1 /*
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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.
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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).
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23 */
24
25 #ifndef SHARE_GC_SHARED_SPACE_INLINE_HPP
26 #define SHARE_GC_SHARED_SPACE_INLINE_HPP
27
28 #include "gc/shared/space.hpp"
29
30 #include "gc/shared/blockOffsetTable.inline.hpp"
31 #include "gc/shared/collectedHeap.hpp"
32 #include "gc/shared/generation.hpp"
33 #include "gc/shared/genCollectedHeap.hpp"
34 #include "gc/shared/spaceDecorator.hpp"
35 #include "oops/oopsHierarchy.hpp"
36 #include "oops/oop.inline.hpp"
37 #include "runtime/prefetch.inline.hpp"
38 #include "runtime/safepoint.hpp"
39 #if INCLUDE_SERIALGC
40 #include "gc/serial/markSweep.inline.hpp"
41 #endif
42
43 inline HeapWord* Space::block_start(const void* p) {
44 return block_start_const(p);
45 }
46
47 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
48 HeapWord* res = ContiguousSpace::allocate(size);
49 if (res != NULL) {
50 _offsets.alloc_block(res, size);
51 }
52 return res;
53 }
54
55 // Because of the requirement of keeping "_offsets" up to date with the
56 // allocations, we sequentialize these with a lock. Therefore, best if
57 // this is used for larger LAB allocations only.
58 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
59 MutexLocker x(&_par_alloc_lock);
60 // This ought to be just "allocate", because of the lock above, but that
61 // ContiguousSpace::allocate asserts that either the allocating thread
62 // holds the heap lock or it is the VM thread and we're at a safepoint.
63 // The best I (dld) could figure was to put a field in ContiguousSpace
64 // meaning "locking at safepoint taken care of", and set/reset that
65 // here. But this will do for now, especially in light of the comment
66 // above. Perhaps in the future some lock-free manner of keeping the
67 // coordination.
68 HeapWord* res = ContiguousSpace::par_allocate(size);
69 if (res != NULL) {
70 _offsets.alloc_block(res, size);
71 }
72 return res;
73 }
74
75 inline HeapWord*
76 OffsetTableContigSpace::block_start_const(const void* p) const {
77 return _offsets.block_start(p);
78 }
79
80 size_t CompactibleSpace::obj_size(const HeapWord* addr) const {
81 return cast_to_oop(addr)->size();
82 }
83
84 #if INCLUDE_SERIALGC
85
86 class DeadSpacer : StackObj {
87 size_t _allowed_deadspace_words;
88 bool _active;
89 CompactibleSpace* _space;
90
91 public:
92 DeadSpacer(CompactibleSpace* space) : _allowed_deadspace_words(0), _space(space) {
93 size_t ratio = _space->allowed_dead_ratio();
94 _active = ratio > 0;
95
96 if (_active) {
97 assert(!UseG1GC, "G1 should not be using dead space");
98
99 // We allow some amount of garbage towards the bottom of the space, so
100 // we don't start compacting before there is a significant gain to be made.
101 // Occasionally, we want to ensure a full compaction, which is determined
102 // by the MarkSweepAlwaysCompactCount parameter.
103 if ((MarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0) {
104 _allowed_deadspace_words = (space->capacity() * ratio / 100) / HeapWordSize;
105 } else {
106 _active = false;
107 }
108 }
109 }
110
111
112 bool insert_deadspace(HeapWord* dead_start, HeapWord* dead_end) {
113 if (!_active) {
114 return false;
115 }
116
117 size_t dead_length = pointer_delta(dead_end, dead_start);
118 if (_allowed_deadspace_words >= dead_length) {
119 _allowed_deadspace_words -= dead_length;
120 CollectedHeap::fill_with_object(dead_start, dead_length);
121 oop obj = cast_to_oop(dead_start);
122 obj->set_mark(obj->mark().set_marked());
123
124 assert(dead_length == (size_t)obj->size(), "bad filler object size");
125 log_develop_trace(gc, compaction)("Inserting object to dead space: " PTR_FORMAT ", " PTR_FORMAT ", " SIZE_FORMAT "b",
126 p2i(dead_start), p2i(dead_end), dead_length * HeapWordSize);
127
128 return true;
129 } else {
130 _active = false;
131 return false;
132 }
133 }
134
135 };
136
137 template <class SpaceType>
138 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
139 // Compute the new addresses for the live objects and store it in the mark
140 // Used by universe::mark_sweep_phase2()
141
142 // We're sure to be here before any objects are compacted into this
143 // space, so this is a good time to initialize this:
144 space->set_compaction_top(space->bottom());
145
146 if (cp->space == NULL) {
147 assert(cp->gen != NULL, "need a generation");
148 assert(cp->threshold == NULL, "just checking");
149 assert(cp->gen->first_compaction_space() == space, "just checking");
150 cp->space = cp->gen->first_compaction_space();
151 cp->threshold = cp->space->initialize_threshold();
152 cp->space->set_compaction_top(cp->space->bottom());
153 }
154
155 HeapWord* compact_top = cp->space->compaction_top(); // This is where we are currently compacting to.
156
157 DeadSpacer dead_spacer(space);
158
159 HeapWord* end_of_live = space->bottom(); // One byte beyond the last byte of the last live object.
160 HeapWord* first_dead = NULL; // The first dead object.
161
162 const intx interval = PrefetchScanIntervalInBytes;
163
164 HeapWord* cur_obj = space->bottom();
165 HeapWord* scan_limit = space->scan_limit();
166
167 SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
168 while (cur_obj < scan_limit) {
169 if (space->scanned_block_is_obj(cur_obj) && cast_to_oop(cur_obj)->is_gc_marked()) {
170 // prefetch beyond cur_obj
171 Prefetch::write(cur_obj, interval);
172 size_t size = space->scanned_block_size(cur_obj);
173 compact_top = cp->space->forward(cast_to_oop(cur_obj), size, cp, compact_top, forwarding);
174 cur_obj += size;
175 end_of_live = cur_obj;
176 } else {
177 // run over all the contiguous dead objects
178 HeapWord* end = cur_obj;
179 do {
180 // prefetch beyond end
181 Prefetch::write(end, interval);
182 end += space->scanned_block_size(end);
183 } while (end < scan_limit && (!space->scanned_block_is_obj(end) || !cast_to_oop(end)->is_gc_marked()));
184
185 // see if we might want to pretend this object is alive so that
186 // we don't have to compact quite as often.
187 if (cur_obj == compact_top && dead_spacer.insert_deadspace(cur_obj, end)) {
188 oop obj = cast_to_oop(cur_obj);
189 compact_top = cp->space->forward(obj, obj->size(), cp, compact_top, forwarding);
190 end_of_live = end;
191 } else {
192 // otherwise, it really is a free region.
193
194 // cur_obj is a pointer to a dead object. Use this dead memory to store a pointer to the next live object.
195 *(HeapWord**)cur_obj = end;
196
197 // see if this is the first dead region.
198 if (first_dead == NULL) {
199 first_dead = cur_obj;
200 }
201 }
202
203 // move on to the next object
204 cur_obj = end;
205 }
206 }
207
208 assert(cur_obj == scan_limit, "just checking");
209 space->_end_of_live = end_of_live;
210 if (first_dead != NULL) {
211 space->_first_dead = first_dead;
212 } else {
213 space->_first_dead = end_of_live;
214 }
215
216 // save the compaction_top of the compaction space.
217 cp->space->set_compaction_top(compact_top);
218 }
219
220 template <class SpaceType>
221 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
222 // adjust all the interior pointers to point at the new locations of objects
223 // Used by MarkSweep::mark_sweep_phase3()
224
225 HeapWord* cur_obj = space->bottom();
226 HeapWord* const end_of_live = space->_end_of_live; // Established by "scan_and_forward".
227 HeapWord* const first_dead = space->_first_dead; // Established by "scan_and_forward".
228 const SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
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 || cast_to_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(forwarding, cast_to_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 && !cast_to_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(!cast_to_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 || !cast_to_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 && !cast_to_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 const SlidingForwarding* const forwarding = GenCollectedHeap::heap()->forwarding();
323
324 debug_only(HeapWord* prev_obj = NULL);
325 while (cur_obj < end_of_live) {
326 if (!cast_to_oop(cur_obj)->is_gc_marked()) {
327 debug_only(prev_obj = cur_obj);
328 // The first word of the dead object contains a pointer to the next live object or end of space.
329 cur_obj = *(HeapWord**)cur_obj;
330 assert(cur_obj > prev_obj, "we should be moving forward through memory");
331 } else {
332 // prefetch beyond q
333 Prefetch::read(cur_obj, scan_interval);
334
335 // size and destination
336 size_t size = space->obj_size(cur_obj);
337 HeapWord* compaction_top = cast_from_oop<HeapWord*>(forwarding->forwardee(cast_to_oop(cur_obj)));
338
339 // prefetch beyond compaction_top
340 Prefetch::write(compaction_top, copy_interval);
341
342 // copy object and reinit its mark
343 assert(cur_obj != compaction_top, "everything in this pass should be moving");
344 Copy::aligned_conjoint_words(cur_obj, compaction_top, size);
345 cast_to_oop(compaction_top)->init_mark();
346 assert(cast_to_oop(compaction_top)->klass() != NULL, "should have a class");
347
348 debug_only(prev_obj = cur_obj);
349 cur_obj += size;
350 }
351 }
352
353 clear_empty_region(space);
354 }
355
356 #endif // INCLUDE_SERIALGC
357
358 size_t ContiguousSpace::scanned_block_size(const HeapWord* addr) const {
359 return cast_to_oop(addr)->size();
360 }
361
362 template <typename OopClosureType>
363 void ContiguousSpace::oop_since_save_marks_iterate(OopClosureType* blk) {
364 HeapWord* t;
365 HeapWord* p = saved_mark_word();
366 assert(p != NULL, "expected saved mark");
367
368 const intx interval = PrefetchScanIntervalInBytes;
369 do {
370 t = top();
371 while (p < t) {
372 Prefetch::write(p, interval);
373 debug_only(HeapWord* prev = p);
374 oop m = cast_to_oop(p);
375 p += m->oop_iterate_size(blk);
376 }
377 } while (t < top());
378
379 set_saved_mark_word(p);
380 }
381
382 #endif // SHARE_GC_SHARED_SPACE_INLINE_HPP