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    SubjectRe: [linux-pm] [PATCH 0/8] Suspend block api (version 6)
    Date
    On Thursday 13 May 2010, Tony Lindgren wrote:
    > * Alan Stern <stern@rowland.harvard.edu> [100513 14:32]:
    > > On Thu, 13 May 2010, Tony Lindgren wrote:
    > >
    > > > The difference between echo mem > /sys/power/state and suspend blocks
    > > > is that with suspend blocks the system keeps running.
    > >
    > > Irrelevant. Paul wasn't talking about the suspend blockers; he was
    > > talking about opportunistic suspend. So what's the difference between
    > > opportunistic suspend and "echo mem >/sys/power/state"? Especially
    > > when suspend blockers aren't being used?
    >
    > Opportunistic suspend is really trying to do runtime PM, see below.

    NO, IT IS NOT! What it does is to detect situations in which it is desirable
    to put the _entire_ _system_ to sleep, while runtime PM works on a per-device
    basis.

    > > > And that's why
    > > > it should be handled by runtime power management instead.
    > >
    > > Runtime PM is not capable of freezing userspace and shutting down CPUs.
    > > More or less by definition -- if it could then it wouldn't be "runtime"
    > > any more, since the processor wouldn't be running.
    >
    > Not true. We are already powering off CPUs and rebooting them for
    > at least omaps in every idle loop using cpuidle. The memory stays on.

    What about user space, though? Do you freeze it?

    > > > The suspend blocks seems like a hack to spam filter good and bad
    > > > apps from timer usage point of view. Applications are categorized
    > > > as good or bad depending if they grab a susped blocker or not.
    > >
    > > You're referring just to the userspace part of the suspend blocker
    > > API. What about the kernel part?
    >
    > IMHO some timer flags should be used in the kernel too. Currently
    > there's no way of knowing which timers are good or bad from suspend
    > point of view.

    How is that answering the Alan's question?

    Rafael


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