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From Charles Reitzel <creit...@rcn.com>
Subject Re: How Do I Create A Per-Worker Pool?
Date Thu, 26 Sep 2002 17:49:26 GMT
Thanks for telling me what I need to know: "you can't get there from here."

I don't want to start a philosophical debate, but it is a common idiom 
(yea, verily a "pattern") in multi-threaded programming to avoid contention 
by duplicating singletons in each thread.  This can be done either by using 
platform-specific thread-local storage or, portably, by passing in the 
needed singleton (or a place to put it) into the worker thread.

A mutex-free, per-thread pool would serve this purpose perfectly.  Change 
the word "thread" to "worker" in the above, and you have made it portable 
across MPM models.

A per-thread pool would assist a great deal in bringing many Apache 1.x 
modules over to 2.x.  In essence, you move the globals into the per-thread 
pool, and the remaining application semantics are unchanged.

You can't "just add synchronization" to most 
applications/modules.  Usually, you need to redesign much of it to make it 
work without killing performance.

Convinced?

take it easy,
Charlie

On Wed, 26 Sep 2002, Ryan Bloom wrote:
>You shouldn't be trying to access a per-thread pool. It isn't necessary. 
>The pool in the request-rec, is by definition, only available within that 
>request, which is limited to a single thread. The only reason to access a 
>per-thread pool, is if you want to allocate memory that has the same 
>lifetime as the thread itself. There is currently no way to do that, but 
>there also hasn't been a convincing reason to do it. Ryan


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