Add stats on how objects are passed to GC.

Author: markshannon

Include/pystats.h

@@ -81,6 +81,7 @@ typedef struct _object_stats {
 typedef struct _gc_stats {
     uint64_t collections;
     uint64_t object_visits;
+    uint64_t objects_queued;
     uint64_t objects_collected;
 } GCStats;
 

Modules/gcmodule.c

@@ -1295,14 +1295,16 @@ gc_collect_young(PyThreadState *tstate,
     PyGC_Head *young = &gcstate->young.head;
     PyGC_Head *aging = &gcstate->old[gcstate->aging_space].head;
     validate_old(gcstate);
-    if (gcstate->aging_space) {
-        /* objects in aging space have bit set, so we need to
-         * do that here */
+#ifdef Py_STATS
+    {
+        Py_ssize_t count = 0;
         PyGC_Head *gc;
         for (gc = GC_NEXT(young); gc != young; gc = GC_NEXT(gc)) {
-            gc_set_old_space(gc, 1);
+            count++;
         }
+        GC_STAT_ADD(0, objects_queued, count);
     }
+#endif
     validate_old(gcstate);
     PyGC_Head survivors;
     gc_list_init(&survivors);
@@ -1465,6 +1467,16 @@ gc_collect_increment(PyThreadState *tstate, struct gc_collection_stats *stats)
     }
     validate_old(gcstate);
     validate_list_is_aging(&increment);
+#ifdef Py_STATS
+    {
+        Py_ssize_t count = 0;
+        PyGC_Head *gc;
+        for (gc = GC_NEXT(&increment); gc != &increment; gc = GC_NEXT(gc)) {
+            count++;
+        }
+        GC_STAT_ADD(NUM_GENERATIONS, objects_queued, count);
+    }
+#endif
     gc_collect_region(tstate, &increment, aging, 0, stats);
     validate_old(gcstate);
     assert(gc_list_is_empty(&increment));