2 * sgen-minor-copy-object.h: Copy functions for nursery collections.
4 * Copyright 2001-2003 Ximian, Inc
5 * Copyright 2003-2010 Novell, Inc.
6 * Copyright (C) 2012 Xamarin Inc
8 * This library is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Library General Public
10 * License 2.0 as published by the Free Software Foundation;
12 * This library is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 * Library General Public License for more details.
17 * You should have received a copy of the GNU Library General Public
18 * License 2.0 along with this library; if not, write to the Free
19 * Software Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
22 #define collector_pin_object(obj, queue) sgen_pin_object (obj, queue);
23 #define COLLECTOR_SERIAL_ALLOC_FOR_PROMOTION alloc_for_promotion
24 #define COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION par_alloc_for_promotion
26 extern long long stat_nursery_copy_object_failed_to_space; /* from sgen-gc.c */
28 #include "mono/utils/mono-compiler.h"
30 #include "sgen-copy-object.h"
33 * This is how the copying happens from the nursery to the old generation.
34 * We assume that at this time all the pinned objects have been identified and
36 * We run scan_object() for each pinned object so that each referenced
37 * objects if possible are copied. The new gray objects created can have
38 * scan_object() run on them right away, too.
39 * Then we run copy_object() for the precisely tracked roots. At this point
40 * all the roots are either gray or black. We run scan_object() on the gray
41 * objects until no more gray objects are created.
42 * At the end of the process we walk again the pinned list and we unmark
43 * the pinned flag. As we go we also create the list of free space for use
44 * in the next allocation runs.
46 * We need to remember objects from the old generation that point to the new one
47 * (or just addresses?).
49 * copy_object could be made into a macro once debugged (use inline for now).
52 static MONO_ALWAYS_INLINE void
53 SERIAL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
56 char *obj = *obj_slot;
58 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy from a %d generation collection", current_collection_generation);
60 HEAVY_STAT (++stat_copy_object_called_nursery);
62 if (!sgen_ptr_in_nursery (obj)) {
63 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
67 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
70 * Before we can copy the object we must make sure that we are
71 * allowed to, i.e. that the object not pinned, not already
72 * forwarded or belongs to the nursery To Space.
75 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
76 SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
77 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
78 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
79 *obj_slot = forwarded;
82 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
83 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
84 SGEN_LOG (9, " (pinned, no change)");
85 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
89 #ifndef SGEN_SIMPLE_NURSERY
90 if (sgen_nursery_is_to_space (obj)) {
91 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
92 SGEN_LOG (9, " (tospace, no change)");
93 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
98 HEAVY_STAT (++stat_objects_copied_nursery);
100 *obj_slot = copy_object_no_checks (obj, queue);
104 * SERIAL_COPY_OBJECT_FROM_OBJ:
106 * Similar to SERIAL_COPY_OBJECT, but assumes that OBJ_SLOT is part of an object, so it handles global remsets as well.
108 static MONO_ALWAYS_INLINE void
109 SERIAL_COPY_OBJECT_FROM_OBJ (void **obj_slot, SgenGrayQueue *queue)
112 char *obj = *obj_slot;
115 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy-from-obj from a %d generation collection", current_collection_generation);
117 HEAVY_STAT (++stat_copy_object_called_nursery);
119 if (!sgen_ptr_in_nursery (obj)) {
120 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
124 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
127 * Before we can copy the object we must make sure that we are
128 * allowed to, i.e. that the object not pinned, not already
129 * forwarded or belongs to the nursery To Space.
132 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
133 SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
134 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
135 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
136 *obj_slot = forwarded;
137 #ifndef SGEN_SIMPLE_NURSERY
138 if (G_UNLIKELY (sgen_ptr_in_nursery (forwarded) && !sgen_ptr_in_nursery (obj_slot)))
139 sgen_add_to_global_remset (obj_slot, forwarded);
143 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
144 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
145 SGEN_LOG (9, " (pinned, no change)");
146 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
147 if (!sgen_ptr_in_nursery (obj_slot))
148 sgen_add_to_global_remset (obj_slot, obj);
152 #ifndef SGEN_SIMPLE_NURSERY
153 if (sgen_nursery_is_to_space (obj)) {
154 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
155 SGEN_LOG (9, " (tospace, no change)");
156 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
161 * The card table scanning code sometimes clears cards
162 * that have just been set for a global remset. In
163 * the split nursery the following situation can
166 * Let's say object A starts in card C but continues
167 * into C+1. Within A, at offset O there's a
168 * reference to a new nursery object X. A+O is in
169 * card C+1. Now card C is scanned, and as part of
170 * it, object A. The reference at A+O is processed by
171 * copying X into nursery to-space at Y. Since it's
172 * still in the nursery, a global remset must be added
173 * for A+O, so card C+1 is marked. Now, however, card
174 * C+1 is scanned, which means that it's cleared
175 * first. This wouldn't be terribly bad if reference
176 * A+O were re-scanned and the global remset re-added,
177 * but since the reference points to to-space, that
178 * doesn't happen, and C+1 remains cleared: the remset
181 * There's at least two ways to fix this. The easy
182 * one is to re-add the remset on the re-scan. This
183 * is that - the following two lines of code.
185 * The proper solution appears to be to first make a
186 * copy of the cards before scanning a block, then to
187 * clear all the cards and scan from the copy, so no
188 * remsets will be overwritten. Scanning objects at
189 * most once would be the icing on the cake.
191 if (!sgen_ptr_in_nursery (obj_slot))
192 sgen_add_to_global_remset (obj_slot, obj);
198 HEAVY_STAT (++stat_objects_copied_nursery);
200 copy = copy_object_no_checks (obj, queue);
202 #ifndef SGEN_SIMPLE_NURSERY
203 if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
204 sgen_add_to_global_remset (obj_slot, copy);
206 /* copy_object_no_checks () can return obj on OOM */
207 if (G_UNLIKELY (obj == copy)) {
208 if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
209 sgen_add_to_global_remset (obj_slot, copy);
215 PARALLEL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
217 char *obj = *obj_slot;
218 mword vtable_word, objsize;
221 gboolean has_references;
223 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-par-copy from a %d generation collection", current_collection_generation);
225 HEAVY_STAT (++stat_copy_object_called_nursery);
227 if (!sgen_ptr_in_nursery (obj)) {
228 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
232 vtable_word = *(mword*)obj;
233 vt = (MonoVTable*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);
236 * Before we can copy the object we must make sure that we are
237 * allowed to, i.e. that the object not pinned, not already
238 * forwarded and not in the nursery To Space.
241 if (vtable_word & SGEN_FORWARDED_BIT) {
242 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
246 if (vtable_word & SGEN_PINNED_BIT) {
247 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
251 if (sgen_nursery_is_to_space (obj)) {
252 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
256 HEAVY_STAT (++stat_objects_copied_nursery);
258 objsize = SGEN_ALIGN_UP (sgen_par_object_get_size (vt, (MonoObject*)obj));
259 has_references = SGEN_VTABLE_HAS_REFERENCES (vt);
261 destination = COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION (vt, obj, objsize, has_references);
263 if (G_UNLIKELY (!destination)) {
264 sgen_parallel_pin_or_update (obj_slot, obj, vt, queue);
268 *(MonoVTable**)destination = vt;
270 if (SGEN_CAS_PTR ((void*)obj, (void*)((mword)destination | SGEN_FORWARDED_BIT), vt) == vt) {
271 par_copy_object_no_checks (destination, vt, obj, objsize, has_references ? queue : NULL);
275 /* FIXME: unify with code in major_copy_or_mark_object() */
277 /* FIXME: Give destination back to the allocator. */
278 /*The major collector only needs the first word zeroed and nursery requires all bits to be. */
279 if (!sgen_ptr_in_nursery (destination))
280 *(void**)destination = NULL;
282 memset (destination, 0, objsize);
284 vtable_word = *(mword*)obj;
285 g_assert (vtable_word & SGEN_FORWARDED_BIT);
287 obj = (void*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);
291 HEAVY_STAT (++stat_slots_allocated_in_vain);
295 #define FILL_MINOR_COLLECTOR_COPY_OBJECT(collector) do { \
296 (collector)->serial_ops.copy_or_mark_object = SERIAL_COPY_OBJECT; \
297 (collector)->parallel_ops.copy_or_mark_object = PARALLEL_COPY_OBJECT; \