[boost] Re: Asynchronous I/O

From: Patrick Mézard (pmezard_at_[hidden])
Date: 2005-03-23 16:07:04

Don G <dongryphon <at> yahoo.com> writes:

> 
> Of the mechanisms discussed, I am not sure I understand what you mean
> by async I/O with only one thread. I can imagine a nonblocking/select
> style approach that has no extra threads, but as soon as the main
> thread is not waiting on I/O itself (my interpretation of "async"),
> there needs to be threads to do the waiting. Unless I am missing
> something (which happens often<g>) or we are having terminology
> problems (also a frustratingly frequent occurrence).

You should take a look at the python Twisted framework 
<http://twistedmatrix.com/>. There are performance issues in python with 
threads because of the Global Interpreter Lock (GIL). The framework is a 
workaround, performing every task in an asynchronous way from a single 
thread. The design of the Defer class is interesting and is the key of 
asychronous tasks control flows 
(<http://twistedmatrix.com/projects/core/documentation/howto/defer.html>).

By the way, there were and will be lengthy discussions about which 
approach is the "best" to build scalable concurrent programs. I think 
that multithreading and event-driven programming were proven to be 
equivalent from a theorical point of view, but there real differences 
in implementation. You could read this one and many items from its 
bibliography too:

<http://capriccio.cs.berkeley.edu/pubs/threads-hotos-2003.pdf> 
(The Capriccio project was really interesting too, on the paper. I do 
not know where they are now).

Patrick Mézard