So I finally got some time to play with this and I still can't wrap my head around it.

If I understand it correctly, the trick is in the fact that you:

  1. load the whole DB as a memdb with shared cache
  2. then use the 
    shared_clone( $dbh )

    [download]
    to get this memory where the DB is loaded shared with all the threads
  3. and then inside the thread create a new DB handler, but thanks to the fact you're using the same memdb with shared cache, it reuses the same memory as the DB handler in the main thread

Is that even remotely correct? :-) And if so:

  1. Why do the shared_clone( $dbh )? Isn't the shared memdb enough for the threads to have access to the same memory? I've been trying to somehow see the difference between the two scenarios (with and without passing the shared_clone( $dbh )) and I'm probably not measuring this right, but the memory usage (vm_stat) seems to be similar in both cases.
  2. What's the purpose of the 
    $Q->nq( ('Wakey wakey') x $T );
...
$Q->dq; ## Wait for DB

    [download]
    ? Why pass the string to the thread and then just dequeue it? And what's the relation to waiting for DB?

In reply to Re^6: threads::shared seems to kill performance (Workaround). by Jacobs
in thread threads::shared seems to kill performance by Jacobs

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