bitbake: runqueue: Optimise setscene loop processing

Rather than looping through things we looped through on the previous execution,
start looping where we left off for setscene processing. This gives speed
improvements depending on the kind of build being executed.

(Bitbake rev: 28569e9796d4b34d7b77b4f79074ab7854850386)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit 00f4d932e3af0eeb333339cbe942010fc76dee0f)
Signed-off-by: Steve Sakoman <steve@sakoman.com>

bitbake/lib/bb/runqueue.py

@@ -14,6 +14,7 @@ import os
 import sys
 import stat
 import errno
+import itertools
 import logging
 import re
 import bb
@@ -2189,11 +2190,16 @@ class RunQueueExecute:
         if not hasattr(self, "sorted_setscene_tids"):
             # Don't want to sort this set every execution
             self.sorted_setscene_tids = sorted(self.rqdata.runq_setscene_tids)
+            # Resume looping where we left off when we returned to feed the mainloop
+            self.setscene_tids_generator = itertools.cycle(self.rqdata.runq_setscene_tids)
 
         task = None
         if not self.sqdone and self.can_start_task():
-            # Find the next setscene to run
-            for nexttask in self.sorted_setscene_tids:
+            loopcount = 0
+            # Find the next setscene to run, exit the loop when we've processed all tids or found something to execute
+            while loopcount < len(self.rqdata.runq_setscene_tids):
+                loopcount += 1
+                nexttask = next(self.setscene_tids_generator)
                 if nexttask in self.sq_buildable and nexttask not in self.sq_running and self.sqdata.stamps[nexttask] not in self.build_stamps.values() and nexttask not in self.sq_harddep_deferred:
                     if nexttask in self.sq_deferred and self.sq_deferred[nexttask] not in self.runq_complete:
                         # Skip deferred tasks quickly before the 'expensive' tests below - this is key to performant multiconfig builds