Merge pull request #60359 from MaxKellermann/Dispatcher__marrival_simplified

msg/Dispatcher: simplify and optimize the `marrival` tree

diff --cc src/msg/DispatchQueue.cc
index 4694bdff587135cc2406f97b411392a8bcb92b7d,841479503189ac4877937e23611eaf2da711c027..5aac94c183f96add97730da7c1845f9201987e66
--- 1/src/msg/DispatchQueue.cc
--- 2/src/msg/DispatchQueue.cc
+++ b/src/msg/DispatchQueue.cc
@@@ -87,13 -87,14 +87,14 @@@ void DispatchQueue::enqueue(const ref_t
      return;
    }
    ldout(cct,20) << "queue " << m << " prio " << priority << dendl;
-   add_arrival(m);
+   QueueItem item{m};
+   add_arrival(item);
    if (priority >= CEPH_MSG_PRIO_LOW) {
-     mqueue.enqueue_strict(id, priority, QueueItem(m));
+     mqueue.enqueue_strict(id, priority, std::move(item));
    } else {
-     mqueue.enqueue(id, priority, m->get_cost(), QueueItem(m));
+     mqueue.enqueue(id, priority, m->get_cost(), std::move(item));
    }
 -  cond.notify_all();
 +  cond.notify_one();
  }
  
  void DispatchQueue::local_delivery(const ref_t<Message>& m, int priority)