From: rex goxman <lists@...>
Date: 2012-07-06T21:40:43+09:00
Subject: Re: Green threads in 1.9.* ?

Robert Klemme wrote in post #1067663:
> So far rex provides a solution he wants
> to use but I cannot really see the reasoning behind it.

*Sigh*.  I did not provide a "solution I want to use."  I provided a 
CRAPPY EXAMPLE off the top of my head that was advertised as a CRAPPY 
EXAMPLE before giving the CRAPPY EXAMPLE.

I do not intend to divulge any real use cases for green threads because 
they are intuitively obvious, apparent, easy to find or dream up for 
one's self, and the literature is abundant and easily available.  It's 
sort of like being asked to give a use case for a hammer.  I'm not here 
to educate.  If people want education, it's up to them to get it, not up 
to me to provide it.

Use cases for green threads aren't controversial, and there is no debate 
on it anywhere that I'm aware of... except perhaps here I guess.  I 
don't intend to debate whether or not green threads can be a good thing 
and whether there are many use cases for them any more than I wish to 
debate whether 2 + 2 = 4.

Now, whether Ruby wants to deploy and maintain a green threads solution 
or not is another issue entirely, completely separate from the issue of 
whether "green threads are good," or "green threads have many valid use 
cases."  The answers to the latter two issues are an unequivocal 'yes.' 
The answer to the former could be anything, and rightly or wrongly so.

Ruby might have good reasons or not so good reasons for wanting or not 
wanting to maintain green threads.  I don't care, and I'm not here to 
comment on that either way.  While I did say I was somewhat surprised 
that Ruby would ditch green threads altogether vs. keeping them around 
and deploying kernel threads alongside, there may very well be good 
reasons for such a decision, not least of which may simply be limited 
resources to devote to a threading implementation, and thus a need to 
simply pick one and go with it (just a guess).

> And from a global perspective
> which covers operating system as well as hardware trends Matz's
> decision to go for kernel threads is wise because that will eventually
> give us better performance (once GIL is gone).

Perhaps I have a clue here as to some of the... "interesting" responses 
I have received on this.  Perhaps it's a classic case of an "outsider" 
being perceived as coming into a community and criticizing the leader of 
the community.

If so, let me be clear.  I have said nothing regarding Matz, nor of his 
decision to go for kernel threads, nor the wisdom of that decision. 
Whether green threads are "good" or not, and whether Matz made a wise 
decision in ditching them for kernel threads, is two separate issues. 
In other words, it is possible that "green threads are good" and "Matz 
made a great decision and is a genius" are both true.

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