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
25 extern guint64 stat_nursery_copy_object_failed_to_space; /* from sgen-gc.c */
27 #include "sgen-copy-object.h"
30 * This is how the copying happens from the nursery to the old generation.
31 * We assume that at this time all the pinned objects have been identified and
33 * We run scan_object() for each pinned object so that each referenced
34 * objects if possible are copied. The new gray objects created can have
35 * scan_object() run on them right away, too.
36 * Then we run copy_object() for the precisely tracked roots. At this point
37 * all the roots are either gray or black. We run scan_object() on the gray
38 * objects until no more gray objects are created.
39 * At the end of the process we walk again the pinned list and we unmark
40 * the pinned flag. As we go we also create the list of free space for use
41 * in the next allocation runs.
43 * We need to remember objects from the old generation that point to the new one
44 * (or just addresses?).
46 * copy_object could be made into a macro once debugged (use inline for now).
49 static MONO_ALWAYS_INLINE void
50 SERIAL_COPY_OBJECT (GCObject **obj_slot, SgenGrayQueue *queue)
54 GCObject *obj = *obj_slot;
56 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy from a %d generation collection", current_collection_generation);
58 HEAVY_STAT (++stat_copy_object_called_nursery);
60 if (!sgen_ptr_in_nursery (obj)) {
61 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
65 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
68 * Before we can copy the object we must make sure that we are
69 * allowed to, i.e. that the object not pinned, not already
70 * forwarded or belongs to the nursery To Space.
73 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
74 SGEN_ASSERT (9, sgen_obj_get_descriptor (forwarded), "forwarded object %p has no gc descriptor", forwarded);
75 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
76 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
77 SGEN_UPDATE_REFERENCE (obj_slot, forwarded);
80 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
81 SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "pinned object %p has no gc descriptor", obj);
82 SGEN_LOG (9, " (pinned, no change)");
83 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
87 #ifndef SGEN_SIMPLE_NURSERY
88 if (sgen_nursery_is_to_space (obj)) {
89 SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "to space object %p has no gc descriptor", obj);
90 SGEN_LOG (9, " (tospace, no change)");
91 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
96 HEAVY_STAT (++stat_objects_copied_nursery);
98 copy = copy_object_no_checks (obj, queue);
99 SGEN_UPDATE_REFERENCE (obj_slot, copy);
103 * SERIAL_COPY_OBJECT_FROM_OBJ:
105 * Similar to SERIAL_COPY_OBJECT, but assumes that OBJ_SLOT is part of an object, so it handles global remsets as well.
107 static MONO_ALWAYS_INLINE void
108 SERIAL_COPY_OBJECT_FROM_OBJ (GCObject **obj_slot, SgenGrayQueue *queue)
111 GCObject *obj = *obj_slot;
114 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy-from-obj from a %d generation collection", current_collection_generation);
116 HEAVY_STAT (++stat_copy_object_called_nursery);
118 if (!sgen_ptr_in_nursery (obj)) {
119 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
123 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
126 * Before we can copy the object we must make sure that we are
127 * allowed to, i.e. that the object not pinned, not already
128 * forwarded or belongs to the nursery To Space.
131 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
132 SGEN_ASSERT (9, sgen_obj_get_descriptor (forwarded), "forwarded object %p has no gc descriptor", forwarded);
133 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
134 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
135 SGEN_UPDATE_REFERENCE (obj_slot, forwarded);
136 #ifndef SGEN_SIMPLE_NURSERY
137 if (G_UNLIKELY (sgen_ptr_in_nursery (forwarded) && !sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (forwarded)))
138 sgen_add_to_global_remset (obj_slot, forwarded);
142 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
143 SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "pinned object %p has no gc descriptor", obj);
144 SGEN_LOG (9, " (pinned, no change)");
145 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
146 if (!sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (obj))
147 sgen_add_to_global_remset (obj_slot, obj);
151 #ifndef SGEN_SIMPLE_NURSERY
152 if (sgen_nursery_is_to_space (obj)) {
153 /* FIXME: all of these could just use `sgen_obj_get_descriptor_safe()` */
154 SGEN_ASSERT (9, sgen_vtable_get_descriptor (SGEN_LOAD_VTABLE(obj)), "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) && !SGEN_OBJECT_IS_CEMENTED (obj))
192 sgen_add_to_global_remset (obj_slot, obj);
198 HEAVY_STAT (++stat_objects_copied_nursery);
200 copy = copy_object_no_checks (obj, queue);
201 SGEN_UPDATE_REFERENCE (obj_slot, copy);
202 #ifndef SGEN_SIMPLE_NURSERY
203 if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot) && !SGEN_OBJECT_IS_CEMENTED (copy)))
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) && !SGEN_OBJECT_IS_CEMENTED (copy)))
209 sgen_add_to_global_remset (obj_slot, copy);
214 #define FILL_MINOR_COLLECTOR_COPY_OBJECT(collector) do { \
215 (collector)->serial_ops.copy_or_mark_object = SERIAL_COPY_OBJECT; \