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 "cppstdlib/new.hpp"
34 #include "gc/parallel/objectStartArray.inline.hpp"
35 #include "gc/parallel/parallelArguments.hpp"
36 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
37 #include "gc/parallel/parMarkBitMap.inline.hpp"
38 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
39 #include "gc/parallel/psCompactionManager.inline.hpp"
40 #include "gc/parallel/psOldGen.hpp"
41 #include "gc/parallel/psParallelCompact.inline.hpp"
42 #include "gc/parallel/psPromotionManager.inline.hpp"
43 #include "gc/parallel/psRootType.hpp"
44 #include "gc/parallel/psScavenge.hpp"
45 #include "gc/parallel/psStringDedup.hpp"
46 #include "gc/parallel/psYoungGen.hpp"
47 #include "gc/shared/classUnloadingContext.hpp"
48 #include "gc/shared/collectedHeap.inline.hpp"
49 #include "gc/shared/fullGCForwarding.inline.hpp"
50 #include "gc/shared/gcCause.hpp"
51 #include "gc/shared/gcHeapSummary.hpp"
52 #include "gc/shared/gcId.hpp"
53 #include "gc/shared/gcLocker.hpp"
54 #include "gc/shared/gcTimer.hpp"
55 #include "gc/shared/gcTrace.hpp"
56 #include "gc/shared/gcTraceTime.inline.hpp"
57 #include "gc/shared/gcVMOperations.hpp"
58 #include "gc/shared/isGCActiveMark.hpp"
59 #include "gc/shared/oopStorage.inline.hpp"
60 #include "gc/shared/oopStorageSet.inline.hpp"
61 #include "gc/shared/oopStorageSetParState.inline.hpp"
62 #include "gc/shared/parallelCleaning.hpp"
63 #include "gc/shared/preservedMarks.inline.hpp"
64 #include "gc/shared/referencePolicy.hpp"
65 #include "gc/shared/referenceProcessor.hpp"
66 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
67 #include "gc/shared/spaceDecorator.hpp"
68 #include "gc/shared/taskTerminator.hpp"
69 #include "gc/shared/weakProcessor.inline.hpp"
70 #include "gc/shared/workerPolicy.hpp"
71 #include "gc/shared/workerThread.hpp"
72 #include "gc/shared/workerUtils.hpp"
73 #include "logging/log.hpp"
74 #include "memory/iterator.inline.hpp"
75 #include "memory/memoryReserver.hpp"
76 #include "memory/metaspaceUtils.hpp"
77 #include "memory/resourceArea.hpp"
78 #include "memory/universe.hpp"
79 #include "nmt/memTracker.hpp"
80 #include "oops/access.inline.hpp"
81 #include "oops/instanceClassLoaderKlass.inline.hpp"
82 #include "oops/instanceKlass.inline.hpp"
83 #include "oops/instanceMirrorKlass.inline.hpp"
84 #include "oops/methodData.hpp"
85 #include "oops/objArrayKlass.inline.hpp"
86 #include "oops/oop.inline.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
100 #include <math.h>
101
102 // All sizes are in HeapWords.
103 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
104 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
105 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
106 const size_t ParallelCompactData::RegionSizeBytes =
107 RegionSize << LogHeapWordSize;
108 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
109 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
110 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
111
112 const ParallelCompactData::RegionData::region_sz_t
113 ParallelCompactData::RegionData::dc_shift = 27;
114
115 const ParallelCompactData::RegionData::region_sz_t
116 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
117
118 const ParallelCompactData::RegionData::region_sz_t
119 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
120
121 const ParallelCompactData::RegionData::region_sz_t
122 ParallelCompactData::RegionData::los_mask = ~dc_mask;
123
124 const ParallelCompactData::RegionData::region_sz_t
125 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
126
127 const ParallelCompactData::RegionData::region_sz_t
128 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
129
130 bool ParallelCompactData::RegionData::is_clear() {
131 return (_destination == nullptr) &&
132 (_source_region == 0) &&
133 (_partial_obj_addr == nullptr) &&
134 (_partial_obj_size == 0) &&
135 (dc_and_los() == 0) &&
136 (shadow_state() == 0);
137 }
138
139 #ifdef ASSERT
140 void ParallelCompactData::RegionData::verify_clear() {
141 assert(_destination == nullptr, "inv");
142 assert(_source_region == 0, "inv");
143 assert(_partial_obj_addr == nullptr, "inv");
144 assert(_partial_obj_size == 0, "inv");
145 assert(dc_and_los() == 0, "inv");
146 assert(shadow_state() == 0, "inv");
147 }
148 #endif
149
150 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
151
152 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
153 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
154
155 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
156 assert(split_region_idx != 0, "precondition");
157
158 // Obj denoted by split_point will be deferred to the next space.
159 assert(split_point != nullptr, "precondition");
160
161 const ParallelCompactData& sd = PSParallelCompact::summary_data();
162
163 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
164 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
165
166 HeapWord* preceding_destination = split_region_ptr->destination();
167 assert(preceding_destination != nullptr, "inv");
168
169 // How many regions does the preceding part occupy
170 uint preceding_destination_count;
171 if (preceding_live_words == 0) {
172 preceding_destination_count = 0;
173 } else {
174 // -1 so that the ending address doesn't fall on the region-boundary
175 if (sd.region_align_down(preceding_destination) ==
176 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
177 preceding_destination_count = 1;
178 } else {
179 preceding_destination_count = 2;
180 }
181 }
182
183 _split_region_idx = split_region_idx;
184 _split_point = split_point;
185 _preceding_live_words = preceding_live_words;
186 _preceding_destination = preceding_destination;
187 _preceding_destination_count = preceding_destination_count;
188 }
189
190 void SplitInfo::clear()
191 {
192 _split_region_idx = 0;
193 _split_point = nullptr;
194 _preceding_live_words = 0;
195 _preceding_destination = nullptr;
196 _preceding_destination_count = 0;
197 assert(!is_valid(), "sanity");
198 }
199
200 #ifdef ASSERT
201 void SplitInfo::verify_clear()
202 {
203 assert(_split_region_idx == 0, "not clear");
204 assert(_split_point == nullptr, "not clear");
205 assert(_preceding_live_words == 0, "not clear");
206 assert(_preceding_destination == nullptr, "not clear");
207 assert(_preceding_destination_count == 0, "not clear");
208 }
209 #endif // #ifdef ASSERT
210
211
212 void PSParallelCompact::print_on(outputStream* st) {
213 _mark_bitmap.print_on(st);
214 }
215
216 ParallelCompactData::ParallelCompactData() :
217 _heap_start(nullptr),
218 DEBUG_ONLY(_heap_end(nullptr) COMMA)
219 _region_vspace(nullptr),
220 _reserved_byte_size(0),
221 _region_data(nullptr),
222 _region_count(0) {}
223
224 bool ParallelCompactData::initialize(MemRegion reserved_heap)
225 {
226 _heap_start = reserved_heap.start();
227 const size_t heap_size = reserved_heap.word_size();
228 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
229
230 assert(region_align_down(_heap_start) == _heap_start,
231 "region start not aligned");
232 assert(is_aligned(heap_size, RegionSize), "precondition");
233
234 const size_t count = heap_size >> Log2RegionSize;
235 const size_t raw_bytes = count * sizeof(RegionData);
236 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
237 const size_t granularity = os::vm_allocation_granularity();
238 const size_t rs_align = MAX2(page_sz, granularity);
239
240 _reserved_byte_size = align_up(raw_bytes, rs_align);
241
242 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
243 rs_align,
244 page_sz,
245 mtGC);
246
247 if (!rs.is_reserved()) {
248 // Failed to reserve memory.
249 return false;
250 }
251
252 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
253 rs.size(), page_sz);
254
255 MemTracker::record_virtual_memory_tag(rs, mtGC);
256
257 PSVirtualSpace* region_vspace = new PSVirtualSpace(rs, page_sz);
258
259 if (!region_vspace->expand_by(_reserved_byte_size)) {
260 // Failed to commit memory.
261
262 delete region_vspace;
263
264 // Release memory reserved in the space.
265 MemoryReserver::release(rs);
266
267 return false;
268 }
269
270 _region_vspace = region_vspace;
271 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
272 _region_count = count;
273 return true;
274 }
275
276 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
277 assert(beg_region <= _region_count, "beg_region out of range");
278 assert(end_region <= _region_count, "end_region out of range");
279
280 for (size_t i = beg_region; i < end_region; i++) {
281 ::new (&_region_data[i]) RegionData{};
282 }
283 }
284
285 // The total live words on src_region would overflow the target space, so find
286 // the overflowing object and record the split point. The invariant is that an
287 // obj should not cross space boundary.
288 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
289 SplitInfo& split_info,
290 HeapWord* const destination,
291 HeapWord* const target_end,
292 HeapWord** target_next) {
293 assert(destination <= target_end, "sanity");
294 assert(destination + _region_data[src_region].data_size() > target_end,
295 "region should not fit into target space");
296 assert(is_region_aligned(target_end), "sanity");
297
298 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
299
300 if (destination + partial_obj_size > target_end) {
301 assert(partial_obj_size > 0, "inv");
302 // The overflowing obj is from a previous region.
303 //
304 // source-regions:
305 //
306 // ***************
307 // | A|AA |
308 // ***************
309 // ^
310 // | split-point
311 //
312 // dest-region:
313 //
314 // ********
315 // |~~~~A |
316 // ********
317 // ^^
318 // || target-space-end
319 // |
320 // | destination
321 //
322 // AAA would overflow target-space.
323 //
324 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
325 size_t split_region = addr_to_region_idx(overflowing_obj);
326
327 // The number of live words before the overflowing object on this split region
328 size_t preceding_live_words;
329 if (is_region_aligned(overflowing_obj)) {
330 preceding_live_words = 0;
331 } else {
332 // Words accounted by the overflowing object on the split region
333 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
334 preceding_live_words = region(split_region)->data_size() - overflowing_size;
335 }
336
337 split_info.record(split_region, overflowing_obj, preceding_live_words);
338
339 // The [overflowing_obj, src_region_start) part has been accounted for, so
340 // must move back the new_top, now that this overflowing obj is deferred.
341 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
342
343 // If the overflowing obj was relocated to its original destination,
344 // those destination regions would have their source_region set. Now that
345 // this overflowing obj is relocated somewhere else, reset the
346 // source_region.
347 {
348 size_t range_start = addr_to_region_idx(region_align_up(new_top));
349 size_t range_end = addr_to_region_idx(region_align_up(destination));
350 for (size_t i = range_start; i < range_end; ++i) {
351 region(i)->set_source_region(0);
352 }
353 }
354
355 // Update new top of target space
356 *target_next = new_top;
357
358 return overflowing_obj;
359 }
360
361 // Obj-iteration to locate the overflowing obj
362 HeapWord* region_start = region_to_addr(src_region);
363 HeapWord* region_end = region_start + RegionSize;
364 HeapWord* cur_addr = region_start + partial_obj_size;
365 size_t live_words = partial_obj_size;
366
367 while (true) {
368 assert(cur_addr < region_end, "inv");
369 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
370 // There must be an overflowing obj in this region
371 assert(cur_addr < region_end, "inv");
372
373 oop obj = cast_to_oop(cur_addr);
374 size_t obj_size = obj->size();
375 if (destination + live_words + obj_size > target_end) {
376 // Found the overflowing obj
377 split_info.record(src_region, cur_addr, live_words);
378 *target_next = destination + live_words;
379 return cur_addr;
380 }
381
382 live_words += obj_size;
383 cur_addr += obj_size;
384 }
385 }
386
387 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
388 HeapWord** full_region_prefix_end) {
389 size_t cur_region = addr_to_region_idx(space->bottom());
390 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
391 size_t live_words = 0;
392 if (full_region_prefix_end == nullptr) {
393 for (/* empty */; cur_region < end_region; ++cur_region) {
394 live_words += _region_data[cur_region].data_size();
395 }
396 } else {
397 bool first_set = false;
398 for (/* empty */; cur_region < end_region; ++cur_region) {
399 size_t live_words_in_region = _region_data[cur_region].data_size();
400 if (!first_set && live_words_in_region < RegionSize) {
401 *full_region_prefix_end = region_to_addr(cur_region);
402 first_set = true;
403 }
404 live_words += live_words_in_region;
405 }
406 if (!first_set) {
407 // All regions are full of live objs.
408 assert(is_region_aligned(space->top()), "inv");
409 *full_region_prefix_end = space->top();
410 }
411 assert(*full_region_prefix_end != nullptr, "postcondition");
412 assert(is_region_aligned(*full_region_prefix_end), "inv");
413 assert(*full_region_prefix_end >= space->bottom(), "in-range");
414 assert(*full_region_prefix_end <= space->top(), "in-range");
415 }
416 return live_words;
417 }
418
419 bool ParallelCompactData::summarize(SplitInfo& split_info,
420 HeapWord* source_beg, HeapWord* source_end,
421 HeapWord** source_next,
422 HeapWord* target_beg, HeapWord* target_end,
423 HeapWord** target_next)
424 {
425 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
426 log_develop_trace(gc, compaction)(
427 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
428 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
429 p2i(source_beg), p2i(source_end), p2i(source_next_val),
430 p2i(target_beg), p2i(target_end), p2i(*target_next));
431
432 size_t cur_region = addr_to_region_idx(source_beg);
433 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
434
435 HeapWord *dest_addr = target_beg;
436 for (/* empty */; cur_region < end_region; cur_region++) {
437 size_t words = _region_data[cur_region].data_size();
438
439 // Skip empty ones
440 if (words == 0) {
441 continue;
442 }
443
444 if (split_info.is_split(cur_region)) {
445 assert(words > split_info.preceding_live_words(), "inv");
446 words -= split_info.preceding_live_words();
447 }
448
449 _region_data[cur_region].set_destination(dest_addr);
450
451 // If cur_region does not fit entirely into the target space, find a point
452 // at which the source space can be 'split' so that part is copied to the
453 // target space and the rest is copied elsewhere.
454 if (dest_addr + words > target_end) {
455 assert(source_next != nullptr, "source_next is null when splitting");
456 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
457 target_end, target_next);
458 return false;
459 }
460
461 uint destination_count = split_info.is_split(cur_region)
462 ? split_info.preceding_destination_count()
463 : 0;
464
465 HeapWord* const last_addr = dest_addr + words - 1;
466 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
467 const size_t dest_region_2 = addr_to_region_idx(last_addr);
468
469 // Initially assume that the destination regions will be the same and
470 // adjust the value below if necessary. Under this assumption, if
471 // cur_region == dest_region_2, then cur_region will be compacted
472 // completely into itself.
473 destination_count += cur_region == dest_region_2 ? 0 : 1;
474 if (dest_region_1 != dest_region_2) {
475 // Destination regions differ; adjust destination_count.
476 destination_count += 1;
477 // Data from cur_region will be copied to the start of dest_region_2.
478 _region_data[dest_region_2].set_source_region(cur_region);
479 } else if (is_region_aligned(dest_addr)) {
480 // Data from cur_region will be copied to the start of the destination
481 // region.
482 _region_data[dest_region_1].set_source_region(cur_region);
483 }
484
485 _region_data[cur_region].set_destination_count(destination_count);
486 dest_addr += words;
487 }
488
489 *target_next = dest_addr;
490 return true;
491 }
492
493 #ifdef ASSERT
494 void ParallelCompactData::verify_clear() {
495 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
496 if (!region(cur_idx)->is_clear()) {
497 log_warning(gc)("Uncleared Region: %u", cur_idx);
498 region(cur_idx)->verify_clear();
499 }
500 }
501 }
502 #endif // #ifdef ASSERT
503
504 STWGCTimer PSParallelCompact::_gc_timer;
505 ParallelOldTracer PSParallelCompact::_gc_tracer;
506 elapsedTimer PSParallelCompact::_accumulated_time;
507 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
508 CollectorCounters* PSParallelCompact::_counters = nullptr;
509 ParMarkBitMap PSParallelCompact::_mark_bitmap;
510 ParallelCompactData PSParallelCompact::_summary_data;
511
512 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
513
514 class PCAdjustPointerClosureNew: public BasicOopIterateClosure {
515 template <typename T>
516 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
517
518 public:
519 virtual void do_oop(oop* p) { do_oop_work(p); }
520 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
521
522 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
523 };
524
525 static PCAdjustPointerClosureNew pc_adjust_pointer_closure;
526
527 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
528
529 void PSParallelCompact::post_initialize() {
530 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
531 _span_based_discoverer.set_span(heap->reserved_region());
532 _ref_processor =
533 new ReferenceProcessor(&_span_based_discoverer,
534 ParallelGCThreads, // mt processing degree
535 ParallelGCThreads, // mt discovery degree
536 false, // concurrent_discovery
537 &_is_alive_closure); // non-header is alive closure
538
539 _counters = new CollectorCounters("Parallel full collection pauses", 1);
540
541 // Initialize static fields in ParCompactionManager.
542 ParCompactionManager::initialize(mark_bitmap());
543 }
544
545 bool PSParallelCompact::initialize_aux_data() {
546 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
547 MemRegion mr = heap->reserved_region();
548 assert(mr.byte_size() != 0, "heap should be reserved");
549
550 initialize_space_info();
551
552 if (!_mark_bitmap.initialize(mr)) {
553 vm_shutdown_during_initialization(
554 err_msg("Unable to allocate %zuKB bitmaps for parallel "
555 "garbage collection for the requested %zuKB heap.",
556 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
557 return false;
558 }
559
560 if (!_summary_data.initialize(mr)) {
561 vm_shutdown_during_initialization(
562 err_msg("Unable to allocate %zuKB card tables for parallel "
563 "garbage collection for the requested %zuKB heap.",
564 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
565 return false;
566 }
567
568 return true;
569 }
570
571 void PSParallelCompact::initialize_space_info()
572 {
573 memset(&_space_info, 0, sizeof(_space_info));
574
575 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
576 PSYoungGen* young_gen = heap->young_gen();
577
578 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
579 _space_info[eden_space_id].set_space(young_gen->eden_space());
580 _space_info[from_space_id].set_space(young_gen->from_space());
581 _space_info[to_space_id].set_space(young_gen->to_space());
582
583 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
584 }
585
586 void
587 PSParallelCompact::clear_data_covering_space(SpaceId id)
588 {
589 // At this point, top is the value before GC, new_top() is the value that will
590 // be set at the end of GC. The marking bitmap is cleared to top; nothing
591 // should be marked above top. The summary data is cleared to the larger of
592 // top & new_top.
593 MutableSpace* const space = _space_info[id].space();
594 HeapWord* const bot = space->bottom();
595 HeapWord* const top = space->top();
596 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
597
598 _mark_bitmap.clear_range(bot, top);
599
600 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
601 const size_t end_region =
602 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
603 _summary_data.clear_range(beg_region, end_region);
604
605 // Clear the data used to 'split' regions.
606 SplitInfo& split_info = _space_info[id].split_info();
607 if (split_info.is_valid()) {
608 split_info.clear();
609 }
610 DEBUG_ONLY(split_info.verify_clear();)
611 }
612
613 void PSParallelCompact::pre_compact()
614 {
615 // Update the from & to space pointers in space_info, since they are swapped
616 // at each young gen gc. Do the update unconditionally (even though a
617 // promotion failure does not swap spaces) because an unknown number of young
618 // collections will have swapped the spaces an unknown number of times.
619 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
620 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
621 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
622 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
623
624 heap->increment_total_collections(true);
625
626 CodeCache::on_gc_marking_cycle_start();
627
628 heap->print_before_gc();
629 heap->trace_heap_before_gc(&_gc_tracer);
630
631 // Fill in TLABs
632 heap->ensure_parsability(true); // retire TLABs
633
634 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
635 Universe::verify("Before GC");
636 }
637
638 DEBUG_ONLY(mark_bitmap()->verify_clear();)
639 DEBUG_ONLY(summary_data().verify_clear();)
640 }
641
642 void PSParallelCompact::post_compact()
643 {
644 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
645 ParCompactionManager::remove_all_shadow_regions();
646
647 CodeCache::on_gc_marking_cycle_finish();
648 CodeCache::arm_all_nmethods();
649
650 // Need to clear claim bits for the next full-gc (marking and adjust-pointers).
651 ClassLoaderDataGraph::clear_claimed_marks();
652
653 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
654 // Clear the marking bitmap, summary data and split info.
655 clear_data_covering_space(SpaceId(id));
656 {
657 MutableSpace* space = _space_info[id].space();
658 HeapWord* top = space->top();
659 HeapWord* new_top = _space_info[id].new_top();
660 if (ZapUnusedHeapArea && new_top < top) {
661 space->mangle_region(MemRegion(new_top, top));
662 }
663 // Update top(). Must be done after clearing the bitmap and summary data.
664 space->set_top(new_top);
665 }
666 }
667
668 #ifdef ASSERT
669 {
670 mark_bitmap()->verify_clear();
671 summary_data().verify_clear();
672 }
673 #endif
674
675 ParCompactionManager::flush_all_string_dedup_requests();
676
677 MutableSpace* const eden_space = _space_info[eden_space_id].space();
678 MutableSpace* const from_space = _space_info[from_space_id].space();
679 MutableSpace* const to_space = _space_info[to_space_id].space();
680
681 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
682 bool eden_empty = eden_space->is_empty();
683
684 // Update heap occupancy information which is used as input to the soft ref
685 // clearing policy at the next gc.
686 Universe::heap()->update_capacity_and_used_at_gc();
687
688 bool young_gen_empty = eden_empty && from_space->is_empty() &&
689 to_space->is_empty();
690
691 PSCardTable* ct = heap->card_table();
692 MemRegion old_mr = heap->old_gen()->committed();
693 if (young_gen_empty) {
694 ct->clear_MemRegion(old_mr);
695 } else {
696 ct->dirty_MemRegion(old_mr);
697 }
698
699 heap->prune_scavengable_nmethods();
700
701 #ifdef COMPILER2
702 DerivedPointerTable::update_pointers();
703 #endif // COMPILER2
704
705 // Signal that we have completed a visit to all live objects.
706 Universe::heap()->record_whole_heap_examined_timestamp();
707 }
708
709 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
710 HeapWord* full_region_prefix_end) {
711 const size_t region_size = ParallelCompactData::RegionSize;
712 const ParallelCompactData& sd = summary_data();
713
714 // Iteration starts with the region *after* the full-region-prefix-end.
715 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
716 // If final region is not full, iteration stops before that region,
717 // because fill_dense_prefix_end assumes that prefix_end <= top.
718 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
719 assert(start_region <= end_region, "inv");
720
721 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
722 const RegionData* cur_region = start_region;
723 for (/* empty */; cur_region < end_region; ++cur_region) {
724 assert(region_size >= cur_region->data_size(), "inv");
725 size_t dead_size = region_size - cur_region->data_size();
726 if (max_waste < dead_size) {
727 break;
728 }
729 max_waste -= dead_size;
730 }
731
732 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
733 assert(sd.is_region_aligned(prefix_end), "postcondition");
734 assert(prefix_end >= full_region_prefix_end, "in-range");
735 assert(prefix_end <= old_space->top(), "in-range");
736 return prefix_end;
737 }
738
739 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
740 // Comparing two sizes to decide if filling is required:
741 //
742 // The size of the filler (min-obj-size) is 2 heap words with the default
743 // MinObjAlignment, since both markword and klass take 1 heap word.
744 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
745 // because the Klass* gets encoded in the mark-word.
746 //
747 // The size of the gap (if any) right before dense-prefix-end is
748 // MinObjAlignment.
749 //
750 // Need to fill in the gap only if it's smaller than min-obj-size, and the
751 // filler obj will extend to next region.
752
753 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
754 return;
755 }
756
757 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
758 assert(CollectedHeap::min_fill_size() == 2, "inv");
759 HeapWord* const dense_prefix_end = dense_prefix(id);
760 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
761 assert(dense_prefix_end <= space(id)->top(), "precondition");
762 if (dense_prefix_end == space(id)->top()) {
763 // Must not have single-word gap right before prefix-end/top.
764 return;
765 }
766 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
767
768 if (region_after_dense_prefix->partial_obj_size() != 0 ||
769 _mark_bitmap.is_marked(dense_prefix_end)) {
770 // The region after the dense prefix starts with live bytes.
771 return;
772 }
773
774 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
775 if (block_start == dense_prefix_end - 1) {
776 assert(!_mark_bitmap.is_marked(block_start), "inv");
777 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
778 // The filler object will extend into region_after_dense_prefix.
779 const size_t obj_len = 2; // min-fill-size
780 HeapWord* const obj_beg = dense_prefix_end - 1;
781 CollectedHeap::fill_with_object(obj_beg, obj_len);
782 _mark_bitmap.mark_obj(obj_beg);
783 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
784 region_after_dense_prefix->set_partial_obj_size(1);
785 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
786 assert(start_array(id) != nullptr, "sanity");
787 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
788 }
789 }
790
791 bool PSParallelCompact::check_maximum_compaction(bool should_do_max_compaction,
792 size_t total_live_words,
793 MutableSpace* const old_space,
794 HeapWord* full_region_prefix_end) {
795
796 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
797
798 // Check System.GC
799 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
800 && GCCause::is_user_requested_gc(heap->gc_cause());
801
802 // Check if all live objs are too much for old-gen.
803 const bool is_old_gen_too_full = (total_live_words >= old_space->capacity_in_words());
804
805 // If all regions in old-gen are full
806 const bool is_region_full =
807 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
808
809 return should_do_max_compaction
810 || is_max_on_system_gc
811 || is_old_gen_too_full
812 || is_region_full;
813 }
814
815 void PSParallelCompact::summary_phase(bool should_do_max_compaction)
816 {
817 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
818
819 MutableSpace* const old_space = _space_info[old_space_id].space();
820 {
821 size_t total_live_words = 0;
822 HeapWord* full_region_prefix_end = nullptr;
823 {
824 // old-gen
825 size_t live_words = _summary_data.live_words_in_space(old_space,
826 &full_region_prefix_end);
827 total_live_words += live_words;
828 }
829 // young-gen
830 for (uint i = eden_space_id; i < last_space_id; ++i) {
831 const MutableSpace* space = _space_info[i].space();
832 size_t live_words = _summary_data.live_words_in_space(space);
833 total_live_words += live_words;
834 _space_info[i].set_new_top(space->bottom() + live_words);
835 _space_info[i].set_dense_prefix(space->bottom());
836 }
837
838 should_do_max_compaction = check_maximum_compaction(should_do_max_compaction,
839 total_live_words,
840 old_space,
841 full_region_prefix_end);
842 {
843 GCTraceTime(Info, gc, phases) tm("Summary Phase: expand", &_gc_timer);
844 // Try to expand old-gen in order to fit all live objs and waste.
845 size_t target_capacity_bytes = total_live_words * HeapWordSize
846 + old_space->capacity_in_bytes() * (MarkSweepDeadRatio / 100);
847 ParallelScavengeHeap::heap()->old_gen()->try_expand_till_size(target_capacity_bytes);
848 }
849
850 HeapWord* dense_prefix_end = should_do_max_compaction
851 ? full_region_prefix_end
852 : compute_dense_prefix_for_old_space(old_space,
853 full_region_prefix_end);
854 SpaceId id = old_space_id;
855 _space_info[id].set_dense_prefix(dense_prefix_end);
856
857 if (dense_prefix_end != old_space->bottom()) {
858 fill_dense_prefix_end(id);
859 }
860
861 // Compacting objs in [dense_prefix_end, old_space->top())
862 _summary_data.summarize(_space_info[id].split_info(),
863 dense_prefix_end, old_space->top(), nullptr,
864 dense_prefix_end, old_space->end(),
865 _space_info[id].new_top_addr());
866 }
867
868 // Summarize the remaining spaces in the young gen. The initial target space
869 // is the old gen. If a space does not fit entirely into the target, then the
870 // remainder is compacted into the space itself and that space becomes the new
871 // target.
872 SpaceId dst_space_id = old_space_id;
873 HeapWord* dst_space_end = old_space->end();
874 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
875 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
876 const MutableSpace* space = _space_info[id].space();
877 const size_t live = pointer_delta(_space_info[id].new_top(),
878 space->bottom());
879 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
880
881 if (live > 0 && live <= available) {
882 // All the live data will fit.
883 bool done = _summary_data.summarize(_space_info[id].split_info(),
884 space->bottom(), space->top(),
885 nullptr,
886 *new_top_addr, dst_space_end,
887 new_top_addr);
888 assert(done, "space must fit into old gen");
889
890 // Reset the new_top value for the space.
891 _space_info[id].set_new_top(space->bottom());
892 } else if (live > 0) {
893 // Attempt to fit part of the source space into the target space.
894 HeapWord* next_src_addr = nullptr;
895 bool done = _summary_data.summarize(_space_info[id].split_info(),
896 space->bottom(), space->top(),
897 &next_src_addr,
898 *new_top_addr, dst_space_end,
899 new_top_addr);
900 assert(!done, "space should not fit into old gen");
901 assert(next_src_addr != nullptr, "sanity");
902
903 // The source space becomes the new target, so the remainder is compacted
904 // within the space itself.
905 dst_space_id = SpaceId(id);
906 dst_space_end = space->end();
907 new_top_addr = _space_info[id].new_top_addr();
908 done = _summary_data.summarize(_space_info[id].split_info(),
909 next_src_addr, space->top(),
910 nullptr,
911 space->bottom(), dst_space_end,
912 new_top_addr);
913 assert(done, "space must fit when compacted into itself");
914 assert(*new_top_addr <= space->top(), "usage should not grow");
915 }
916 }
917 }
918
919 void PSParallelCompact::report_object_count_after_gc() {
920 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
921 // The heap is compacted, all objects are iterable. However there may be
922 // filler objects in the heap which we should ignore.
923 class SkipFillerObjectClosure : public BoolObjectClosure {
924 public:
925 bool do_object_b(oop obj) override { return !CollectedHeap::is_filler_object(obj); }
926 } cl;
927 _gc_tracer.report_object_count_after_gc(&cl, &ParallelScavengeHeap::heap()->workers());
928 }
929
930 bool PSParallelCompact::invoke(bool clear_all_soft_refs, bool should_do_max_compaction) {
931 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
932 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
933 "should be in vm thread");
934 assert(ref_processor() != nullptr, "Sanity");
935
936 SvcGCMarker sgcm(SvcGCMarker::FULL);
937 IsSTWGCActiveMark mark;
938
939 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
940
941 GCIdMark gc_id_mark;
942 _gc_timer.register_gc_start();
943 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
944
945 GCCause::Cause gc_cause = heap->gc_cause();
946 PSOldGen* old_gen = heap->old_gen();
947 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
948
949 // Make sure data structures are sane, make the heap parsable, and do other
950 // miscellaneous bookkeeping.
951 pre_compact();
952
953 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
954
955 {
956 const uint active_workers =
957 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
958 ParallelScavengeHeap::heap()->workers().active_workers(),
959 Threads::number_of_non_daemon_threads());
960 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
961
962 GCTraceCPUTime tcpu(&_gc_tracer);
963 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
964
965 heap->pre_full_gc_dump(&_gc_timer);
966
967 TraceCollectorStats tcs(counters());
968 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
969
970 if (log_is_enabled(Debug, gc, heap, exit)) {
971 accumulated_time()->start();
972 }
973
974 // Let the size policy know we're starting
975 size_policy->major_collection_begin();
976
977 #ifdef COMPILER2
978 DerivedPointerTable::clear();
979 #endif // COMPILER2
980
981 ref_processor()->start_discovery(clear_all_soft_refs);
982
983 marking_phase(&_gc_tracer);
984
985 summary_phase(should_do_max_compaction);
986
987 #ifdef COMPILER2
988 assert(DerivedPointerTable::is_active(), "Sanity");
989 DerivedPointerTable::set_active(false);
990 #endif // COMPILER2
991
992 FullGCForwarding::begin();
993
994 forward_to_new_addr();
995
996 adjust_pointers();
997
998 compact();
999
1000 FullGCForwarding::end();
1001
1002 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1003
1004 ParCompactionManager::verify_all_region_stack_empty();
1005
1006 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1007 // done before resizing.
1008 post_compact();
1009
1010 size_policy->major_collection_end();
1011
1012 size_policy->sample_old_gen_used_bytes(MAX2(pre_gc_values.old_gen_used(), old_gen->used_in_bytes()));
1013
1014 if (UseAdaptiveSizePolicy) {
1015 heap->resize_after_full_gc();
1016 }
1017
1018 heap->resize_all_tlabs();
1019
1020 // Resize the metaspace capacity after a collection
1021 MetaspaceGC::compute_new_size();
1022
1023 if (log_is_enabled(Debug, gc, heap, exit)) {
1024 accumulated_time()->stop();
1025 }
1026
1027 heap->print_heap_change(pre_gc_values);
1028
1029 report_object_count_after_gc();
1030
1031 // Track memory usage and detect low memory
1032 MemoryService::track_memory_usage();
1033 heap->update_counters();
1034
1035 heap->post_full_gc_dump(&_gc_timer);
1036
1037 size_policy->record_gc_pause_end_instant();
1038 }
1039
1040 heap->gc_epilogue(true);
1041
1042 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1043 Universe::verify("After GC");
1044 }
1045
1046 heap->print_after_gc();
1047 heap->trace_heap_after_gc(&_gc_tracer);
1048
1049 _gc_timer.register_gc_end();
1050
1051 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1052 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1053
1054 return true;
1055 }
1056
1057 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1058 ParCompactionManager* _cm;
1059
1060 public:
1061 PCAddThreadRootsMarkingTaskClosure(ParCompactionManager* cm) : _cm(cm) { }
1062 void do_thread(Thread* thread) {
1063 ResourceMark rm;
1064
1065 MarkingNMethodClosure mark_and_push_in_blobs(&_cm->_mark_and_push_closure);
1066
1067 thread->oops_do(&_cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1068
1069 // Do the real work
1070 _cm->follow_marking_stacks();
1071 }
1072 };
1073
1074 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1075 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1076
1077 ParCompactionManager* cm =
1078 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1079
1080 do {
1081 ScannerTask task;
1082 if (ParCompactionManager::steal(worker_id, task)) {
1083 cm->follow_contents(task, true);
1084 }
1085 cm->follow_marking_stacks();
1086 } while (!terminator.offer_termination());
1087 }
1088
1089 class MarkFromRootsTask : public WorkerTask {
1090 NMethodMarkingScope _nmethod_marking_scope;
1091 ThreadsClaimTokenScope _threads_claim_token_scope;
1092 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1093 TaskTerminator _terminator;
1094 uint _active_workers;
1095
1096 public:
1097 MarkFromRootsTask(uint active_workers) :
1098 WorkerTask("MarkFromRootsTask"),
1099 _nmethod_marking_scope(),
1100 _threads_claim_token_scope(),
1101 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1102 _active_workers(active_workers) {}
1103
1104 virtual void work(uint worker_id) {
1105 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1106 cm->create_marking_stats_cache();
1107 {
1108 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1109 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1110
1111 // Do the real work
1112 cm->follow_marking_stacks();
1113 }
1114
1115 {
1116 PCAddThreadRootsMarkingTaskClosure closure(cm);
1117 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1118 }
1119
1120 // Mark from OopStorages
1121 {
1122 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1123 // Do the real work
1124 cm->follow_marking_stacks();
1125 }
1126
1127 if (_active_workers > 1) {
1128 steal_marking_work(_terminator, worker_id);
1129 }
1130 }
1131 };
1132
1133 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1134 TaskTerminator _terminator;
1135
1136 public:
1137 ParallelCompactRefProcProxyTask(uint max_workers)
1138 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1139 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1140
1141 void work(uint worker_id) override {
1142 assert(worker_id < _max_workers, "sanity");
1143 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1144 BarrierEnqueueDiscoveredFieldClosure enqueue;
1145 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1146 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1147 }
1148
1149 void prepare_run_task_hook() override {
1150 _terminator.reset_for_reuse(_queue_count);
1151 }
1152 };
1153
1154 static void flush_marking_stats_cache(const uint num_workers) {
1155 for (uint i = 0; i < num_workers; ++i) {
1156 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1157 cm->flush_and_destroy_marking_stats_cache();
1158 }
1159 }
1160
1161 class PSParallelCleaningTask : public WorkerTask {
1162 bool _unloading_occurred;
1163 CodeCacheUnloadingTask _code_cache_task;
1164 // Prune dead klasses from subklass/sibling/implementor lists.
1165 KlassCleaningTask _klass_cleaning_task;
1166
1167 public:
1168 PSParallelCleaningTask(bool unloading_occurred) :
1169 WorkerTask("PS Parallel Cleaning"),
1170 _unloading_occurred(unloading_occurred),
1171 _code_cache_task(unloading_occurred),
1172 _klass_cleaning_task() {}
1173
1174 void work(uint worker_id) {
1175 // Do first pass of code cache cleaning.
1176 _code_cache_task.work(worker_id);
1177
1178 // Clean all klasses that were not unloaded.
1179 // The weak metadata in klass doesn't need to be
1180 // processed if there was no unloading.
1181 if (_unloading_occurred) {
1182 _klass_cleaning_task.work();
1183 }
1184 }
1185 };
1186
1187 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1188 // Recursively traverse all live objects and mark them
1189 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1190
1191 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1192
1193 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1194 {
1195 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1196
1197 MarkFromRootsTask task(active_gc_threads);
1198 ParallelScavengeHeap::heap()->workers().run_task(&task);
1199 }
1200
1201 // Process reference objects found during marking
1202 {
1203 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1204
1205 ReferenceProcessorStats stats;
1206 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1207
1208 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1209 stats = ref_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
1210
1211 gc_tracer->report_gc_reference_stats(stats);
1212 pt.print_all_references();
1213 }
1214
1215 {
1216 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1217
1218 flush_marking_stats_cache(active_gc_threads);
1219 }
1220
1221 // This is the point where the entire marking should have completed.
1222 ParCompactionManager::verify_all_marking_stack_empty();
1223
1224 {
1225 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1226 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1227 is_alive_closure(),
1228 &do_nothing_cl,
1229 1);
1230 }
1231
1232 {
1233 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1234
1235 ClassUnloadingContext ctx(active_gc_threads /* num_nmethod_unlink_workers */,
1236 false /* unregister_nmethods_during_purge */,
1237 false /* lock_nmethod_free_separately */);
1238
1239 {
1240 CodeCache::UnlinkingScope scope(is_alive_closure());
1241
1242 // Follow system dictionary roots and unload classes.
1243 bool unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1244
1245 PSParallelCleaningTask task{unloading_occurred};
1246 ParallelScavengeHeap::heap()->workers().run_task(&task);
1247 }
1248
1249 {
1250 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1251 // Release unloaded nmethod's memory.
1252 ctx.purge_nmethods();
1253 }
1254 {
1255 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1256 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1257 }
1258 {
1259 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1260 ctx.free_nmethods();
1261 }
1262 {
1263 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1264 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
1265 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1266 DEBUG_ONLY(MetaspaceUtils::verify();)
1267 }
1268 }
1269
1270 #if TASKQUEUE_STATS
1271 ParCompactionManager::print_and_reset_taskqueue_stats();
1272 #endif
1273 }
1274
1275 void PSParallelCompact::adjust_in_space_helper(SpaceId id, Atomic<uint>* claim_counter) {
1276 MutableSpace* sp = PSParallelCompact::space(id);
1277 HeapWord* const bottom = sp->bottom();
1278 HeapWord* const top = sp->top();
1279 if (bottom == top) {
1280 return;
1281 }
1282
1283 const uint num_regions_per_stripe = 2;
1284 const size_t region_size = ParallelCompactData::RegionSize;
1285 const size_t stripe_size = num_regions_per_stripe * region_size;
1286
1287 while (true) {
1288 uint counter = claim_counter->fetch_then_add(num_regions_per_stripe);
1289 HeapWord* cur_stripe = bottom + counter * region_size;
1290 if (cur_stripe >= top) {
1291 break;
1292 }
1293 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1294 adjust_in_stripe(cur_stripe, stripe_end);
1295 }
1296 }
1297
1298 size_t PSParallelCompact::adjust_in_obj_with_limit(HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1299 precond(mark_bitmap()->is_marked(obj_start));
1300 oop obj = cast_to_oop(obj_start);
1301 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1302 }
1303
1304 void PSParallelCompact::adjust_in_stripe(HeapWord* stripe_start, HeapWord* stripe_end) {
1305 precond(_summary_data.is_region_aligned(stripe_start));
1306
1307 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1308 HeapWord* obj_start;
1309 if (cur_region->partial_obj_size() != 0) {
1310 obj_start = cur_region->partial_obj_addr();
1311 obj_start += adjust_in_obj_with_limit(obj_start, stripe_start, stripe_end);
1312 } else {
1313 obj_start = stripe_start;
1314 }
1315
1316 while (obj_start < stripe_end) {
1317 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1318 if (obj_start >= stripe_end) {
1319 break;
1320 }
1321 obj_start += adjust_in_obj_with_limit(obj_start, stripe_start, stripe_end);
1322 }
1323 }
1324
1325 void PSParallelCompact::adjust_in_old_space(Atomic<uint>* claim_counter) {
1326 // Regions in old-space shouldn't be split.
1327 precond(!_space_info[old_space_id].split_info().is_valid());
1328
1329 adjust_in_space_helper(old_space_id, claim_counter);
1330 }
1331
1332 void PSParallelCompact::adjust_in_young_space(SpaceId id, Atomic<uint>* claim_counter) {
1333 adjust_in_space_helper(id, claim_counter);
1334 }
1335
1336 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, Atomic<uint>* claim_counters) {
1337 auto start_time = Ticks::now();
1338 adjust_in_old_space(&claim_counters[0]);
1339 for (uint id = eden_space_id; id < last_space_id; ++id) {
1340 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1341 }
1342 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1343 }
1344
1345 class PSAdjustTask final : public WorkerTask {
1346 ThreadsClaimTokenScope _threads_claim_token_scope;
1347 WeakProcessor::Task _weak_proc_task;
1348 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1349 uint _nworkers;
1350 Atomic<bool> _code_cache_claimed;
1351 Atomic<uint> _claim_counters[PSParallelCompact::last_space_id];
1352
1353 bool try_claim_code_cache_task() {
1354 return _code_cache_claimed.load_relaxed() == false
1355 && _code_cache_claimed.compare_set(false, true);
1356 }
1357
1358 public:
1359 PSAdjustTask(uint nworkers) :
1360 WorkerTask("PSAdjust task"),
1361 _threads_claim_token_scope(),
1362 _weak_proc_task(nworkers),
1363 _oop_storage_iter(),
1364 _nworkers(nworkers),
1365 _code_cache_claimed(false),
1366 _claim_counters{} {
1367
1368 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1369 }
1370
1371 void work(uint worker_id) {
1372 {
1373 // Pointers in heap.
1374 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1375 cm->preserved_marks()->adjust_during_full_gc();
1376
1377 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1378 }
1379
1380 {
1381 // All (strong and weak) CLDs.
1382 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1383 ClassLoaderDataGraph::cld_do(&cld_closure);
1384 }
1385
1386 {
1387 // Threads stack frames. No need to visit on-stack nmethods, because all
1388 // nmethods are visited in one go via CodeCache::nmethods_do.
1389 ResourceMark rm;
1390 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1391 if (try_claim_code_cache_task()) {
1392 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1393 CodeCache::nmethods_do(&adjust_code);
1394 }
1395 }
1396
1397 {
1398 // VM internal strong and weak roots.
1399 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1400 AlwaysTrueClosure always_alive;
1401 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1402 }
1403 }
1404 };
1405
1406 void PSParallelCompact::adjust_pointers() {
1407 // Adjust the pointers to reflect the new locations
1408 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1409 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1410 PSAdjustTask task(nworkers);
1411 ParallelScavengeHeap::heap()->workers().run_task(&task);
1412 }
1413
1414 // Split [start, end) evenly for a number of workers and return the
1415 // range for worker_id.
1416 static void split_regions_for_worker(size_t start, size_t end,
1417 uint worker_id, uint num_workers,
1418 size_t* worker_start, size_t* worker_end) {
1419 assert(start < end, "precondition");
1420 assert(num_workers > 0, "precondition");
1421 assert(worker_id < num_workers, "precondition");
1422
1423 size_t num_regions = end - start;
1424 size_t num_regions_per_worker = num_regions / num_workers;
1425 size_t remainder = num_regions % num_workers;
1426 // The first few workers will get one extra.
1427 *worker_start = start + worker_id * num_regions_per_worker
1428 + MIN2(checked_cast<size_t>(worker_id), remainder);
1429 *worker_end = *worker_start + num_regions_per_worker
1430 + (worker_id < remainder ? 1 : 0);
1431 }
1432
1433 void PSParallelCompact::forward_to_new_addr() {
1434 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1435 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1436
1437 struct ForwardTask final : public WorkerTask {
1438 uint _num_workers;
1439
1440 explicit ForwardTask(uint num_workers) :
1441 WorkerTask("PSForward task"),
1442 _num_workers(num_workers) {}
1443
1444 static void forward_objs_in_range(ParCompactionManager* cm,
1445 HeapWord* start,
1446 HeapWord* end,
1447 HeapWord* destination) {
1448 HeapWord* cur_addr = start;
1449 HeapWord* new_addr = destination;
1450
1451 while (cur_addr < end) {
1452 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1453 if (cur_addr >= end) {
1454 return;
1455 }
1456 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1457 oop obj = cast_to_oop(cur_addr);
1458 if (new_addr != cur_addr) {
1459 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1460 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1461 }
1462 size_t obj_size = obj->size();
1463 new_addr += obj_size;
1464 cur_addr += obj_size;
1465 }
1466 }
1467
1468 void work(uint worker_id) override {
1469 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1470 for (uint id = old_space_id; id < last_space_id; ++id) {
1471 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1472 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1473 HeapWord* top = sp->top();
1474
1475 if (dense_prefix_addr == top) {
1476 // Empty space
1477 continue;
1478 }
1479
1480 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1481 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1482 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1483 size_t start_region;
1484 size_t end_region;
1485 split_regions_for_worker(dense_prefix_region, top_region,
1486 worker_id, _num_workers,
1487 &start_region, &end_region);
1488 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1489 RegionData* region_ptr = _summary_data.region(cur_region);
1490 size_t partial_obj_size = region_ptr->partial_obj_size();
1491
1492 if (partial_obj_size == ParallelCompactData::RegionSize) {
1493 // No obj-start
1494 continue;
1495 }
1496
1497 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1498 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1499
1500 if (split_info.is_split(cur_region)) {
1501 // Part 1: will be relocated to space-1
1502 HeapWord* preceding_destination = split_info.preceding_destination();
1503 HeapWord* split_point = split_info.split_point();
1504 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1505
1506 // Part 2: will be relocated to space-2
1507 HeapWord* destination = region_ptr->destination();
1508 forward_objs_in_range(cm, split_point, region_end, destination);
1509 } else {
1510 HeapWord* destination = region_ptr->destination();
1511 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1512 }
1513 }
1514 }
1515 }
1516 } task(nworkers);
1517
1518 ParallelScavengeHeap::heap()->workers().run_task(&task);
1519 DEBUG_ONLY(verify_forward();)
1520 }
1521
1522 #ifdef ASSERT
1523 void PSParallelCompact::verify_forward() {
1524 HeapWord* const old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1525 // The destination addr for the first live obj after dense-prefix.
1526 HeapWord* bump_ptr = old_dense_prefix_addr
1527 + _summary_data.addr_to_region_ptr(old_dense_prefix_addr)->partial_obj_size();
1528 SpaceId bump_ptr_space = old_space_id;
1529
1530 for (uint id = old_space_id; id < last_space_id; ++id) {
1531 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1532 // Only verify objs after dense-prefix, because those before dense-prefix are not moved (forwarded).
1533 HeapWord* cur_addr = dense_prefix(SpaceId(id));
1534 HeapWord* top = sp->top();
1535
1536 while (cur_addr < top) {
1537 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1538 if (cur_addr >= top) {
1539 break;
1540 }
1541 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1542 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1543 // Move to the space containing cur_addr
1544 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1545 bump_ptr = space(space_id(cur_addr))->bottom();
1546 bump_ptr_space = space_id(bump_ptr);
1547 }
1548 oop obj = cast_to_oop(cur_addr);
1549 if (cur_addr == bump_ptr) {
1550 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1551 } else {
1552 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1553 }
1554 bump_ptr += obj->size();
1555 cur_addr += obj->size();
1556 }
1557 }
1558 }
1559 #endif
1560
1561 // Helper class to print 8 region numbers per line and then print the total at the end.
1562 class FillableRegionLogger : public StackObj {
1563 private:
1564 Log(gc, compaction) log;
1565 static const int LineLength = 8;
1566 size_t _regions[LineLength];
1567 int _next_index;
1568 bool _enabled;
1569 size_t _total_regions;
1570 public:
1571 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1572 ~FillableRegionLogger() {
1573 log.trace("%zu initially fillable regions", _total_regions);
1574 }
1575
1576 void print_line() {
1577 if (!_enabled || _next_index == 0) {
1578 return;
1579 }
1580 FormatBuffer<> line("Fillable: ");
1581 for (int i = 0; i < _next_index; i++) {
1582 line.append(" %7zu", _regions[i]);
1583 }
1584 log.trace("%s", line.buffer());
1585 _next_index = 0;
1586 }
1587
1588 void handle(size_t region) {
1589 if (!_enabled) {
1590 return;
1591 }
1592 _regions[_next_index++] = region;
1593 if (_next_index == LineLength) {
1594 print_line();
1595 }
1596 _total_regions++;
1597 }
1598 };
1599
1600 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1601 {
1602 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1603
1604 // Find the threads that are active
1605 uint worker_id = 0;
1606
1607 // Find all regions that are available (can be filled immediately) and
1608 // distribute them to the thread stacks. The iteration is done in reverse
1609 // order (high to low) so the regions will be removed in ascending order.
1610
1611 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1612
1613 // id + 1 is used to test termination so unsigned can
1614 // be used with an old_space_id == 0.
1615 FillableRegionLogger region_logger;
1616 for (unsigned int id = last_space_id - 1; id + 1 > old_space_id; --id) {
1617 SpaceInfo* const space_info = _space_info + id;
1618 HeapWord* const new_top = space_info->new_top();
1619
1620 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1621 const size_t end_region =
1622 sd.addr_to_region_idx(sd.region_align_up(new_top));
1623
1624 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1625 if (sd.region(cur)->claim_unsafe()) {
1626 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1627 bool result = sd.region(cur)->mark_normal();
1628 assert(result, "Must succeed at this point.");
1629 cm->region_stack()->push(cur);
1630 region_logger.handle(cur);
1631 // Assign regions to tasks in round-robin fashion.
1632 if (++worker_id == parallel_gc_threads) {
1633 worker_id = 0;
1634 }
1635 }
1636 }
1637 region_logger.print_line();
1638 }
1639 }
1640
1641 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1642 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1643
1644 ParCompactionManager* cm =
1645 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1646
1647 // Drain the stacks that have been preloaded with regions
1648 // that are ready to fill.
1649
1650 cm->drain_region_stacks();
1651
1652 guarantee(cm->region_stack()->is_empty(), "Not empty");
1653
1654 size_t region_index = 0;
1655
1656 while (true) {
1657 if (ParCompactionManager::steal(worker_id, region_index)) {
1658 PSParallelCompact::fill_and_update_region(cm, region_index);
1659 cm->drain_region_stacks();
1660 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1661 // Fill and update an unavailable region with the help of a shadow region
1662 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1663 cm->drain_region_stacks();
1664 } else {
1665 if (terminator->offer_termination()) {
1666 break;
1667 }
1668 // Go around again.
1669 }
1670 }
1671 }
1672
1673 class FillDensePrefixAndCompactionTask: public WorkerTask {
1674 TaskTerminator _terminator;
1675
1676 public:
1677 FillDensePrefixAndCompactionTask(uint active_workers) :
1678 WorkerTask("FillDensePrefixAndCompactionTask"),
1679 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1680 }
1681
1682 virtual void work(uint worker_id) {
1683 if (worker_id == 0) {
1684 auto start = Ticks::now();
1685 PSParallelCompact::fill_dead_objs_in_dense_prefix();
1686 log_trace(gc, phases)("Fill dense prefix by worker 0: %.3f ms", (Ticks::now() - start).seconds() * 1000);
1687 }
1688 compaction_with_stealing_work(&_terminator, worker_id);
1689 }
1690 };
1691
1692 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1693 #ifdef ASSERT
1694 {
1695 assert(start < end, "precondition");
1696 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1697 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1698 if (start != bottom) {
1699 // The preceding live obj.
1700 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1701 HeapWord* obj_end = obj_start + cast_to_oop(obj_start)->size();
1702 assert(obj_end == start, "precondition");
1703 }
1704 }
1705 #endif
1706
1707 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1708 HeapWord* addr = start;
1709 do {
1710 size_t size = cast_to_oop(addr)->size();
1711 start_array(old_space_id)->update_for_block(addr, addr + size);
1712 addr += size;
1713 } while (addr < end);
1714 }
1715
1716 void PSParallelCompact::fill_dead_objs_in_dense_prefix() {
1717 ParMarkBitMap* bitmap = mark_bitmap();
1718
1719 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1720 HeapWord* const prefix_end = dense_prefix(old_space_id);
1721
1722 const size_t region_size = ParallelCompactData::RegionSize;
1723
1724 // Fill dead space in [start_addr, end_addr)
1725 HeapWord* const start_addr = bottom;
1726 HeapWord* const end_addr = prefix_end;
1727
1728 for (HeapWord* cur_addr = start_addr; cur_addr < end_addr; /* empty */) {
1729 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1730 if (cur_region_ptr->data_size() == region_size) {
1731 // Full; no dead space. Next region.
1732 if (_summary_data.is_region_aligned(cur_addr)) {
1733 cur_addr += region_size;
1734 } else {
1735 cur_addr = _summary_data.region_align_up(cur_addr);
1736 }
1737 continue;
1738 }
1739
1740 // Fill dead space inside cur_region.
1741 if (_summary_data.is_region_aligned(cur_addr)) {
1742 cur_addr += cur_region_ptr->partial_obj_size();
1743 }
1744
1745 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1746 assert(region_end_addr <= end_addr, "inv");
1747 while (cur_addr < region_end_addr) {
1748 // Use end_addr to allow filler-obj to cross region boundary.
1749 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, end_addr);
1750 if (cur_addr != live_start) {
1751 // Found dead space [cur_addr, live_start).
1752 fill_range_in_dense_prefix(cur_addr, live_start);
1753 }
1754 if (live_start >= region_end_addr) {
1755 cur_addr = live_start;
1756 break;
1757 }
1758 assert(bitmap->is_marked(live_start), "inv");
1759 cur_addr = live_start + cast_to_oop(live_start)->size();
1760 }
1761 }
1762 }
1763
1764 void PSParallelCompact::compact() {
1765 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1766
1767 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1768
1769 initialize_shadow_regions(active_gc_threads);
1770 prepare_region_draining_tasks(active_gc_threads);
1771
1772 {
1773 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1774
1775 FillDensePrefixAndCompactionTask task(active_gc_threads);
1776 ParallelScavengeHeap::heap()->workers().run_task(&task);
1777
1778 #ifdef ASSERT
1779 verify_filler_in_dense_prefix();
1780
1781 // Verify that all regions have been processed.
1782 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1783 verify_complete(SpaceId(id));
1784 }
1785 #endif
1786 }
1787 }
1788
1789 #ifdef ASSERT
1790 void PSParallelCompact::verify_filler_in_dense_prefix() {
1791 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1792 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1793
1794 const size_t region_size = ParallelCompactData::RegionSize;
1795
1796 for (HeapWord* cur_addr = bottom; cur_addr < dense_prefix_end; /* empty */) {
1797 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1798 if (cur_region_ptr->data_size() == region_size) {
1799 // Full; no dead space. Next region.
1800 if (_summary_data.is_region_aligned(cur_addr)) {
1801 cur_addr += region_size;
1802 } else {
1803 cur_addr = _summary_data.region_align_up(cur_addr);
1804 }
1805 continue;
1806 }
1807
1808 // This region contains filler objs.
1809 if (_summary_data.is_region_aligned(cur_addr)) {
1810 cur_addr += cur_region_ptr->partial_obj_size();
1811 }
1812
1813 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1814 assert(region_end_addr <= dense_prefix_end, "inv");
1815
1816 while (cur_addr < region_end_addr) {
1817 oop obj = cast_to_oop(cur_addr);
1818 oopDesc::verify(obj);
1819 if (!mark_bitmap()->is_marked(cur_addr)) {
1820 assert(CollectedHeap::is_filler_object(cast_to_oop(cur_addr)), "inv");
1821 }
1822 cur_addr += obj->size();
1823 }
1824 }
1825 }
1826
1827 void PSParallelCompact::verify_complete(SpaceId space_id) {
1828 // All Regions served as compaction targets, from dense_prefix() to
1829 // new_top(), should be marked as filled and all Regions between new_top()
1830 // and top() should be available (i.e., should have been emptied).
1831 ParallelCompactData& sd = summary_data();
1832 SpaceInfo si = _space_info[space_id];
1833 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1834 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1835 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1836 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1837 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1838
1839 size_t cur_region;
1840 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1841 const RegionData* const c = sd.region(cur_region);
1842 assert(c->completed(), "region %zu not filled: destination_count=%u",
1843 cur_region, c->destination_count());
1844 }
1845
1846 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1847 const RegionData* const c = sd.region(cur_region);
1848 assert(c->available(), "region %zu not empty: destination_count=%u",
1849 cur_region, c->destination_count());
1850 }
1851 }
1852 #endif // #ifdef ASSERT
1853
1854 // Return the SpaceId for the space containing addr. If addr is not in the
1855 // heap, last_space_id is returned. In debug mode it expects the address to be
1856 // in the heap and asserts such.
1857 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1858 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1859
1860 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1861 if (_space_info[id].space()->contains(addr)) {
1862 return SpaceId(id);
1863 }
1864 }
1865
1866 assert(false, "no space contains the addr");
1867 return last_space_id;
1868 }
1869
1870 // Skip over count live words starting from beg, and return the address of the
1871 // next live word. Callers must also ensure that there are enough live words in
1872 // the range [beg, end) to skip.
1873 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1874 {
1875 ParMarkBitMap* m = mark_bitmap();
1876 HeapWord* cur_addr = beg;
1877 while (true) {
1878 cur_addr = m->find_obj_beg(cur_addr, end);
1879 assert(cur_addr < end, "inv");
1880 size_t obj_size = cast_to_oop(cur_addr)->size();
1881 // Strictly greater-than
1882 if (obj_size > count) {
1883 return cur_addr + count;
1884 }
1885 count -= obj_size;
1886 cur_addr += obj_size;
1887 }
1888 }
1889
1890 // On starting to fill a destination region (dest-region), we need to know the
1891 // location of the word that will be at the start of the dest-region after
1892 // compaction. A dest-region can have one or more source regions, but only the
1893 // first source-region contains this location. This location is retrieved by
1894 // calling `first_src_addr` on a dest-region.
1895 // Conversely, a source-region has a dest-region which holds the destination of
1896 // the first live word on this source-region, based on which the destination
1897 // for the rest of live words can be derived.
1898 //
1899 // Note:
1900 // There is some complication due to space-boundary-fragmentation (an obj can't
1901 // cross space-boundary) -- a source-region may be split and behave like two
1902 // distinct regions with their own dest-region, as depicted below.
1903 //
1904 // source-region: region-n
1905 //
1906 // **********************
1907 // | A|A~~~~B|B |
1908 // **********************
1909 // n-1 n n+1
1910 //
1911 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
1912 //
1913 // Assuming the dest-region for region-n is the final region before
1914 // old-space-end and its first-live-word is the middle of AA, the heap content
1915 // will look like the following after compaction:
1916 //
1917 // ************** *************
1918 // A|A~~~~ | |BB |
1919 // ************** *************
1920 // ^ ^
1921 // | old-space-end | eden-space-start
1922 //
1923 // Therefore, in this example, region-n will have two dest-regions:
1924 // 1. the final region in old-space
1925 // 2. the first region in eden-space.
1926 // To handle this special case, we introduce the concept of split-region, whose
1927 // contents are relocated to two spaces. `SplitInfo` captures all necessary
1928 // info about the split, the first part, spliting-point, and the second part.
1929 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
1930 SpaceId src_space_id,
1931 size_t src_region_idx)
1932 {
1933 const size_t RegionSize = ParallelCompactData::RegionSize;
1934 const ParallelCompactData& sd = summary_data();
1935 assert(sd.is_region_aligned(dest_addr), "precondition");
1936
1937 const RegionData* const src_region_ptr = sd.region(src_region_idx);
1938 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
1939
1940 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
1941 HeapWord* const src_region_destination = src_region_ptr->destination();
1942
1943 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
1944 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
1945
1946 // Identify the actual destination for the first live words on this region,
1947 // taking split-region into account.
1948 HeapWord* region_start_destination;
1949 const SplitInfo& split_info = _space_info[src_space_id].split_info();
1950 if (split_info.is_split(src_region_idx)) {
1951 // The second part of this split region; use the recorded split point.
1952 if (dest_addr == src_region_destination) {
1953 return split_info.split_point();
1954 }
1955 region_start_destination = split_info.preceding_destination();
1956 } else {
1957 region_start_destination = src_region_destination;
1958 }
1959
1960 // Calculate the offset to be skipped
1961 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
1962
1963 HeapWord* result;
1964 if (partial_obj_size > words_to_skip) {
1965 result = region_start + words_to_skip;
1966 } else {
1967 words_to_skip -= partial_obj_size;
1968 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
1969 }
1970
1971 if (split_info.is_split(src_region_idx)) {
1972 assert(result < split_info.split_point(), "postcondition");
1973 } else {
1974 assert(result < region_end, "postcondition");
1975 }
1976
1977 return result;
1978 }
1979
1980 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
1981 SpaceId src_space_id,
1982 size_t beg_region,
1983 HeapWord* end_addr)
1984 {
1985 ParallelCompactData& sd = summary_data();
1986
1987 #ifdef ASSERT
1988 MutableSpace* const src_space = _space_info[src_space_id].space();
1989 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
1990 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
1991 "src_space_id does not match beg_addr");
1992 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
1993 "src_space_id does not match end_addr");
1994 #endif // #ifdef ASSERT
1995
1996 RegionData* const beg = sd.region(beg_region);
1997 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
1998
1999 // Regions up to new_top() are enqueued if they become available.
2000 HeapWord* const new_top = _space_info[src_space_id].new_top();
2001 RegionData* const enqueue_end =
2002 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2003
2004 for (RegionData* cur = beg; cur < end; ++cur) {
2005 assert(cur->data_size() > 0, "region must have live data");
2006 cur->decrement_destination_count();
2007 if (cur < enqueue_end && cur->available() && cur->claim()) {
2008 if (cur->mark_normal()) {
2009 cm->push_region(sd.region(cur));
2010 } else if (cur->mark_copied()) {
2011 // Try to copy the content of the shadow region back to its corresponding
2012 // heap region if the shadow region is filled. Otherwise, the GC thread
2013 // fills the shadow region will copy the data back (see
2014 // MoveAndUpdateShadowClosure::complete_region).
2015 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2016 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2017 cur->set_completed();
2018 }
2019 }
2020 }
2021 }
2022
2023 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2024 SpaceId& src_space_id,
2025 HeapWord*& src_space_top,
2026 HeapWord* end_addr)
2027 {
2028 ParallelCompactData& sd = PSParallelCompact::summary_data();
2029
2030 size_t src_region_idx = 0;
2031
2032 // Skip empty regions (if any) up to the top of the space.
2033 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2034 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2035 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2036 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2037
2038 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2039 ++src_region_ptr;
2040 }
2041
2042 if (src_region_ptr < top_region_ptr) {
2043 // Found the first non-empty region in the same space.
2044 src_region_idx = sd.region(src_region_ptr);
2045 closure.set_source(sd.region_to_addr(src_region_idx));
2046 return src_region_idx;
2047 }
2048
2049 // Switch to a new source space and find the first non-empty region.
2050 uint space_id = src_space_id + 1;
2051 assert(space_id < last_space_id, "not enough spaces");
2052
2053 for (/* empty */; space_id < last_space_id; ++space_id) {
2054 HeapWord* bottom = _space_info[space_id].space()->bottom();
2055 HeapWord* top = _space_info[space_id].space()->top();
2056 // Skip empty space
2057 if (bottom == top) {
2058 continue;
2059 }
2060
2061 // Identify the first region that contains live words in this space
2062 size_t cur_region = sd.addr_to_region_idx(bottom);
2063 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2064
2065 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2066 RegionData* cur = sd.region(cur_region);
2067 if (cur->live_obj_size() > 0) {
2068 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2069
2070 src_space_id = SpaceId(space_id);
2071 src_space_top = top;
2072 closure.set_source(region_start_addr);
2073 return cur_region;
2074 }
2075 }
2076 }
2077
2078 ShouldNotReachHere();
2079 }
2080
2081 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2082 ParallelCompactData& sd = summary_data();
2083 assert(sd.is_region_aligned(region_start_addr), "precondition");
2084
2085 // Use per-region partial_obj_size to locate the end of the obj, that extends
2086 // to region_start_addr.
2087 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2088 size_t end_region_idx = sd.region_count();
2089 size_t accumulated_size = 0;
2090 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2091 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2092 accumulated_size += cur_partial_obj_size;
2093 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2094 break;
2095 }
2096 }
2097 return region_start_addr + accumulated_size;
2098 }
2099
2100 // Use region_idx as the destination region, and evacuate all live objs on its
2101 // source regions to this destination region.
2102 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2103 {
2104 ParMarkBitMap* const bitmap = mark_bitmap();
2105 ParallelCompactData& sd = summary_data();
2106 RegionData* const region_ptr = sd.region(region_idx);
2107
2108 // Get the source region and related info.
2109 size_t src_region_idx = region_ptr->source_region();
2110 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2111 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2112 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2113
2114 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2115
2116 // Adjust src_region_idx to prepare for decrementing destination counts (the
2117 // destination count is not decremented when a region is copied to itself).
2118 if (src_region_idx == region_idx) {
2119 src_region_idx += 1;
2120 }
2121
2122 // source-region:
2123 //
2124 // **********
2125 // | ~~~ |
2126 // **********
2127 // ^
2128 // |-- closure.source() / first_src_addr
2129 //
2130 //
2131 // ~~~ : live words
2132 //
2133 // destination-region:
2134 //
2135 // **********
2136 // | |
2137 // **********
2138 // ^
2139 // |-- region-start
2140 if (bitmap->is_unmarked(closure.source())) {
2141 // An object overflows the previous destination region, so this
2142 // destination region should copy the remainder of the object or as much as
2143 // will fit.
2144 HeapWord* const old_src_addr = closure.source();
2145 {
2146 HeapWord* region_start = sd.region_align_down(closure.source());
2147 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2148 HeapWord* obj_end;
2149 if (obj_start != closure.source()) {
2150 assert(bitmap->is_marked(obj_start), "inv");
2151 // Found the actual obj-start, try to find the obj-end using either
2152 // size() if this obj is completely contained in the current region.
2153 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2154 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2155 ? nullptr
2156 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2157 // This obj extends to next region iff partial_obj_addr of the *next*
2158 // region is the same as obj-start.
2159 if (partial_obj_start == obj_start) {
2160 // This obj extends to next region.
2161 obj_end = partial_obj_end(next_region_start);
2162 } else {
2163 // Completely contained in this region; safe to use size().
2164 obj_end = obj_start + cast_to_oop(obj_start)->size();
2165 }
2166 } else {
2167 // This obj extends to current region.
2168 obj_end = partial_obj_end(region_start);
2169 }
2170 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2171 closure.copy_partial_obj(partial_obj_size);
2172 }
2173
2174 if (closure.is_full()) {
2175 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2176 closure.complete_region(dest_addr, region_ptr);
2177 return;
2178 }
2179
2180 // Finished copying without using up the current destination-region
2181 HeapWord* const end_addr = sd.region_align_down(closure.source());
2182 if (sd.region_align_down(old_src_addr) != end_addr) {
2183 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2184 // The partial object was copied from more than one source region.
2185 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2186
2187 // Move to the next source region, possibly switching spaces as well. All
2188 // args except end_addr may be modified.
2189 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2190 }
2191 }
2192
2193 // Handle the rest obj-by-obj, where we know obj-start.
2194 do {
2195 HeapWord* cur_addr = closure.source();
2196 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2197 src_space_top);
2198 // To handle the case where the final obj in source region extends to next region.
2199 HeapWord* final_obj_start = (end_addr == src_space_top)
2200 ? nullptr
2201 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2202 // Apply closure on objs inside [cur_addr, end_addr)
2203 do {
2204 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2205 if (cur_addr == end_addr) {
2206 break;
2207 }
2208 size_t obj_size;
2209 if (final_obj_start == cur_addr) {
2210 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2211 } else {
2212 // This obj doesn't extend into next region; size() is safe to use.
2213 obj_size = cast_to_oop(cur_addr)->size();
2214 }
2215 closure.do_addr(cur_addr, obj_size);
2216 cur_addr += obj_size;
2217 } while (cur_addr < end_addr && !closure.is_full());
2218
2219 if (closure.is_full()) {
2220 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2221 closure.complete_region(dest_addr, region_ptr);
2222 return;
2223 }
2224
2225 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2226
2227 // Move to the next source region, possibly switching spaces as well. All
2228 // args except end_addr may be modified.
2229 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2230 } while (true);
2231 }
2232
2233 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2234 {
2235 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2236 fill_region(cm, cl, region_idx);
2237 }
2238
2239 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2240 {
2241 // Get a shadow region first
2242 ParallelCompactData& sd = summary_data();
2243 RegionData* const region_ptr = sd.region(region_idx);
2244 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2245 // The InvalidShadow return value indicates the corresponding heap region is available,
2246 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2247 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2248 if (shadow_region == ParCompactionManager::InvalidShadow) {
2249 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2250 region_ptr->shadow_to_normal();
2251 return fill_region(cm, cl, region_idx);
2252 } else {
2253 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2254 return fill_region(cm, cl, region_idx);
2255 }
2256 }
2257
2258 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2259 {
2260 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2261 }
2262
2263 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2264 {
2265 size_t next = cm->next_shadow_region();
2266 ParallelCompactData& sd = summary_data();
2267 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2268 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2269
2270 while (next < old_new_top) {
2271 if (sd.region(next)->mark_shadow()) {
2272 region_idx = next;
2273 return true;
2274 }
2275 next = cm->move_next_shadow_region_by(active_gc_threads);
2276 }
2277
2278 return false;
2279 }
2280
2281 // The shadow region is an optimization to address region dependencies in full GC. The basic
2282 // idea is making more regions available by temporally storing their live objects in empty
2283 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2284 // GC threads need not wait destination regions to be available before processing sources.
2285 //
2286 // A typical workflow would be:
2287 // After draining its own stack and failing to steal from others, a GC worker would pick an
2288 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2289 // the shadow region by copying live objects from source regions of the unavailable one. Once
2290 // the unavailable region becomes available, the data in the shadow region will be copied back.
2291 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2292 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2293 {
2294 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2295
2296 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2297 SpaceInfo* const space_info = _space_info + id;
2298 MutableSpace* const space = space_info->space();
2299
2300 const size_t beg_region =
2301 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2302 const size_t end_region =
2303 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2304
2305 for (size_t cur = beg_region; cur < end_region; ++cur) {
2306 ParCompactionManager::push_shadow_region(cur);
2307 }
2308 }
2309
2310 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2311 for (uint i = 0; i < parallel_gc_threads; i++) {
2312 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2313 cm->set_next_shadow_region(beg_region + i);
2314 }
2315 }
2316
2317 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2318 {
2319 size_t words = MIN2(partial_obj_size, words_remaining());
2320
2321 // This test is necessary; if omitted, the pointer updates to a partial object
2322 // that crosses the dense prefix boundary could be overwritten.
2323 if (source() != copy_destination()) {
2324 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2325 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2326 }
2327 update_state(words);
2328 }
2329
2330 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2331 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2332 region_ptr->set_completed();
2333 }
2334
2335 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2336 assert(destination() != nullptr, "sanity");
2337 _source = addr;
2338
2339 // The start_array must be updated even if the object is not moving.
2340 if (_start_array != nullptr) {
2341 _start_array->update_for_block(destination(), destination() + words);
2342 }
2343
2344 // Avoid overflow
2345 words = MIN2(words, words_remaining());
2346 assert(words > 0, "inv");
2347
2348 if (copy_destination() != source()) {
2349 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2350 assert(source() != destination(), "inv");
2351 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2352 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2353 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2354 cast_to_oop(copy_destination())->reinit_mark();
2355 }
2356
2357 update_state(words);
2358 }
2359
2360 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2361 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2362 // Record the shadow region index
2363 region_ptr->set_shadow_region(_shadow);
2364 // Mark the shadow region as filled to indicate the data is ready to be
2365 // copied back
2366 region_ptr->mark_filled();
2367 // Try to copy the content of the shadow region back to its corresponding
2368 // heap region if available; the GC thread that decreases the destination
2369 // count to zero will do the copying otherwise (see
2370 // PSParallelCompact::decrement_destination_counts).
2371 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2372 region_ptr->set_completed();
2373 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2374 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2375 }
2376 }