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    SubjectRe: Attempted summary of suspend-blockers LKML thread, take three
    Date
    On Saturday, August 07, 2010, Rafael J. Wysocki wrote:
    > On Saturday, August 07, 2010, Ted Ts'o wrote:
    > > On Fri, Aug 06, 2010 at 08:14:09PM -0700, david@lang.hm wrote:
    > > >
    > > > that description sounds far more like normal sleep power management
    > > > that suspending. especially since they want to set timers to wake
    > > > the system up and the defining characteristic of suspend (according
    > > > to this thread) is that timers don't fire while suspended.
    > > >
    > > > as I am seeing it, there are two reasons why this don't "just work"
    > > >
    > > > 1. sleeping can't currently save as much power as suspending
    > >
    > > No, I don't think that's the case at all. The key thing here is that
    > > *most* applications don't need to be modified to use suspend locks,
    > > because even though they might be in an event loop, when the user user
    > > turns off the display, the user generally doesn't want it doing things
    > > on their behalf.
    > >
    > > Again, take for example the Mac Book, since Apple has gotten this
    > > right for most users' use cases. When you close the lid, you even if
    > > the application is under the misguided belief that it should be
    > > checking every five seconds to see whether or not the web page has
    > > reloaded --- actually, that's not what you want. You probably want
    > > the application to be forcibly put to sleep. So the whole point of
    > > the suspend blocker design is that you don't have to modify most
    > > applications; they just simply get put to sleep when you close the
    > > MacBook lid, or, in the case of the Android device, you push the
    > > button that turns off the screen.
    >
    > But in principle that need not mean suspending the entire system.
    > To get applications out of the way, you need to freeze user space.
    > However, that's not sufficient, because in addition to that you need to
    > prevent deactivate the majority of interrupt sources to avoid waking up the
    > CPU (from C-states) too often.

    s/prevent deactivate/deactivate/

    Rafael


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