Stability and Memory Pressure in 8.2

[Jim Gettys]

There are four classes of things we can/should/could do:
	1) understand where our memory is being used.  Individual bugs can have
a large effect.  Something stupid could be hurting us badly, and we
won't know unless we look.  What is more, we need to invest in tools
that allow us to monitor this.
	2) there are some band-aids that have been discussed, such as rlimits,
which we can experiment with, and that *might* improve the situation
without the real solutions the next two items go into.
	3) the oom killer's default algorithms are pretty terrible, taking
little into account in the choice of what gets killed.  Between
Sugar/Rainbow, and knowledge that the window manager has, one could do
much better.
	4) we provide no end user feedback on memory usage, either.  We should
investigate whether revisiting our previous attempt to give such
feedback, now that Linux can provide much better information than it
could when we abandoned our previous donut attempt.  The users could
really help, if only we let them know a bit about what was going on...

In terms of priority: immediately examining what is going on with memory
usage in case we have a bad leak is clearly worthwhile (1).  We need to
budget for tool-building to monitor the situation going forward
immediately.

2) and *possibly* (a beginning on) 3 may be 8.2.1 fodder, but without
feedback from more users, we won't know if this isn't just keys under
the lamppost (e.g. our multiple bug reports about browse ooming because
of our amazingly stupid hardware wiki page, which is one of the most
egregious pages I've seen in recent memory.

Doing 3) pretty well I suspect is 9.1 fodder, but only if we start very
soon.  My gut tells me its some man-months of work.  We might get lucky
and should investigate if any of the embedded folks have something we
can use.  Unfortunately, the Nokia folks I had thought might have
something didn't, when I last checked a year ago.  But we can/should
check a bit first before diving in; it's a year later.
http://dev.laptop.org/ticket/1995

I urge we investigate quickly whether 4) is, in fact, feasible, so that
it can go on the Sugar roadmap in time to be done for 9.1.
                        - Jim


On Tue, 2008-09-09 at 13:02 +0200, Tomeu Vizoso wrote:
> On Tue, Sep 9, 2008 at 6:10 AM, Michael Stone <michael at laptop.org> wrote:
> >
> >  * We need to find out why the oom-killer is not killing things fast
> >    enough. Based on our results, we might consider configuring
> >    /proc/$pid/oom_adj to preferentially kill some processes (e.g., the
> >    foreground [or background?] activities.)
> 
> Any reason why killing first activities' processes wouldn't solve the
> stability issue? AFAIK, we haven't seen OOM conditions without any
> activity open.
> 
> Just in case, I'm not saying that isn't worth to do any of the other
> things on your list.
> 
> Regards,
> 
> Tomeu
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-- 
Jim Gettys <jg at laptop.org>
One Laptop Per Child