[Server-devel] Yummy incron

[Bill Bogstad]

On Tue, Jun 24, 2008 at 8:54 PM, Martin Langhoff <martin at laptop.org> wrote:
> Looking for a (memory, cpu, power) efficient way to trigger
> events/scripts on the XS, I came across incrond. It weights ~600KB
> according to ps_mem.py, and it looks like the kind of tool we want to
> be using. There are a few processes I have on the XS that signal
> completion by touching a file in a tmpdir, so that a different process
> (with different privileges) can perform other steps. Using incron
> rather than poll frequently from an in-memory process or crond seems
> much smarter.
>
> <rant>
> Yes, this a bit like DBus, but DBus was designed for a desktop with
> Gobs Of Mighty RAM, and it requires that your process must be running
> in memory, and that it'd be forking/threaded if you want to process
> stuff in parallel. This means our (mostly python) processes are
> sitting idly on memory we don't have the luxury to spare. And that
> little or nothing happens in parallel.

I'm confused.   Won't the XS servers always have swap/paging space?
Idle processes should take hardly any RAM at all.
Not being familar with python's threading model, it may be that idle
threads (in a single process) will still take up memory.   Even then
though, partial process/thread paging should be active.  Does DBUS
wake up processes it shouldn't?  (creating RAM thrashing problems)
That seems to me to be more of a problem with DBUS message types not
being specific enough.

OTOH, If you were talking about the XO platform (paging to flash
probably being a bad idea), I would agree with you.

Bill Bogstad