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 "sgen-copy-object.h"
31 * This is how the copying happens from the nursery to the old generation.
32 * We assume that at this time all the pinned objects have been identified and
34 * We run scan_object() for each pinned object so that each referenced
35 * objects if possible are copied. The new gray objects created can have
36 * scan_object() run on them right away, too.
37 * Then we run copy_object() for the precisely tracked roots. At this point
38 * all the roots are either gray or black. We run scan_object() on the gray
39 * objects until no more gray objects are created.
40 * At the end of the process we walk again the pinned list and we unmark
41 * the pinned flag. As we go we also create the list of free space for use
42 * in the next allocation runs.
44 * We need to remember objects from the old generation that point to the new one
45 * (or just addresses?).
47 * copy_object could be made into a macro once debugged (use inline for now).
51 static __forceinline void
53 static inline void __attribute__((always_inline))
55 SERIAL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
58 char *obj = *obj_slot;
60 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy from a %d generation collection", current_collection_generation);
62 HEAVY_STAT (++stat_copy_object_called_nursery);
64 if (!sgen_ptr_in_nursery (obj)) {
65 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
69 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
72 * Before we can copy the object we must make sure that we are
73 * allowed to, i.e. that the object not pinned, not already
74 * forwarded or belongs to the nursery To Space.
77 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
78 SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
79 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
80 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
81 *obj_slot = forwarded;
84 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
85 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
86 SGEN_LOG (9, " (pinned, no change)");
87 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
91 #ifndef SGEN_SIMPLE_NURSERY
92 if (sgen_nursery_is_to_space (obj)) {
93 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
94 SGEN_LOG (9, " (tospace, no change)");
95 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
100 HEAVY_STAT (++stat_objects_copied_nursery);
102 *obj_slot = copy_object_no_checks (obj, queue);
106 * SERIAL_COPY_OBJECT_FROM_OBJ:
108 * Similar to SERIAL_COPY_OBJECT, but assumes that OBJ_SLOT is part of an object, so it handles global remsets as well.
111 static __forceinline void
113 static inline void __attribute__((always_inline))
115 SERIAL_COPY_OBJECT_FROM_OBJ (void **obj_slot, SgenGrayQueue *queue)
118 char *obj = *obj_slot;
121 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-serial-copy-from-obj from a %d generation collection", current_collection_generation);
123 HEAVY_STAT (++stat_copy_object_called_nursery);
125 if (!sgen_ptr_in_nursery (obj)) {
126 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
130 SGEN_LOG (9, "Precise copy of %p from %p", obj, obj_slot);
133 * Before we can copy the object we must make sure that we are
134 * allowed to, i.e. that the object not pinned, not already
135 * forwarded or belongs to the nursery To Space.
138 if ((forwarded = SGEN_OBJECT_IS_FORWARDED (obj))) {
139 SGEN_ASSERT (9, (*(MonoVTable**)SGEN_LOAD_VTABLE (obj))->gc_descr, "forwarded object %p has no gc descriptor", forwarded);
140 SGEN_LOG (9, " (already forwarded to %p)", forwarded);
141 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
142 *obj_slot = forwarded;
143 #ifndef SGEN_SIMPLE_NURSERY
144 if (G_UNLIKELY (sgen_ptr_in_nursery (forwarded) && !sgen_ptr_in_nursery (obj_slot)))
145 sgen_add_to_global_remset (obj_slot, forwarded);
149 if (G_UNLIKELY (SGEN_OBJECT_IS_PINNED (obj))) {
150 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "pinned object %p has no gc descriptor", obj);
151 SGEN_LOG (9, " (pinned, no change)");
152 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
153 if (!sgen_ptr_in_nursery (obj_slot))
154 sgen_add_to_global_remset (obj_slot, obj);
158 #ifndef SGEN_SIMPLE_NURSERY
159 if (sgen_nursery_is_to_space (obj)) {
160 SGEN_ASSERT (9, ((MonoVTable*)SGEN_LOAD_VTABLE(obj))->gc_descr, "to space object %p has no gc descriptor", obj);
161 SGEN_LOG (9, " (tospace, no change)");
162 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
167 * The card table scanning code sometimes clears cards
168 * that have just been set for a global remset. In
169 * the split nursery the following situation can
172 * Let's say object A starts in card C but continues
173 * into C+1. Within A, at offset O there's a
174 * reference to a new nursery object X. A+O is in
175 * card C+1. Now card C is scanned, and as part of
176 * it, object A. The reference at A+O is processed by
177 * copying X into nursery to-space at Y. Since it's
178 * still in the nursery, a global remset must be added
179 * for A+O, so card C+1 is marked. Now, however, card
180 * C+1 is scanned, which means that it's cleared
181 * first. This wouldn't be terribly bad if reference
182 * A+O were re-scanned and the global remset re-added,
183 * but since the reference points to to-space, that
184 * doesn't happen, and C+1 remains cleared: the remset
187 * There's at least two ways to fix this. The easy
188 * one is to re-add the remset on the re-scan. This
189 * is that - the following two lines of code.
191 * The proper solution appears to be to first make a
192 * copy of the cards before scanning a block, then to
193 * clear all the cards and scan from the copy, so no
194 * remsets will be overwritten. Scanning objects at
195 * most once would be the icing on the cake.
197 if (!sgen_ptr_in_nursery (obj_slot))
198 sgen_add_to_global_remset (obj_slot, obj);
204 HEAVY_STAT (++stat_objects_copied_nursery);
206 copy = copy_object_no_checks (obj, queue);
208 #ifndef SGEN_SIMPLE_NURSERY
209 if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
210 sgen_add_to_global_remset (obj_slot, copy);
212 /* copy_object_no_checks () can return obj on OOM */
213 if (G_UNLIKELY (obj == copy)) {
214 if (G_UNLIKELY (sgen_ptr_in_nursery (copy) && !sgen_ptr_in_nursery (obj_slot)))
215 sgen_add_to_global_remset (obj_slot, copy);
221 PARALLEL_COPY_OBJECT (void **obj_slot, SgenGrayQueue *queue)
223 char *obj = *obj_slot;
224 mword vtable_word, objsize;
227 gboolean has_references;
229 SGEN_ASSERT (9, current_collection_generation == GENERATION_NURSERY, "calling minor-par-copy from a %d generation collection", current_collection_generation);
231 HEAVY_STAT (++stat_copy_object_called_nursery);
233 if (!sgen_ptr_in_nursery (obj)) {
234 HEAVY_STAT (++stat_nursery_copy_object_failed_from_space);
238 vtable_word = *(mword*)obj;
239 vt = (MonoVTable*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);
242 * Before we can copy the object we must make sure that we are
243 * allowed to, i.e. that the object not pinned, not already
244 * forwarded and not in the nursery To Space.
247 if (vtable_word & SGEN_FORWARDED_BIT) {
248 HEAVY_STAT (++stat_nursery_copy_object_failed_forwarded);
252 if (vtable_word & SGEN_PINNED_BIT) {
253 HEAVY_STAT (++stat_nursery_copy_object_failed_pinned);
257 if (sgen_nursery_is_to_space (obj)) {
258 HEAVY_STAT (++stat_nursery_copy_object_failed_to_space);
262 HEAVY_STAT (++stat_objects_copied_nursery);
264 objsize = SGEN_ALIGN_UP (sgen_par_object_get_size (vt, (MonoObject*)obj));
265 has_references = SGEN_VTABLE_HAS_REFERENCES (vt);
267 destination = COLLECTOR_PARALLEL_ALLOC_FOR_PROMOTION (vt, obj, objsize, has_references);
269 if (G_UNLIKELY (!destination)) {
270 sgen_parallel_pin_or_update (obj_slot, obj, vt, queue);
274 *(MonoVTable**)destination = vt;
276 if (SGEN_CAS_PTR ((void*)obj, (void*)((mword)destination | SGEN_FORWARDED_BIT), vt) == vt) {
277 par_copy_object_no_checks (destination, vt, obj, objsize, has_references ? queue : NULL);
281 /* FIXME: unify with code in major_copy_or_mark_object() */
283 /* FIXME: Give destination back to the allocator. */
284 /*The major collector only needs the first word zeroed and nursery requires all bits to be. */
285 if (!sgen_ptr_in_nursery (destination))
286 *(void**)destination = NULL;
288 memset (destination, 0, objsize);
290 vtable_word = *(mword*)obj;
291 g_assert (vtable_word & SGEN_FORWARDED_BIT);
293 obj = (void*)(vtable_word & ~SGEN_VTABLE_BITS_MASK);
297 HEAVY_STAT (++stat_slots_allocated_in_vain);
301 #define FILL_MINOR_COLLECTOR_COPY_OBJECT(collector) do { \
302 (collector)->serial_ops.copy_or_mark_object = SERIAL_COPY_OBJECT; \
303 (collector)->parallel_ops.copy_or_mark_object = PARALLEL_COPY_OBJECT; \