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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47 #include "sgen-bridge.h"
48 #include "sgen-hash-table.h"
49 #include "utils/mono-logger-internal.h"
50 #include "utils/mono-time.h"
60 #define DYN_ARRAY_REF(da,i) ((void*)((da)->data + (i) * (da)->elem_size))
61 #define DYN_ARRAY_PTR_REF(da,i) (((void**)(da)->data) [(i)])
62 #define DYN_ARRAY_INT_REF(da,i) (((int*)(da)->data) [(i)])
63 #define DYN_ARRAY_PTR_STATIC_INITIALIZER { 0, sizeof (void*), 0, NULL }
64 #define DYN_ARRAY_INT_STATIC_INITIALIZER { 0, sizeof (int), 0, NULL }
67 dyn_array_init (DynArray *da, int elem_size)
70 da->elem_size = elem_size;
76 dyn_array_ptr_init (DynArray *da)
78 dyn_array_init (da, sizeof (void*));
82 dyn_array_int_init (DynArray *da)
84 dyn_array_init (da, sizeof (int));
88 dyn_array_uninit (DynArray *da)
90 if (da->capacity <= 0)
93 sgen_free_internal_dynamic (da->data, da->elem_size * da->capacity, INTERNAL_MEM_BRIDGE_DATA);
98 dyn_array_ensure_capacity (DynArray *da, int capacity)
100 int old_capacity = da->capacity;
103 if (capacity <= old_capacity)
106 if (da->capacity == 0)
108 while (capacity > da->capacity)
111 new_data = sgen_alloc_internal_dynamic (da->elem_size * da->capacity, INTERNAL_MEM_BRIDGE_DATA, TRUE);
112 memcpy (new_data, da->data, da->elem_size * da->size);
113 sgen_free_internal_dynamic (da->data, da->elem_size * old_capacity, INTERNAL_MEM_BRIDGE_DATA);
118 dyn_array_add (DynArray *da)
122 dyn_array_ensure_capacity (da, da->size + 1);
124 p = DYN_ARRAY_REF (da, da->size);
130 dyn_array_ptr_add (DynArray *da, void *ptr)
132 void **p = dyn_array_add (da);
136 #define dyn_array_ptr_push dyn_array_ptr_add
139 dyn_array_ptr_pop (DynArray *da)
142 g_assert (da->size > 0);
143 p = DYN_ARRAY_PTR_REF (da, da->size - 1);
149 dyn_array_int_add (DynArray *da, int x)
151 int *p = dyn_array_add (da);
157 dyn_array_ptr_contains (DynArray *da, void *ptr)
160 for (i = 0; i < da->size; ++i)
161 if (DYN_ARRAY_PTR_REF (da, i) == ptr)
168 dyn_array_int_contains (DynArray *da, int x)
171 for (i = 0; i < da->size; ++i)
172 if (DYN_ARRAY_INT_REF (da, i) == x)
177 static DynArray merge_array;
180 dyn_array_int_merge (DynArray *dst, DynArray *src)
184 dyn_array_ensure_capacity (&merge_array, dst->size + src->size);
185 merge_array.size = 0;
187 for (i = j = 0; i < dst->size || j < src->size; ) {
188 if (i < dst->size && j < src->size) {
189 int a = DYN_ARRAY_INT_REF (dst, i);
190 int b = DYN_ARRAY_INT_REF (src, j);
192 dyn_array_int_add (&merge_array, a);
195 dyn_array_int_add (&merge_array, a);
199 dyn_array_int_add (&merge_array, b);
202 } else if (i < dst->size) {
203 dyn_array_int_add (&merge_array, DYN_ARRAY_INT_REF (dst, i));
206 dyn_array_int_add (&merge_array, DYN_ARRAY_INT_REF (src, j));
211 if (merge_array.size > dst->size) {
212 dyn_array_ensure_capacity (dst, merge_array.size);
213 memcpy (DYN_ARRAY_REF (dst, 0), DYN_ARRAY_REF (&merge_array, 0), merge_array.size * merge_array.elem_size);
214 dst->size = merge_array.size;
219 dyn_array_int_merge_one (DynArray *array, int value)
223 int end = array->size;
225 for (i = 0; i < end; ++i) {
226 if (DYN_ARRAY_INT_REF (array, i) == value)
228 else if (DYN_ARRAY_INT_REF (array, i) > value)
232 dyn_array_ensure_capacity (array, array->size + 1);
235 tmp = DYN_ARRAY_INT_REF (array, i);
236 for (; i <= end; ++i) {
237 DYN_ARRAY_INT_REF (array, i) = value;
239 tmp = DYN_ARRAY_INT_REF (array, i + 1);
241 DYN_ARRAY_INT_REF (array, end + 1) = tmp;
243 DYN_ARRAY_INT_REF (array, end) = value;
249 * FIXME: Optimizations:
251 * Don't allocate a scrs array for just one source. Most objects have
252 * just one source, so use the srcs pointer itself.
254 typedef struct _HashEntry {
255 MonoObject *obj; /* This is a duplicate - it's already stored in the hash table */
267 typedef struct _SCC {
270 int num_bridge_entries;
271 DynArray xrefs; /* these are incoming, not outgoing */
274 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);
276 static MonoGCBridgeCallbacks bridge_callbacks;
278 static int current_time;
280 gboolean bridge_processing_in_progress = FALSE;
283 mono_gc_wait_for_bridge_processing (void)
285 if (!bridge_processing_in_progress)
288 mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "GC_BRIDGE waiting for bridge processing to finish");
295 mono_gc_register_bridge_callbacks (MonoGCBridgeCallbacks *callbacks)
297 if (callbacks->bridge_version != SGEN_BRIDGE_VERSION)
298 g_error ("Invalid bridge callback version. Expected %d but got %d\n", SGEN_BRIDGE_VERSION, callbacks->bridge_version);
300 bridge_callbacks = *callbacks;
304 sgen_is_bridge_object (MonoObject *obj)
306 if ((obj->vtable->gc_bits & SGEN_GC_BIT_BRIDGE_OBJECT) != SGEN_GC_BIT_BRIDGE_OBJECT)
308 return bridge_callbacks.is_bridge_object (obj);
312 sgen_is_bridge_class (MonoClass *class)
314 return bridge_callbacks.is_bridge_class (class);
318 sgen_need_bridge_processing (void)
320 return bridge_callbacks.cross_references != NULL;
324 get_hash_entry (MonoObject *obj, gboolean *existing)
326 HashEntry *entry = sgen_hash_table_lookup (&hash_table, obj);
337 memset (&new_entry, 0, sizeof (HashEntry));
340 dyn_array_ptr_init (&new_entry.srcs);
341 new_entry.finishing_time = -1;
342 new_entry.scc_index = -1;
344 sgen_hash_table_replace (&hash_table, obj, &new_entry, NULL);
346 return sgen_hash_table_lookup (&hash_table, obj);
350 add_source (HashEntry *entry, HashEntry *src)
352 dyn_array_ptr_add (&entry->srcs, src);
363 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
364 total_srcs += entry->srcs.size;
365 if (entry->srcs.size > max_srcs)
366 max_srcs = entry->srcs.size;
367 dyn_array_uninit (&entry->srcs);
368 } SGEN_HASH_TABLE_FOREACH_END;
370 sgen_hash_table_clean (&hash_table);
372 dyn_array_uninit (&merge_array);
373 //g_print ("total srcs %d - max %d\n", total_srcs, max_srcs);
377 register_bridge_object (MonoObject *obj)
379 HashEntry *entry = get_hash_entry (obj, NULL);
380 entry->is_bridge = TRUE;
385 register_finishing_time (HashEntry *entry, int t)
387 g_assert (entry->finishing_time < 0);
388 entry->finishing_time = t;
392 object_is_live (MonoObject **objp)
394 MonoObject *obj = *objp;
395 MonoObject *fwd = SGEN_OBJECT_IS_FORWARDED (obj);
398 return sgen_hash_table_lookup (&hash_table, fwd) == NULL;
400 if (!sgen_object_is_live (obj))
402 return sgen_hash_table_lookup (&hash_table, obj) == NULL;
405 static DynArray registered_bridges = DYN_ARRAY_PTR_STATIC_INITIALIZER;
406 static DynArray dfs_stack;
408 static int dsf1_passes, dsf2_passes;
412 #define HANDLE_PTR(ptr,obj) do { \
413 MonoObject *dst = (MonoObject*)*(ptr); \
414 if (dst && !object_is_live (&dst)) { \
415 dyn_array_ptr_push (&dfs_stack, obj_entry); \
416 dyn_array_ptr_push (&dfs_stack, get_hash_entry (dst, NULL)); \
421 dfs1 (HashEntry *obj_entry, HashEntry *src)
423 g_assert (dfs_stack.size == 0);
425 dyn_array_ptr_push (&dfs_stack, src);
426 dyn_array_ptr_push (&dfs_stack, obj_entry);
433 obj_entry = dyn_array_ptr_pop (&dfs_stack);
435 src = dyn_array_ptr_pop (&dfs_stack);
437 obj = obj_entry->obj;
441 //g_print ("link %s -> %s\n", sgen_safe_name (src->obj), sgen_safe_name (obj));
442 add_source (obj_entry, src);
444 //g_print ("starting with %s\n", sgen_safe_name (obj));
447 if (obj_entry->is_visited)
450 obj_entry->is_visited = TRUE;
452 dyn_array_ptr_push (&dfs_stack, obj_entry);
453 /* NULL marks that the next entry is to be finished */
454 dyn_array_ptr_push (&dfs_stack, NULL);
456 #include "sgen-scan-object.h"
458 obj_entry = dyn_array_ptr_pop (&dfs_stack);
460 //g_print ("finish %s\n", sgen_safe_name (obj_entry->obj));
461 register_finishing_time (obj_entry, current_time++);
463 } while (dfs_stack.size > 0);
467 scc_add_xref (SCC *src, SCC *dst)
469 g_assert (src != dst);
470 g_assert (src->index != dst->index);
472 if (dyn_array_int_contains (&dst->xrefs, src->index))
474 if (src->num_bridge_entries) {
475 dyn_array_int_merge_one (&dst->xrefs, src->index);
478 dyn_array_int_merge (&dst->xrefs, &src->xrefs);
479 for (i = 0; i < dst->xrefs.size; ++i)
480 g_assert (DYN_ARRAY_INT_REF (&dst->xrefs, i) != dst->index);
485 scc_add_entry (SCC *scc, HashEntry *entry)
487 g_assert (entry->scc_index < 0);
488 entry->scc_index = scc->index;
489 if (entry->is_bridge)
490 ++scc->num_bridge_entries;
493 static DynArray sccs;
494 static SCC *current_scc;
497 dfs2 (HashEntry *entry)
501 g_assert (dfs_stack.size == 0);
503 dyn_array_ptr_push (&dfs_stack, entry);
506 entry = dyn_array_ptr_pop (&dfs_stack);
509 if (entry->scc_index >= 0) {
510 if (entry->scc_index != current_scc->index)
511 scc_add_xref (DYN_ARRAY_REF (&sccs, entry->scc_index), current_scc);
515 scc_add_entry (current_scc, entry);
517 for (i = 0; i < entry->srcs.size; ++i)
518 dyn_array_ptr_push (&dfs_stack, DYN_ARRAY_PTR_REF (&entry->srcs, i));
519 } while (dfs_stack.size > 0);
523 compare_hash_entries (const void *ep1, const void *ep2)
525 HashEntry *e1 = *(HashEntry**)ep1;
526 HashEntry *e2 = *(HashEntry**)ep2;
527 return e2->finishing_time - e1->finishing_time;
530 static unsigned long step_1, step_2, step_3, step_4, step_5, step_6, step_7, step_8;
531 static int fist_pass_links, second_pass_links, sccs_links;
532 static int max_sccs_links = 0;
535 sgen_bridge_register_finalized_object (MonoObject *obj)
537 g_assert (sgen_need_bridge_processing ());
538 dyn_array_ptr_push (®istered_bridges, obj);
542 sgen_bridge_reset_data (void)
544 registered_bridges.size = 0;
548 sgen_bridge_processing_stw_step (void)
551 SGEN_TV_DECLARE (atv);
552 SGEN_TV_DECLARE (btv);
554 if (!registered_bridges.size)
558 * bridge_processing_in_progress must be set with the world
559 * stopped. If not there would be race conditions.
561 g_assert (!bridge_processing_in_progress);
562 bridge_processing_in_progress = TRUE;
564 SGEN_TV_GETTIME (btv);
568 dyn_array_ptr_init (&dfs_stack);
569 dyn_array_int_init (&merge_array);
572 for (i = 0; i < registered_bridges.size; ++i)
573 dfs1 (register_bridge_object (DYN_ARRAY_PTR_REF (®istered_bridges, i)), NULL);
575 SGEN_TV_GETTIME (atv);
576 step_2 = SGEN_TV_ELAPSED (btv, atv);
580 is_bridge_object_alive (MonoObject *obj, void *data)
582 SgenHashTable *table = data;
583 unsigned char *value = sgen_hash_table_lookup (table, obj);
590 sgen_bridge_processing_finish (int generation)
593 int num_sccs, num_xrefs;
594 int max_entries, max_xrefs;
595 int hash_table_size, sccs_size;
598 int num_registered_bridges;
599 HashEntry **all_entries;
600 MonoGCBridgeSCC **api_sccs;
601 MonoGCBridgeXRef *api_xrefs;
602 SgenHashTable alive_hash = SGEN_HASH_TABLE_INIT (INTERNAL_MEM_BRIDGE_ALIVE_HASH_TABLE, INTERNAL_MEM_BRIDGE_ALIVE_HASH_TABLE_ENTRY, 1, mono_aligned_addr_hash, NULL);
603 SGEN_TV_DECLARE (atv);
604 SGEN_TV_DECLARE (btv);
606 if (!registered_bridges.size)
609 g_assert (bridge_processing_in_progress);
611 SGEN_TV_GETTIME (atv);
613 /* alloc and fill array of all entries */
615 all_entries = sgen_alloc_internal_dynamic (sizeof (HashEntry*) * hash_table.num_entries, INTERNAL_MEM_BRIDGE_DATA, TRUE);
618 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
619 g_assert (entry->finishing_time >= 0);
620 all_entries [j++] = entry;
621 fist_pass_links += entry->srcs.size;
622 } SGEN_HASH_TABLE_FOREACH_END;
623 g_assert (j == hash_table.num_entries);
624 hash_table_size = hash_table.num_entries;
626 /* sort array according to decreasing finishing time */
628 qsort (all_entries, hash_table.num_entries, sizeof (HashEntry*), compare_hash_entries);
630 SGEN_TV_GETTIME (btv);
631 step_3 = SGEN_TV_ELAPSED (atv, btv);
633 /* second DFS pass */
635 dyn_array_init (&sccs, sizeof (SCC));
636 for (i = 0; i < hash_table.num_entries; ++i) {
637 HashEntry *entry = all_entries [i];
638 if (entry->scc_index < 0) {
639 int index = sccs.size;
640 current_scc = dyn_array_add (&sccs);
641 current_scc->index = index;
642 current_scc->num_bridge_entries = 0;
643 current_scc->api_index = -1;
644 dyn_array_int_init (¤t_scc->xrefs);
650 sccs_size = sccs.size;
652 for (i = 0; i < hash_table.num_entries; ++i) {
653 HashEntry *entry = all_entries [i];
654 second_pass_links += entry->srcs.size;
657 SGEN_TV_GETTIME (atv);
658 step_4 = SGEN_TV_ELAPSED (btv, atv);
660 //g_print ("%d sccs\n", sccs.size);
662 dyn_array_uninit (&dfs_stack);
664 /* init data for callback */
667 for (i = 0; i < sccs.size; ++i) {
668 SCC *scc = DYN_ARRAY_REF (&sccs, i);
669 g_assert (scc->index == i);
670 if (scc->num_bridge_entries)
672 sccs_links += scc->xrefs.size;
673 max_sccs_links = MAX (max_sccs_links, scc->xrefs.size);
676 api_sccs = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC*) * num_sccs, INTERNAL_MEM_BRIDGE_DATA, TRUE);
679 for (i = 0; i < sccs.size; ++i) {
680 SCC *scc = DYN_ARRAY_REF (&sccs, i);
681 if (!scc->num_bridge_entries)
684 api_sccs [j] = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeSCC) + sizeof (MonoObject*) * scc->num_bridge_entries, INTERNAL_MEM_BRIDGE_DATA, TRUE);
685 api_sccs [j]->is_alive = FALSE;
686 api_sccs [j]->num_objs = scc->num_bridge_entries;
687 scc->num_bridge_entries = 0;
688 scc->api_index = j++;
690 num_xrefs += scc->xrefs.size;
693 SGEN_HASH_TABLE_FOREACH (&hash_table, obj, entry) {
694 if (entry->is_bridge) {
695 SCC *scc = DYN_ARRAY_REF (&sccs, entry->scc_index);
696 api_sccs [scc->api_index]->objs [scc->num_bridge_entries++] = entry->obj;
698 } SGEN_HASH_TABLE_FOREACH_END;
700 api_xrefs = sgen_alloc_internal_dynamic (sizeof (MonoGCBridgeXRef) * num_xrefs, INTERNAL_MEM_BRIDGE_DATA, TRUE);
702 for (i = 0; i < sccs.size; ++i) {
704 SCC *scc = DYN_ARRAY_REF (&sccs, i);
705 if (!scc->num_bridge_entries)
707 for (k = 0; k < scc->xrefs.size; ++k) {
708 SCC *src_scc = DYN_ARRAY_REF (&sccs, DYN_ARRAY_INT_REF (&scc->xrefs, k));
709 if (!src_scc->num_bridge_entries)
711 api_xrefs [j].src_scc_index = src_scc->api_index;
712 api_xrefs [j].dst_scc_index = scc->api_index;
717 SGEN_TV_GETTIME (btv);
718 step_5 = SGEN_TV_ELAPSED (atv, btv);
723 max_entries = max_xrefs = 0;
724 for (i = 0; i < sccs.size; ++i) {
725 SCC *scc = DYN_ARRAY_REF (&sccs, i);
726 if (scc->num_bridge_entries)
728 if (scc->num_bridge_entries > max_entries)
729 max_entries = scc->num_bridge_entries;
730 if (scc->xrefs.size > max_xrefs)
731 max_xrefs = scc->xrefs.size;
732 dyn_array_uninit (&scc->xrefs);
735 dyn_array_uninit (&sccs);
737 sgen_free_internal_dynamic (all_entries, sizeof (HashEntry*) * hash_table.num_entries, INTERNAL_MEM_BRIDGE_DATA);
740 /* Empty the registered bridges array */
741 num_registered_bridges = registered_bridges.size;
742 registered_bridges.size = 0;
744 SGEN_TV_GETTIME (atv);
745 step_6 = SGEN_TV_ELAPSED (btv, atv);
747 //g_print ("%d sccs containing bridges - %d max bridge objects - %d max xrefs\n", j, max_entries, max_xrefs);
751 bridge_callbacks.cross_references (num_sccs, api_sccs, num_xrefs, api_xrefs);
753 /* Release for finalization those objects we no longer care. */
754 SGEN_TV_GETTIME (btv);
755 step_7 = SGEN_TV_ELAPSED (atv, btv);
757 for (i = 0; i < num_sccs; ++i) {
758 unsigned char alive = api_sccs [i]->is_alive ? 1 : 0;
759 for (j = 0; j < api_sccs [i]->num_objs; ++j) {
760 /* Build hash table for nulling weak links. */
761 sgen_hash_table_replace (&alive_hash, api_sccs [i]->objs [j], &alive, NULL);
763 /* Release for finalization those objects we no longer care. */
764 if (!api_sccs [i]->is_alive)
765 sgen_mark_bridge_object (api_sccs [i]->objs [j]);
769 /* Null weak links to dead objects. */
770 sgen_null_links_with_predicate (GENERATION_NURSERY, is_bridge_object_alive, &alive_hash);
771 if (generation == GENERATION_OLD)
772 sgen_null_links_with_predicate (GENERATION_OLD, is_bridge_object_alive, &alive_hash);
774 sgen_hash_table_clean (&alive_hash);
776 /* free callback data */
778 for (i = 0; i < num_sccs; ++i) {
779 sgen_free_internal_dynamic (api_sccs [i],
780 sizeof (MonoGCBridgeSCC) + sizeof (MonoObject*) * api_sccs [i]->num_objs,
781 INTERNAL_MEM_BRIDGE_DATA);
783 sgen_free_internal_dynamic (api_sccs, sizeof (MonoGCBridgeSCC*) * num_sccs, INTERNAL_MEM_BRIDGE_DATA);
785 sgen_free_internal_dynamic (api_xrefs, sizeof (MonoGCBridgeXRef) * num_xrefs, INTERNAL_MEM_BRIDGE_DATA);
787 SGEN_TV_GETTIME (atv);
788 step_8 = SGEN_TV_ELAPSED (btv, atv);
790 mono_trace (G_LOG_LEVEL_INFO, MONO_TRACE_GC, "GC_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 user-cb %.2fms clenanup %.2fms links %d/%d/%d/%d dfs passes %d/%d",
791 num_registered_bridges, hash_table_size, sccs.size,
800 fist_pass_links, second_pass_links, sccs_links, max_sccs_links,
801 dsf1_passes, dsf2_passes);
803 step_1 = 0; /* We must cleanup since this value is used as an accumulator. */
805 bridge_processing_in_progress = FALSE;
808 static const char *bridge_class;
811 bridge_test_is_bridge_class (MonoClass *class)
813 return !strcmp (bridge_class, class->name);
817 bridge_test_is_bridge_object (MonoObject *object)
823 bridge_test_cross_reference (int num_sccs, MonoGCBridgeSCC **sccs, int num_xrefs, MonoGCBridgeXRef *xrefs)
826 for (i = 0; i < num_sccs; ++i) {
828 // g_print ("--- SCC %d\n", i);
829 for (j = 0; j < sccs [i]->num_objs; ++j) {
830 // g_print (" %s\n", sgen_safe_name (sccs [i]->objs [j]));
831 if (i & 1) /*retain half of the bridged objects */
832 sccs [i]->objs [0] = NULL;
835 for (i = 0; i < num_xrefs; ++i) {
836 g_assert (xrefs [i].src_scc_index >= 0 && xrefs [i].src_scc_index < num_sccs);
837 g_assert (xrefs [i].dst_scc_index >= 0 && xrefs [i].dst_scc_index < num_sccs);
838 // g_print ("%d -> %d\n", xrefs [i].src_scc_index, xrefs [i].dst_scc_index);
844 sgen_register_test_bridge_callbacks (const char *bridge_class_name)
846 MonoGCBridgeCallbacks callbacks;
847 callbacks.bridge_version = SGEN_BRIDGE_VERSION;
848 callbacks.is_bridge_class = bridge_test_is_bridge_class;
849 callbacks.is_bridge_object = bridge_test_is_bridge_object;
850 callbacks.cross_references = bridge_test_cross_reference;
851 mono_gc_register_bridge_callbacks (&callbacks);
852 bridge_class = bridge_class_name;