1 /*
2 * Copyright (c) 2000, 2018, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
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 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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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/shared/collectedHeap.hpp"
29 #include "gc/shared/generation.hpp"
30 #include "gc/shared/space.hpp"
31 #include "gc/shared/spaceDecorator.hpp"
32 #include "memory/universe.hpp"
33 #include "oops/oopsHierarchy.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/prefetch.inline.hpp"
36 #include "runtime/safepoint.hpp"
37 #if INCLUDE_SERIALGC
38 #include "gc/serial/markSweep.inline.hpp"
39 #endif
40
41 inline HeapWord* Space::block_start(const void* p) {
42 return block_start_const(p);
43 }
44
45 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
46 HeapWord* res = ContiguousSpace::allocate(size);
47 if (res != NULL) {
48 _offsets.alloc_block(res, size);
49 }
50 return res;
51 }
52
53 // Because of the requirement of keeping "_offsets" up to date with the
54 // allocations, we sequentialize these with a lock. Therefore, best if
55 // this is used for larger LAB allocations only.
56 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
57 MutexLocker x(&_par_alloc_lock);
58 // This ought to be just "allocate", because of the lock above, but that
59 // ContiguousSpace::allocate asserts that either the allocating thread
60 // holds the heap lock or it is the VM thread and we're at a safepoint.
61 // The best I (dld) could figure was to put a field in ContiguousSpace
62 // meaning "locking at safepoint taken care of", and set/reset that
63 // here. But this will do for now, especially in light of the comment
64 // above. Perhaps in the future some lock-free manner of keeping the
65 // coordination.
66 HeapWord* res = ContiguousSpace::par_allocate(size);
67 if (res != NULL) {
68 _offsets.alloc_block(res, size);
69 }
70 return res;
71 }
72
73 inline HeapWord*
74 OffsetTableContigSpace::block_start_const(const void* p) const {
75 return _offsets.block_start(p);
76 }
77
78 size_t CompactibleSpace::obj_size(const HeapWord* addr) const {
79 return oop(addr)->size();
80 }
81
82 #if INCLUDE_SERIALGC
83
84 class DeadSpacer : StackObj {
85 size_t _allowed_deadspace_words;
86 bool _active;
87 CompactibleSpace* _space;
88
89 public:
90 DeadSpacer(CompactibleSpace* space) : _space(space), _allowed_deadspace_words(0) {
91 size_t ratio = _space->allowed_dead_ratio();
92 _active = ratio > 0;
93
94 if (_active) {
95 assert(!UseG1GC, "G1 should not be using dead space");
96
97 // We allow some amount of garbage towards the bottom of the space, so
98 // we don't start compacting before there is a significant gain to be made.
99 // Occasionally, we want to ensure a full compaction, which is determined
100 // by the MarkSweepAlwaysCompactCount parameter.
101 if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) {
102 _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
103 } else {
104 _active = false;
105 }
106 }
107 }
108
109
110 bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
111 if (!_active) {
112 return false;
113 }
114
115 size_t dead_length = pointer_delta(dead_end, dead_start);
116 if (_allowed_deadspace_words >= dead_length) {
117 _allowed_deadspace_words -= dead_length;
118 CollectedHeap::fill_with_object(dead_start, dead_length);
119 oop obj = oop(dead_start);
120 obj->set_mark_raw(obj->mark_raw()->set_marked());
121
122 assert(dead_length == (size_t)obj->size(), "bad filler object size");
123 log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",
124 p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
125
126 return true;
127 } else {
128 _active = false;
129 return false;
130 }
131 }
132
133 };
134
135 template <class SpaceType>
136 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
137 // Compute the new addresses for the live objects and store it in the mark
138 // Used by universe::mark_sweep_phase2()
139
140 // We're sure to be here before any objects are compacted into this
141 // space, so this is a good time to initialize this:
142 space->set_compaction_top(space->bottom());
143
144 if (cp->space == NULL) {
145 assert(cp->gen != NULL, "need a generation");
146 assert(cp->threshold == NULL, "just checking");
147 assert(cp->gen->first_compaction_space() == space, "just checking");
148 cp->space = cp->gen->first_compaction_space();
149 cp->threshold = cp->space->initialize_threshold();
150 cp->space->set_compaction_top(cp->space->bottom());
151 }
152
153 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
154
155 DeadSpacer dead_spacer(space);
156
157 HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object.
158 HeapWord* first_dead = NULL; // The first dead object.
159
160 const intx interval = PrefetchScanIntervalInBytes;
161
162 HeapWord* cur_obj = space->bottom();
163 HeapWord* scan_limit = space->scan_limit();
164
165 while (cur_obj < scan_limit) {
166 assert(!space->scanned_block_is_obj(cur_obj) ||
167 oop(cur_obj)->mark_raw()->is_marked() || oop(cur_obj)->mark_raw()->is_unlocked() ||
168 oop(cur_obj)->mark_raw()->has_bias_pattern(),
169 "these are the only valid states during a mark sweep");
170 if (space->scanned_block_is_obj(cur_obj) && oop(cur_obj)->is_gc_marked()) {
171 // prefetch beyond cur_obj
172 Prefetch::write(cur_obj, interval);
173 size_t size = space->scanned_block_size(cur_obj);
174 compact_top = cp->space->forward(oop(cur_obj), size, cp, compact_top);
175 cur_obj += size;
176 end_of_live = cur_obj;
177 } else {
178 // run over all the contiguous dead objects
179 HeapWord* end = cur_obj;
180 do {
181 // prefetch beyond end
182 Prefetch::write(end, interval);
183 end += space->scanned_block_size(end);
184 } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !oop(end)->is_gc_marked()));
185
186 // see if we might want to pretend this object is alive so that
187 // we don't have to compact quite as often.
188 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
189 oop obj = oop(cur_obj);
190 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top);
191 end_of_live = end;
192 } else {
193 // otherwise, it really is a free region.
194
195 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
196 *(HeapWord**)cur_obj = end;
197
198 // see if this is the first dead region.
199 if (first_dead == NULL) {
200 first_dead = cur_obj;
201 }
202 }
203
204 // move on to the next object
205 cur_obj = end;
206 }
207 }
208
209 assert(cur_obj == scan_limit, "just checking");
210 space->_end_of_live = end_of_live;
211 if (first_dead != NULL) {
212 space->_first_dead = first_dead;
213 } else {
214 space->_first_dead = end_of_live;
215 }
216
217 // save the compaction_top of the compaction space.
218 cp->space->set_compaction_top(compact_top);
219 }
220
221 template <class SpaceType>
222 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
223 // adjust all the interior pointers to point at the new locations of objects
224 // Used by MarkSweep::mark_sweep_phase3()
225
226 HeapWord* cur_obj = space->bottom();
227 HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward".
228 HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward".
229
230 assert(first_dead <= end_of_live, "Stands to reason, no?");
231
232 const intx interval = PrefetchScanIntervalInBytes;
233
234 debug_only(HeapWord* prev_obj = NULL);
235 while (cur_obj < end_of_live) {
236 Prefetch::write(cur_obj, interval);
237 if (cur_obj < first_dead || oop(cur_obj)->is_gc_marked()) {
238 // cur_obj is alive
239 // point all the oops to the new location
240 size_t size = MarkSweep::adjust_pointers(oop(cur_obj));
241 size = space->adjust_obj_size(size);
242 debug_only(prev_obj = cur_obj);
243 cur_obj += size;
244 } else {
245 debug_only(prev_obj = cur_obj);
246 // cur_obj is not a live object, instead it points at the next live object
247 cur_obj = *(HeapWord**)cur_obj;
248 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));
249 }
250 }
251
252 assert(cur_obj == end_of_live, "just checking");
253 }
254
255 #ifdef ASSERT
256 template <class SpaceType>
257 inline void CompactibleSpace::verify_up_to_first_dead(SpaceType* space) {
258 HeapWord* cur_obj = space->bottom();
259
260 if (cur_obj < space->_end_of_live && space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
261 // we have a chunk of the space which hasn't moved and we've reinitialized
262 // the mark word during the previous pass, so we can't use is_gc_marked for
263 // the traversal.
264 HeapWord* prev_obj = NULL;
265
266 while (cur_obj < space->_first_dead) {
267 size_t size = space->obj_size(cur_obj);
268 assert(!oop(cur_obj)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
269 prev_obj = cur_obj;
270 cur_obj += size;
271 }
272 }
273 }
274 #endif
275
276 template <class SpaceType>
277 inline void CompactibleSpace::clear_empty_region(SpaceType* space) {
278 // Let's remember if we were empty before we did the compaction.
279 bool was_empty = space->used_region().is_empty();
280 // Reset space after compaction is complete
281 space->reset_after_compaction();
282 // We do this clear, below, since it has overloaded meanings for some
283 // space subtypes. For example, OffsetTableContigSpace's that were
284 // compacted into will have had their offset table thresholds updated
285 // continuously, but those that weren't need to have their thresholds
286 // re-initialized. Also mangles unused area for debugging.
287 if (space->used_region().is_empty()) {
288 if (!was_empty) space->clear(SpaceDecorator::Mangle);
289 } else {
290 if (ZapUnusedHeapArea) space->mangle_unused_area();
291 }
292 }
293
294 template <class SpaceType>
295 inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
296 // Copy all live objects to their new location
297 // Used by MarkSweep::mark_sweep_phase4()
298
299 verify_up_to_first_dead(space);
300
301 HeapWord* const bottom = space->bottom();
302 HeapWord* const end_of_live = space->_end_of_live;
303
304 assert(space->_first_dead <= end_of_live, "Invariant. _first_dead: " PTR_FORMAT " <= end_of_live: " PTR_FORMAT, p2i(space->_first_dead), p2i(end_of_live));
305 if (space->_first_dead == end_of_live && (bottom == end_of_live || !oop(bottom)->is_gc_marked())) {
306 // Nothing to compact. The space is either empty or all live object should be left in place.
307 clear_empty_region(space);
308 return;
309 }
310
311 const intx scan_interval = PrefetchScanIntervalInBytes;
312 const intx copy_interval = PrefetchCopyIntervalInBytes;
313
314 assert(bottom < end_of_live, "bottom: " PTR_FORMAT " should be < end_of_live: " PTR_FORMAT, p2i(bottom), p2i(end_of_live));
315 HeapWord* cur_obj = bottom;
316 if (space->_first_dead > cur_obj && !oop(cur_obj)->is_gc_marked()) {
317 // All object before _first_dead can be skipped. They should not be moved.
318 // A pointer to the first live object is stored at the memory location for _first_dead.
319 cur_obj = *(HeapWord**)(space->_first_dead);
320 }
321
322 debug_only(HeapWord* prev_obj = NULL);
323 while (cur_obj < end_of_live) {
324 if (!oop(cur_obj)->is_gc_marked()) {
325 debug_only(prev_obj = cur_obj);
326 // The first word of the dead object contains a pointer to the next live object or end of space.
327 cur_obj = *(HeapWord**)cur_obj;
328 assert(cur_obj > prev_obj, "we should be moving forward through memory");
329 } else {
330 // prefetch beyond q
331 Prefetch::read(cur_obj, scan_interval);
332
333 // size and destination
334 size_t size = space->obj_size(cur_obj);
335 HeapWord* compaction_top = (HeapWord*)oop(cur_obj)->forwardee();
336
337 // prefetch beyond compaction_top
338 Prefetch::write(compaction_top, copy_interval);
339
340 // copy object and reinit its mark
341 assert(cur_obj != compaction_top, "everything in this pass should be moving");
342 Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
343 oop(compaction_top)->init_mark_raw();
344 assert(oop(compaction_top)->klass() != NULL, "should have a class");
345
346 debug_only(prev_obj = cur_obj);
347 cur_obj += size;
348 }
349 }
350
351 clear_empty_region(space);
352 }
353
354 #endif // INCLUDE_SERIALGC
355
356 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const {
357 return oop(addr)->size();
358 }
359
360 template <typename OopClosureType>
361 void ContiguousSpace::oop_since_save_marks_iterate(OopClosureType* blk) {
362 HeapWord* t;
363 HeapWord* p = saved_mark_word();
364 assert(p != NULL, "expected saved mark");
365
366 const intx interval = PrefetchScanIntervalInBytes;
367 do {
368 t = top();
369 while (p < t) {
370 Prefetch::write(p, interval);
371 debug_only(HeapWord* prev = p);
372 oop m = oop(p);
373 p += m->oop_iterate_size(blk);
374 }
375 } while (t < top());
376
377 set_saved_mark_word(p);
378 }
379
380 template <typename OopClosureType>
381 void ContiguousSpace::par_oop_iterate(MemRegion mr, OopClosureType* blk) {
382 HeapWord* obj_addr = mr.start();
383 HeapWord* t = mr.end();
384 while (obj_addr < t) {
385 assert(oopDesc::is_oop(oop(obj_addr)), "Should be an oop");
386 obj_addr += oop(obj_addr)->oop_iterate_size(blk);
387 }
388 }
389
390 #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP