From: Dave Thomas <Dave@...>
Date: 2001-12-20T05:54:14+09:00
Subject: [ruby-talk:28987] Re: A Ruby programmer walked into a bar and ordered a Ruby-Thread

Luc Heinrich <lucsky@mac.com> writes:

> On 19/12/2001 15:46, "Harry Ohlsen" <harryo@zip.com.au> wrote:
> 
> > A little investigation shows that what appears to be happening is that
> > the first of two threads that is created has taken complete control of
> > the CPU, thus starving the main thread and not allowing any further
> > processing.
> 
> To quote the Pickaxe:
> (http://www.rubycentral.com/book/tut_threads.html and page 113 of the
> printed version)
> 
> "[Ruby threads] are totally in-process, implemented within the Ruby
> interpreter. That makes the Ruby threads completely portable---there is no
> reliance on the operating system---but you don't get certain benefits from
> having native threads. You may experience thread starvation (that's where a
> low-priority thread doesn't get a chance to run). If you manage to get your
> threads deadlocked, the whole process may grind to a halt. And if some
> thread happens to make a call to the operating system that takes a long time
> to complete, all threads will hang until the interpreter gets control back."
> 
> So, although quite unfortunate, this would be some kind of an "expected"
> behavior, I guess.

Well, not really. Under Windows, there doesn't seem to be any
switching between threads in some circumstances. Each thread runs to
completion, and then another starts. Although arguably correct in a
theoretical sense, it isn't much use in practice. Under Unix, threads
play nicely with each other (hence the example with counters in the
book).

> Which leads me to the same question I recently asked on the #ruby-lang
> channel: what kind of impact would have the introduction of native threads
> in Ruby ?

The interpreter is not thread safe, and the consensus seems to be that
making it so would be a waste of time, given the upcoming rewrite. A
secondary issue is the extensions that are already out there. How many
of there are also not thread safe, and what impact would running under
a native threading model have on them?


Regards


Dave