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From Mark Thomas <ma...@apache.org>
Subject Re: Executor thread lifecycle
Date Tue, 20 Sep 2011 19:11:53 GMT
On 20/09/2011 20:06, Dan Checkoway wrote:
> To be specific, we're having a major issue with garbage generation.  To
> avoid this, we're pre-allocating pools of instances (up until now
> ThreadLocal, but that's obviously changing).  When a request is processed it
> may need anywhere between 1 and N objects from the pool, which it grabs and
> uses, and then returns them to the pool when finished.  If N > pool size,
> new instances get allocated on the fly, and they get added to the pool as
> well.
> 
> Sounds like a big memory leak in the making, right?  Yeah, except there's a
> rational cap on the total # of instances each thread will ever need.  So
> this ended up being dramatically more efficient because it generated
> essentially zero garbage over time.  GC could keep up again...
> 
> Until this proved to be its own garbage generator.  :-)  As threads got
> recycled, the ThreadLocal pools got turned to garbage.  Foiled again!  :-)
> 
> So yeah, I'm going to centralize the pool and just synchronize management of
> it.  Oy.

You might want to take a look at Commons Pool trunk. It has been
completely re-written for 2.0 for performance. There is still some work
to do before a release but the GenericObjectPool should be OK and
performs well in a multi-threaded environment (the
GenericKeyedObjectPool has a known bug I need to fix).

Mark

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