From: Mario Camou <mcamou@...>
Date: 2009-08-23T02:43:54+09:00
Subject: Re: Process or Thread?

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On Sat, Aug 22, 2009 at 16:47, 7stud -- <bbxx789_05ss@yahoo.com> wrote:

> Pito Salas wrote:
>
It doesn't sound like your situation will result in improved performance
> with threads.  Things don't actually get done at the same time with
> threads--that's an illusion.  What happens is that there is very fast
> switching between different tasks.  However, if your tasks do not have
> dead time during the processing, then using threads won't improve
> performance.  For instance, suppose you have two tasks that each take 3
> minutes to complete.  The processing might happen in this order with
> threads:
>
> task1: 1 minute
> task2: 1 minute
> task1: 1 minute
> task2: 1 minute
> task1: 1 minute
> task2: 1 minute
> --------------
> total =3D 6 minutes
>

That's  true if you=B4re running MRI, since it uses "green" threads (i.e., =
you
really have a single OS-level thread that gets task-switched by Ruby
itself). However, if you run on JRuby, the Ruby Thread support gets mapped
onto the Java Thread support, which *does* map to OS-level threads and
therefore will take advantage of multiple cores if you have them. In that
case you *would* get faster processing.

Hope this helps,
-Mario.

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