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From Charles Reitzel <>
Subject How Do I Create A Per-Worker Pool?
Date Wed, 25 Sep 2002 17:48:48 GMT
Hi All,

This is a thorny (to me) module development question.  I have asked on the 
module list and searched the archives, but have found only a partial 
answer.  Any pointers will be appreciated.

Objective: to create a mutex-free pool per worker in non-MPM-specific way.

I found this exchange in a June posting:
> > Another change we made, as I mentioned in a previous
> > Email, was using non-mutexing per-thread memory
> > pools (HeapCreate(HEAP_NO_SERIALIZE, ...)). > To get
> > best performance with Apache 2 we would really need
> > such a memory pool.
>And we already have it! Just do:
>     apr_allocator_t *allocator;
>     apr_allocator_create(&allocator);
>     apr_pool_create_ex(&pool, parent_pool, abort_fn, allocator);
>     apr_allocator_owner_set(allocator, pool);
>Now you have a mutexless allocator associated with a pool. All child pools 
>of this pool will use the same allocator and will therefor also have no mutex.

Looks good.  But I have questions.  What is the correct place to put this 
code and where do keep the pool pointer afterwards.  I.e. how do you find 
the pool from within a module handler?

To my mind, the Apache module API is missing an important data structure: 
worker_rec.   It is obviously redundant (but does no harm) in the prefork 
MPM, but is a necessary ingredient in _any_ threaded MPM.  Such a structure 
would allow modules to be written as thread-safe - independent of the MPM 
currently configured by the user.  The request record could and should 
contain a pointer to the current worker for easy access.  In the absence of 
a worker_rec, however, some guidance on the above would be helpful.


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