bitbake: runqueue: Optimise task migration code slightly

Move the calls to difference_update out a code level which improves efficiency
significantly.

Also further combine the outer loop for efficiency too.

These two changes remove a bottleneck from the performance charts.

(Bitbake rev: 57df7f191755dd887827d51b125d246c1af3e1b6)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>
(cherry picked from commit e28ec69356f1797de3e4e3fca0fef710bc4564de)
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 9 insertions, 8 deletions

diff --git a/bitbake/lib/bb/runqueue.py b/bitbake/lib/bb/runqueue.py
index 2ba4557f9f..6da612b719 100644
--- a/bitbake/lib/bb/runqueue.py
+++ b/bitbake/lib/bb/runqueue.py
@@ -2268,15 +2268,16 @@ class RunQueueExecute:
 
         # Work out all tasks which depend upon these
         total = set()
+        next = set()
         for p in toprocess:
-            next = set(self.rqdata.runtaskentries[p].revdeps)
-            while next:
-                current = next.copy()
-                total = total | next
-                next = set()
-                for ntid in current:
-                    next |= self.rqdata.runtaskentries[ntid].revdeps
-                    next.difference_update(total)
+            next |= self.rqdata.runtaskentries[p].revdeps
+        while next:
+            current = next.copy()
+            total = total | next
+            next = set()
+            for ntid in current:
+                next |= self.rqdata.runtaskentries[ntid].revdeps
+            next.difference_update(total)
 
         # Now iterate those tasks in dependency order to regenerate their taskhash/unihash
         next = set()