From: Robert Klemme <shortcutter@...>
Date: 2008-09-11T15:33:25+09:00
Subject: Re: How to detect blocking?

On 11.09.2008 06:48, David Masover wrote:
> I've been (barely, occasionally) writing an Actor system for Ruby.
> 
> It was actually pretty easy, when I was doing one thread per actor, but that 
> has some serious drawbacks -- among them that threads can't be garbage 
> collected (can they?), whereas actors really should be collectable.
> 
> So now I'm considering running a smaller number of threads -- at least one per 
> usable CPU (so at least one on mainline Ruby, more on JRuby) -- but more, 
> since operations might block.
> 
> The problem is, how do I detect a blocked thread, and execute some code when 
> that happens?

Block on what?  IO?  In that case you probably want to use more threads 
as Ruby does handle this nicely.

> The best I can think of is to poll, checking for #stop?, but that's hackish, 
> and performance would be awful. Poll too often, and I burn CPU -- not often 
> enough, and I end up with large windows of my app waiting for the poll thread 
> to wake up.

I do not have a clear idea of your app but usually with multiple threads 
you use some form of synchronization (blocking queues, condition 
variables etc.).  HTH

Kind regards

	robert