.
---

Well, I assume the policy manager is telling something in the kernel to
actually set the operating point. Once it has made that request, it
doesn't need to run any longer.

---
|
| Yes, it is important that interfaces are different. Would you argue
| for using same interface for slowing down machine and for turning
| machine off?
|
| And suspend-to-disk *is* turning machine off.
---

An interesting question. While it's turning the machine off, it's not
turning it off in the same sense as shutdown, because otherwise you
wouldn't come back via resume.

In any case, I could imagine OFF being another point in the operating
point continuum, except that it's not something I would expect to be
part of the range available to a policy manager (probably; I guess there
are emergency situations where the policy manager might want to shut the
machine down).

---
|
| Of course, we could use same interface for both. No, it is not good
| idea. We want reasonably clean interface. If it means rewriting
| powerop two or three times... we'll need to do it.
---

Not speaking to either of the current code submissions, I would say that
having a kernel interface for defining OPs and a kernel interface for
setting the OP, was a reasonably clean interface.

scott

--
scott preece
motorola mobile devices, il67, 1800 s. oak st., champaign, il 61820
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