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Re: NIO multiplexing + thread pooling

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On Sat, 24 Sep 2011, Giovanni Azua wrote:

> would it increase performance to setup a Thread Pool and associate one 
> SelectionKey to one specific Thread in the pool so that all read/write 
> operations for each specific channel go through one specific Thread from 
> the Pool?

That would not be a thread pool. That would be a thread-per-connection 
model. I can't say that the performance would be worse than with a real 
thread pool, but i doubt it would be better than using blocking IO.

> From all code examples/tutorials/books I have reviewed online the 
> "Selector Thread" seems like a bottleneck to me.

If the selector thread's only job is to identify channels which are ready 
to be worked on, handing them off to worker threads to be processed, then 
it doesn't really have a lot of work of its own to do, and so it's 
unlikely to be a bottleneck.

If you're processing the channels in the selector thread (in which case 
it's not really a selector thread), then it could be a bottleneck. So, you 
can have several of them; Selector.select() is threadsafe, so with a 
little attention to locking, you can have many threads selecting and then 
working. This is called the leader/followers model.

One thing you could consider, if using a single selector thread and a pool 
of worker threads, is trying to create some affinity between channels and 
threads, so that the same thread always handles the work on a particular 
channel (and on several channels); on a multiprocessor machine, this 
should increase cache performance, but is not otherwise particularly 
valuable. This is not entirely straightforward, because of thread and 
channel starvation issues; you should read up on work-stealing if you want 
to do that.

tom

-- 
And the future is certain, give us time to work it out

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Thread

NIO multiplexing + thread pooling Giovanni Azua <bravegag@hotmail.com> - 2011-09-24 20:32 +0200
  Re: NIO multiplexing + thread pooling Tom Anderson <twic@urchin.earth.li> - 2011-09-24 20:46 +0100
    Re: NIO multiplexing + thread pooling Giovanni Azua <bravegag@hotmail.com> - 2011-09-24 23:09 +0200
    Re: NIO multiplexing + thread pooling Robert Klemme <shortcutter@googlemail.com> - 2011-09-25 11:33 +0200
      Re: NIO multiplexing + thread pooling Tom Anderson <twic@urchin.earth.li> - 2011-09-27 20:52 +0100
        Re: NIO multiplexing + thread pooling Robert Klemme <shortcutter@googlemail.com> - 2011-09-28 08:21 +0200
          Re: NIO multiplexing + thread pooling markspace <-@.> - 2011-09-28 08:20 -0700
            Re: NIO multiplexing + thread pooling Robert Klemme <shortcutter@googlemail.com> - 2011-09-28 18:56 +0200
              Re: NIO multiplexing + thread pooling markspace <-@.> - 2011-09-28 11:07 -0700
            Re: NIO multiplexing + thread pooling Peter Duniho <NpOeStPeAdM@NnOwSlPiAnMk.com> - 2011-09-28 17:39 -0700
              Re: NIO multiplexing + thread pooling markspace <-@.> - 2011-09-29 09:25 -0700
                Re: NIO multiplexing + thread pooling Lew <lewbloch@gmail.com> - 2011-09-30 07:46 -0700
                Re: NIO multiplexing + thread pooling markspace <-@.> - 2011-09-30 08:22 -0700
                Re: NIO multiplexing + thread pooling Lew <lewbloch@gmail.com> - 2011-09-30 08:30 -0700
                Re: NIO multiplexing + thread pooling markspace <-@.> - 2011-09-30 08:49 -0700
                Re: NIO multiplexing + thread pooling Robert Klemme <shortcutter@googlemail.com> - 2011-09-30 20:57 +0200
  Re: NIO multiplexing + thread pooling "John B. Matthews" <nospam@nospam.invalid> - 2011-09-25 00:26 -0400
    Re: NIO multiplexing + thread pooling Giovanni Azua <bravegag@hotmail.com> - 2011-09-25 11:13 +0200

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