shrinking memory consumptions

[Ivan Krstić]

Jens Axboe wrote:
> Didn't figure I would :-) And yeah, I don't mind taking a look at low
> memory and OOM situations.

I don't really know that there's that much to work on with regards to
OOM. When we hit OOM, we've lost already -- we need to make an arbitrary
decision to kill something, and there's no good heuristic to make sure
we don't kill whatever is most precious to the user at the moment.

In my mind, the OOM solution is a relatively straightforward one: when
-- sans buffers and cache -- we've allocated 256-x MB, with x being 5 or
10, the kernel emits a warning to userland through some interface
(netlink? something else we can epoll?). Sugar picks up warning, freezes
execution of currently-running activity, and gives the user a "low
memory; pick an application to close" chooser. After the user makes the
selection, the target application is sent a 'save anything you have open
and emergency close' message via D-BUS, and terminated seconds later if
it fails to comply. If I remember correctly my conversation with Sampsa
of the Maemo team at Nokia, they wanted to do something similar.

All of the above can be implemented today, except we'd have to poll;
optimizing that to be epollable is worth it, but either way, I strongly
believe OOM should be a last resort, not a "solution".

-- 
Ivan Krstić <krstic at solarsail.hcs.harvard.edu> | GPG: 0x147C722D