OOM conditions

[Martin Dengler]

On Fri, Oct 30, 2009 at 11:22:13PM +0100, Tomeu Vizoso wrote:
> On Fri, Oct 30, 2009 at 16:58, Richard A. Smith <richard at laptop.org> wrote:
> > Working the table at the Boston book festival I was reminded how
> > painful the OOM stuff is on a gen 1. The demo machines were in
> > this state a lot as each visitor would open up a new
> > program.  Basically you have to just turn the unit off and restart
> > as trying to recover is futile.
> 
> What if activities had a higher oom_score? Would that protect enough
> the processes that once killed require a system restart (X, shell,
> etc)?

See patch vs sugar-toolkit HEAD below[1] (I can backport to 0.82 if
wanted).

> Maybe even have the background activities have a higher
> oom_score than the one in the foreground?

Interesting.  Another approach I'd love feedback on would be to set
the allowed number of simultaneous running activities to be 2 (1 +
Journal) and writing a simple control panel extension that would allow
tweaking that, this oom_adj, and other related gconf values.
 
> Regards,
> 
> Tomeu

Martin


1. patch against
http://cgit.sugarlabs.org/sugar-toolkit/mainline/tree/src/sugar/activity/main.py :

diff --git a/src/sugar/activity/main.py b/src/sugar/activity/main.py
index 93f34e6..c868e11 100644
--- a/src/sugar/activity/main.py
+++ b/src/sugar/activity/main.py
@@ -31,7 +31,40 @@ from sugar.bundle.activitybundle import ActivityBundle
 from sugar import logger
 
 
+def __oom_adj_self(omm_adj_value=None):
+    """ Change this process' OOM likelihood to oom_adj_value.
+
+    By default, use the value of gconf path
+    "/desktop/sugar/performance/oom_adj_default"; if none exists, make
+    this process most likely to be killed (oom_adj_value=15).
+
+    Linux-specific.  See http://linux-mm.org/OOM_Killer for details.
+    """
+    oom_adj_fullpath = "/proc/self/oom_adj"
+    if os.path.exists(oom_adj_fullpath):
+        try:
+
+            # get values/defaults from gconf
+            import gconf
+            gconf_dir = "/desktop/sugar/performance"
+            gconf_key = "oom_adj_default"
+            client = gconf.client_get_default()
+            if not client.dir_exists(gconf_dir):
+                client.add_dir(gconf_dir, gconf.CLIENT_PRELOAD_NONE)
+            if oom_adj_value is None:
+                oom_adj_value = client.get_int(gconf_dir + "/" + gconf_key)
+                if oom_adj_value is None:
+                    oom_adj_value = 15
+                    client.set_int(gconf_dir + "/" + gconf_key,
+                                   oom_adj_value)
+
+            file(oom_adj_fullpath).write(oom_adj_value)
+
+        except:
+            pass
+
 def create_activity_instance(constructor, handle):
+    __oom_adj_self()
     activity = constructor(handle)
     activity.show()
 
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