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annotate src/share/vm/gc_implementation/parallelScavenge/psMarkSweepDecorator.cpp @ 20256:b0b97602393a
8033923: Use BufferingOopClosure for G1 code root scanning
Reviewed-by: mgerdin, brutisso
author | stefank |
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date | Mon, 10 Feb 2014 12:58:09 +0100 |
parents | c49dcaf78a65 |
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0 | 1 /* |
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2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved. |
0 | 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. | |
18 * | |
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19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA |
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20 * or visit www.oracle.com if you need additional information or have any |
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21 * questions. |
0 | 22 * |
23 */ | |
24 | |
1972 | 25 #include "precompiled.hpp" |
26 #include "classfile/systemDictionary.hpp" | |
27 #include "gc_implementation/parallelScavenge/objectStartArray.hpp" | |
28 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp" | |
29 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp" | |
30 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp" | |
31 #include "gc_implementation/shared/liveRange.hpp" | |
32 #include "gc_implementation/shared/markSweep.inline.hpp" | |
33 #include "gc_implementation/shared/spaceDecorator.hpp" | |
34 #include "oops/oop.inline.hpp" | |
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35 #include "runtime/prefetch.inline.hpp" |
0 | 36 |
37 PSMarkSweepDecorator* PSMarkSweepDecorator::_destination_decorator = NULL; | |
38 | |
39 | |
40 void PSMarkSweepDecorator::set_destination_decorator_tenured() { | |
41 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
42 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); | |
43 | |
44 _destination_decorator = heap->old_gen()->object_mark_sweep(); | |
45 } | |
46 | |
47 void PSMarkSweepDecorator::advance_destination_decorator() { | |
48 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap(); | |
49 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity"); | |
50 | |
51 assert(_destination_decorator != NULL, "Sanity"); | |
52 | |
53 PSMarkSweepDecorator* first = heap->old_gen()->object_mark_sweep(); | |
54 PSMarkSweepDecorator* second = heap->young_gen()->eden_mark_sweep(); | |
55 PSMarkSweepDecorator* third = heap->young_gen()->from_mark_sweep(); | |
56 PSMarkSweepDecorator* fourth = heap->young_gen()->to_mark_sweep(); | |
57 | |
58 if ( _destination_decorator == first ) { | |
59 _destination_decorator = second; | |
60 } else if ( _destination_decorator == second ) { | |
61 _destination_decorator = third; | |
62 } else if ( _destination_decorator == third ) { | |
63 _destination_decorator = fourth; | |
64 } else { | |
65 fatal("PSMarkSweep attempting to advance past last compaction area"); | |
66 } | |
67 } | |
68 | |
69 PSMarkSweepDecorator* PSMarkSweepDecorator::destination_decorator() { | |
70 assert(_destination_decorator != NULL, "Sanity"); | |
71 | |
72 return _destination_decorator; | |
73 } | |
74 | |
75 // FIX ME FIX ME FIX ME FIX ME!!!!!!!!! | |
76 // The object forwarding code is duplicated. Factor this out!!!!! | |
77 // | |
78 // This method "precompacts" objects inside its space to dest. It places forwarding | |
79 // pointers into markOops for use by adjust_pointers. If "dest" should overflow, we | |
80 // finish by compacting into our own space. | |
81 | |
82 void PSMarkSweepDecorator::precompact() { | |
83 // Reset our own compact top. | |
84 set_compaction_top(space()->bottom()); | |
85 | |
86 /* We allow some amount of garbage towards the bottom of the space, so | |
87 * we don't start compacting before there is a significant gain to be made. | |
88 * Occasionally, we want to ensure a full compaction, which is determined | |
89 * by the MarkSweepAlwaysCompactCount parameter. This is a significant | |
90 * performance improvement! | |
91 */ | |
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92 bool skip_dead = ((PSMarkSweep::total_invocations() % MarkSweepAlwaysCompactCount) != 0); |
0 | 93 |
438 | 94 size_t allowed_deadspace = 0; |
0 | 95 if (skip_dead) { |
438 | 96 const size_t ratio = allowed_dead_ratio(); |
97 allowed_deadspace = space()->capacity_in_words() * ratio / 100; | |
0 | 98 } |
99 | |
100 // Fetch the current destination decorator | |
101 PSMarkSweepDecorator* dest = destination_decorator(); | |
102 ObjectStartArray* start_array = dest->start_array(); | |
103 | |
104 HeapWord* compact_top = dest->compaction_top(); | |
105 HeapWord* compact_end = dest->space()->end(); | |
106 | |
107 HeapWord* q = space()->bottom(); | |
108 HeapWord* t = space()->top(); | |
109 | |
110 HeapWord* end_of_live= q; /* One byte beyond the last byte of the last | |
111 live object. */ | |
112 HeapWord* first_dead = space()->end(); /* The first dead object. */ | |
113 LiveRange* liveRange = NULL; /* The current live range, recorded in the | |
114 first header of preceding free area. */ | |
115 _first_dead = first_dead; | |
116 | |
117 const intx interval = PrefetchScanIntervalInBytes; | |
118 | |
119 while (q < t) { | |
120 assert(oop(q)->mark()->is_marked() || oop(q)->mark()->is_unlocked() || | |
121 oop(q)->mark()->has_bias_pattern(), | |
122 "these are the only valid states during a mark sweep"); | |
123 if (oop(q)->is_gc_marked()) { | |
124 /* prefetch beyond q */ | |
125 Prefetch::write(q, interval); | |
126 size_t size = oop(q)->size(); | |
127 | |
128 size_t compaction_max_size = pointer_delta(compact_end, compact_top); | |
129 | |
130 // This should only happen if a space in the young gen overflows the | |
131 // old gen. If that should happen, we null out the start_array, because | |
132 // the young spaces are not covered by one. | |
133 while(size > compaction_max_size) { | |
134 // First record the last compact_top | |
135 dest->set_compaction_top(compact_top); | |
136 | |
137 // Advance to the next compaction decorator | |
138 advance_destination_decorator(); | |
139 dest = destination_decorator(); | |
140 | |
141 // Update compaction info | |
142 start_array = dest->start_array(); | |
143 compact_top = dest->compaction_top(); | |
144 compact_end = dest->space()->end(); | |
145 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use"); | |
146 assert(compact_end > compact_top, "Must always be space remaining"); | |
147 compaction_max_size = | |
148 pointer_delta(compact_end, compact_top); | |
149 } | |
150 | |
151 // store the forwarding pointer into the mark word | |
152 if (q != compact_top) { | |
153 oop(q)->forward_to(oop(compact_top)); | |
154 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark"); | |
155 } else { | |
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156 // if the object isn't moving we can just set the mark to the default |
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157 // mark and handle it specially later on. |
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158 oop(q)->init_mark(); |
0 | 159 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL"); |
160 } | |
161 | |
162 // Update object start array | |
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163 if (start_array) { |
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164 start_array->allocate_block(compact_top); |
0 | 165 } |
166 | |
167 compact_top += size; | |
168 assert(compact_top <= dest->space()->end(), | |
169 "Exceeding space in destination"); | |
170 | |
171 q += size; | |
172 end_of_live = q; | |
173 } else { | |
174 /* run over all the contiguous dead objects */ | |
175 HeapWord* end = q; | |
176 do { | |
177 /* prefetch beyond end */ | |
178 Prefetch::write(end, interval); | |
179 end += oop(end)->size(); | |
180 } while (end < t && (!oop(end)->is_gc_marked())); | |
181 | |
182 /* see if we might want to pretend this object is alive so that | |
183 * we don't have to compact quite as often. | |
184 */ | |
185 if (allowed_deadspace > 0 && q == compact_top) { | |
186 size_t sz = pointer_delta(end, q); | |
187 if (insert_deadspace(allowed_deadspace, q, sz)) { | |
188 size_t compaction_max_size = pointer_delta(compact_end, compact_top); | |
189 | |
190 // This should only happen if a space in the young gen overflows the | |
191 // old gen. If that should happen, we null out the start_array, because | |
192 // the young spaces are not covered by one. | |
193 while (sz > compaction_max_size) { | |
194 // First record the last compact_top | |
195 dest->set_compaction_top(compact_top); | |
196 | |
197 // Advance to the next compaction decorator | |
198 advance_destination_decorator(); | |
199 dest = destination_decorator(); | |
200 | |
201 // Update compaction info | |
202 start_array = dest->start_array(); | |
203 compact_top = dest->compaction_top(); | |
204 compact_end = dest->space()->end(); | |
205 assert(compact_top == dest->space()->bottom(), "Advanced to space already in use"); | |
206 assert(compact_end > compact_top, "Must always be space remaining"); | |
207 compaction_max_size = | |
208 pointer_delta(compact_end, compact_top); | |
209 } | |
210 | |
211 // store the forwarding pointer into the mark word | |
212 if (q != compact_top) { | |
213 oop(q)->forward_to(oop(compact_top)); | |
214 assert(oop(q)->is_gc_marked(), "encoding the pointer should preserve the mark"); | |
215 } else { | |
216 // if the object isn't moving we can just set the mark to the default | |
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217 // mark and handle it specially later on. |
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218 oop(q)->init_mark(); |
0 | 219 assert(oop(q)->forwardee() == NULL, "should be forwarded to NULL"); |
220 } | |
221 | |
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222 // Update object start array |
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223 if (start_array) { |
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224 start_array->allocate_block(compact_top); |
0 | 225 } |
226 | |
227 compact_top += sz; | |
228 assert(compact_top <= dest->space()->end(), | |
229 "Exceeding space in destination"); | |
230 | |
231 q = end; | |
232 end_of_live = end; | |
233 continue; | |
234 } | |
235 } | |
236 | |
237 /* for the previous LiveRange, record the end of the live objects. */ | |
238 if (liveRange) { | |
239 liveRange->set_end(q); | |
240 } | |
241 | |
242 /* record the current LiveRange object. | |
243 * liveRange->start() is overlaid on the mark word. | |
244 */ | |
245 liveRange = (LiveRange*)q; | |
246 liveRange->set_start(end); | |
247 liveRange->set_end(end); | |
248 | |
249 /* see if this is the first dead region. */ | |
250 if (q < first_dead) { | |
251 first_dead = q; | |
252 } | |
253 | |
254 /* move on to the next object */ | |
255 q = end; | |
256 } | |
257 } | |
258 | |
259 assert(q == t, "just checking"); | |
260 if (liveRange != NULL) { | |
261 liveRange->set_end(q); | |
262 } | |
263 _end_of_live = end_of_live; | |
264 if (end_of_live < first_dead) { | |
265 first_dead = end_of_live; | |
266 } | |
267 _first_dead = first_dead; | |
268 | |
269 // Update compaction top | |
270 dest->set_compaction_top(compact_top); | |
271 } | |
272 | |
438 | 273 bool PSMarkSweepDecorator::insert_deadspace(size_t& allowed_deadspace_words, |
274 HeapWord* q, size_t deadlength) { | |
275 if (allowed_deadspace_words >= deadlength) { | |
276 allowed_deadspace_words -= deadlength; | |
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277 CollectedHeap::fill_with_object(q, deadlength); |
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278 oop(q)->set_mark(oop(q)->mark()->set_marked()); |
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279 assert((int) deadlength == oop(q)->size(), "bad filler object size"); |
0 | 280 // Recall that we required "q == compaction_top". |
281 return true; | |
282 } else { | |
283 allowed_deadspace_words = 0; | |
284 return false; | |
285 } | |
286 } | |
287 | |
288 void PSMarkSweepDecorator::adjust_pointers() { | |
289 // adjust all the interior pointers to point at the new locations of objects | |
290 // Used by MarkSweep::mark_sweep_phase3() | |
291 | |
292 HeapWord* q = space()->bottom(); | |
293 HeapWord* t = _end_of_live; // Established by "prepare_for_compaction". | |
294 | |
295 assert(_first_dead <= _end_of_live, "Stands to reason, no?"); | |
296 | |
297 if (q < t && _first_dead > q && | |
298 !oop(q)->is_gc_marked()) { | |
299 // we have a chunk of the space which hasn't moved and we've | |
300 // reinitialized the mark word during the previous pass, so we can't | |
301 // use is_gc_marked for the traversal. | |
302 HeapWord* end = _first_dead; | |
303 | |
304 while (q < end) { | |
305 // point all the oops to the new location | |
306 size_t size = oop(q)->adjust_pointers(); | |
307 q += size; | |
308 } | |
309 | |
310 if (_first_dead == t) { | |
311 q = t; | |
312 } else { | |
313 // $$$ This is funky. Using this to read the previously written | |
314 // LiveRange. See also use below. | |
315 q = (HeapWord*)oop(_first_dead)->mark()->decode_pointer(); | |
316 } | |
317 } | |
318 const intx interval = PrefetchScanIntervalInBytes; | |
319 | |
320 debug_only(HeapWord* prev_q = NULL); | |
321 while (q < t) { | |
322 // prefetch beyond q | |
323 Prefetch::write(q, interval); | |
324 if (oop(q)->is_gc_marked()) { | |
325 // q is alive | |
326 // point all the oops to the new location | |
327 size_t size = oop(q)->adjust_pointers(); | |
328 debug_only(prev_q = q); | |
329 q += size; | |
330 } else { | |
331 // q is not a live object, so its mark should point at the next | |
332 // live object | |
333 debug_only(prev_q = q); | |
334 q = (HeapWord*) oop(q)->mark()->decode_pointer(); | |
335 assert(q > prev_q, "we should be moving forward through memory"); | |
336 } | |
337 } | |
338 | |
339 assert(q == t, "just checking"); | |
340 } | |
341 | |
342 void PSMarkSweepDecorator::compact(bool mangle_free_space ) { | |
343 // Copy all live objects to their new location | |
344 // Used by MarkSweep::mark_sweep_phase4() | |
345 | |
346 HeapWord* q = space()->bottom(); | |
347 HeapWord* const t = _end_of_live; | |
348 debug_only(HeapWord* prev_q = NULL); | |
349 | |
350 if (q < t && _first_dead > q && | |
351 !oop(q)->is_gc_marked()) { | |
352 #ifdef ASSERT | |
353 // we have a chunk of the space which hasn't moved and we've reinitialized the | |
354 // mark word during the previous pass, so we can't use is_gc_marked for the | |
355 // traversal. | |
356 HeapWord* const end = _first_dead; | |
357 | |
358 while (q < end) { | |
359 size_t size = oop(q)->size(); | |
360 assert(!oop(q)->is_gc_marked(), "should be unmarked (special dense prefix handling)"); | |
361 debug_only(prev_q = q); | |
362 q += size; | |
363 } | |
364 #endif | |
365 | |
366 if (_first_dead == t) { | |
367 q = t; | |
368 } else { | |
369 // $$$ Funky | |
370 q = (HeapWord*) oop(_first_dead)->mark()->decode_pointer(); | |
371 } | |
372 } | |
373 | |
374 const intx scan_interval = PrefetchScanIntervalInBytes; | |
375 const intx copy_interval = PrefetchCopyIntervalInBytes; | |
376 | |
377 while (q < t) { | |
378 if (!oop(q)->is_gc_marked()) { | |
379 // mark is pointer to next marked oop | |
380 debug_only(prev_q = q); | |
381 q = (HeapWord*) oop(q)->mark()->decode_pointer(); | |
382 assert(q > prev_q, "we should be moving forward through memory"); | |
383 } else { | |
384 // prefetch beyond q | |
385 Prefetch::read(q, scan_interval); | |
386 | |
387 // size and destination | |
388 size_t size = oop(q)->size(); | |
389 HeapWord* compaction_top = (HeapWord*)oop(q)->forwardee(); | |
390 | |
391 // prefetch beyond compaction_top | |
392 Prefetch::write(compaction_top, copy_interval); | |
393 | |
394 // copy object and reinit its mark | |
395 assert(q != compaction_top, "everything in this pass should be moving"); | |
396 Copy::aligned_conjoint_words(q, compaction_top, size); | |
397 oop(compaction_top)->init_mark(); | |
398 assert(oop(compaction_top)->klass() != NULL, "should have a class"); | |
399 | |
400 debug_only(prev_q = q); | |
401 q += size; | |
402 } | |
403 } | |
404 | |
405 assert(compaction_top() >= space()->bottom() && compaction_top() <= space()->end(), | |
406 "should point inside space"); | |
407 space()->set_top(compaction_top()); | |
408 | |
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409 if (mangle_free_space) { |
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410 space()->mangle_unused_area(); |
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411 } |
0 | 412 } |