| From: Pavel Machek<pavel at 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 e-mail: preece at motorola.com fax: +1-217-384-8550 phone: +1-217-384-8589 cell: +1-217-433-6114 pager: 2174336114 at vtext.com
