[pypy-commit] stmgc c8-private-pages: fix the slowdown for sort.duh. Still, the real fix would be to avoid adding tons of objs to the modified_old_objects list

[Raemi]

Author: Remi Meier <remi.meier at inf.ethz.ch>
Branch: c8-private-pages
Changeset: r1560:24ba707614c4
Date: 2015-01-20 17:51 +0100
http://bitbucket.org/pypy/stmgc/changeset/24ba707614c4/

Log:	fix the slowdown for sort.duh. Still, the real fix would be to avoid
	adding tons of objs to the modified_old_objects list

diff --git a/c7/stm/gcpage.c b/c7/stm/gcpage.c
--- a/c7/stm/gcpage.c
+++ b/c7/stm/gcpage.c
@@ -434,8 +434,8 @@
             get_priv_segment(i)->modified_old_objects,
             object_t * /*item*/,
             ({
-                mark_visited_test_and_set(item);
-                mark_trace(item, stm_object_pages);  /* shared version */
+                if (!mark_visited_test_and_set(item))
+                    mark_trace(item, stm_object_pages);  /* shared version */
                 mark_trace(item, base);              /* private version */
             }));
     }
diff --git a/c8/stm/gcpage.c b/c8/stm/gcpage.c
--- a/c8/stm/gcpage.c
+++ b/c8/stm/gcpage.c
@@ -227,14 +227,11 @@
 
     /* trace all references found in sharing seg0 (should always be
        up-to-date and not cause segfaults) */
-    while (1) {
+    while (!list_is_empty(marked_objects_to_trace)) {
+        obj = (object_t *)list_pop_item(marked_objects_to_trace);
+
         realobj = (struct object_s *)REAL_ADDRESS(stm_object_pages, obj);
         stmcb_trace(realobj, &mark_record_trace);
-
-        if (list_is_empty(marked_objects_to_trace))
-            break;
-
-        obj = (object_t *)list_pop_item(marked_objects_to_trace);
     }
 }
 
@@ -283,23 +280,53 @@
        some of the pages) */
 
     long i;
+    struct list_s *uniques = list_create();
     for (i = 1; i < NB_SEGMENTS; i++) {
         char *base = get_segment_base(i);
+        OPT_ASSERT(list_is_empty(uniques));
 
+        /* the list of modified_old_objs can be huge and contain a lot
+           of duplicated (same obj, different slice) entries. It seems
+           worth it to build a new list without duplicates.
+           The reason is that newly created objs, when moved out of the
+           nursery, don't have WB_EXECUTED flag. Thus we execute waaay
+           too many write barriers per transaction and add them all
+           to this list (and the commit log). XXXXX */
         struct list_s *lst = get_priv_segment(i)->modified_old_objects;
-        long j, count = list_count(lst);
-        for (j = 0; j < count; j += 3) {
-            object_t *item = (object_t*)list_item(lst, j);
-            /* All modified objs have all pages accessible for now.
-               This is because we create a backup of the whole obj
-               and thus make all pages accessible. */
-            assert_obj_accessible_in(i, item);
 
-            mark_visited_test_and_set(item);
-            mark_and_trace(item, stm_object_pages);  /* shared, committed version */
-            mark_and_trace(item, base);          /* private, modified version */
+        struct stm_undo_s *undo = (struct stm_undo_s *)lst->items;
+        struct stm_undo_s *end = (struct stm_undo_s *)(lst->items + lst->count);
+        for (; undo < end; undo++) {
+            object_t *obj = undo->object;
+            struct object_s *dst = (struct object_s*)REAL_ADDRESS(base, obj);
+
+            if (!(dst->stm_flags & GCFLAG_VISITED)) {
+                LIST_APPEND(uniques, obj);
+                dst->stm_flags |= GCFLAG_VISITED;
+            }
         }
+
+
+        LIST_FOREACH_R(uniques, object_t*,
+           ({
+               /* clear the VISITED flags again and actually visit them */
+               struct object_s *dst = (struct object_s*)REAL_ADDRESS(base, item);
+               dst->stm_flags &= ~GCFLAG_VISITED;
+
+               /* All modified objs have all pages accessible for now.
+                  This is because we create a backup of the whole obj
+                  and thus make all pages accessible. */
+               assert_obj_accessible_in(i, item);
+
+               if (!mark_visited_test_and_set(item))
+                   mark_and_trace(item, stm_object_pages);  /* shared, committed version */
+               mark_and_trace(item, base);          /* private, modified version */
+           }));
+
+
+        list_clear(uniques);
     }
+    LIST_FREE(uniques);
 }
 
 static void mark_visit_from_roots(void)