1 /*
2 * Copyright (c) 2005, 2026, 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.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/javaClasses.inline.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/nmethod.hpp"
32 #include "compiler/oopMap.hpp"
33 #include "gc/parallel/objectStartArray.inline.hpp"
34 #include "gc/parallel/parallelArguments.hpp"
35 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
36 #include "gc/parallel/parMarkBitMap.inline.hpp"
37 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
38 #include "gc/parallel/psCompactionManager.inline.hpp"
39 #include "gc/parallel/psOldGen.hpp"
40 #include "gc/parallel/psParallelCompact.inline.hpp"
41 #include "gc/parallel/psPromotionManager.inline.hpp"
42 #include "gc/parallel/psRootType.hpp"
43 #include "gc/parallel/psScavenge.hpp"
44 #include "gc/parallel/psStringDedup.hpp"
45 #include "gc/parallel/psYoungGen.hpp"
46 #include "gc/shared/classUnloadingContext.hpp"
47 #include "gc/shared/collectedHeap.inline.hpp"
48 #include "gc/shared/fullGCForwarding.inline.hpp"
49 #include "gc/shared/gcCause.hpp"
50 #include "gc/shared/gcHeapSummary.hpp"
51 #include "gc/shared/gcId.hpp"
52 #include "gc/shared/gcLocker.hpp"
53 #include "gc/shared/gcTimer.hpp"
54 #include "gc/shared/gcTrace.hpp"
55 #include "gc/shared/gcTraceTime.inline.hpp"
56 #include "gc/shared/gcVMOperations.hpp"
57 #include "gc/shared/isGCActiveMark.hpp"
58 #include "gc/shared/oopStorage.inline.hpp"
59 #include "gc/shared/oopStorageSet.inline.hpp"
60 #include "gc/shared/oopStorageSetParState.inline.hpp"
61 #include "gc/shared/parallelCleaning.hpp"
62 #include "gc/shared/preservedMarks.inline.hpp"
63 #include "gc/shared/referencePolicy.hpp"
64 #include "gc/shared/referenceProcessor.hpp"
65 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
66 #include "gc/shared/spaceDecorator.hpp"
67 #include "gc/shared/taskTerminator.hpp"
68 #include "gc/shared/weakProcessor.inline.hpp"
69 #include "gc/shared/workerPolicy.hpp"
70 #include "gc/shared/workerThread.hpp"
71 #include "gc/shared/workerUtils.hpp"
72 #include "logging/log.hpp"
73 #include "memory/iterator.inline.hpp"
74 #include "memory/memoryReserver.hpp"
75 #include "memory/metaspaceUtils.hpp"
76 #include "memory/resourceArea.hpp"
77 #include "memory/universe.hpp"
78 #include "nmt/memTracker.hpp"
79 #include "oops/access.inline.hpp"
80 #include "oops/instanceClassLoaderKlass.inline.hpp"
81 #include "oops/instanceKlass.inline.hpp"
82 #include "oops/instanceMirrorKlass.inline.hpp"
83 #include "oops/methodData.hpp"
84 #include "oops/objArrayKlass.inline.hpp"
85 #include "oops/oop.inline.hpp"
86 #include "runtime/atomicAccess.hpp"
87 #include "runtime/handles.inline.hpp"
88 #include "runtime/java.hpp"
89 #include "runtime/safepoint.hpp"
90 #include "runtime/threads.hpp"
91 #include "runtime/vmThread.hpp"
92 #include "services/memoryService.hpp"
93 #include "utilities/align.hpp"
94 #include "utilities/debug.hpp"
95 #include "utilities/events.hpp"
96 #include "utilities/formatBuffer.hpp"
97 #include "utilities/macros.hpp"
98 #include "utilities/stack.inline.hpp"
99 #if INCLUDE_JVMCI
100 #include "jvmci/jvmci.hpp"
101 #endif
102
103 #include <math.h>
104
105 // All sizes are in HeapWords.
106 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
107 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
108 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
109 const size_t ParallelCompactData::RegionSizeBytes =
110 RegionSize << LogHeapWordSize;
111 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
112 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
113 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
114
115 const ParallelCompactData::RegionData::region_sz_t
116 ParallelCompactData::RegionData::dc_shift = 27;
117
118 const ParallelCompactData::RegionData::region_sz_t
119 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
120
121 const ParallelCompactData::RegionData::region_sz_t
122 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
123
124 const ParallelCompactData::RegionData::region_sz_t
125 ParallelCompactData::RegionData::los_mask = ~dc_mask;
126
127 const ParallelCompactData::RegionData::region_sz_t
128 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
129
130 const ParallelCompactData::RegionData::region_sz_t
131 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
132
133 bool ParallelCompactData::RegionData::is_clear() {
134 return (_destination == nullptr) &&
135 (_source_region == 0) &&
136 (_partial_obj_addr == nullptr) &&
137 (_partial_obj_size == 0) &&
138 (_dc_and_los == 0) &&
139 (_shadow_state == 0);
140 }
141
142 #ifdef ASSERT
143 void ParallelCompactData::RegionData::verify_clear() {
144 assert(_destination == nullptr, "inv");
145 assert(_source_region == 0, "inv");
146 assert(_partial_obj_addr == nullptr, "inv");
147 assert(_partial_obj_size == 0, "inv");
148 assert(_dc_and_los == 0, "inv");
149 assert(_shadow_state == 0, "inv");
150 }
151 #endif
152
153 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
154
155 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
156 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
157
158 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
159 assert(split_region_idx != 0, "precondition");
160
161 // Obj denoted by split_point will be deferred to the next space.
162 assert(split_point != nullptr, "precondition");
163
164 const ParallelCompactData& sd = PSParallelCompact::summary_data();
165
166 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
167 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
168
169 HeapWord* preceding_destination = split_region_ptr->destination();
170 assert(preceding_destination != nullptr, "inv");
171
172 // How many regions does the preceding part occupy
173 uint preceding_destination_count;
174 if (preceding_live_words == 0) {
175 preceding_destination_count = 0;
176 } else {
177 // -1 so that the ending address doesn't fall on the region-boundary
178 if (sd.region_align_down(preceding_destination) ==
179 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
180 preceding_destination_count = 1;
181 } else {
182 preceding_destination_count = 2;
183 }
184 }
185
186 _split_region_idx = split_region_idx;
187 _split_point = split_point;
188 _preceding_live_words = preceding_live_words;
189 _preceding_destination = preceding_destination;
190 _preceding_destination_count = preceding_destination_count;
191 }
192
193 void SplitInfo::clear()
194 {
195 _split_region_idx = 0;
196 _split_point = nullptr;
197 _preceding_live_words = 0;
198 _preceding_destination = nullptr;
199 _preceding_destination_count = 0;
200 assert(!is_valid(), "sanity");
201 }
202
203 #ifdef ASSERT
204 void SplitInfo::verify_clear()
205 {
206 assert(_split_region_idx == 0, "not clear");
207 assert(_split_point == nullptr, "not clear");
208 assert(_preceding_live_words == 0, "not clear");
209 assert(_preceding_destination == nullptr, "not clear");
210 assert(_preceding_destination_count == 0, "not clear");
211 }
212 #endif // #ifdef ASSERT
213
214
215 void PSParallelCompact::print_on(outputStream* st) {
216 _mark_bitmap.print_on(st);
217 }
218
219 ParallelCompactData::ParallelCompactData() :
220 _heap_start(nullptr),
221 DEBUG_ONLY(_heap_end(nullptr) COMMA)
222 _region_vspace(nullptr),
223 _reserved_byte_size(0),
224 _region_data(nullptr),
225 _region_count(0) {}
226
227 bool ParallelCompactData::initialize(MemRegion reserved_heap)
228 {
229 _heap_start = reserved_heap.start();
230 const size_t heap_size = reserved_heap.word_size();
231 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
232
233 assert(region_align_down(_heap_start) == _heap_start,
234 "region start not aligned");
235
236 return initialize_region_data(heap_size);
237 }
238
239 PSVirtualSpace*
240 ParallelCompactData::create_vspace(size_t count, size_t element_size)
241 {
242 const size_t raw_bytes = count * element_size;
243 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
244 const size_t granularity = os::vm_allocation_granularity();
245 const size_t rs_align = MAX2(page_sz, granularity);
246
247 _reserved_byte_size = align_up(raw_bytes, rs_align);
248
249 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
250 rs_align,
251 page_sz,
252 mtGC);
253
254 if (!rs.is_reserved()) {
255 // Failed to reserve memory.
256 return nullptr;
257 }
258
259 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
260 rs.size(), page_sz);
261
262 MemTracker::record_virtual_memory_tag(rs, mtGC);
263
264 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
265
266 if (!vspace->expand_by(_reserved_byte_size)) {
267 // Failed to commit memory.
268
269 delete vspace;
270
271 // Release memory reserved in the space.
272 MemoryReserver::release(rs);
273
274 return nullptr;
275 }
276
277 return vspace;
278 }
279
280 bool ParallelCompactData::initialize_region_data(size_t heap_size)
281 {
282 assert(is_aligned(heap_size, RegionSize), "precondition");
283
284 const size_t count = heap_size >> Log2RegionSize;
285 _region_vspace = create_vspace(count, sizeof(RegionData));
286 if (_region_vspace != nullptr) {
287 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
288 _region_count = count;
289 return true;
290 }
291 return false;
292 }
293
294 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
295 assert(beg_region <= _region_count, "beg_region out of range");
296 assert(end_region <= _region_count, "end_region out of range");
297
298 const size_t region_cnt = end_region - beg_region;
299 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
300 }
301
302 // The total live words on src_region would overflow the target space, so find
303 // the overflowing object and record the split point. The invariant is that an
304 // obj should not cross space boundary.
305 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
306 SplitInfo& split_info,
307 HeapWord* const destination,
308 HeapWord* const target_end,
309 HeapWord** target_next) {
310 assert(destination <= target_end, "sanity");
311 assert(destination + _region_data[src_region].data_size() > target_end,
312 "region should not fit into target space");
313 assert(is_region_aligned(target_end), "sanity");
314
315 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
316
317 if (destination + partial_obj_size > target_end) {
318 assert(partial_obj_size > 0, "inv");
319 // The overflowing obj is from a previous region.
320 //
321 // source-regions:
322 //
323 // ***************
324 // | A|AA |
325 // ***************
326 // ^
327 // | split-point
328 //
329 // dest-region:
330 //
331 // ********
332 // |~~~~A |
333 // ********
334 // ^^
335 // || target-space-end
336 // |
337 // | destination
338 //
339 // AAA would overflow target-space.
340 //
341 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
342 size_t split_region = addr_to_region_idx(overflowing_obj);
343
344 // The number of live words before the overflowing object on this split region
345 size_t preceding_live_words;
346 if (is_region_aligned(overflowing_obj)) {
347 preceding_live_words = 0;
348 } else {
349 // Words accounted by the overflowing object on the split region
350 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
351 preceding_live_words = region(split_region)->data_size() - overflowing_size;
352 }
353
354 split_info.record(split_region, overflowing_obj, preceding_live_words);
355
356 // The [overflowing_obj, src_region_start) part has been accounted for, so
357 // must move back the new_top, now that this overflowing obj is deferred.
358 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
359
360 // If the overflowing obj was relocated to its original destination,
361 // those destination regions would have their source_region set. Now that
362 // this overflowing obj is relocated somewhere else, reset the
363 // source_region.
364 {
365 size_t range_start = addr_to_region_idx(region_align_up(new_top));
366 size_t range_end = addr_to_region_idx(region_align_up(destination));
367 for (size_t i = range_start; i < range_end; ++i) {
368 region(i)->set_source_region(0);
369 }
370 }
371
372 // Update new top of target space
373 *target_next = new_top;
374
375 return overflowing_obj;
376 }
377
378 // Obj-iteration to locate the overflowing obj
379 HeapWord* region_start = region_to_addr(src_region);
380 HeapWord* region_end = region_start + RegionSize;
381 HeapWord* cur_addr = region_start + partial_obj_size;
382 size_t live_words = partial_obj_size;
383
384 while (true) {
385 assert(cur_addr < region_end, "inv");
386 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
387 // There must be an overflowing obj in this region
388 assert(cur_addr < region_end, "inv");
389
390 oop obj = cast_to_oop(cur_addr);
391 size_t obj_size = obj->size();
392 if (destination + live_words + obj_size > target_end) {
393 // Found the overflowing obj
394 split_info.record(src_region, cur_addr, live_words);
395 *target_next = destination + live_words;
396 return cur_addr;
397 }
398
399 live_words += obj_size;
400 cur_addr += obj_size;
401 }
402 }
403
404 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
405 HeapWord** full_region_prefix_end) {
406 size_t cur_region = addr_to_region_idx(space->bottom());
407 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
408 size_t live_words = 0;
409 if (full_region_prefix_end == nullptr) {
410 for (/* empty */; cur_region < end_region; ++cur_region) {
411 live_words += _region_data[cur_region].data_size();
412 }
413 } else {
414 bool first_set = false;
415 for (/* empty */; cur_region < end_region; ++cur_region) {
416 size_t live_words_in_region = _region_data[cur_region].data_size();
417 if (!first_set && live_words_in_region < RegionSize) {
418 *full_region_prefix_end = region_to_addr(cur_region);
419 first_set = true;
420 }
421 live_words += live_words_in_region;
422 }
423 if (!first_set) {
424 // All regions are full of live objs.
425 assert(is_region_aligned(space->top()), "inv");
426 *full_region_prefix_end = space->top();
427 }
428 assert(*full_region_prefix_end != nullptr, "postcondition");
429 assert(is_region_aligned(*full_region_prefix_end), "inv");
430 assert(*full_region_prefix_end >= space->bottom(), "in-range");
431 assert(*full_region_prefix_end <= space->top(), "in-range");
432 }
433 return live_words;
434 }
435
436 bool ParallelCompactData::summarize(SplitInfo& split_info,
437 HeapWord* source_beg, HeapWord* source_end,
438 HeapWord** source_next,
439 HeapWord* target_beg, HeapWord* target_end,
440 HeapWord** target_next)
441 {
442 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
443 log_develop_trace(gc, compaction)(
444 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
445 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
446 p2i(source_beg), p2i(source_end), p2i(source_next_val),
447 p2i(target_beg), p2i(target_end), p2i(*target_next));
448
449 size_t cur_region = addr_to_region_idx(source_beg);
450 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
451
452 HeapWord *dest_addr = target_beg;
453 for (/* empty */; cur_region < end_region; cur_region++) {
454 size_t words = _region_data[cur_region].data_size();
455
456 // Skip empty ones
457 if (words == 0) {
458 continue;
459 }
460
461 if (split_info.is_split(cur_region)) {
462 assert(words > split_info.preceding_live_words(), "inv");
463 words -= split_info.preceding_live_words();
464 }
465
466 _region_data[cur_region].set_destination(dest_addr);
467
468 // If cur_region does not fit entirely into the target space, find a point
469 // at which the source space can be 'split' so that part is copied to the
470 // target space and the rest is copied elsewhere.
471 if (dest_addr + words > target_end) {
472 assert(source_next != nullptr, "source_next is null when splitting");
473 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
474 target_end, target_next);
475 return false;
476 }
477
478 uint destination_count = split_info.is_split(cur_region)
479 ? split_info.preceding_destination_count()
480 : 0;
481
482 HeapWord* const last_addr = dest_addr + words - 1;
483 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
484 const size_t dest_region_2 = addr_to_region_idx(last_addr);
485
486 // Initially assume that the destination regions will be the same and
487 // adjust the value below if necessary. Under this assumption, if
488 // cur_region == dest_region_2, then cur_region will be compacted
489 // completely into itself.
490 destination_count += cur_region == dest_region_2 ? 0 : 1;
491 if (dest_region_1 != dest_region_2) {
492 // Destination regions differ; adjust destination_count.
493 destination_count += 1;
494 // Data from cur_region will be copied to the start of dest_region_2.
495 _region_data[dest_region_2].set_source_region(cur_region);
496 } else if (is_region_aligned(dest_addr)) {
497 // Data from cur_region will be copied to the start of the destination
498 // region.
499 _region_data[dest_region_1].set_source_region(cur_region);
500 }
501
502 _region_data[cur_region].set_destination_count(destination_count);
503 dest_addr += words;
504 }
505
506 *target_next = dest_addr;
507 return true;
508 }
509
510 #ifdef ASSERT
511 void ParallelCompactData::verify_clear() {
512 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
513 if (!region(cur_idx)->is_clear()) {
514 log_warning(gc)("Uncleared Region: %u", cur_idx);
515 region(cur_idx)->verify_clear();
516 }
517 }
518 }
519 #endif // #ifdef ASSERT
520
521 STWGCTimer PSParallelCompact::_gc_timer;
522 ParallelOldTracer PSParallelCompact::_gc_tracer;
523 elapsedTimer PSParallelCompact::_accumulated_time;
524 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
525 CollectorCounters* PSParallelCompact::_counters = nullptr;
526 ParMarkBitMap PSParallelCompact::_mark_bitmap;
527 ParallelCompactData PSParallelCompact::_summary_data;
528
529 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
530
531 class PCAdjustPointerClosure: public BasicOopIterateClosure {
532 template <typename T>
533 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
534
535 public:
536 virtual void do_oop(oop* p) { do_oop_work(p); }
537 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
538
539 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
540 };
541
542 static PCAdjustPointerClosure pc_adjust_pointer_closure;
543
544 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
545
546 void PSParallelCompact::post_initialize() {
547 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
548 _span_based_discoverer.set_span(heap->reserved_region());
549 _ref_processor =
550 new ReferenceProcessor(&_span_based_discoverer,
551 ParallelGCThreads, // mt processing degree
552 ParallelGCThreads, // mt discovery degree
553 false, // concurrent_discovery
554 &_is_alive_closure); // non-header is alive closure
555
556 _counters = new CollectorCounters("Parallel full collection pauses", 1);
557
558 // Initialize static fields in ParCompactionManager.
559 ParCompactionManager::initialize(mark_bitmap());
560 }
561
562 bool PSParallelCompact::initialize_aux_data() {
563 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
564 MemRegion mr = heap->reserved_region();
565 assert(mr.byte_size() != 0, "heap should be reserved");
566
567 initialize_space_info();
568
569 if (!_mark_bitmap.initialize(mr)) {
570 vm_shutdown_during_initialization(
571 err_msg("Unable to allocate %zuKB bitmaps for parallel "
572 "garbage collection for the requested %zuKB heap.",
573 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
574 return false;
575 }
576
577 if (!_summary_data.initialize(mr)) {
578 vm_shutdown_during_initialization(
579 err_msg("Unable to allocate %zuKB card tables for parallel "
580 "garbage collection for the requested %zuKB heap.",
581 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
582 return false;
583 }
584
585 return true;
586 }
587
588 void PSParallelCompact::initialize_space_info()
589 {
590 memset(&_space_info, 0, sizeof(_space_info));
591
592 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
593 PSYoungGen* young_gen = heap->young_gen();
594
595 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
596 _space_info[eden_space_id].set_space(young_gen->eden_space());
597 _space_info[from_space_id].set_space(young_gen->from_space());
598 _space_info[to_space_id].set_space(young_gen->to_space());
599
600 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
601 }
602
603 void
604 PSParallelCompact::clear_data_covering_space(SpaceId id)
605 {
606 // At this point, top is the value before GC, new_top() is the value that will
607 // be set at the end of GC. The marking bitmap is cleared to top; nothing
608 // should be marked above top. The summary data is cleared to the larger of
609 // top & new_top.
610 MutableSpace* const space = _space_info[id].space();
611 HeapWord* const bot = space->bottom();
612 HeapWord* const top = space->top();
613 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
614
615 _mark_bitmap.clear_range(bot, top);
616
617 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
618 const size_t end_region =
619 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
620 _summary_data.clear_range(beg_region, end_region);
621
622 // Clear the data used to 'split' regions.
623 SplitInfo& split_info = _space_info[id].split_info();
624 if (split_info.is_valid()) {
625 split_info.clear();
626 }
627 DEBUG_ONLY(split_info.verify_clear();)
628 }
629
630 void PSParallelCompact::pre_compact()
631 {
632 // Update the from & to space pointers in space_info, since they are swapped
633 // at each young gen gc. Do the update unconditionally (even though a
634 // promotion failure does not swap spaces) because an unknown number of young
635 // collections will have swapped the spaces an unknown number of times.
636 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
637 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
638 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
639 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
640
641 heap->increment_total_collections(true);
642
643 CodeCache::on_gc_marking_cycle_start();
644
645 heap->print_before_gc();
646 heap->trace_heap_before_gc(&_gc_tracer);
647
648 // Fill in TLABs
649 heap->ensure_parsability(true); // retire TLABs
650
651 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
652 Universe::verify("Before GC");
653 }
654
655 DEBUG_ONLY(mark_bitmap()->verify_clear();)
656 DEBUG_ONLY(summary_data().verify_clear();)
657 }
658
659 void PSParallelCompact::post_compact()
660 {
661 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
662 ParCompactionManager::remove_all_shadow_regions();
663
664 CodeCache::on_gc_marking_cycle_finish();
665 CodeCache::arm_all_nmethods();
666
667 // Need to clear claim bits for the next full-gc (marking and adjust-pointers).
668 ClassLoaderDataGraph::clear_claimed_marks();
669
670 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
671 // Clear the marking bitmap, summary data and split info.
672 clear_data_covering_space(SpaceId(id));
673 {
674 MutableSpace* space = _space_info[id].space();
675 HeapWord* top = space->top();
676 HeapWord* new_top = _space_info[id].new_top();
677 if (ZapUnusedHeapArea && new_top < top) {
678 space->mangle_region(MemRegion(new_top, top));
679 }
680 // Update top(). Must be done after clearing the bitmap and summary data.
681 space->set_top(new_top);
682 }
683 }
684
685 #ifdef ASSERT
686 {
687 mark_bitmap()->verify_clear();
688 summary_data().verify_clear();
689 }
690 #endif
691
692 ParCompactionManager::flush_all_string_dedup_requests();
693
694 MutableSpace* const eden_space = _space_info[eden_space_id].space();
695 MutableSpace* const from_space = _space_info[from_space_id].space();
696 MutableSpace* const to_space = _space_info[to_space_id].space();
697
698 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
699 bool eden_empty = eden_space->is_empty();
700
701 // Update heap occupancy information which is used as input to the soft ref
702 // clearing policy at the next gc.
703 Universe::heap()->update_capacity_and_used_at_gc();
704
705 bool young_gen_empty = eden_empty && from_space->is_empty() &&
706 to_space->is_empty();
707
708 PSCardTable* ct = heap->card_table();
709 MemRegion old_mr = heap->old_gen()->committed();
710 if (young_gen_empty) {
711 ct->clear_MemRegion(old_mr);
712 } else {
713 ct->dirty_MemRegion(old_mr);
714 }
715
716 heap->prune_scavengable_nmethods();
717
718 #if COMPILER2_OR_JVMCI
719 DerivedPointerTable::update_pointers();
720 #endif
721
722 // Signal that we have completed a visit to all live objects.
723 Universe::heap()->record_whole_heap_examined_timestamp();
724 }
725
726 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
727 HeapWord* full_region_prefix_end) {
728 const size_t region_size = ParallelCompactData::RegionSize;
729 const ParallelCompactData& sd = summary_data();
730
731 // Iteration starts with the region *after* the full-region-prefix-end.
732 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
733 // If final region is not full, iteration stops before that region,
734 // because fill_dense_prefix_end assumes that prefix_end <= top.
735 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
736 assert(start_region <= end_region, "inv");
737
738 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
739 const RegionData* cur_region = start_region;
740 for (/* empty */; cur_region < end_region; ++cur_region) {
741 assert(region_size >= cur_region->data_size(), "inv");
742 size_t dead_size = region_size - cur_region->data_size();
743 if (max_waste < dead_size) {
744 break;
745 }
746 max_waste -= dead_size;
747 }
748
749 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
750 assert(sd.is_region_aligned(prefix_end), "postcondition");
751 assert(prefix_end >= full_region_prefix_end, "in-range");
752 assert(prefix_end <= old_space->top(), "in-range");
753 return prefix_end;
754 }
755
756 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
757 // Comparing two sizes to decide if filling is required:
758 //
759 // The size of the filler (min-obj-size) is 2 heap words with the default
760 // MinObjAlignment, since both markword and klass take 1 heap word.
761 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
762 // because the Klass* gets encoded in the mark-word.
763 //
764 // The size of the gap (if any) right before dense-prefix-end is
765 // MinObjAlignment.
766 //
767 // Need to fill in the gap only if it's smaller than min-obj-size, and the
768 // filler obj will extend to next region.
769
770 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
771 return;
772 }
773
774 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
775 assert(CollectedHeap::min_fill_size() == 2, "inv");
776 HeapWord* const dense_prefix_end = dense_prefix(id);
777 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
778 assert(dense_prefix_end <= space(id)->top(), "precondition");
779 if (dense_prefix_end == space(id)->top()) {
780 // Must not have single-word gap right before prefix-end/top.
781 return;
782 }
783 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
784
785 if (region_after_dense_prefix->partial_obj_size() != 0 ||
786 _mark_bitmap.is_marked(dense_prefix_end)) {
787 // The region after the dense prefix starts with live bytes.
788 return;
789 }
790
791 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
792 if (block_start == dense_prefix_end - 1) {
793 assert(!_mark_bitmap.is_marked(block_start), "inv");
794 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
795 // The filler object will extend into region_after_dense_prefix.
796 const size_t obj_len = 2; // min-fill-size
797 HeapWord* const obj_beg = dense_prefix_end - 1;
798 CollectedHeap::fill_with_object(obj_beg, obj_len);
799 _mark_bitmap.mark_obj(obj_beg);
800 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
801 region_after_dense_prefix->set_partial_obj_size(1);
802 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
803 assert(start_array(id) != nullptr, "sanity");
804 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
805 }
806 }
807
808 bool PSParallelCompact::check_maximum_compaction(bool should_do_max_compaction,
809 size_t total_live_words,
810 MutableSpace* const old_space,
811 HeapWord* full_region_prefix_end) {
812
813 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
814
815 // Check System.GC
816 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
817 && GCCause::is_user_requested_gc(heap->gc_cause());
818
819 // Check if all live objs are too much for old-gen.
820 const bool is_old_gen_too_full = (total_live_words >= old_space->capacity_in_words());
821
822 // If all regions in old-gen are full
823 const bool is_region_full =
824 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
825
826 return should_do_max_compaction
827 || is_max_on_system_gc
828 || is_old_gen_too_full
829 || is_region_full;
830 }
831
832 void PSParallelCompact::summary_phase(bool should_do_max_compaction)
833 {
834 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
835
836 MutableSpace* const old_space = _space_info[old_space_id].space();
837 {
838 size_t total_live_words = 0;
839 HeapWord* full_region_prefix_end = nullptr;
840 {
841 // old-gen
842 size_t live_words = _summary_data.live_words_in_space(old_space,
843 &full_region_prefix_end);
844 total_live_words += live_words;
845 }
846 // young-gen
847 for (uint i = eden_space_id; i < last_space_id; ++i) {
848 const MutableSpace* space = _space_info[i].space();
849 size_t live_words = _summary_data.live_words_in_space(space);
850 total_live_words += live_words;
851 _space_info[i].set_new_top(space->bottom() + live_words);
852 _space_info[i].set_dense_prefix(space->bottom());
853 }
854
855 should_do_max_compaction = check_maximum_compaction(should_do_max_compaction,
856 total_live_words,
857 old_space,
858 full_region_prefix_end);
859 {
860 GCTraceTime(Info, gc, phases) tm("Summary Phase: expand", &_gc_timer);
861 // Try to expand old-gen in order to fit all live objs and waste.
862 size_t target_capacity_bytes = total_live_words * HeapWordSize
863 + old_space->capacity_in_bytes() * (MarkSweepDeadRatio / 100);
864 ParallelScavengeHeap::heap()->old_gen()->try_expand_till_size(target_capacity_bytes);
865 }
866
867 HeapWord* dense_prefix_end = should_do_max_compaction
868 ? full_region_prefix_end
869 : compute_dense_prefix_for_old_space(old_space,
870 full_region_prefix_end);
871 SpaceId id = old_space_id;
872 _space_info[id].set_dense_prefix(dense_prefix_end);
873
874 if (dense_prefix_end != old_space->bottom()) {
875 fill_dense_prefix_end(id);
876 }
877
878 // Compacting objs in [dense_prefix_end, old_space->top())
879 _summary_data.summarize(_space_info[id].split_info(),
880 dense_prefix_end, old_space->top(), nullptr,
881 dense_prefix_end, old_space->end(),
882 _space_info[id].new_top_addr());
883 }
884
885 // Summarize the remaining spaces in the young gen. The initial target space
886 // is the old gen. If a space does not fit entirely into the target, then the
887 // remainder is compacted into the space itself and that space becomes the new
888 // target.
889 SpaceId dst_space_id = old_space_id;
890 HeapWord* dst_space_end = old_space->end();
891 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
892 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
893 const MutableSpace* space = _space_info[id].space();
894 const size_t live = pointer_delta(_space_info[id].new_top(),
895 space->bottom());
896 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
897
898 if (live > 0 && live <= available) {
899 // All the live data will fit.
900 bool done = _summary_data.summarize(_space_info[id].split_info(),
901 space->bottom(), space->top(),
902 nullptr,
903 *new_top_addr, dst_space_end,
904 new_top_addr);
905 assert(done, "space must fit into old gen");
906
907 // Reset the new_top value for the space.
908 _space_info[id].set_new_top(space->bottom());
909 } else if (live > 0) {
910 // Attempt to fit part of the source space into the target space.
911 HeapWord* next_src_addr = nullptr;
912 bool done = _summary_data.summarize(_space_info[id].split_info(),
913 space->bottom(), space->top(),
914 &next_src_addr,
915 *new_top_addr, dst_space_end,
916 new_top_addr);
917 assert(!done, "space should not fit into old gen");
918 assert(next_src_addr != nullptr, "sanity");
919
920 // The source space becomes the new target, so the remainder is compacted
921 // within the space itself.
922 dst_space_id = SpaceId(id);
923 dst_space_end = space->end();
924 new_top_addr = _space_info[id].new_top_addr();
925 done = _summary_data.summarize(_space_info[id].split_info(),
926 next_src_addr, space->top(),
927 nullptr,
928 space->bottom(), dst_space_end,
929 new_top_addr);
930 assert(done, "space must fit when compacted into itself");
931 assert(*new_top_addr <= space->top(), "usage should not grow");
932 }
933 }
934 }
935
936 void PSParallelCompact::report_object_count_after_gc() {
937 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
938 // The heap is compacted, all objects are iterable. However there may be
939 // filler objects in the heap which we should ignore.
940 class SkipFillerObjectClosure : public BoolObjectClosure {
941 public:
942 bool do_object_b(oop obj) override { return !CollectedHeap::is_filler_object(obj); }
943 } cl;
944 _gc_tracer.report_object_count_after_gc(&cl, &ParallelScavengeHeap::heap()->workers());
945 }
946
947 bool PSParallelCompact::invoke(bool clear_all_soft_refs, bool should_do_max_compaction) {
948 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
949 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
950 "should be in vm thread");
951 assert(ref_processor() != nullptr, "Sanity");
952
953 SvcGCMarker sgcm(SvcGCMarker::FULL);
954 IsSTWGCActiveMark mark;
955
956 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
957
958 GCIdMark gc_id_mark;
959 _gc_timer.register_gc_start();
960 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
961
962 GCCause::Cause gc_cause = heap->gc_cause();
963 PSOldGen* old_gen = heap->old_gen();
964 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
965
966 // Make sure data structures are sane, make the heap parsable, and do other
967 // miscellaneous bookkeeping.
968 pre_compact();
969
970 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
971
972 {
973 const uint active_workers =
974 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
975 ParallelScavengeHeap::heap()->workers().active_workers(),
976 Threads::number_of_non_daemon_threads());
977 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
978
979 GCTraceCPUTime tcpu(&_gc_tracer);
980 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
981
982 heap->pre_full_gc_dump(&_gc_timer);
983
984 TraceCollectorStats tcs(counters());
985 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
986
987 if (log_is_enabled(Debug, gc, heap, exit)) {
988 accumulated_time()->start();
989 }
990
991 // Let the size policy know we're starting
992 size_policy->major_collection_begin();
993
994 #if COMPILER2_OR_JVMCI
995 DerivedPointerTable::clear();
996 #endif
997
998 ref_processor()->start_discovery(clear_all_soft_refs);
999
1000 marking_phase(&_gc_tracer);
1001
1002 summary_phase(should_do_max_compaction);
1003
1004 #if COMPILER2_OR_JVMCI
1005 assert(DerivedPointerTable::is_active(), "Sanity");
1006 DerivedPointerTable::set_active(false);
1007 #endif
1008
1009 forward_to_new_addr();
1010
1011 adjust_pointers();
1012
1013 compact();
1014
1015 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1016
1017 ParCompactionManager::verify_all_region_stack_empty();
1018
1019 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1020 // done before resizing.
1021 post_compact();
1022
1023 size_policy->major_collection_end();
1024
1025 size_policy->sample_old_gen_used_bytes(MAX2(pre_gc_values.old_gen_used(), old_gen->used_in_bytes()));
1026
1027 if (UseAdaptiveSizePolicy) {
1028 heap->resize_after_full_gc();
1029 }
1030
1031 heap->resize_all_tlabs();
1032
1033 // Resize the metaspace capacity after a collection
1034 MetaspaceGC::compute_new_size();
1035
1036 if (log_is_enabled(Debug, gc, heap, exit)) {
1037 accumulated_time()->stop();
1038 }
1039
1040 heap->print_heap_change(pre_gc_values);
1041
1042 report_object_count_after_gc();
1043
1044 // Track memory usage and detect low memory
1045 MemoryService::track_memory_usage();
1046 heap->update_counters();
1047
1048 heap->post_full_gc_dump(&_gc_timer);
1049
1050 size_policy->record_gc_pause_end_instant();
1051 }
1052
1053 heap->gc_epilogue(true);
1054
1055 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1056 Universe::verify("After GC");
1057 }
1058
1059 heap->print_after_gc();
1060 heap->trace_heap_after_gc(&_gc_tracer);
1061
1062 _gc_timer.register_gc_end();
1063
1064 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1065 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1066
1067 return true;
1068 }
1069
1070 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1071 ParCompactionManager* _cm;
1072
1073 public:
1074 PCAddThreadRootsMarkingTaskClosure(ParCompactionManager* cm) : _cm(cm) { }
1075 void do_thread(Thread* thread) {
1076 ResourceMark rm;
1077
1078 MarkingNMethodClosure mark_and_push_in_blobs(&_cm->_mark_and_push_closure);
1079
1080 thread->oops_do(&_cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1081
1082 // Do the real work
1083 _cm->follow_marking_stacks();
1084 }
1085 };
1086
1087 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1088 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1089
1090 ParCompactionManager* cm =
1091 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1092
1093 do {
1094 ScannerTask task;
1095 if (ParCompactionManager::steal(worker_id, task)) {
1096 cm->follow_contents(task, true);
1097 }
1098 cm->follow_marking_stacks();
1099 } while (!terminator.offer_termination());
1100 }
1101
1102 class MarkFromRootsTask : public WorkerTask {
1103 NMethodMarkingScope _nmethod_marking_scope;
1104 ThreadsClaimTokenScope _threads_claim_token_scope;
1105 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1106 TaskTerminator _terminator;
1107 uint _active_workers;
1108
1109 public:
1110 MarkFromRootsTask(uint active_workers) :
1111 WorkerTask("MarkFromRootsTask"),
1112 _nmethod_marking_scope(),
1113 _threads_claim_token_scope(),
1114 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1115 _active_workers(active_workers) {}
1116
1117 virtual void work(uint worker_id) {
1118 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1119 cm->create_marking_stats_cache();
1120 {
1121 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1122 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1123
1124 // Do the real work
1125 cm->follow_marking_stacks();
1126 }
1127
1128 {
1129 PCAddThreadRootsMarkingTaskClosure closure(cm);
1130 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1131 }
1132
1133 // Mark from OopStorages
1134 {
1135 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1136 // Do the real work
1137 cm->follow_marking_stacks();
1138 }
1139
1140 if (_active_workers > 1) {
1141 steal_marking_work(_terminator, worker_id);
1142 }
1143 }
1144 };
1145
1146 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1147 TaskTerminator _terminator;
1148
1149 public:
1150 ParallelCompactRefProcProxyTask(uint max_workers)
1151 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1152 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1153
1154 void work(uint worker_id) override {
1155 assert(worker_id < _max_workers, "sanity");
1156 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1157 BarrierEnqueueDiscoveredFieldClosure enqueue;
1158 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1159 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1160 }
1161
1162 void prepare_run_task_hook() override {
1163 _terminator.reset_for_reuse(_queue_count);
1164 }
1165 };
1166
1167 static void flush_marking_stats_cache(const uint num_workers) {
1168 for (uint i = 0; i < num_workers; ++i) {
1169 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1170 cm->flush_and_destroy_marking_stats_cache();
1171 }
1172 }
1173
1174 class PSParallelCleaningTask : public WorkerTask {
1175 bool _unloading_occurred;
1176 CodeCacheUnloadingTask _code_cache_task;
1177 // Prune dead klasses from subklass/sibling/implementor lists.
1178 KlassCleaningTask _klass_cleaning_task;
1179
1180 public:
1181 PSParallelCleaningTask(bool unloading_occurred) :
1182 WorkerTask("PS Parallel Cleaning"),
1183 _unloading_occurred(unloading_occurred),
1184 _code_cache_task(unloading_occurred),
1185 _klass_cleaning_task() {}
1186
1187 void work(uint worker_id) {
1188 #if INCLUDE_JVMCI
1189 if (EnableJVMCI && worker_id == 0) {
1190 // Serial work; only first worker.
1191 // Clean JVMCI metadata handles.
1192 JVMCI::do_unloading(_unloading_occurred);
1193 }
1194 #endif
1195
1196 // Do first pass of code cache cleaning.
1197 _code_cache_task.work(worker_id);
1198
1199 // Clean all klasses that were not unloaded.
1200 // The weak metadata in klass doesn't need to be
1201 // processed if there was no unloading.
1202 if (_unloading_occurred) {
1203 _klass_cleaning_task.work();
1204 }
1205 }
1206 };
1207
1208 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1209 // Recursively traverse all live objects and mark them
1210 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1211
1212 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1213
1214 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1215 {
1216 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1217
1218 MarkFromRootsTask task(active_gc_threads);
1219 ParallelScavengeHeap::heap()->workers().run_task(&task);
1220 }
1221
1222 // Process reference objects found during marking
1223 {
1224 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1225
1226 ReferenceProcessorStats stats;
1227 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1228
1229 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1230 stats = ref_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
1231
1232 gc_tracer->report_gc_reference_stats(stats);
1233 pt.print_all_references();
1234 }
1235
1236 {
1237 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1238
1239 flush_marking_stats_cache(active_gc_threads);
1240 }
1241
1242 // This is the point where the entire marking should have completed.
1243 ParCompactionManager::verify_all_marking_stack_empty();
1244
1245 {
1246 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1247 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1248 is_alive_closure(),
1249 &do_nothing_cl,
1250 1);
1251 }
1252
1253 {
1254 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1255
1256 ClassUnloadingContext ctx(active_gc_threads /* num_nmethod_unlink_workers */,
1257 false /* unregister_nmethods_during_purge */,
1258 false /* lock_nmethod_free_separately */);
1259
1260 {
1261 CodeCache::UnlinkingScope scope(is_alive_closure());
1262
1263 // Follow system dictionary roots and unload classes.
1264 bool unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1265
1266 PSParallelCleaningTask task{unloading_occurred};
1267 ParallelScavengeHeap::heap()->workers().run_task(&task);
1268 }
1269
1270 {
1271 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1272 // Release unloaded nmethod's memory.
1273 ctx.purge_nmethods();
1274 }
1275 {
1276 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1277 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1278 }
1279 {
1280 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1281 ctx.free_nmethods();
1282 }
1283 {
1284 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1285 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
1286 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1287 DEBUG_ONLY(MetaspaceUtils::verify();)
1288 }
1289 }
1290
1291 #if TASKQUEUE_STATS
1292 ParCompactionManager::print_and_reset_taskqueue_stats();
1293 #endif
1294 }
1295
1296 template<typename Func>
1297 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1298 MutableSpace* sp = PSParallelCompact::space(id);
1299 HeapWord* const bottom = sp->bottom();
1300 HeapWord* const top = sp->top();
1301 if (bottom == top) {
1302 return;
1303 }
1304
1305 const uint num_regions_per_stripe = 2;
1306 const size_t region_size = ParallelCompactData::RegionSize;
1307 const size_t stripe_size = num_regions_per_stripe * region_size;
1308
1309 while (true) {
1310 uint counter = AtomicAccess::fetch_then_add(claim_counter, num_regions_per_stripe);
1311 HeapWord* cur_stripe = bottom + counter * region_size;
1312 if (cur_stripe >= top) {
1313 break;
1314 }
1315 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1316 on_stripe(cur_stripe, stripe_end);
1317 }
1318 }
1319
1320 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1321 // Regions in old-space shouldn't be split.
1322 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1323
1324 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1325 assert(mark_bitmap()->is_marked(obj_start), "inv");
1326 oop obj = cast_to_oop(obj_start);
1327 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1328 };
1329
1330 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1331 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1332 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1333 HeapWord* obj_start;
1334 if (cur_region->partial_obj_size() != 0) {
1335 obj_start = cur_region->partial_obj_addr();
1336 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1337 } else {
1338 obj_start = stripe_start;
1339 }
1340
1341 while (obj_start < stripe_end) {
1342 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1343 if (obj_start >= stripe_end) {
1344 break;
1345 }
1346 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1347 }
1348 });
1349 }
1350
1351 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1352 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1353 HeapWord* obj_start = stripe_start;
1354 while (obj_start < stripe_end) {
1355 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1356 if (obj_start >= stripe_end) {
1357 break;
1358 }
1359 oop obj = cast_to_oop(obj_start);
1360 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1361 }
1362 });
1363 }
1364
1365 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1366 auto start_time = Ticks::now();
1367 adjust_in_old_space(&claim_counters[0]);
1368 for (uint id = eden_space_id; id < last_space_id; ++id) {
1369 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1370 }
1371 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1372 }
1373
1374 class PSAdjustTask final : public WorkerTask {
1375 ThreadsClaimTokenScope _threads_claim_token_scope;
1376 WeakProcessor::Task _weak_proc_task;
1377 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1378 uint _nworkers;
1379 volatile bool _code_cache_claimed;
1380 volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1381
1382 bool try_claim_code_cache_task() {
1383 return AtomicAccess::load(&_code_cache_claimed) == false
1384 && AtomicAccess::cmpxchg(&_code_cache_claimed, false, true) == false;
1385 }
1386
1387 public:
1388 PSAdjustTask(uint nworkers) :
1389 WorkerTask("PSAdjust task"),
1390 _threads_claim_token_scope(),
1391 _weak_proc_task(nworkers),
1392 _oop_storage_iter(),
1393 _nworkers(nworkers),
1394 _code_cache_claimed(false) {
1395
1396 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1397 }
1398
1399 void work(uint worker_id) {
1400 {
1401 // Pointers in heap.
1402 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1403 cm->preserved_marks()->adjust_during_full_gc();
1404
1405 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1406 }
1407
1408 {
1409 // All (strong and weak) CLDs.
1410 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1411 ClassLoaderDataGraph::cld_do(&cld_closure);
1412 }
1413
1414 {
1415 // Threads stack frames. No need to visit on-stack nmethods, because all
1416 // nmethods are visited in one go via CodeCache::nmethods_do.
1417 ResourceMark rm;
1418 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1419 if (try_claim_code_cache_task()) {
1420 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1421 CodeCache::nmethods_do(&adjust_code);
1422 }
1423 }
1424
1425 {
1426 // VM internal strong and weak roots.
1427 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1428 AlwaysTrueClosure always_alive;
1429 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1430 }
1431 }
1432 };
1433
1434 void PSParallelCompact::adjust_pointers() {
1435 // Adjust the pointers to reflect the new locations
1436 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1437 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1438 PSAdjustTask task(nworkers);
1439 ParallelScavengeHeap::heap()->workers().run_task(&task);
1440 }
1441
1442 // Split [start, end) evenly for a number of workers and return the
1443 // range for worker_id.
1444 static void split_regions_for_worker(size_t start, size_t end,
1445 uint worker_id, uint num_workers,
1446 size_t* worker_start, size_t* worker_end) {
1447 assert(start < end, "precondition");
1448 assert(num_workers > 0, "precondition");
1449 assert(worker_id < num_workers, "precondition");
1450
1451 size_t num_regions = end - start;
1452 size_t num_regions_per_worker = num_regions / num_workers;
1453 size_t remainder = num_regions % num_workers;
1454 // The first few workers will get one extra.
1455 *worker_start = start + worker_id * num_regions_per_worker
1456 + MIN2(checked_cast<size_t>(worker_id), remainder);
1457 *worker_end = *worker_start + num_regions_per_worker
1458 + (worker_id < remainder ? 1 : 0);
1459 }
1460
1461 void PSParallelCompact::forward_to_new_addr() {
1462 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1463 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1464
1465 struct ForwardTask final : public WorkerTask {
1466 uint _num_workers;
1467
1468 explicit ForwardTask(uint num_workers) :
1469 WorkerTask("PSForward task"),
1470 _num_workers(num_workers) {}
1471
1472 static void forward_objs_in_range(ParCompactionManager* cm,
1473 HeapWord* start,
1474 HeapWord* end,
1475 HeapWord* destination) {
1476 HeapWord* cur_addr = start;
1477 HeapWord* new_addr = destination;
1478
1479 while (cur_addr < end) {
1480 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1481 if (cur_addr >= end) {
1482 return;
1483 }
1484 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1485 oop obj = cast_to_oop(cur_addr);
1486 if (new_addr != cur_addr) {
1487 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1488 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1489 }
1490 size_t obj_size = obj->size();
1491 new_addr += obj_size;
1492 cur_addr += obj_size;
1493 }
1494 }
1495
1496 void work(uint worker_id) override {
1497 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1498 for (uint id = old_space_id; id < last_space_id; ++id) {
1499 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1500 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1501 HeapWord* top = sp->top();
1502
1503 if (dense_prefix_addr == top) {
1504 // Empty space
1505 continue;
1506 }
1507
1508 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1509 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1510 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1511 size_t start_region;
1512 size_t end_region;
1513 split_regions_for_worker(dense_prefix_region, top_region,
1514 worker_id, _num_workers,
1515 &start_region, &end_region);
1516 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1517 RegionData* region_ptr = _summary_data.region(cur_region);
1518 size_t partial_obj_size = region_ptr->partial_obj_size();
1519
1520 if (partial_obj_size == ParallelCompactData::RegionSize) {
1521 // No obj-start
1522 continue;
1523 }
1524
1525 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1526 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1527
1528 if (split_info.is_split(cur_region)) {
1529 // Part 1: will be relocated to space-1
1530 HeapWord* preceding_destination = split_info.preceding_destination();
1531 HeapWord* split_point = split_info.split_point();
1532 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1533
1534 // Part 2: will be relocated to space-2
1535 HeapWord* destination = region_ptr->destination();
1536 forward_objs_in_range(cm, split_point, region_end, destination);
1537 } else {
1538 HeapWord* destination = region_ptr->destination();
1539 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1540 }
1541 }
1542 }
1543 }
1544 } task(nworkers);
1545
1546 ParallelScavengeHeap::heap()->workers().run_task(&task);
1547 DEBUG_ONLY(verify_forward();)
1548 }
1549
1550 #ifdef ASSERT
1551 void PSParallelCompact::verify_forward() {
1552 HeapWord* const old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1553 // The destination addr for the first live obj after dense-prefix.
1554 HeapWord* bump_ptr = old_dense_prefix_addr
1555 + _summary_data.addr_to_region_ptr(old_dense_prefix_addr)->partial_obj_size();
1556 SpaceId bump_ptr_space = old_space_id;
1557
1558 for (uint id = old_space_id; id < last_space_id; ++id) {
1559 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1560 // Only verify objs after dense-prefix, because those before dense-prefix are not moved (forwarded).
1561 HeapWord* cur_addr = dense_prefix(SpaceId(id));
1562 HeapWord* top = sp->top();
1563
1564 while (cur_addr < top) {
1565 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1566 if (cur_addr >= top) {
1567 break;
1568 }
1569 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1570 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1571 // Move to the space containing cur_addr
1572 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1573 bump_ptr = space(space_id(cur_addr))->bottom();
1574 bump_ptr_space = space_id(bump_ptr);
1575 }
1576 oop obj = cast_to_oop(cur_addr);
1577 if (cur_addr == bump_ptr) {
1578 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1579 } else {
1580 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1581 }
1582 bump_ptr += obj->size();
1583 cur_addr += obj->size();
1584 }
1585 }
1586 }
1587 #endif
1588
1589 // Helper class to print 8 region numbers per line and then print the total at the end.
1590 class FillableRegionLogger : public StackObj {
1591 private:
1592 Log(gc, compaction) log;
1593 static const int LineLength = 8;
1594 size_t _regions[LineLength];
1595 int _next_index;
1596 bool _enabled;
1597 size_t _total_regions;
1598 public:
1599 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1600 ~FillableRegionLogger() {
1601 log.trace("%zu initially fillable regions", _total_regions);
1602 }
1603
1604 void print_line() {
1605 if (!_enabled || _next_index == 0) {
1606 return;
1607 }
1608 FormatBuffer<> line("Fillable: ");
1609 for (int i = 0; i < _next_index; i++) {
1610 line.append(" %7zu", _regions[i]);
1611 }
1612 log.trace("%s", line.buffer());
1613 _next_index = 0;
1614 }
1615
1616 void handle(size_t region) {
1617 if (!_enabled) {
1618 return;
1619 }
1620 _regions[_next_index++] = region;
1621 if (_next_index == LineLength) {
1622 print_line();
1623 }
1624 _total_regions++;
1625 }
1626 };
1627
1628 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1629 {
1630 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1631
1632 // Find the threads that are active
1633 uint worker_id = 0;
1634
1635 // Find all regions that are available (can be filled immediately) and
1636 // distribute them to the thread stacks. The iteration is done in reverse
1637 // order (high to low) so the regions will be removed in ascending order.
1638
1639 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1640
1641 // id + 1 is used to test termination so unsigned can
1642 // be used with an old_space_id == 0.
1643 FillableRegionLogger region_logger;
1644 for (unsigned int id = last_space_id - 1; id + 1 > old_space_id; --id) {
1645 SpaceInfo* const space_info = _space_info + id;
1646 HeapWord* const new_top = space_info->new_top();
1647
1648 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1649 const size_t end_region =
1650 sd.addr_to_region_idx(sd.region_align_up(new_top));
1651
1652 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1653 if (sd.region(cur)->claim_unsafe()) {
1654 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1655 bool result = sd.region(cur)->mark_normal();
1656 assert(result, "Must succeed at this point.");
1657 cm->region_stack()->push(cur);
1658 region_logger.handle(cur);
1659 // Assign regions to tasks in round-robin fashion.
1660 if (++worker_id == parallel_gc_threads) {
1661 worker_id = 0;
1662 }
1663 }
1664 }
1665 region_logger.print_line();
1666 }
1667 }
1668
1669 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1670 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1671
1672 ParCompactionManager* cm =
1673 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1674
1675 // Drain the stacks that have been preloaded with regions
1676 // that are ready to fill.
1677
1678 cm->drain_region_stacks();
1679
1680 guarantee(cm->region_stack()->is_empty(), "Not empty");
1681
1682 size_t region_index = 0;
1683
1684 while (true) {
1685 if (ParCompactionManager::steal(worker_id, region_index)) {
1686 PSParallelCompact::fill_and_update_region(cm, region_index);
1687 cm->drain_region_stacks();
1688 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1689 // Fill and update an unavailable region with the help of a shadow region
1690 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1691 cm->drain_region_stacks();
1692 } else {
1693 if (terminator->offer_termination()) {
1694 break;
1695 }
1696 // Go around again.
1697 }
1698 }
1699 }
1700
1701 class FillDensePrefixAndCompactionTask: public WorkerTask {
1702 TaskTerminator _terminator;
1703
1704 public:
1705 FillDensePrefixAndCompactionTask(uint active_workers) :
1706 WorkerTask("FillDensePrefixAndCompactionTask"),
1707 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1708 }
1709
1710 virtual void work(uint worker_id) {
1711 if (worker_id == 0) {
1712 auto start = Ticks::now();
1713 PSParallelCompact::fill_dead_objs_in_dense_prefix();
1714 log_trace(gc, phases)("Fill dense prefix by worker 0: %.3f ms", (Ticks::now() - start).seconds() * 1000);
1715 }
1716 compaction_with_stealing_work(&_terminator, worker_id);
1717 }
1718 };
1719
1720 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1721 #ifdef ASSERT
1722 {
1723 assert(start < end, "precondition");
1724 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1725 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1726 if (start != bottom) {
1727 // The preceding live obj.
1728 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1729 HeapWord* obj_end = obj_start + cast_to_oop(obj_start)->size();
1730 assert(obj_end == start, "precondition");
1731 }
1732 }
1733 #endif
1734
1735 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1736 HeapWord* addr = start;
1737 do {
1738 size_t size = cast_to_oop(addr)->size();
1739 start_array(old_space_id)->update_for_block(addr, addr + size);
1740 addr += size;
1741 } while (addr < end);
1742 }
1743
1744 void PSParallelCompact::fill_dead_objs_in_dense_prefix() {
1745 ParMarkBitMap* bitmap = mark_bitmap();
1746
1747 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1748 HeapWord* const prefix_end = dense_prefix(old_space_id);
1749
1750 const size_t region_size = ParallelCompactData::RegionSize;
1751
1752 // Fill dead space in [start_addr, end_addr)
1753 HeapWord* const start_addr = bottom;
1754 HeapWord* const end_addr = prefix_end;
1755
1756 for (HeapWord* cur_addr = start_addr; cur_addr < end_addr; /* empty */) {
1757 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1758 if (cur_region_ptr->data_size() == region_size) {
1759 // Full; no dead space. Next region.
1760 if (_summary_data.is_region_aligned(cur_addr)) {
1761 cur_addr += region_size;
1762 } else {
1763 cur_addr = _summary_data.region_align_up(cur_addr);
1764 }
1765 continue;
1766 }
1767
1768 // Fill dead space inside cur_region.
1769 if (_summary_data.is_region_aligned(cur_addr)) {
1770 cur_addr += cur_region_ptr->partial_obj_size();
1771 }
1772
1773 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1774 assert(region_end_addr <= end_addr, "inv");
1775 while (cur_addr < region_end_addr) {
1776 // Use end_addr to allow filler-obj to cross region boundary.
1777 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, end_addr);
1778 if (cur_addr != live_start) {
1779 // Found dead space [cur_addr, live_start).
1780 fill_range_in_dense_prefix(cur_addr, live_start);
1781 }
1782 if (live_start >= region_end_addr) {
1783 cur_addr = live_start;
1784 break;
1785 }
1786 assert(bitmap->is_marked(live_start), "inv");
1787 cur_addr = live_start + cast_to_oop(live_start)->size();
1788 }
1789 }
1790 }
1791
1792 void PSParallelCompact::compact() {
1793 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1794
1795 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1796
1797 initialize_shadow_regions(active_gc_threads);
1798 prepare_region_draining_tasks(active_gc_threads);
1799
1800 {
1801 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1802
1803 FillDensePrefixAndCompactionTask task(active_gc_threads);
1804 ParallelScavengeHeap::heap()->workers().run_task(&task);
1805
1806 #ifdef ASSERT
1807 verify_filler_in_dense_prefix();
1808
1809 // Verify that all regions have been processed.
1810 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1811 verify_complete(SpaceId(id));
1812 }
1813 #endif
1814 }
1815 }
1816
1817 #ifdef ASSERT
1818 void PSParallelCompact::verify_filler_in_dense_prefix() {
1819 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1820 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1821
1822 const size_t region_size = ParallelCompactData::RegionSize;
1823
1824 for (HeapWord* cur_addr = bottom; cur_addr < dense_prefix_end; /* empty */) {
1825 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1826 if (cur_region_ptr->data_size() == region_size) {
1827 // Full; no dead space. Next region.
1828 if (_summary_data.is_region_aligned(cur_addr)) {
1829 cur_addr += region_size;
1830 } else {
1831 cur_addr = _summary_data.region_align_up(cur_addr);
1832 }
1833 continue;
1834 }
1835
1836 // This region contains filler objs.
1837 if (_summary_data.is_region_aligned(cur_addr)) {
1838 cur_addr += cur_region_ptr->partial_obj_size();
1839 }
1840
1841 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1842 assert(region_end_addr <= dense_prefix_end, "inv");
1843
1844 while (cur_addr < region_end_addr) {
1845 oop obj = cast_to_oop(cur_addr);
1846 oopDesc::verify(obj);
1847 if (!mark_bitmap()->is_marked(cur_addr)) {
1848 assert(CollectedHeap::is_filler_object(cast_to_oop(cur_addr)), "inv");
1849 }
1850 cur_addr += obj->size();
1851 }
1852 }
1853 }
1854
1855 void PSParallelCompact::verify_complete(SpaceId space_id) {
1856 // All Regions served as compaction targets, from dense_prefix() to
1857 // new_top(), should be marked as filled and all Regions between new_top()
1858 // and top() should be available (i.e., should have been emptied).
1859 ParallelCompactData& sd = summary_data();
1860 SpaceInfo si = _space_info[space_id];
1861 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1862 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1863 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1864 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1865 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1866
1867 size_t cur_region;
1868 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1869 const RegionData* const c = sd.region(cur_region);
1870 assert(c->completed(), "region %zu not filled: destination_count=%u",
1871 cur_region, c->destination_count());
1872 }
1873
1874 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1875 const RegionData* const c = sd.region(cur_region);
1876 assert(c->available(), "region %zu not empty: destination_count=%u",
1877 cur_region, c->destination_count());
1878 }
1879 }
1880 #endif // #ifdef ASSERT
1881
1882 // Return the SpaceId for the space containing addr. If addr is not in the
1883 // heap, last_space_id is returned. In debug mode it expects the address to be
1884 // in the heap and asserts such.
1885 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1886 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1887
1888 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1889 if (_space_info[id].space()->contains(addr)) {
1890 return SpaceId(id);
1891 }
1892 }
1893
1894 assert(false, "no space contains the addr");
1895 return last_space_id;
1896 }
1897
1898 // Skip over count live words starting from beg, and return the address of the
1899 // next live word. Callers must also ensure that there are enough live words in
1900 // the range [beg, end) to skip.
1901 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1902 {
1903 ParMarkBitMap* m = mark_bitmap();
1904 HeapWord* cur_addr = beg;
1905 while (true) {
1906 cur_addr = m->find_obj_beg(cur_addr, end);
1907 assert(cur_addr < end, "inv");
1908 size_t obj_size = cast_to_oop(cur_addr)->size();
1909 // Strictly greater-than
1910 if (obj_size > count) {
1911 return cur_addr + count;
1912 }
1913 count -= obj_size;
1914 cur_addr += obj_size;
1915 }
1916 }
1917
1918 // On starting to fill a destination region (dest-region), we need to know the
1919 // location of the word that will be at the start of the dest-region after
1920 // compaction. A dest-region can have one or more source regions, but only the
1921 // first source-region contains this location. This location is retrieved by
1922 // calling `first_src_addr` on a dest-region.
1923 // Conversely, a source-region has a dest-region which holds the destination of
1924 // the first live word on this source-region, based on which the destination
1925 // for the rest of live words can be derived.
1926 //
1927 // Note:
1928 // There is some complication due to space-boundary-fragmentation (an obj can't
1929 // cross space-boundary) -- a source-region may be split and behave like two
1930 // distinct regions with their own dest-region, as depicted below.
1931 //
1932 // source-region: region-n
1933 //
1934 // **********************
1935 // | A|A~~~~B|B |
1936 // **********************
1937 // n-1 n n+1
1938 //
1939 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
1940 //
1941 // Assuming the dest-region for region-n is the final region before
1942 // old-space-end and its first-live-word is the middle of AA, the heap content
1943 // will look like the following after compaction:
1944 //
1945 // ************** *************
1946 // A|A~~~~ | |BB |
1947 // ************** *************
1948 // ^ ^
1949 // | old-space-end | eden-space-start
1950 //
1951 // Therefore, in this example, region-n will have two dest-regions:
1952 // 1. the final region in old-space
1953 // 2. the first region in eden-space.
1954 // To handle this special case, we introduce the concept of split-region, whose
1955 // contents are relocated to two spaces. `SplitInfo` captures all necessary
1956 // info about the split, the first part, spliting-point, and the second part.
1957 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
1958 SpaceId src_space_id,
1959 size_t src_region_idx)
1960 {
1961 const size_t RegionSize = ParallelCompactData::RegionSize;
1962 const ParallelCompactData& sd = summary_data();
1963 assert(sd.is_region_aligned(dest_addr), "precondition");
1964
1965 const RegionData* const src_region_ptr = sd.region(src_region_idx);
1966 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
1967
1968 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
1969 HeapWord* const src_region_destination = src_region_ptr->destination();
1970
1971 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
1972 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
1973
1974 // Identify the actual destination for the first live words on this region,
1975 // taking split-region into account.
1976 HeapWord* region_start_destination;
1977 const SplitInfo& split_info = _space_info[src_space_id].split_info();
1978 if (split_info.is_split(src_region_idx)) {
1979 // The second part of this split region; use the recorded split point.
1980 if (dest_addr == src_region_destination) {
1981 return split_info.split_point();
1982 }
1983 region_start_destination = split_info.preceding_destination();
1984 } else {
1985 region_start_destination = src_region_destination;
1986 }
1987
1988 // Calculate the offset to be skipped
1989 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
1990
1991 HeapWord* result;
1992 if (partial_obj_size > words_to_skip) {
1993 result = region_start + words_to_skip;
1994 } else {
1995 words_to_skip -= partial_obj_size;
1996 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
1997 }
1998
1999 if (split_info.is_split(src_region_idx)) {
2000 assert(result < split_info.split_point(), "postcondition");
2001 } else {
2002 assert(result < region_end, "postcondition");
2003 }
2004
2005 return result;
2006 }
2007
2008 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2009 SpaceId src_space_id,
2010 size_t beg_region,
2011 HeapWord* end_addr)
2012 {
2013 ParallelCompactData& sd = summary_data();
2014
2015 #ifdef ASSERT
2016 MutableSpace* const src_space = _space_info[src_space_id].space();
2017 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2018 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2019 "src_space_id does not match beg_addr");
2020 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2021 "src_space_id does not match end_addr");
2022 #endif // #ifdef ASSERT
2023
2024 RegionData* const beg = sd.region(beg_region);
2025 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2026
2027 // Regions up to new_top() are enqueued if they become available.
2028 HeapWord* const new_top = _space_info[src_space_id].new_top();
2029 RegionData* const enqueue_end =
2030 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2031
2032 for (RegionData* cur = beg; cur < end; ++cur) {
2033 assert(cur->data_size() > 0, "region must have live data");
2034 cur->decrement_destination_count();
2035 if (cur < enqueue_end && cur->available() && cur->claim()) {
2036 if (cur->mark_normal()) {
2037 cm->push_region(sd.region(cur));
2038 } else if (cur->mark_copied()) {
2039 // Try to copy the content of the shadow region back to its corresponding
2040 // heap region if the shadow region is filled. Otherwise, the GC thread
2041 // fills the shadow region will copy the data back (see
2042 // MoveAndUpdateShadowClosure::complete_region).
2043 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2044 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2045 cur->set_completed();
2046 }
2047 }
2048 }
2049 }
2050
2051 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2052 SpaceId& src_space_id,
2053 HeapWord*& src_space_top,
2054 HeapWord* end_addr)
2055 {
2056 ParallelCompactData& sd = PSParallelCompact::summary_data();
2057
2058 size_t src_region_idx = 0;
2059
2060 // Skip empty regions (if any) up to the top of the space.
2061 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2062 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2063 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2064 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2065
2066 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2067 ++src_region_ptr;
2068 }
2069
2070 if (src_region_ptr < top_region_ptr) {
2071 // Found the first non-empty region in the same space.
2072 src_region_idx = sd.region(src_region_ptr);
2073 closure.set_source(sd.region_to_addr(src_region_idx));
2074 return src_region_idx;
2075 }
2076
2077 // Switch to a new source space and find the first non-empty region.
2078 uint space_id = src_space_id + 1;
2079 assert(space_id < last_space_id, "not enough spaces");
2080
2081 for (/* empty */; space_id < last_space_id; ++space_id) {
2082 HeapWord* bottom = _space_info[space_id].space()->bottom();
2083 HeapWord* top = _space_info[space_id].space()->top();
2084 // Skip empty space
2085 if (bottom == top) {
2086 continue;
2087 }
2088
2089 // Identify the first region that contains live words in this space
2090 size_t cur_region = sd.addr_to_region_idx(bottom);
2091 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2092
2093 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2094 RegionData* cur = sd.region(cur_region);
2095 if (cur->live_obj_size() > 0) {
2096 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2097
2098 src_space_id = SpaceId(space_id);
2099 src_space_top = top;
2100 closure.set_source(region_start_addr);
2101 return cur_region;
2102 }
2103 }
2104 }
2105
2106 ShouldNotReachHere();
2107 }
2108
2109 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2110 ParallelCompactData& sd = summary_data();
2111 assert(sd.is_region_aligned(region_start_addr), "precondition");
2112
2113 // Use per-region partial_obj_size to locate the end of the obj, that extends
2114 // to region_start_addr.
2115 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2116 size_t end_region_idx = sd.region_count();
2117 size_t accumulated_size = 0;
2118 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2119 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2120 accumulated_size += cur_partial_obj_size;
2121 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2122 break;
2123 }
2124 }
2125 return region_start_addr + accumulated_size;
2126 }
2127
2128 // Use region_idx as the destination region, and evacuate all live objs on its
2129 // source regions to this destination region.
2130 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2131 {
2132 ParMarkBitMap* const bitmap = mark_bitmap();
2133 ParallelCompactData& sd = summary_data();
2134 RegionData* const region_ptr = sd.region(region_idx);
2135
2136 // Get the source region and related info.
2137 size_t src_region_idx = region_ptr->source_region();
2138 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2139 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2140 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2141
2142 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2143
2144 // Adjust src_region_idx to prepare for decrementing destination counts (the
2145 // destination count is not decremented when a region is copied to itself).
2146 if (src_region_idx == region_idx) {
2147 src_region_idx += 1;
2148 }
2149
2150 // source-region:
2151 //
2152 // **********
2153 // | ~~~ |
2154 // **********
2155 // ^
2156 // |-- closure.source() / first_src_addr
2157 //
2158 //
2159 // ~~~ : live words
2160 //
2161 // destination-region:
2162 //
2163 // **********
2164 // | |
2165 // **********
2166 // ^
2167 // |-- region-start
2168 if (bitmap->is_unmarked(closure.source())) {
2169 // An object overflows the previous destination region, so this
2170 // destination region should copy the remainder of the object or as much as
2171 // will fit.
2172 HeapWord* const old_src_addr = closure.source();
2173 {
2174 HeapWord* region_start = sd.region_align_down(closure.source());
2175 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2176 HeapWord* obj_end;
2177 if (obj_start != closure.source()) {
2178 assert(bitmap->is_marked(obj_start), "inv");
2179 // Found the actual obj-start, try to find the obj-end using either
2180 // size() if this obj is completely contained in the current region.
2181 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2182 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2183 ? nullptr
2184 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2185 // This obj extends to next region iff partial_obj_addr of the *next*
2186 // region is the same as obj-start.
2187 if (partial_obj_start == obj_start) {
2188 // This obj extends to next region.
2189 obj_end = partial_obj_end(next_region_start);
2190 } else {
2191 // Completely contained in this region; safe to use size().
2192 obj_end = obj_start + cast_to_oop(obj_start)->size();
2193 }
2194 } else {
2195 // This obj extends to current region.
2196 obj_end = partial_obj_end(region_start);
2197 }
2198 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2199 closure.copy_partial_obj(partial_obj_size);
2200 }
2201
2202 if (closure.is_full()) {
2203 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2204 closure.complete_region(dest_addr, region_ptr);
2205 return;
2206 }
2207
2208 // Finished copying without using up the current destination-region
2209 HeapWord* const end_addr = sd.region_align_down(closure.source());
2210 if (sd.region_align_down(old_src_addr) != end_addr) {
2211 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2212 // The partial object was copied from more than one source region.
2213 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2214
2215 // Move to the next source region, possibly switching spaces as well. All
2216 // args except end_addr may be modified.
2217 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2218 }
2219 }
2220
2221 // Handle the rest obj-by-obj, where we know obj-start.
2222 do {
2223 HeapWord* cur_addr = closure.source();
2224 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2225 src_space_top);
2226 // To handle the case where the final obj in source region extends to next region.
2227 HeapWord* final_obj_start = (end_addr == src_space_top)
2228 ? nullptr
2229 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2230 // Apply closure on objs inside [cur_addr, end_addr)
2231 do {
2232 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2233 if (cur_addr == end_addr) {
2234 break;
2235 }
2236 size_t obj_size;
2237 if (final_obj_start == cur_addr) {
2238 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2239 } else {
2240 // This obj doesn't extend into next region; size() is safe to use.
2241 obj_size = cast_to_oop(cur_addr)->size();
2242 }
2243 closure.do_addr(cur_addr, obj_size);
2244 cur_addr += obj_size;
2245 } while (cur_addr < end_addr && !closure.is_full());
2246
2247 if (closure.is_full()) {
2248 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2249 closure.complete_region(dest_addr, region_ptr);
2250 return;
2251 }
2252
2253 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2254
2255 // Move to the next source region, possibly switching spaces as well. All
2256 // args except end_addr may be modified.
2257 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2258 } while (true);
2259 }
2260
2261 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2262 {
2263 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2264 fill_region(cm, cl, region_idx);
2265 }
2266
2267 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2268 {
2269 // Get a shadow region first
2270 ParallelCompactData& sd = summary_data();
2271 RegionData* const region_ptr = sd.region(region_idx);
2272 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2273 // The InvalidShadow return value indicates the corresponding heap region is available,
2274 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2275 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2276 if (shadow_region == ParCompactionManager::InvalidShadow) {
2277 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2278 region_ptr->shadow_to_normal();
2279 return fill_region(cm, cl, region_idx);
2280 } else {
2281 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2282 return fill_region(cm, cl, region_idx);
2283 }
2284 }
2285
2286 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2287 {
2288 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2289 }
2290
2291 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2292 {
2293 size_t next = cm->next_shadow_region();
2294 ParallelCompactData& sd = summary_data();
2295 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2296 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2297
2298 while (next < old_new_top) {
2299 if (sd.region(next)->mark_shadow()) {
2300 region_idx = next;
2301 return true;
2302 }
2303 next = cm->move_next_shadow_region_by(active_gc_threads);
2304 }
2305
2306 return false;
2307 }
2308
2309 // The shadow region is an optimization to address region dependencies in full GC. The basic
2310 // idea is making more regions available by temporally storing their live objects in empty
2311 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2312 // GC threads need not wait destination regions to be available before processing sources.
2313 //
2314 // A typical workflow would be:
2315 // After draining its own stack and failing to steal from others, a GC worker would pick an
2316 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2317 // the shadow region by copying live objects from source regions of the unavailable one. Once
2318 // the unavailable region becomes available, the data in the shadow region will be copied back.
2319 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2320 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2321 {
2322 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2323
2324 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2325 SpaceInfo* const space_info = _space_info + id;
2326 MutableSpace* const space = space_info->space();
2327
2328 const size_t beg_region =
2329 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2330 const size_t end_region =
2331 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2332
2333 for (size_t cur = beg_region; cur < end_region; ++cur) {
2334 ParCompactionManager::push_shadow_region(cur);
2335 }
2336 }
2337
2338 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2339 for (uint i = 0; i < parallel_gc_threads; i++) {
2340 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2341 cm->set_next_shadow_region(beg_region + i);
2342 }
2343 }
2344
2345 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2346 {
2347 size_t words = MIN2(partial_obj_size, words_remaining());
2348
2349 // This test is necessary; if omitted, the pointer updates to a partial object
2350 // that crosses the dense prefix boundary could be overwritten.
2351 if (source() != copy_destination()) {
2352 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2353 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2354 }
2355 update_state(words);
2356 }
2357
2358 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2359 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2360 region_ptr->set_completed();
2361 }
2362
2363 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2364 assert(destination() != nullptr, "sanity");
2365 _source = addr;
2366
2367 // The start_array must be updated even if the object is not moving.
2368 if (_start_array != nullptr) {
2369 _start_array->update_for_block(destination(), destination() + words);
2370 }
2371
2372 // Avoid overflow
2373 words = MIN2(words, words_remaining());
2374 assert(words > 0, "inv");
2375
2376 if (copy_destination() != source()) {
2377 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2378 assert(source() != destination(), "inv");
2379 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2380 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2381 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2382 cast_to_oop(copy_destination())->init_mark();
2383 }
2384
2385 update_state(words);
2386 }
2387
2388 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2389 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2390 // Record the shadow region index
2391 region_ptr->set_shadow_region(_shadow);
2392 // Mark the shadow region as filled to indicate the data is ready to be
2393 // copied back
2394 region_ptr->mark_filled();
2395 // Try to copy the content of the shadow region back to its corresponding
2396 // heap region if available; the GC thread that decreases the destination
2397 // count to zero will do the copying otherwise (see
2398 // PSParallelCompact::decrement_destination_counts).
2399 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2400 region_ptr->set_completed();
2401 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2402 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2403 }
2404 }