[maemo-developers] Hibernation of applications during ptrace

[From: Philip Van Hoof]

On Tue, 2007-09-25 at 19:23 +0300, Eero Tamminen wrote:
> Hi,

> Desktop kills only applications that have announced themselves to be 
> killable.  Application should do that only when they've saved state,
> are in the background (i.e. not interacting with the user) and able
> to restore the state when restarted.  I.e. it would be a problem in
> the application I think.

Interesting, how would this work? I don't think our application is ever
setting itself in this state, so I wonder why this hibernation key is
created? :-\

> And desktop does this only when it's notified that the device is low
> on memory.  So, close extra applications and if that doesn't help,
> add swap.  You might also try using gdbserver as Gdb can take quite
> a lot of memory.

This also happens in Scratchbox running on a desktop with 2GB of ram.

Using gdbserver is something I can try, yes. Measuring memory
availability shows me that around 20MB is still available when testing
this on a device.

> Another alternative is that the device runs so low on memory that
> your application is OOM-killed.  You can see this from the syslog.

Checked. This ain't happening. Thanks for the hint, though.

> In this case add swap or use gdbserver.  If you know that the device
> should still survive with the amount of memory Gdb and your app
> are using, you could set those processes OOM-protected with:
> 	echo -17 > /proc/PID/oom_adj

Aha, also very useful indeed.

> And OOM-unprotect it afterwards by using "0" instead of -17 (as root
> of course), but don't be surprised if the device reboots if they
> use too much memory. :-)

I wont :)

Thanks for the interesting info. Although I think it doesn't yet explain
the ptrace problem that I experience :-(


-- 
Philip Van Hoof, software developer
home: me at pvanhoof dot be 
gnome: pvanhoof at gnome dot org 
http://www.pvanhoof.be/blog