[bitbake-devel] [PATCH] runqueue: Reimplement recrdepends so it works more correctly

[Richard Purdie]

Currently, recrdepends is extremely greedy. For example:

do_foo[rdepends] = "somedep:sometask"
addtask foo

which adds foo with *no* dependencies, will suddenly start appearing
as a dependency in every task which uses recrdepends. So far this has
been mildy annoying but we now have use cases where this makes no sense
at all.

This reworks the recrdepends code to avoid this problem. To do this we
can no longer collapse things into lists just based on file ID. The problem
is this code is extremely performance sensitive. The "preparing runqueue"
phase spends a lot of time in these recursive dependency calculations so any
change here could negatively impact the user experience.

As such, this code has been carefully tested on convoluted dependency trees
with operations like "time bitbake world -g". The net result of this change
and the preceding changes combined is a net speed up of these operations in
all cases measured.

Tests were made comparing "bitbake world -g" task-depends.dot before and after
this patch. There *are* differences, particularly that a lot of *-native
dependencies now disappear from recrdepends tasks like do_build. Also, -nativesdk
do_build dependencies on -native recipes are no longer present. All removed
dependencies appear to be sensible improvements to the system. The "rdepends"
cross contamination issue above is also fixed.

As a result of this, people are going to notice significant falls in the numbers
of tasks their standard builds will run, mainly from the removal of many -native
"noexec" tasks. All the signs are this is a good thing.

Signed-off-by: Richard Purdie <richard.purdie at linuxfoundation.org>
---
diff --git a/bitbake/lib/bb/runqueue.py b/bitbake/lib/bb/runqueue.py
index 0621e9e..172e5e4 100644
--- a/bitbake/lib/bb/runqueue.py
+++ b/bitbake/lib/bb/runqueue.py
@@ -376,8 +376,6 @@ class RunQueueData:
 
         runq_build = []
         recursive_tdepends = {}
-        runq_recrdepends = []
-        tdepends_fnid = {}
 
         taskData = self.taskData
 
@@ -465,8 +463,6 @@ class RunQueueData:
                 #
                 # e.g. do_sometask[depends] = "targetname:do_someothertask"
                 # (makes sure sometask runs after targetname's someothertask)
-                if fnid not in tdepends_fnid:
-                    tdepends_fnid[fnid] = set()
                 idepends = taskData.tasks_idepends[task]
                 for (depid, idependtask) in idepends:
                     if depid in taskData.build_targets:
@@ -477,8 +473,6 @@ class RunQueueData:
                             if taskid is None:
                                 bb.msg.fatal("RunQueue", "Task %s in %s depends upon non-existent task %s in %s" % (taskData.tasks_name[task], fn, idependtask, dep))
                             depends.add(taskid)
-                            if depdata != fnid:
-                                tdepends_fnid[fnid].add(taskid)
                 irdepends = taskData.tasks_irdepends[task]
                 for (depid, idependtask) in irdepends:
                     if depid in taskData.run_targets:
@@ -489,19 +483,27 @@ class RunQueueData:
                             if taskid is None:
                                 bb.msg.fatal("RunQueue", "Task %s in %s rdepends upon non-existent task %s in %s" % (taskData.tasks_name[task], fn, idependtask, dep))
                             depends.add(taskid)
-                            if depdata != fnid:
-                                tdepends_fnid[fnid].add(taskid)
 
-                # Resolve recursive 'recrdeptask' dependencies (A)
+                # Resolve recursive 'recrdeptask' dependencies
                 #
                 # e.g. do_sometask[recrdeptask] = "do_someothertask"
                 # (makes sure sometask runs after someothertask of all DEPENDS, RDEPENDS and intertask dependencies, recursively)
                 # We cover the recursive part of the dependencies below
                 if 'recrdeptask' in task_deps and taskData.tasks_name[task] in task_deps['recrdeptask']:
-                    for taskname in task_deps['recrdeptask'][taskData.tasks_name[task]].split():
-                        recrdepends.append(taskname)
-                        add_build_dependencies(taskData.depids[fnid], [taskname], depends)
-                        add_runtime_dependencies(taskData.rdepids[fnid], [taskname], depends)
+                    tasknames = task_deps['recrdeptask'][taskData.tasks_name[task]].split()
+                    seenfnid = []
+                    def generate_recdeps(f):
+                        newfnids = set(add_build_dependencies(taskData.depids[f], tasknames, depends))
+                        newfnids.update(add_runtime_dependencies(taskData.rdepids[f], tasknames, depends))
+                        seenfnid.append(f)
+                        for f in newfnids:
+                            if f not in seenfnid:
+                                generate_recdeps(f)
+                    newfnids = set([fnid])
+                    for d in depends:
+                        newfnids.add(taskData.tasks_fnid[d])
+                    for f in newfnids:
+                        generate_recdeps(f)
 
                 # Rmove all self references
                 if task in depends:
@@ -515,48 +517,6 @@ class RunQueueData:
             self.runq_hash.append("")
 
             runq_build.append(0)
-            runq_recrdepends.append(recrdepends)
-
-        #
-        # Build a list of recursive cumulative dependencies for each fnid
-        # We do this by fnid, since if A depends on some task in B
-        # we're interested in later tasks B's fnid might have but B itself
-        # doesn't depend on
-        #
-        # Algorithm is O(tasks) + O(tasks)*O(fnids)
-        #
-        reccumdepends = {}
-        for task in xrange(len(self.runq_fnid)):
-            fnid = self.runq_fnid[task]
-            if fnid not in reccumdepends:
-                if fnid in tdepends_fnid:
-                    reccumdepends[fnid] = tdepends_fnid[fnid]
-                else:
-                    reccumdepends[fnid] = set()
-            reccumdepends[fnid].update(self.runq_depends[task])
-        for task in xrange(len(self.runq_fnid)):
-            taskfnid = self.runq_fnid[task]
-            for fnid in reccumdepends:
-                if task in reccumdepends[fnid]:
-                    reccumdepends[fnid].add(task)
-                    if taskfnid in reccumdepends:
-                        reccumdepends[fnid].update(reccumdepends[taskfnid])
-
-
-        # Resolve recursive 'recrdeptask' dependencies (B)
-        #
-        # e.g. do_sometask[recrdeptask] = "do_someothertask"
-        # (makes sure sometask runs after someothertask of all DEPENDS, RDEPENDS and intertask dependencies, recursively)
-        for task in xrange(len(self.runq_fnid)):
-            if len(runq_recrdepends[task]) > 0:
-                taskfnid = self.runq_fnid[task]
-                for dep in reccumdepends[taskfnid]:
-                    # Ignore self references
-                    if dep == task:
-                        continue
-                    for taskname in runq_recrdepends[task]:
-                        if taskData.tasks_name[dep] == taskname:
-                            self.runq_depends[task].add(dep)
 
         # Step B - Mark all active tasks
         #