bitbake: runqueue: Fix next_buildable_task performance problem

Looking at the profile information, a lot of time is being spent in
next_buildable_task. This is probably due to the generator expressions
not working well with the empty test.

The easiest way to improve things is to switch to using set manipulations.
We also don't need to update self.buildable the way the original code did
as we don't rely on that anywhere.

(Bitbake rev: 3bcf9ad4964b7e42d1a02ce231e9db42a81ead2a)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/runqueue.py

@@ -133,7 +133,7 @@ class RunQueueScheduler(object):
 
         self.prio_map = [self.rqdata.runtaskentries.keys()]
 
-        self.buildable = []
+        self.buildable = set()
         self.skip_maxthread = {}
         self.stamps = {}
         for tid in self.rqdata.runtaskentries:
@@ -148,8 +148,10 @@ class RunQueueScheduler(object):
         """
         Return the id of the first task we find that is buildable
         """
-        self.buildable = [x for x in self.buildable if x not in self.rq.runq_running]
-        buildable = [x for x in self.buildable if (x in self.rq.tasks_covered or x in self.rq.tasks_notcovered) and x not in self.rq.holdoff_tasks]
+        buildable = set(self.buildable)
+        buildable.difference_update(self.rq.runq_running)
+        buildable.difference_update(self.rq.holdoff_tasks)
+        buildable.intersection_update(self.rq.tasks_covered | self.rq.tasks_notcovered)
         if not buildable:
             return None
 
@@ -167,7 +169,7 @@ class RunQueueScheduler(object):
                 skip_buildable[rtaskname] = 1
 
         if len(buildable) == 1:
-            tid = buildable[0]
+            tid = buildable.pop()
             taskname = taskname_from_tid(tid)
             if taskname in skip_buildable and skip_buildable[taskname] >= int(self.skip_maxthread[taskname]):
                 return None
@@ -204,7 +206,7 @@ class RunQueueScheduler(object):
             return self.next_buildable_task()
 
     def newbuildable(self, task):
-        self.buildable.append(task)
+        self.buildable.add(task)
 
     def removebuildable(self, task):
         self.buildable.remove(task)