From: Ben Giddings <bg-rubytalk@...>
Date: 2007-01-18T08:06:30+09:00
Subject: Re: local interprocess communication ideas.

On Jan 17, 2007, at 17:30, James Mills wrote:
> So, I have an embedded ARM proc with about 200MHz, and I want this app
> to feel as responsive as possible.  The GUI and controller will both
> run on this machine.  When a button on the GUI is pressed, the command
> is sent to the controller, the controller sends a command out of the
> serial port, and an action is taken.


How responsive are we talking about here?  Do you need "twitch" video  
game type responsiveness (tens of ms) or something less?  Unless you  
need twitch video game responsiveness, I'm pretty sure anything over  
the local loopback would be fast enough.  I've written CGIs that ran  
on the webserver of an ARM-based embedded device, and despite the  
overhead of a *real* network between me and them, they seemed very  
responsive.

If you need tens-of-ms type responsiveness, you might want to use  
some shared memory.  This couldn't be done natively in Ruby, but it  
would be pretty easy to write some simple C, write a Ruby extension,  
and use it that way.

Keep in mind that in my experience, you'll never be able to get any  
better than say 20ms responsiveness, since that's the task-switching  
overhead inherent in using Linux (and I assume other OSes would be  
similar).  You *could* get faster by writing kernel extensions, but  
that's even further from a pure Ruby implementation.

Ben