On Wed, Aug 04, 2010 at 07:02:55PM -0700, Brian Swetland wrote: > On Wed, Aug 4, 2010 at 6:58 PM, Matt Helsley <matthltc@xxxxxxxxxx> wrote: > > On Wed, Aug 04, 2010 at 05:35:09PM +0100, Matthew Garrett wrote: > >> > >> The main problem I see with the cgroups solution is that it doesn't seem > >> to do anything to handle avoiding loss of wakeup events. > > > > cgroups alone don't but there is a solution which doesn't require routing > > all event data through a single server -- use SIGIO. > > > > Suppose we've got two cgroups of tasks -- those in the initial freezer > > cgroup and those in a freezer cgroup meant for power-naive apps. Let's > > call the second cgroup the naive cgroup. > > > > One task -- let's call it the "waker" -- is in the initial cgroup is normaly > > asleep waiting for SIGIO. Note it's not an "app" -- it's been trusted/blessed > > to be a non-power-naive task. It will be signaled via SIGIO by the > > applications which want to be unfrozen when an event comes in. > > > > When the power-naive app in the naive cgroup opens a file descriptor it's > > going through the Android interpretter to make the syscall. The interpretter > > can do fcntl() on the fd to cause SIGIO to be delivered to the waker task. > > When the waker gets SIGIO it unfreezes the naive cgroup and thus wakes the > > power-naive app. When the power-naive app wakes it will > > poll/return-from-poll/read/return-from-read and thus retrieve the event. > > The Android execution model includes native code in addition to the > dalvik VM, and in the future could include other runtimes -- there are > many standard libraries that directly make posix file IO calls, and > apps can bundle native libraries which can also directly make > syscalls. It's not practical to instrument every piece of userspace > code that opens a fd somehow to make additional fcntl calls in various > places. Perhaps using an LD_PRELOAD will work. Cheers, -Matt Helsley _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
