With a test sending 5000 messages to a queue, I see heavy CPU use on the broker side (v 5.12.2). Using Yourkit it shows that the hot spot methods are
FilePendingMessageCursor.isEmpty() iterates over in-memory messages and therefore (as it is a prioritized queue) uses PrioritizedPendingListIterator which uses OrderedPendingList.getAsList() which turns out to be an expensive method as it converts the self-managed linked list to a Java ArrayList. I wonder if anyone else has seen this issue? Perhaps PrioritizedPendingListIterator could be improved to walk the priority lists via OrderedPendingList iterators, as these are implemented efficiently. - Martin
