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From Brian Pane <>
Subject Re: [PATCH] worker MPM: reuse transaction pools
Date Mon, 10 Sep 2001 22:13:48 GMT
Aaron Bannert wrote:


>1) "short and sweet"
> - single listener
>   - creates a new transaction pool
>   - uses that pool for the next accept()
>   - push()es the newly accepted socket and pool on the fd_queue
> - multiple workers
>   - waiting in pop() on the fd_queue
>   - performs process_socket() with the socket and pool received from pop()
>   - destroys the pool
> Notes: this is almost identical to what was in CVS before the patch
>        discussed below. The only change I would make would be to
>        remove one of the two condition variables.
>2) "time-space tradeoff"
> - single listener
>   - pop()s the next available worker-thread
>   - uses the pool from this worker-thread to make the call to accept()
>   - signals a condition in that worker-thread after the accept()
> - multiple workers
>   - creates a transaction pool
>     - push()es thread info (pool, socket-pointer, etc)
>     - waits on signal from listener
>     - (check that listener woke us up)
>     - perform process_socket() with the socket set from the listener
>     - clear the pool
I suppose there are a total of four candidate designs, right?  It looks
like you're varying two independent dimensions:
  * condition variable strategy: one CV, or one per thread
  * pool strategy: worker-managed, or listener-managed.
so there are four possible permutations.  (The other two
permutations would look like hybrids of "short and sweet" and
"time-space tradeoff."  I don't know whether they're interesting
algorithms or not, but it's worth noting that these hybrids are
a possibility if you find in testing that neither of the first
two designs stands out as the clear winner.)
In the "pool strategy" dimension, I think a worker-managed pool design (as
used in "time-space tradeoff") is a better choice than a 
listener-managed one.
With worker-managed, you can clear and re-use the pool, which is cheaper 
destroying and recreating it.  And it's very easy to eliminate locking for
subpool creation by adding a thread-private free list (you could dig up my
old patch for this, or Sander's patch which is a more general-purpose 

In the "CV strategy" dimension, I'll wait for benchmark results before I try
to guess which approach is fastest. :-)


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