2 * sgen-bridge.c: Simple generational GC.
4 * Copyright 2011 Novell, Inc (http://www.novell.com)
5 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
7 * THIS MATERIAL IS PROVIDED AS IS, WITH ABSOLUTELY NO WARRANTY EXPRESSED
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17 * Copyright 2001-2003 Ximian, Inc
18 * Copyright 2003-2010 Novell, Inc.
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48 #include "sgen-bridge.h"
49 #include "sgen-hash-table.h"
50 #include "sgen-qsort.h"
51 #include "sgen-client.h"
52 #include "tabledefs.h"
53 #include "utils/mono-logger-internal.h"
57 //#define TEST_NEW_XREFS
60 #if !defined(NEW_XREFS) || defined(TEST_NEW_XREFS)
65 #define XREFS new_xrefs
67 #define XREFS old_xrefs
70 #define OPTIMIZATION_COPY
71 #define OPTIMIZATION_FORWARD
72 #define OPTIMIZATION_SINGLETON_DYN_ARRAY
76 int capacity; /* if negative, data points to another DynArray's data */
96 * FIXME: Optimizations:
98 * Don't allocate a scrs array for just one source. Most objects have
99 * just one source, so use the srcs pointer itself.
101 typedef struct _HashEntry {
106 guint32 is_visited : 1;
107 guint32 finishing_time : 31;
108 struct _HashEntry *forwarded_to;
121 } HashEntryWithAccounting;
123 typedef struct _SCC {
126 int num_bridge_entries;
129 * New and old xrefs are typically mutually exclusive. Only when TEST_NEW_XREFS is
130 * enabled we do both, and compare the results. This should only be done for
131 * debugging, obviously.
134 DynIntArray old_xrefs; /* these are incoming, not outgoing */
137 DynIntArray new_xrefs;
141 static SgenHashTable hash_table = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_BRIDGE_HASH_TABLE, INTERNAL_MEM_BRIDGE_HASH_TABLE_ENTRY, sizeof (HashEntry), mono_aligned_addr_hash, NULL);
143 static guint32 current_time;
145 static gboolean bridge_accounting_enabled = FALSE;
147 static SgenBridgeProcessor *bridge_processor;
155 dyn_array_init (DynArray *da)
163 dyn_array_uninit (DynArray *da, int elem_size)
165 if (da->capacity < 0) {
170 if (da->capacity == 0)
173 sgen_free_internal_dynamic (da->data, elem_size * da->capacity, INTERNAL_MEM_BRIDGE_DATA);
178 dyn_array_empty (DynArray *da)
180 if (da->capacity < 0)
187 dyn_array_ensure_capacity (DynArray *da, int capacity, int elem_size)
189 int old_capacity = da->capacity;
192 g_assert (capacity > 0);
194 if (capacity <= old_capacity)
197 if (old_capacity <= 0)
199 while (capacity > da->capacity)
202 new_data = sgen_alloc_internal_dynamic (elem_size * da->capacity, INTERNAL_MEM_BRIDGE_DATA, TRUE);
203 memcpy (new_data, da->data, elem_size * da->size);
204 if (old_capacity > 0)
205 sgen_free_internal_dynamic (da->data, elem_size * old_capacity, INTERNAL_MEM_BRIDGE_DATA);
210 dyn_array_is_copy (DynArray *da)
212 return da->capacity < 0;
216 dyn_array_ensure_independent (DynArray *da, int elem_size)
218 if (!dyn_array_is_copy (da))
220 dyn_array_ensure_capacity (da, da->size, elem_size);
221 g_assert (da->capacity > 0);
225 dyn_array_add (DynArray *da, int elem_size)
229 dyn_array_ensure_capacity (da, da->size + 1, elem_size);
231 p = da->data + da->size * elem_size;
237 dyn_array_copy (DynArray *dst, DynArray *src, int elem_size)
239 dyn_array_uninit (dst, elem_size);
244 dst->size = src->size;
246 dst->data = src->data;
251 dyn_array_int_init (DynIntArray *da)
253 dyn_array_init (&da->array);
257 dyn_array_int_uninit (DynIntArray *da)
259 dyn_array_uninit (&da->array, sizeof (int));
263 dyn_array_int_size (DynIntArray *da)
265 return da->array.size;
270 dyn_array_int_empty (DynIntArray *da)
272 dyn_array_empty (&da->array);
277 dyn_array_int_add (DynIntArray *da, int x)
279 int *p = dyn_array_add (&da->array, sizeof (int));
284 dyn_array_int_get (DynIntArray *da, int x)
286 return ((int*)da->array.data)[x];
291 dyn_array_int_set (DynIntArray *da, int idx, int val)
293 ((int*)da->array.data)[idx] = val;
298 dyn_array_int_ensure_independent (DynIntArray *da)
300 dyn_array_ensure_independent (&da->array, sizeof (int));
304 dyn_array_int_copy (DynIntArray *dst, DynIntArray *src)
306 dyn_array_copy (&dst->array, &src->array, sizeof (int));
310 dyn_array_int_is_copy (DynIntArray *da)
312 return dyn_array_is_copy (&da->array);
318 dyn_array_ptr_init (DynPtrArray *da)
320 dyn_array_init (&da->array);
324 dyn_array_ptr_uninit (DynPtrArray *da)
326 #ifdef OPTIMIZATION_SINGLETON_DYN_ARRAY
327 if (da->array.capacity == 1)
328 dyn_array_ptr_init (da);
331 dyn_array_uninit (&da->array, sizeof (void*));
335 dyn_array_ptr_size (DynPtrArray *da)
337 return da->array.size;
341 dyn_array_ptr_empty (DynPtrArray *da)
343 #ifdef OPTIMIZATION_SINGLETON_DYN_ARRAY
344 if (da->array.capacity == 1)
345 dyn_array_ptr_init (da);
348 dyn_array_empty (&da->array);
352 dyn_array_ptr_get (DynPtrArray *da, int x)
354 #ifdef OPTIMIZATION_SINGLETON_DYN_ARRAY
355 if (da->array.capacity == 1) {
357 return da->array.data;
360 return ((void**)da->array.data)[x];
364 dyn_array_ptr_add (DynPtrArray *da, void *ptr)
368 #ifdef OPTIMIZATION_SINGLETON_DYN_ARRAY
369 if (da->array.capacity == 0) {
370 da->array.capacity = 1;
372 p = (void**)&da->array.data;
373 } else if (da->array.capacity == 1) {
374 void *ptr0 = da->array.data;
376 dyn_array_init (&da->array);
377 p0 = dyn_array_add (&da->array, sizeof (void*));
379 p = dyn_array_add (&da->array, sizeof (void*));
383 p = dyn_array_add (&da->array, sizeof (void*));
388 #define dyn_array_ptr_push dyn_array_ptr_add
391 dyn_array_ptr_pop (DynPtrArray *da)
393 int size = da->array.size;
396 #ifdef OPTIMIZATION_SINGLETON_DYN_ARRAY
397 if (da->array.capacity == 1) {
398 p = dyn_array_ptr_get (da, 0);
399 dyn_array_init (&da->array);
403 g_assert (da->array.capacity > 1);
404 dyn_array_ensure_independent (&da->array, sizeof (void*));
405 p = dyn_array_ptr_get (da, size - 1);
414 dyn_array_scc_init (DynSCCArray *da)
416 dyn_array_init (&da->array);
420 dyn_array_scc_uninit (DynSCCArray *da)
422 dyn_array_uninit (&da->array, sizeof (SCC));
426 dyn_array_scc_size (DynSCCArray *da)
428 return da->array.size;
432 dyn_array_scc_add (DynSCCArray *da)
434 return dyn_array_add (&da->array, sizeof (SCC));
438 dyn_array_scc_get_ptr (DynSCCArray *da, int x)
440 return &((SCC*)da->array.data)[x];
445 static DynIntArray merge_array;
449 dyn_array_int_contains (DynIntArray *da, int x)
452 for (i = 0; i < dyn_array_int_size (da); ++i)
453 if (dyn_array_int_get (da, i) == x)
460 enable_accounting (void)
462 SgenHashTable table = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_BRIDGE_HASH_TABLE, INTERNAL_MEM_BRIDGE_HASH_TABLE_ENTRY, sizeof (HashEntryWithAccounting), mono_aligned_addr_hash, NULL);
463 bridge_accounting_enabled = TRUE;
467 static MonoGCBridgeObjectKind
468 class_kind (MonoClass *class)
470 MonoGCBridgeObjectKind res = bridge_callbacks.bridge_class_kind (class);
472 /* If it's a bridge, nothing we can do about it. */
473 if (res == GC_BRIDGE_TRANSPARENT_BRIDGE_CLASS || res == GC_BRIDGE_OPAQUE_BRIDGE_CLASS)
476 /* Non bridge classes with no pointers will never point to a bridge, so we can savely ignore them. */
477 if (!class->has_references) {
478 SGEN_LOG (6, "class %s is opaque\n", class->name);
479 return GC_BRIDGE_OPAQUE_CLASS;
482 /* Some arrays can be ignored */
483 if (class->rank == 1) {
484 MonoClass *elem_class = class->element_class;
486 /* FIXME the bridge check can be quite expensive, cache it at the class level. */
487 /* An array of a sealed type that is not a bridge will never get to a bridge */
488 if ((elem_class->flags & TYPE_ATTRIBUTE_SEALED) && !elem_class->has_references && !bridge_callbacks.bridge_class_kind (elem_class)) {
489 SGEN_LOG (6, "class %s is opaque\n", class->name);
490 return GC_BRIDGE_OPAQUE_CLASS;
494 return GC_BRIDGE_TRANSPARENT_CLASS;
498 get_hash_entry (MonoObject *obj, gboolean *existing)
500 HashEntry *entry = sgen_hash_table_lookup (&hash_table, obj);
511 memset (&new_entry, 0, sizeof (HashEntry));
513 dyn_array_ptr_init (&new_entry.srcs);
514 new_entry.v.dfs1.finishing_time = 0;
516 sgen_hash_table_replace (&hash_table, obj, &new_entry, NULL);
518 return sgen_hash_table_lookup (&hash_table, obj);
522 add_source (HashEntry *entry, HashEntry *src)
524 dyn_array_ptr_add (&entry->srcs, src);
530 MonoObject *obj G_GNUC_UNUSED;
535 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
536 int entry_size = dyn_array_ptr_size (&entry->srcs);
537 total_srcs += entry_size;
538 if (entry_size > max_srcs)
539 max_srcs = entry_size;
540 dyn_array_ptr_uninit (&entry->srcs);
541 } SGEN_HASH_TABLE_FOREACH_END;
543 sgen_hash_table_clean (&hash_table);
545 dyn_array_int_uninit (&merge_array);
546 //g_print ("total srcs %d - max %d\n", total_srcs, max_srcs);
550 register_bridge_object (MonoObject *obj)
552 HashEntry *entry = get_hash_entry (obj, NULL);
553 entry->is_bridge = TRUE;
558 register_finishing_time (HashEntry *entry, guint32 t)
560 g_assert (entry->v.dfs1.finishing_time == 0);
561 /* finishing_time has 31 bits, so it must be within signed int32 range. */
562 g_assert (t > 0 && t <= G_MAXINT32);
563 entry->v.dfs1.finishing_time = t;
566 static int ignored_objects;
569 is_opaque_object (MonoObject *obj)
571 if ((obj->vtable->gc_bits & SGEN_GC_BIT_BRIDGE_OPAQUE_OBJECT) == SGEN_GC_BIT_BRIDGE_OPAQUE_OBJECT) {
572 SGEN_LOG (6, "ignoring %s\n", obj->vtable->klass->name);
580 object_needs_expansion (MonoObject **objp)
582 MonoObject *obj = *objp;
583 MonoObject *fwd = SGEN_OBJECT_IS_FORWARDED (obj);
586 if (is_opaque_object (fwd))
588 return sgen_hash_table_lookup (&hash_table, fwd) != NULL;
590 if (is_opaque_object (obj))
592 if (!sgen_object_is_live (obj))
594 return sgen_hash_table_lookup (&hash_table, obj) != NULL;
598 follow_forward (HashEntry *entry)
600 #ifdef OPTIMIZATION_FORWARD
601 while (entry->v.dfs1.forwarded_to) {
602 HashEntry *next = entry->v.dfs1.forwarded_to;
603 if (next->v.dfs1.forwarded_to)
604 entry->v.dfs1.forwarded_to = next->v.dfs1.forwarded_to;
608 g_assert (!entry->v.dfs1.forwarded_to);
613 static DynPtrArray registered_bridges;
614 static DynPtrArray dfs_stack;
616 static int dfs1_passes, dfs2_passes;
619 * DFS1 maintains a stack, where each two entries are effectively one entry. (FIXME:
620 * Optimize this via pointer tagging.) There are two different types of entries:
622 * entry, src: entry needs to be expanded via scanning, and linked to from src
623 * NULL, entry: entry has already been expanded and needs to be finished
627 #define HANDLE_PTR(ptr,obj) do { \
628 GCObject *dst = (GCObject*)*(ptr); \
629 if (dst && object_needs_expansion (&dst)) { \
631 dyn_array_ptr_push (&dfs_stack, obj_entry); \
632 dyn_array_ptr_push (&dfs_stack, follow_forward (get_hash_entry (dst, NULL))); \
637 dfs1 (HashEntry *obj_entry)
640 g_assert (dyn_array_ptr_size (&dfs_stack) == 0);
642 dyn_array_ptr_push (&dfs_stack, NULL);
643 dyn_array_ptr_push (&dfs_stack, obj_entry);
650 obj_entry = dyn_array_ptr_pop (&dfs_stack);
652 /* obj_entry needs to be expanded */
653 src = dyn_array_ptr_pop (&dfs_stack);
656 g_assert (!src->v.dfs1.forwarded_to);
658 obj_entry = follow_forward (obj_entry);
661 g_assert (!obj_entry->v.dfs1.forwarded_to);
662 obj = sgen_hash_table_key_for_value_pointer (obj_entry);
665 if (!obj_entry->v.dfs1.is_visited) {
667 mword desc = sgen_obj_get_descriptor_safe (start);
669 obj_entry->v.dfs1.is_visited = 1;
671 /* push the finishing entry on the stack */
672 dyn_array_ptr_push (&dfs_stack, obj_entry);
673 dyn_array_ptr_push (&dfs_stack, NULL);
675 #include "sgen-scan-object.h"
678 * We can remove non-bridge objects with a single outgoing
679 * link by forwarding links going to it.
681 * This is the first time we've encountered this object, so
682 * no links to it have yet been added. We'll keep it that
683 * way by setting the forward pointer, and instead of
684 * continuing processing this object, we start over with the
685 * object it points to.
687 #ifdef OPTIMIZATION_FORWARD
688 if (!obj_entry->is_bridge && num_links == 1) {
689 HashEntry *dst_entry = dyn_array_ptr_pop (&dfs_stack);
690 HashEntry *obj_entry_again = dyn_array_ptr_pop (&dfs_stack);
691 g_assert (obj_entry_again == obj_entry);
692 g_assert (!dst_entry->v.dfs1.forwarded_to);
693 if (obj_entry != dst_entry) {
694 obj_entry->v.dfs1.forwarded_to = dst_entry;
695 obj_entry = dst_entry;
703 //g_print ("link %s -> %s\n", sgen_safe_name (src->obj), sgen_safe_name (obj));
704 g_assert (!obj_entry->v.dfs1.forwarded_to);
705 add_source (obj_entry, src);
707 //g_print ("starting with %s\n", sgen_safe_name (obj));
710 /* obj_entry needs to be finished */
712 obj_entry = dyn_array_ptr_pop (&dfs_stack);
714 //g_print ("finish %s\n", sgen_safe_name (obj_entry->obj));
715 register_finishing_time (obj_entry, ++current_time);
717 } while (dyn_array_ptr_size (&dfs_stack) > 0);
720 static DynSCCArray sccs;
721 static SCC *current_scc;
724 * At the end of bridge processing we need to end up with an (acyclyc) graph of bridge
725 * object SCCs, where the links between the nodes (each one an SCC) in that graph represent
726 * the presence of a direct or indirect link between those SCCs. An example:
731 * A -> B -> c -> e -> F
733 * A, B, D and F are SCCs that contain bridge objects, c and e don't contain bridge objects.
734 * The graph we need to produce from this is:
741 * Note that we don't need to produce an edge from A to F. It's sufficient that F is
742 * indirectly reachable from A.
744 * The old algorithm would create a set, for each SCC, of bridge SCCs that can reach it,
745 * directly or indirectly, by merging the ones sets for those that reach it directly. The
746 * sets it would build up are these:
755 * The merge operations on these sets turned out to be huge time sinks.
757 * The new algorithm proceeds in two passes: During DFS2, it only builds up the sets of SCCs
758 * that directly point to each SCC:
767 * This is the adjacency list for the SCC graph, in other words. In a separate step
768 * afterwards, it does a depth-first traversal of that graph, for each bridge node, to get
769 * to the final list. It uses a flag to avoid traversing any node twice.
772 scc_add_xref (SCC *src, SCC *dst)
774 g_assert (src != dst);
775 g_assert (src->index != dst->index);
779 * FIXME: Right now we don't even unique the direct ancestors, but just add to the
780 * list. Doing a containment check slows this algorithm down to almost the speed of
781 * the old one. Use the flag instead!
783 dyn_array_int_add (&dst->new_xrefs, src->index);
787 if (dyn_array_int_is_copy (&dst->old_xrefs)) {
789 dyn_array_int_ensure_independent (&dst->old_xrefs);
790 for (i = 0; i < dyn_array_int_size (&dst->old_xrefs); ++i) {
791 int j = dyn_array_int_get (&dst->old_xrefs, i);
792 SCC *bridge_scc = dyn_array_scc_get_ptr (&sccs, j);
793 g_assert (!bridge_scc->flag);
794 bridge_scc->flag = TRUE;
798 if (src->num_bridge_entries) {
802 dyn_array_int_add (&dst->old_xrefs, src->index);
803 #ifdef OPTIMIZATION_COPY
804 } else if (dyn_array_int_size (&dst->old_xrefs) == 0) {
805 dyn_array_int_copy (&dst->old_xrefs, &src->old_xrefs);
809 for (i = 0; i < dyn_array_int_size (&src->old_xrefs); ++i) {
810 int j = dyn_array_int_get (&src->old_xrefs, i);
811 SCC *bridge_scc = dyn_array_scc_get_ptr (&sccs, j);
812 g_assert (bridge_scc->num_bridge_entries);
813 if (!bridge_scc->flag) {
814 bridge_scc->flag = TRUE;
815 dyn_array_int_add (&dst->old_xrefs, j);
823 scc_add_entry (SCC *scc, HashEntry *entry)
825 g_assert (entry->v.dfs2.scc_index < 0);
826 entry->v.dfs2.scc_index = scc->index;
827 if (entry->is_bridge)
828 ++scc->num_bridge_entries;
832 dfs2 (HashEntry *entry)
836 g_assert (dyn_array_ptr_size (&dfs_stack) == 0);
838 dyn_array_ptr_push (&dfs_stack, entry);
841 entry = dyn_array_ptr_pop (&dfs_stack);
844 if (entry->v.dfs2.scc_index >= 0) {
845 if (entry->v.dfs2.scc_index != current_scc->index)
846 scc_add_xref (dyn_array_scc_get_ptr (&sccs, entry->v.dfs2.scc_index), current_scc);
850 scc_add_entry (current_scc, entry);
852 for (i = 0; i < dyn_array_ptr_size (&entry->srcs); ++i)
853 dyn_array_ptr_push (&dfs_stack, dyn_array_ptr_get (&entry->srcs, i));
854 } while (dyn_array_ptr_size (&dfs_stack) > 0);
857 /* If xrefs is a copy then we haven't set a single flag. */
858 if (dyn_array_int_is_copy (¤t_scc->old_xrefs))
860 for (i = 0; i < dyn_array_int_size (¤t_scc->old_xrefs); ++i) {
861 int j = dyn_array_int_get (¤t_scc->old_xrefs, i);
862 SCC *bridge_scc = dyn_array_scc_get_ptr (&sccs, j);
863 g_assert (bridge_scc->flag);
864 bridge_scc->flag = FALSE;
871 gather_xrefs (SCC *scc)
874 for (i = 0; i < dyn_array_int_size (&scc->new_xrefs); ++i) {
875 int index = dyn_array_int_get (&scc->new_xrefs, i);
876 SCC *src = dyn_array_scc_get_ptr (&sccs, index);
880 if (src->num_bridge_entries)
881 dyn_array_int_add (&merge_array, index);
888 reset_flags (SCC *scc)
891 for (i = 0; i < dyn_array_int_size (&scc->new_xrefs); ++i) {
892 int index = dyn_array_int_get (&scc->new_xrefs, i);
893 SCC *src = dyn_array_scc_get_ptr (&sccs, index);
897 if (!src->num_bridge_entries)
903 static char *dump_prefix = NULL;
908 static int counter = 0;
912 size_t prefix_len = strlen (dump_prefix);
913 char *filename = alloca(prefix_len + 64);
917 sprintf (filename, "%s.%d.gexf", dump_prefix, counter++);
918 file = fopen (filename, "w");
921 fprintf (stderr, "Warning: Could not open bridge dump file `%s` for writing: %s\n", filename, strerror (errno));
925 fprintf (file, "<gexf xmlns=\"http://www.gexf.net/1.2draft\" xmlns:xsi=\"http://www.w3.org/2001/XMLSchema-instance\" xsi:schemaLocation=\"http://www.gexf.net/1.2draft http://www.gexf.net/1.2draft/gexf.xsd\" version=\"1.2\">\n");
927 fprintf (file, "<graph defaultedgetype=\"directed\">\n"
928 "<attributes class=\"node\">\n"
929 "<attribute id=\"0\" title=\"class\" type=\"string\"/>\n"
930 "<attribute id=\"1\" title=\"bridge\" type=\"boolean\"/>\n"
933 fprintf (file, "<nodes>\n");
934 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
935 MonoVTable *vt = (MonoVTable*) SGEN_LOAD_VTABLE (obj);
936 fprintf (file, "<node id=\"%p\"><attvalues><attvalue for=\"0\" value=\"%s.%s\"/><attvalue for=\"1\" value=\"%s\"/></attvalues></node>\n",
937 obj, vt->klass->name_space, vt->klass->name, entry->is_bridge ? "true" : "false");
938 } SGEN_HASH_TABLE_FOREACH_END;
939 fprintf (file, "</nodes>\n");
941 fprintf (file, "<edges>\n");
942 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
944 for (i = 0; i < dyn_array_ptr_size (&entry->srcs); ++i) {
945 HashEntry *src = dyn_array_ptr_get (&entry->srcs, i);
946 fprintf (file, "<edge id=\"%d\" source=\"%p\" target=\"%p\"/>\n", edge_id++, sgen_hash_table_key_for_value_pointer (src), obj);
948 } SGEN_HASH_TABLE_FOREACH_END;
949 fprintf (file, "</edges>\n");
951 fprintf (file, "</graph></gexf>\n");
957 set_dump_prefix (const char *prefix)
959 dump_prefix = strdup (prefix);
963 compare_hash_entries (const HashEntry *e1, const HashEntry *e2)
965 /* We can cast to signed int here because finishing_time has only 31 bits. */
966 return (gint32)e2->v.dfs1.finishing_time - (gint32)e1->v.dfs1.finishing_time;
969 DEF_QSORT_INLINE(hash_entries, HashEntry*, compare_hash_entries)
971 static unsigned long step_1, step_2, step_3, step_4, step_5, step_6;
972 static int fist_pass_links, second_pass_links, sccs_links;
973 static int max_sccs_links = 0;
976 register_finalized_object (GCObject *obj)
978 g_assert (sgen_need_bridge_processing ());
979 dyn_array_ptr_push (®istered_bridges, obj);
985 dyn_array_ptr_empty (®istered_bridges);
989 processing_stw_step (void)
993 MonoObject *obj G_GNUC_UNUSED;
995 SGEN_TV_DECLARE (atv);
996 SGEN_TV_DECLARE (btv);
998 if (!dyn_array_ptr_size (®istered_bridges))
1001 SGEN_TV_GETTIME (btv);
1003 /* first DFS pass */
1005 dyn_array_ptr_init (&dfs_stack);
1006 dyn_array_int_init (&merge_array);
1010 First we insert all bridges into the hash table and then we do dfs1.
1012 It must be done in 2 steps since the bridge arrays doesn't come in reverse topological order,
1013 which means that we can have entry N pointing to entry N + 1.
1015 If we dfs1 entry N before N + 1 is registered we'll not consider N + 1 for this bridge
1016 pass and not create the required xref between the two.
1018 bridge_count = dyn_array_ptr_size (®istered_bridges);
1019 for (i = 0; i < bridge_count ; ++i)
1020 register_bridge_object (dyn_array_ptr_get (®istered_bridges, i));
1022 for (i = 0; i < bridge_count; ++i)
1023 dfs1 (get_hash_entry (dyn_array_ptr_get (®istered_bridges, i), NULL));
1025 /* Remove all forwarded objects. */
1026 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
1027 if (entry->v.dfs1.forwarded_to) {
1028 g_assert (dyn_array_ptr_size (&entry->srcs) == 0);
1029 SGEN_HASH_TABLE_FOREACH_REMOVE (TRUE);
1032 } SGEN_HASH_TABLE_FOREACH_END;
1034 SGEN_TV_GETTIME (atv);
1035 step_2 = SGEN_TV_ELAPSED (btv, atv);
1041 static int num_registered_bridges, hash_table_size;
1044 processing_build_callback_data (int generation)
1047 int num_sccs, num_xrefs;
1048 int max_entries, max_xrefs;
1049 MonoObject *obj G_GNUC_UNUSED;
1051 HashEntry **all_entries;
1052 MonoGCBridgeSCC **api_sccs;
1053 MonoGCBridgeXRef *api_xrefs;
1054 SGEN_TV_DECLARE (atv);
1055 SGEN_TV_DECLARE (btv);
1057 g_assert (bridge_processor->num_sccs == 0 && bridge_processor->num_xrefs == 0);
1058 g_assert (!bridge_processor->api_sccs && !bridge_processor->api_xrefs);
1060 if (!dyn_array_ptr_size (®istered_bridges))
1063 g_assert (bridge_processing_in_progress);
1065 SGEN_TV_GETTIME (atv);
1067 /* alloc and fill array of all entries */
1069 all_entries = sgen_alloc_internal_dynamic (sizeof (HashEntry*) * hash_table.num_entries, INTERNAL_MEM_BRIDGE_DATA, TRUE);
1072 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
1073 g_assert (entry->v.dfs1.finishing_time > 0);
1074 all_entries [j++] = entry;
1075 fist_pass_links += dyn_array_ptr_size (&entry->srcs);
1076 } SGEN_HASH_TABLE_FOREACH_END;
1077 g_assert (j == hash_table.num_entries);
1078 hash_table_size = hash_table.num_entries;
1080 /* sort array according to decreasing finishing time */
1081 qsort_hash_entries (all_entries, hash_table.num_entries);
1083 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
1084 entry->v.dfs2.scc_index = -1;
1085 } SGEN_HASH_TABLE_FOREACH_END;
1087 SGEN_TV_GETTIME (btv);
1088 step_3 = SGEN_TV_ELAPSED (atv, btv);
1090 /* second DFS pass */
1092 dyn_array_scc_init (&sccs);
1093 for (i = 0; i < hash_table.num_entries; ++i) {
1094 HashEntry *entry = all_entries [i];
1095 if (entry->v.dfs2.scc_index < 0) {
1096 int index = dyn_array_scc_size (&sccs);
1097 current_scc = dyn_array_scc_add (&sccs);
1098 current_scc->index = index;
1099 current_scc->num_bridge_entries = 0;
1101 current_scc->flag = FALSE;
1102 dyn_array_int_init (¤t_scc->new_xrefs);
1105 dyn_array_int_init (¤t_scc->old_xrefs);
1107 current_scc->api_index = -1;
1113 * If a node has only one incoming edge, we just copy the source's
1114 * xrefs array, effectively removing the source from the graph.
1115 * This takes care of long linked lists.
1117 if (!current_scc->num_bridge_entries && dyn_array_int_size (¤t_scc->new_xrefs) == 1) {
1119 j = dyn_array_int_get (¤t_scc->new_xrefs, 0);
1120 src = dyn_array_scc_get_ptr (&sccs, j);
1121 if (src->num_bridge_entries)
1122 dyn_array_int_set (¤t_scc->new_xrefs, 0, j);
1124 dyn_array_int_copy (¤t_scc->new_xrefs, &src->new_xrefs);
1131 #ifdef TEST_NEW_XREFS
1132 for (j = 0; j < dyn_array_scc_size (&sccs); ++j) {
1133 SCC *scc = dyn_array_scc_get_ptr (&sccs, j);
1134 g_assert (!scc->flag);
1138 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1139 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1140 g_assert (scc->index == i);
1141 if (!scc->num_bridge_entries)
1144 dyn_array_int_empty (&merge_array);
1147 dyn_array_int_copy (&scc->new_xrefs, &merge_array);
1148 dyn_array_int_ensure_independent (&scc->new_xrefs);
1150 #ifdef TEST_NEW_XREFS
1151 for (j = 0; j < dyn_array_scc_size (&sccs); ++j) {
1152 SCC *scc = dyn_array_scc_get_ptr (&sccs, j);
1153 g_assert (!scc->flag);
1158 #ifdef TEST_NEW_XREFS
1159 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1160 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1161 g_assert (scc->index == i);
1162 if (!scc->num_bridge_entries)
1165 g_assert (dyn_array_int_size (&scc->new_xrefs) == dyn_array_int_size (&scc->old_xrefs));
1166 for (j = 0; j < dyn_array_int_size (&scc->new_xrefs); ++j)
1167 g_assert (dyn_array_int_contains (&scc->old_xrefs, dyn_array_int_get (&scc->new_xrefs, j)));
1173 * Compute the weight of each object. The weight of an object is its size plus the size of all
1174 * objects it points do. When the an object is pointed by multiple objects we distribute it's weight
1175 * equally among them. This distribution gives a rough estimate of the real impact of making the object
1178 * The reasoning for this model is that complex graphs with single roots will have a bridge with very high
1179 * value in comparison to others.
1181 * The all_entries array has all objects topologically sorted. To correctly propagate the weights it must be
1182 * done in reverse topological order - so we calculate the weight of the pointed-to objects before processing
1183 * pointer-from objects.
1185 * We log those objects in the opposite order for no particular reason. The other constrain is that it should use the same
1186 * direction as the other logging loop that records live/dead information.
1188 if (bridge_accounting_enabled) {
1189 for (i = hash_table.num_entries - 1; i >= 0; --i) {
1191 HashEntryWithAccounting *entry = (HashEntryWithAccounting*)all_entries [i];
1193 entry->weight += (double)sgen_safe_object_get_size (sgen_hash_table_key_for_value_pointer (entry));
1194 w = entry->weight / dyn_array_ptr_size (&entry->entry.srcs);
1195 for (j = 0; j < dyn_array_ptr_size (&entry->entry.srcs); ++j) {
1196 HashEntryWithAccounting *other = (HashEntryWithAccounting *)dyn_array_ptr_get (&entry->entry.srcs, j);
1200 for (i = 0; i < hash_table.num_entries; ++i) {
1201 HashEntryWithAccounting *entry = (HashEntryWithAccounting*)all_entries [i];
1202 if (entry->entry.is_bridge) {
1203 MonoObject *obj = sgen_hash_table_key_for_value_pointer (entry);
1204 MonoClass *klass = ((MonoVTable*)SGEN_LOAD_VTABLE (obj))->klass;
1205 mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "OBJECT %s::%s (%p) weight %f", klass->name_space, klass->name, obj, entry->weight);
1210 for (i = 0; i < hash_table.num_entries; ++i) {
1211 HashEntry *entry = all_entries [i];
1212 second_pass_links += dyn_array_ptr_size (&entry->srcs);
1215 SGEN_TV_GETTIME (atv);
1216 step_4 = SGEN_TV_ELAPSED (btv, atv);
1218 //g_print ("%d sccs\n", sccs.size);
1220 dyn_array_ptr_uninit (&dfs_stack);
1222 /* init data for callback */
1225 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1226 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1227 g_assert (scc->index == i);
1228 if (scc->num_bridge_entries)
1230 sccs_links += dyn_array_int_size (&scc->XREFS);
1231 max_sccs_links = MAX (max_sccs_links, dyn_array_int_size (&scc->XREFS));
1234 api_sccs = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC*) * num_sccs, INTERNAL_MEM_BRIDGE_DATA, TRUE);
1237 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1238 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1239 if (!scc->num_bridge_entries)
1242 api_sccs [j] = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC) + sizeof (MonoObject*) * scc->num_bridge_entries, INTERNAL_MEM_BRIDGE_DATA, TRUE);
1243 api_sccs [j]->is_alive = FALSE;
1244 api_sccs [j]->num_objs = scc->num_bridge_entries;
1245 scc->num_bridge_entries = 0;
1246 scc->api_index = j++;
1248 num_xrefs += dyn_array_int_size (&scc->XREFS);
1251 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
1252 if (entry->is_bridge) {
1253 SCC *scc = dyn_array_scc_get_ptr (&sccs, entry->v.dfs2.scc_index);
1254 api_sccs [scc->api_index]->objs [scc->num_bridge_entries++] = sgen_hash_table_key_for_value_pointer (entry);
1256 } SGEN_HASH_TABLE_FOREACH_END;
1258 api_xrefs = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeXRef) * num_xrefs, INTERNAL_MEM_BRIDGE_DATA, TRUE);
1260 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1262 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1263 if (!scc->num_bridge_entries)
1265 for (k = 0; k < dyn_array_int_size (&scc->XREFS); ++k) {
1266 SCC *src_scc = dyn_array_scc_get_ptr (&sccs, dyn_array_int_get (&scc->XREFS, k));
1267 if (!src_scc->num_bridge_entries)
1269 api_xrefs [j].src_scc_index = src_scc->api_index;
1270 api_xrefs [j].dst_scc_index = scc->api_index;
1275 SGEN_TV_GETTIME (btv);
1276 step_5 = SGEN_TV_ELAPSED (atv, btv);
1281 max_entries = max_xrefs = 0;
1282 for (i = 0; i < dyn_array_scc_size (&sccs); ++i) {
1283 SCC *scc = dyn_array_scc_get_ptr (&sccs, i);
1284 if (scc->num_bridge_entries)
1286 if (scc->num_bridge_entries > max_entries)
1287 max_entries = scc->num_bridge_entries;
1288 if (dyn_array_int_size (&scc->XREFS) > max_xrefs)
1289 max_xrefs = dyn_array_int_size (&scc->XREFS);
1291 dyn_array_int_uninit (&scc->new_xrefs);
1294 dyn_array_int_uninit (&scc->old_xrefs);
1298 dyn_array_scc_uninit (&sccs);
1300 sgen_free_internal_dynamic (all_entries, sizeof (HashEntry*) * hash_table.num_entries, INTERNAL_MEM_BRIDGE_DATA);
1303 /* Empty the registered bridges array */
1304 num_registered_bridges = dyn_array_ptr_size (®istered_bridges);
1305 dyn_array_ptr_empty (®istered_bridges);
1307 SGEN_TV_GETTIME (atv);
1308 step_6 = SGEN_TV_ELAPSED (btv, atv);
1310 //g_print ("%d sccs containing bridges - %d max bridge objects - %d max xrefs\n", j, max_entries, max_xrefs);
1312 bridge_processor->num_sccs = num_sccs;
1313 bridge_processor->api_sccs = api_sccs;
1314 bridge_processor->num_xrefs = num_xrefs;
1315 bridge_processor->api_xrefs = api_xrefs;
1319 processing_after_callback (int generation)
1322 int num_sccs = bridge_processor->num_sccs;
1323 MonoGCBridgeSCC **api_sccs = bridge_processor->api_sccs;
1325 if (bridge_accounting_enabled) {
1326 for (i = 0; i < num_sccs; ++i) {
1327 for (j = 0; j < api_sccs [i]->num_objs; ++j)
1328 mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC,
1329 "OBJECT %s (%p) SCC [%d] %s",
1330 sgen_client_object_safe_name (api_sccs [i]->objs [j]), api_sccs [i]->objs [j],
1332 api_sccs [i]->is_alive ? "ALIVE" : "DEAD");
1336 mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "GC_NEW_BRIDGE num-objects %d num_hash_entries %d sccs size %d init %.2fms df1 %.2fms sort %.2fms dfs2 %.2fms setup-cb %.2fms free-data %.2fms links %d/%d/%d/%d dfs passes %d/%d ignored %d",
1337 num_registered_bridges, hash_table_size, dyn_array_scc_size (&sccs),
1344 fist_pass_links, second_pass_links, sccs_links, max_sccs_links,
1345 dfs1_passes, dfs2_passes, ignored_objects);
1347 step_1 = 0; /* We must cleanup since this value is used as an accumulator. */
1348 fist_pass_links = second_pass_links = sccs_links = max_sccs_links = 0;
1349 dfs1_passes = dfs2_passes = ignored_objects = 0;
1353 describe_pointer (GCObject *obj)
1358 for (i = 0; i < dyn_array_ptr_size (®istered_bridges); ++i) {
1359 if (obj == dyn_array_ptr_get (®istered_bridges, i)) {
1360 printf ("Pointer is a registered bridge object.\n");
1365 entry = sgen_hash_table_lookup (&hash_table, obj);
1369 printf ("Bridge hash table entry %p:\n", entry);
1370 printf (" is bridge: %d\n", (int)entry->is_bridge);
1371 printf (" is visited: %d\n", (int)entry->v.dfs1.is_visited);
1375 sgen_new_bridge_init (SgenBridgeProcessor *collector)
1377 collector->reset_data = reset_data;
1378 collector->processing_stw_step = processing_stw_step;
1379 collector->processing_build_callback_data = processing_build_callback_data;
1380 collector->processing_after_callback = processing_after_callback;
1381 collector->class_kind = class_kind;
1382 collector->register_finalized_object = register_finalized_object;
1383 collector->describe_pointer = describe_pointer;
1384 collector->enable_accounting = enable_accounting;
1385 collector->set_dump_prefix = set_dump_prefix;
1387 bridge_processor = collector;