Improve performance with large number of queued prompts (#8176)

* get_current_queue_volatile

* restore get_current_queue method

* remove extra import

execution.py

@@ -909,7 +909,6 @@ class PromptQueue:
         self.currently_running = {}
         self.history = {}
         self.flags = {}
-        server.prompt_queue = self
 
     def put(self, item):
         with self.mutex:
@@ -954,6 +953,7 @@ class PromptQueue:
             self.history[prompt[1]].update(history_result)
             self.server.queue_updated()
 
+    # Note: slow
     def get_current_queue(self):
         with self.mutex:
             out = []
@@ -961,6 +961,13 @@ class PromptQueue:
                 out += [x]
             return (out, copy.deepcopy(self.queue))
 
+    # read-safe as long as queue items are immutable
+    def get_current_queue_volatile(self):
+        with self.mutex:
+            running = [x for x in self.currently_running.values()]
+            queued = copy.copy(self.queue)
+            return (running, queued)
+
     def get_tasks_remaining(self):
         with self.mutex:
             return len(self.queue) + len(self.currently_running)