1 /*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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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/liveRange.hpp"
32 #include "gc/shared/space.hpp"
33 #include "gc/shared/spaceDecorator.hpp"
34 #include "memory/universe.hpp"
35 #include "runtime/prefetch.inline.hpp"
36 #include "runtime/safepoint.hpp"
37
38 inline HeapWord* Space::block_start(const void* p) {
39 return block_start_const(p);
40 }
41
42 inline HeapWord* OffsetTableContigSpace::allocate(size_t size) {
43 HeapWord* res = ContiguousSpace::allocate(size);
44 if (res != NULL) {
45 _offsets.alloc_block(res, size);
46 }
47 return res;
48 }
49
50 // Because of the requirement of keeping "_offsets" up to date with the
51 // allocations, we sequentialize these with a lock. Therefore, best if
52 // this is used for larger LAB allocations only.
53 inline HeapWord* OffsetTableContigSpace::par_allocate(size_t size) {
54 MutexLocker x(&_par_alloc_lock);
55 // This ought to be just "allocate", because of the lock above, but that
56 // ContiguousSpace::allocate asserts that either the allocating thread
57 // holds the heap lock or it is the VM thread and we're at a safepoint.
58 // The best I (dld) could figure was to put a field in ContiguousSpace
59 // meaning "locking at safepoint taken care of", and set/reset that
60 // here. But this will do for now, especially in light of the comment
61 // above. Perhaps in the future some lock-free manner of keeping the
62 // coordination.
63 HeapWord* res = ContiguousSpace::par_allocate(size);
64 if (res != NULL) {
65 _offsets.alloc_block(res, size);
66 }
67 return res;
68 }
69
70 inline HeapWord*
71 OffsetTableContigSpace::block_start_const(const void* p) const {
72 return _offsets.block_start(p);
73 }
74
75 template <class SpaceType>
76 inline void CompactibleSpace::scan_and_forward(SpaceType* space, CompactPoint* cp) {
77 // Compute the new addresses for the live objects and store it in the mark
78 // Used by universe::mark_sweep_phase2()
79 HeapWord* compact_top; // This is where we are currently compacting to.
80
81 // We're sure to be here before any objects are compacted into this
82 // space, so this is a good time to initialize this:
83 space->set_compaction_top(space->bottom());
84
85 if (cp->space == NULL) {
86 assert(cp->gen != NULL, "need a generation");
87 assert(cp->threshold == NULL, "just checking");
88 assert(cp->gen->first_compaction_space() == space, "just checking");
89 cp->space = cp->gen->first_compaction_space();
90 compact_top = cp->space->bottom();
91 cp->space->set_compaction_top(compact_top);
92 cp->threshold = cp->space->initialize_threshold();
93 } else {
94 compact_top = cp->space->compaction_top();
95 }
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 uint invocations = MarkSweep::total_invocations();
102 bool skip_dead = ((invocations % MarkSweepAlwaysCompactCount) != 0);
103
104 size_t allowed_deadspace = 0;
105 if (skip_dead) {
106 const size_t ratio = space->allowed_dead_ratio();
107 allowed_deadspace = (space->capacity() * ratio / 100) / HeapWordSize;
108 }
109
110 HeapWord* q = space->bottom();
111 HeapWord* t = space->scan_limit();
112
113 HeapWord* end_of_live= q; // One byte beyond the last byte of the last
114 // live object.
115 HeapWord* first_dead = space->end(); // The first dead object.
116 LiveRange* liveRange = NULL; // The current live range, recorded in the
117 // first header of preceding free area.
118 space->_first_dead = first_dead;
119
120 const intx interval = PrefetchScanIntervalInBytes;
121
122 while (q < t) {
123 assert(!space->scanned_block_is_obj(q) ||
124 space->make_oop(q)->mark()->is_marked() ||
125 space->make_oop(q)->mark()->is_unlocked() ||
126 space->make_oop(q)->mark()->has_bias_pattern() ||
127 oopDesc::bs()->read_barrier(space->make_oop(q)) != space->make_oop(q),
128 "these are the only valid states during a mark sweep");
129 if (space->scanned_block_is_obj(q) && space->make_oop(q)->is_gc_marked()) {
130 // prefetch beyond q
131 Prefetch::write(q, interval);
132 size_t size = space->scanned_block_size(q);
133 compact_top = cp->space->forward(space->make_oop(q), size, cp, compact_top);
134 q += size;
135 end_of_live = q;
136 } else {
137 // run over all the contiguous dead objects
138 HeapWord* end = q;
139 do {
140 // prefetch beyond end
141 Prefetch::write(end, interval);
142 end += space->scanned_block_size(end);
143 } while (end < t && (!space->scanned_block_is_obj(end) || !space->make_oop(end)->is_gc_marked()));
144
145 // see if we might want to pretend this object is alive so that
146 // we don't have to compact quite as often.
147 if (allowed_deadspace > 0 && q == compact_top) {
148 size_t sz = pointer_delta(end, q);
149 if (space->insert_deadspace(allowed_deadspace, q, sz)) {
150 compact_top = cp->space->forward(space->make_oop(q), sz, cp, compact_top);
151 q = end;
152 end_of_live = end;
153 continue;
154 }
155 }
156
157 // otherwise, it really is a free region.
158
159 // for the previous LiveRange, record the end of the live objects.
160 if (liveRange) {
161 liveRange->set_end(q);
162 }
163
164 // record the current LiveRange object.
165 // liveRange->start() is overlaid on the mark word.
166 liveRange = (LiveRange*) (HeapWord*) space->make_oop(q);
167 liveRange->set_start(end);
168 liveRange->set_end(end);
169
170 // see if this is the first dead region.
171 if (q < first_dead) {
172 first_dead = q;
173 }
174
175 // move on to the next object
176 q = end;
177 }
178 }
179
180 assert(q == t, "just checking");
181 if (liveRange != NULL) {
182 liveRange->set_end(q);
183 }
184 space->_end_of_live = end_of_live;
185 if (end_of_live < first_dead) {
186 first_dead = end_of_live;
187 }
188 space->_first_dead = first_dead;
189
190 // save the compaction_top of the compaction space.
191 cp->space->set_compaction_top(compact_top);
192 }
193
194 template <class SpaceType>
195 inline void CompactibleSpace::scan_and_adjust_pointers(SpaceType* space) {
196 // adjust all the interior pointers to point at the new locations of objects
197 // Used by MarkSweep::mark_sweep_phase3()
198
199 HeapWord* q = space->bottom();
200 HeapWord* t = space->_end_of_live; // Established by "prepare_for_compaction".
201
202 assert(space->_first_dead <= space->_end_of_live, "Stands to reason, no?");
203
204 if (q < t && space->_first_dead > q && !space->make_oop(q)->is_gc_marked()) {
205 // we have a chunk of the space which hasn't moved and we've
206 // reinitialized the mark word during the previous pass, so we can't
207 // use is_gc_marked for the traversal.
208 HeapWord* end = space->_first_dead;
209
210 while (q < end) {
211 // I originally tried to conjoin "block_start(q) == q" to the
212 // assertion below, but that doesn't work, because you can't
213 // accurately traverse previous objects to get to the current one
214 // after their pointers have been
215 // updated, until the actual compaction is done. dld, 4/00
216 assert(space->block_is_obj(q), "should be at block boundaries, and should be looking at objs");
217
218 // point all the oops to the new location
219 size_t size = MarkSweep::adjust_pointers(space->make_oop(q));
220 size = space->adjust_obj_size(size);
221
222 q += size;
223 }
224
225 if (space->_first_dead == t) {
226 q = t;
227 } else {
228 // $$$ This is funky. Using this to read the previously written
229 // LiveRange. See also use below.
230 q = (HeapWord*)oop(space->_first_dead)->mark()->decode_pointer();
231 }
232 }
233
234 const intx interval = PrefetchScanIntervalInBytes;
235
236 debug_only(HeapWord* prev_q = NULL);
237 while (q < t) {
238 // prefetch beyond q
239 Prefetch::write(q, interval);
240 if (space->make_oop(q)->is_gc_marked()) {
241 // q is alive
242 // point all the oops to the new location
243 size_t size = MarkSweep::adjust_pointers(space->make_oop(q));
244 size = space->adjust_obj_size(size);
245 debug_only(prev_q = q);
246 q += size;
247 } else {
248 // q is not a live object, so its mark should point at the next
249 // live object
250 debug_only(prev_q = q);
251 q = (HeapWord*) space->make_oop(q)->mark()->decode_pointer();
252 assert(q > prev_q, "we should be moving forward through memory");
253 }
254 }
255
256 assert(q == t, "just checking");
257 }
258
259 template <class SpaceType>
260 inline void CompactibleSpace::scan_and_compact(SpaceType* space) {
261 // Copy all live objects to their new location
262 // Used by MarkSweep::mark_sweep_phase4()
263
264 HeapWord* q = space->bottom();
265 HeapWord* const t = space->_end_of_live;
266 debug_only(HeapWord* prev_q = NULL);
267
268 if (q < t && space->_first_dead > q && !space->make_oop(q)->is_gc_marked()) {
269 #ifdef ASSERT // Debug only
270 // we have a chunk of the space which hasn't moved and we've reinitialized
271 // the mark word during the previous pass, so we can't use is_gc_marked for
272 // the traversal.
273 HeapWord* const end = space->_first_dead;
274
275 while (q < end) {
276 size_t size = space->obj_size(q);
277 assert(!space->make_oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)");
278 prev_q = q;
279 q += size;
280 }
281 #endif
282
283 if (space->_first_dead == t) {
284 q = t;
285 } else {
286 // $$$ Funky
287 q = (HeapWord*) oop(space->_first_dead)->mark()->decode_pointer();
288 }
289 }
290
291 const intx scan_interval = PrefetchScanIntervalInBytes;
292 const intx copy_interval = PrefetchCopyIntervalInBytes;
293 while (q < t) {
294 if (!space->make_oop(q)->is_gc_marked()) {
295 // mark is pointer to next marked oop
296 debug_only(prev_q = q);
297 q = (HeapWord*) space->make_oop(q)->mark()->decode_pointer();
298 assert(q > prev_q, "we should be moving forward through memory");
299 } else {
300 // prefetch beyond q
301 Prefetch::read(q, scan_interval);
302
303 // size and destination
304 size_t size = space->obj_size(q);
305 HeapWord* compaction_top = (HeapWord*)space->make_oop(q)->forwardee();
306
307 // prefetch beyond compaction_top
308 Prefetch::write(compaction_top, copy_interval);
309
310 // copy object and reinit its mark
311 assert(q != compaction_top, "everything in this pass should be moving");
312 Copy::aligned_conjoint_words((HeapWord*) space->make_oop(q), compaction_top, size);
313 oop(compaction_top)->init_mark();
314 assert(oop(compaction_top)->klass() != NULL, "should have a class");
315
316 debug_only(prev_q = q);
317 q += size;
318 }
319 }
320
321 // Let's remember if we were empty before we did the compaction.
322 bool was_empty = space->used_region().is_empty();
323 // Reset space after compaction is complete
324 space->reset_after_compaction();
325 // We do this clear, below, since it has overloaded meanings for some
326 // space subtypes. For example, OffsetTableContigSpace's that were
327 // compacted into will have had their offset table thresholds updated
328 // continuously, but those that weren't need to have their thresholds
329 // re-initialized. Also mangles unused area for debugging.
330 if (space->used_region().is_empty()) {
331 if (!was_empty) space->clear(SpaceDecorator::Mangle);
332 } else {
333 if (ZapUnusedHeapArea) space->mangle_unused_area();
334 }
335 }
336 #endif // SHARE_VM_GC_SHARED_SPACE_INLINE_HPP