1 /*
2 * Copyright (c) 2000, 2016, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
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23 */
24
25 #ifndef SHARE_VM_GC_SHARED_SPACE_INLINE_HPP
26 #define SHARE_VM_GC_SHARED_SPACE_INLINE_HPP
27
28 #include "gc/serial/markSweep.inline.hpp"
29 #include "gc/shared/collectedHeap.hpp"
30 #include "gc/shared/generation.hpp"
31 #include "gc/shared/space.hpp"
32 #include "gc/shared/spaceDecorator.hpp"
33 #include "memory/universe.hpp"
34 #include "runtime/prefetch.inline.hpp"
35 #include "runtime/safepoint.hpp"
36
37 inline HeapWord* Space::block_start(const void* p) {
38 return block_start_const(p);
39 }
40
41 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
42 HeapWord* res = ContiguousSpace::allocate(size);
43 if (res != NULL) {
44 _offsets.alloc_block(res, size);
45 }
46 return res;
47 }
48
49 // Because of the requirement of keeping "_offsets" up to date with the
50 // allocations, we sequentialize these with a lock. Therefore, best if
51 // this is used for larger LAB allocations only.
52 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
53 MutexLocker x(&_par_alloc_lock);
54 // This ought to be just "allocate", because of the lock above, but that
55 // ContiguousSpace::allocate asserts that either the allocating thread
56 // holds the heap lock or it is the VM thread and we're at a safepoint.
57 // The best I (dld) could figure was to put a field in ContiguousSpace
58 // meaning "locking at safepoint taken care of", and set/reset that
59 // here. But this will do for now, especially in light of the comment
60 // above. Perhaps in the future some lock-free manner of keeping the
61 // coordination.
62 HeapWord* res = ContiguousSpace::par_allocate(size);
63 if (res != NULL) {
64 _offsets.alloc_block(res, size);
65 }
66 return res;
67 }
68
69 inline HeapWord*
70 OffsetTableContigSpace::block_start_const(const void* p) const {
71 return _offsets.block_start(p);
72 }
73
74 size_t CompactibleSpace::obj_size(const HeapWord* addr) const {
75 return oop(addr)->size();
76 }
77
78 template <class SpaceType>
79 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
80 // Compute the new addresses for the live objects and store it in the mark
81 // Used by universe::mark_sweep_phase2()
82
83 // We're sure to be here before any objects are compacted into this
84 // space, so this is a good time to initialize this:
85 space->set_compaction_top(space->bottom());
86
87 if (cp->space == NULL) {
88 assert(cp->gen != NULL, "need a generation");
89 assert(cp->threshold == NULL, "just checking");
90 assert(cp->gen->first_compaction_space() == space, "just checking");
91 cp->space = cp->gen->first_compaction_space();
92 cp->threshold = cp->space->initialize_threshold();
93 cp->space->set_compaction_top(cp->space->bottom());
94 }
95
96 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
97
98 // We allow some amount of garbage towards the bottom of the space, so
99 // we don't start compacting before there is a significant gain to be made.
100 // Occasionally, we want to ensure a full compaction, which is determined
101 // by the MarkSweepAlwaysCompactCount parameter.
102 uint invocations = MarkSweep::total_invocations();
103 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);
104
105 size_t allowed_deadspace = 0;
106 if (skip_dead) {
107 const size_t ratio = space->allowed_dead_ratio();
108 allowed_deadspace = (space->capacity() * ratio / 100) / HeapWordSize;
109 }
110
111 HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object.
112 HeapWord* first_dead = NULL; // The first dead object.
113
114 const intx interval = PrefetchScanIntervalInBytes;
115
116 HeapWord* cur_obj = space->bottom();
117 HeapWord* scan_limit = space->scan_limit();
118
119 while (cur_obj < scan_limit) {
120 assert(!space->scanned_block_is_obj(cur_obj) ||
121 oop(cur_obj)->mark()->is_marked() || oop(cur_obj)->mark()->is_unlocked() ||
122 oop(cur_obj)->mark()->has_bias_pattern(),
123 "these are the only valid states during a mark sweep");
124 if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) {
125 // prefetch beyond q
126 Prefetch::write(cur_obj, interval);
127 size_t size = space->scanned_block_size(cur_obj);
128 compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top);
129 cur_obj += size;
130 end_of_live = cur_obj;
131 } else {
132 // run over all the contiguous dead objects
133 HeapWord* end = cur_obj;
134 do {
135 // prefetch beyond end
136 Prefetch::write(end, interval);
137 end += space->scanned_block_size(end);
138 } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
139
140 // see if we might want to pretend this object is alive so that
141 // we don't have to compact quite as often.
142 if (allowed_deadspace > 0 && cur_obj == compact_top) {
143 assert(!UseG1GC, "G1 should not be allowing dead space");
144 size_t sz = pointer_delta(end, cur_obj);
145 if (space->insert_deadspace(allowed_deadspace, cur_obj, sz)) {
146 compact_top = cp->space->forward(oop(cur_obj), sz, cp, compact_top);
147 cur_obj = end;
148 end_of_live = end;
149 continue;
150 }
151 }
152
153 // otherwise, it really is a free region.
154
155 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
156 *(HeapWord**)cur_obj = end;
157
158 // see if this is the first dead region.
159 if (first_dead == NULL) {
160 first_dead = cur_obj;
161 }
162
163 // move on to the next object
164 cur_obj = end;
165 }
166 }
167
168 assert(cur_obj == scan_limit, "just checking");
169 space->_end_of_live = end_of_live;
170 if (first_dead != NULL) {
171 space->_first_dead = first_dead;
172 } else {
173 space->_first_dead = end_of_live;
174 }
175
176 // save the compaction_top of the compaction space.
177 cp->space->set_compaction_top(compact_top);
178 }
179
180 template <class SpaceType>
181 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
182 // adjust all the interior pointers to point at the new locations of objects
183 // Used by MarkSweep::mark_sweep_phase3()
184
185 HeapWord* cur_obj = space->bottom();
186 HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward".
187 HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward".
188
189 assert(first_dead <= end_of_live, "Stands to reason, no?");
190
191 const intx interval = PrefetchScanIntervalInBytes;
192
193 debug_only(HeapWord* prev_obj = NULL);
194 while (cur_obj < end_of_live) {
195 Prefetch::write(cur_obj, interval);
196 if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) {
197 // cur_obj is alive
198 // point all the oops to the new location
199 size_t size = MarkSweep::adjust_pointers(oop(cur_obj));
200 size = space->adjust_obj_size(size);
201 debug_only(prev_obj = cur_obj);
202 cur_obj += size;
203 } else {
204 debug_only(prev_obj = cur_obj);
205 // cur_obj is not a live object, instead it points at the next live object
206 cur_obj = *(HeapWord**)cur_obj;
207 assert(cur_obj > prev_obj, "we should be moving forward through memory, cur_obj: " PTR_FORMAT ", prev_obj: " PTR_FORMAT, p2i(cur_obj), p2i(prev_obj));
208 }
209 }
210
211 assert(cur_obj == end_of_live, "just checking");
212 }
213
214 template <class SpaceType>
215 inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
216 // Copy all live objects to their new location
217 // Used by MarkSweep::mark_sweep_phase4()
218
219 HeapWord* q = space->bottom();
220 HeapWord* const t = space->_end_of_live;
221 debug_only(HeapWord* prev_q = NULL);
222
223 if (q < t && space->_first_dead > q && !oop(q)->is_gc_marked()) {
224 #ifdef ASSERT // Debug only
225 // we have a chunk of the space which hasn't moved and we've reinitialized
226 // the mark word during the previous pass, so we can't use is_gc_marked for
227 // the traversal.
228 HeapWord* const end = space->_first_dead;
229
230 while (q < end) {
231 size_t size = space->obj_size(q);
232 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
233 prev_q = q;
234 q += size;
235 }
236 #endif
237
238 if (space->_first_dead == t) {
239 q = t;
240 } else {
241 // $$$ Funky
242 q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer();
243 }
244 }
245
246 const intx scan_interval = PrefetchScanIntervalInBytes;
247 const intx copy_interval = PrefetchCopyIntervalInBytes;
248 while (q < t) {
249 if (!oop(q)->is_gc_marked()) {
250 // mark is pointer to next marked oop
251 debug_only(prev_q = q);
252 q = (HeapWord*) oop(q)->mark()->decode_pointer();
253 assert(q > prev_q, "we should be moving forward through memory");
254 } else {
255 // prefetch beyond q
256 Prefetch::read(q, scan_interval);
257
258 // size and destination
259 size_t size = space->obj_size(q);
260 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee();
261
262 // prefetch beyond compaction_top
263 Prefetch::write(compaction_top, copy_interval);
264
265 // copy object and reinit its mark
266 assert(q != compaction_top, "everything in this pass should be moving");
267 Copy::aligned_conjoint_words(q, compaction_top, size);
268 oop(compaction_top)->init_mark();
269 assert(oop(compaction_top)->klass() != NULL, "should have a class");
270
271 debug_only(prev_q = q);
272 q += size;
273 }
274 }
275
276 // Let's remember if we were empty before we did the compaction.
277 bool was_empty = space->used_region().is_empty();
278 // Reset space after compaction is complete
279 space->reset_after_compaction();
280 // We do this clear, below, since it has overloaded meanings for some
281 // space subtypes. For example, OffsetTableContigSpace's that were
282 // compacted into will have had their offset table thresholds updated
283 // continuously, but those that weren't need to have their thresholds
284 // re-initialized. Also mangles unused area for debugging.
285 if (space->used_region().is_empty()) {
286 if (!was_empty) space->clear(SpaceDecorator::Mangle);
287 } else {
288 if (ZapUnusedHeapArea) space->mangle_unused_area();
289 }
290 }
291
292 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const {
293 return oop(addr)->size();
294 }
295
296 #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP