buildrequestdistributor: Sort pending builders only once

Sorting pending builder each time the list is updated is unnecessary overhead.
This can be done once the list is passed on to BuildRequestDistributor._activityLoop.

master/buildbot/process/buildrequestdistributor.py

@@ -331,25 +331,14 @@ def maybeStartBuildsOn(self, new_builders):
 
  @defer.inlineCallbacks
  def _maybeStartBuildsOn(self, new_builders):
- new_builders = set(new_builders)
- existing_pending = set(self._pending_builders)
-
- # if we won't add any builders, there's nothing to do
- if new_builders < existing_pending:
+ # if we won't add any new builders, there's nothing to do
+ if set(new_builders) < set(self._pending_builders):
  return None
 
  # reset the list of pending builders
- @defer.inlineCallbacks
  def resetPendingBuildersList(new_builders):
  try:
- # re-fetch existing_pending, in case it has changed
- # while acquiring the lock
- existing_pending = set(self._pending_builders)
-
- # then sort the new, expanded set of builders
- self._pending_builders = yield self._sortBuilders(
- list(existing_pending | new_builders)
- )
+ self._pending_builders = list(set(self._pending_builders + new_builders))
 
  # start the activity loop, if we aren't already
  # working on that.
@@ -436,12 +425,14 @@ def _activityLoop(self):
  self.pending_builders_lock.release()
  self.activity_lock.release()
  break
- # take that builder list, and run it until the end
+ # take that builder list, sort it and run it until the end
  # we make a copy of it, as it could be modified meanwhile
  pending_builders = copy.copy(self._pending_builders)
  self._pending_builders = []
  self.pending_builders_lock.release()
 
+ pending_builders = yield self._sortBuilders(pending_builders)
+
  bldr_name = pending_builders.pop(0)
 
  # get the actual builder object