Froyo Activity Manager and MAX_HIDDEN_APPS

[davidkrause]

We noticed that in Froyo, some functionality was added in Activity
Manager (AM) to proactively kill "hidden" applications. AM gives
priority to background applications that have activities or content
providers. It does not take into account any services currently
running in the application.

A year or so ago, there was a discussion about OOM killer killing
process that had running services, and it was noted that those
processes were scheduled to restart right away, see
http://groups.google.com/group/android-platform/browse_thread/thread/626f6d0ac0a4361/1e8d94b85b767ac2?lnk=gst&q=activity+manager#1e8d94b85b767ac2

When the MAX_HIDDEN_APPS is set to the default value (15), we can see
that many applications that have services running in them are killed
and them immediately scheduled to be re-started. Is this the desired
behavior, since we know that AM will turn right around and restart
these applications? Since this is proactive killing by AM, would it
be better if AM took into account running services when it decided who
to kill?

Or are we missing something, and these apps with running services
should be created differently, maybe as persistent, to prevent this
from happening?

Also, where did the choice of 15 for MAX_HIDDEN_APPS come from?

Thanks,
-- Dave

[Dianne Hackborn]

Yes this is the desired behavior.  If the device had less memory available, it would have been killing those processes anyway.  This change is just for devices with fairly extreme amounts of memory (such as the nexus one), to avoid keeping around more processes than it makes any sense to.

Note that this does take into account running services -- the max count is for actual background processes.  There could be some confusion though because after a service has been running continuously for a while we sneakily drop it down into the background OOM class from the service OOM class, to ensure that it will be eventually be killed and restarted.  This is to avoid issues with services with memory leaks or other long-running problems.

That said, the actual number we picked is fairly arbitrary. :)

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[pb]

Hi , we observed one scenario where activity manager killed our
application processs(it includes 5 running services) and then re-
started only 1 service(this service was first one to be destroyed) .
What could be the reason for this behavior ?
Does AM checks for available resources before starting any proc ?
Please suggest . Other 4 services were never started by AM .

On Aug 12, 4:43 am, Dianne Hackborn <hack...@android.com> wrote:
> Yes this is the desired behavior.  If the device had less memory available,
> it would have been killing those processes anyway.  This change is just for
> devices with fairly extreme amounts of memory (such as the nexus one), to
> avoid keeping around more processes than it makes any sense to.
>
> Note that this does take into account running services -- the max count is
> for actual background processes.  There could be some confusion though
> because after a service has been running continuously for a while we
> sneakily drop it down into the background OOM class from the service OOM
> class, to ensure that it will be eventually be killed and restarted.  This
> is to avoid issues with services with memory leaks or other long-running
> problems.
>
> That said, the actual number we picked is fairly arbitrary. :)
>
>
>
> On Tue, Aug 10, 2010 at 9:37 PM, davidkrause <david.kra...@gmail.com> wrote:
> > We noticed that in Froyo, some functionality was added in Activity
> > Manager (AM) to proactively kill "hidden" applications.  AM gives
> > priority to background applications that have activities or content
> > providers.  It does not take into account any services currently
> > running in the application.
>
> > A year or so ago, there was a discussion about OOM killer killing
> > process that had running services, and it was noted that those
> > processes were scheduled to restart right away, see
>

> >http://groups.google.com/group/android-platform/browse_thread/thread/...

>
> > When the MAX_HIDDEN_APPS is set to the default value (15), we can see
> > that many applications that have services running in them are killed
> > and them immediately scheduled to be re-started.  Is this the desired
> > behavior, since we know that AM will turn right around and restart
> > these applications?  Since this is proactive killing by AM, would it
> > be better if AM took into account running services when it decided who
> > to kill?
>
> > Or are we missing something, and these apps with running services
> > should be created differently, maybe as persistent, to prevent this
> > from happening?
>
> > Also, where did the choice of 15 for MAX_HIDDEN_APPS come from?
>
> > Thanks,
> > -- Dave
>
> > --
> > You received this message because you are subscribed to the Google Groups
> > "android-platform" group.
> > To post to this group, send email to android-...@googlegroups.com.
> > To unsubscribe from this group, send email to

> > android-platfo...@googlegroups.com<android-platform%2Bunsu...@googlegroups.com>
> > .

> > For more options, visit this group at
> >http://groups.google.com/group/android-platform?hl=en.
>
> --
> Dianne Hackborn
> Android framework engineer

> hack...@android.com

[Dianne Hackborn]

You should probably post SDK developer questions to android-developers or StackOverflow.  There is lots of discussion about services there.  A couple quick things: (1) it is normally and expected for services that have been running a long time to be killed and then restarted; (2) a service can control what happens to it when its process is killed by what is returned from onStartCommand().

To unsubscribe from this group, send email to android-platfo...@googlegroups.com.

For more options, visit this group at http://groups.google.com/group/android-platform?hl=en.

--
Dianne Hackborn
Android framework engineer

hac...@android.com