idea for running out of RAM

[Deepak Saxena]

On Sep 23 2008, at 03:40, Albert Cahalan was caught saying:
> Determining the RAM requirement for an activity goes something like
> the following:
> 
> awk '/Dirty/{x+=$2} END{print x}' < /proc/12345/smaps
> 
> (after exercising all functionality)

I like the idea overall but this part worries me. An activity such
as etoys has a lot of functionality.

> We can refine that, remembering that it will never be perfect.
> Adding a bit more (5 megabytes?) to avoid the slows is important.
> 
> If an activity has lied, there isn't much that can be done. Oh well.
> If the lie is caught before the system gets horribly slow, the OS
> can simply increase the reservation for that activity. (either just
> for that session, or persistently) The OS can log the problem, allowing
> the activity developer to be flamed. Killing the lying activity is not
> a good option, but it could be done, especially if some other activity
> is already running. Once the slows hit, it's back to the power button.

> BTW, the alternative is far more harsh yet easier for kids to deal with.
> We just ditch the whole idea of letting activities run concurrently. :-)
> Seriously, consider it. We're really short on RAM, and activity switching
> is not at all easy for kids.

I've been thinking to myself that this might be the right approach. While
we may think of that as limiting, for a child who has never used a computer
before, it might help focus their attention and be less confusing to 
simply allow one instance of any activity to run.

We can also play tricks like saving state of an activity to flash on
alt-tab and quickly restoring it when tabbing back. This is common 
in the mobile space where we want an illusion of being able to switch
between running applications. Your cellphone will most probably
never crash due to OOM, but you can often run multiple applications
on it. This won't work with shared activities or activities that 
have any network sockets open, but for purely local applications
it should be do-able (though non-trivial).

Something else I am looking into for helping with memory on 8.2.1 and 
9.1 is compressed caching. We can still OOM with this, but my experience
with my little playing I've done with it is that it drastically helps
keep the system useable as memory footprint increases.

~Deepak

-- 
Deepak Saxena - Kernel Developer - dsaxena at laptop.org