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/atomicAccess.hpp"
88 #include "runtime/handles.inline.hpp"
89 #include "runtime/java.hpp"
90 #include "runtime/safepoint.hpp"
91 #include "runtime/threads.hpp"
92 #include "runtime/vmThread.hpp"
93 #include "services/memoryService.hpp"
94 #include "utilities/align.hpp"
95 #include "utilities/debug.hpp"
96 #include "utilities/events.hpp"
97 #include "utilities/formatBuffer.hpp"
98 #include "utilities/macros.hpp"
99 #include "utilities/stack.inline.hpp"
100 #if INCLUDE_JVMCI
101 #include "jvmci/jvmci.hpp"
102 #endif
103
104 #include <math.h>
105
106 // All sizes are in HeapWords.
107 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
108 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
109 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
110 const size_t ParallelCompactData::RegionSizeBytes =
111 RegionSize << LogHeapWordSize;
112 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
113 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
114 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
115
116 const ParallelCompactData::RegionData::region_sz_t
117 ParallelCompactData::RegionData::dc_shift = 27;
118
119 const ParallelCompactData::RegionData::region_sz_t
120 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
121
122 const ParallelCompactData::RegionData::region_sz_t
123 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
124
125 const ParallelCompactData::RegionData::region_sz_t
126 ParallelCompactData::RegionData::los_mask = ~dc_mask;
127
128 const ParallelCompactData::RegionData::region_sz_t
129 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
130
131 const ParallelCompactData::RegionData::region_sz_t
132 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
133
134 bool ParallelCompactData::RegionData::is_clear() {
135 return (_destination == nullptr) &&
136 (_source_region == 0) &&
137 (_partial_obj_addr == nullptr) &&
138 (_partial_obj_size == 0) &&
139 (dc_and_los() == 0) &&
140 (shadow_state() == 0);
141 }
142
143 #ifdef ASSERT
144 void ParallelCompactData::RegionData::verify_clear() {
145 assert(_destination == nullptr, "inv");
146 assert(_source_region == 0, "inv");
147 assert(_partial_obj_addr == nullptr, "inv");
148 assert(_partial_obj_size == 0, "inv");
149 assert(dc_and_los() == 0, "inv");
150 assert(shadow_state() == 0, "inv");
151 }
152 #endif
153
154 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
155
156 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
157 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
158
159 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
160 assert(split_region_idx != 0, "precondition");
161
162 // Obj denoted by split_point will be deferred to the next space.
163 assert(split_point != nullptr, "precondition");
164
165 const ParallelCompactData& sd = PSParallelCompact::summary_data();
166
167 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
168 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
169
170 HeapWord* preceding_destination = split_region_ptr->destination();
171 assert(preceding_destination != nullptr, "inv");
172
173 // How many regions does the preceding part occupy
174 uint preceding_destination_count;
175 if (preceding_live_words == 0) {
176 preceding_destination_count = 0;
177 } else {
178 // -1 so that the ending address doesn't fall on the region-boundary
179 if (sd.region_align_down(preceding_destination) ==
180 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
181 preceding_destination_count = 1;
182 } else {
183 preceding_destination_count = 2;
184 }
185 }
186
187 _split_region_idx = split_region_idx;
188 _split_point = split_point;
189 _preceding_live_words = preceding_live_words;
190 _preceding_destination = preceding_destination;
191 _preceding_destination_count = preceding_destination_count;
192 }
193
194 void SplitInfo::clear()
195 {
196 _split_region_idx = 0;
197 _split_point = nullptr;
198 _preceding_live_words = 0;
199 _preceding_destination = nullptr;
200 _preceding_destination_count = 0;
201 assert(!is_valid(), "sanity");
202 }
203
204 #ifdef ASSERT
205 void SplitInfo::verify_clear()
206 {
207 assert(_split_region_idx == 0, "not clear");
208 assert(_split_point == nullptr, "not clear");
209 assert(_preceding_live_words == 0, "not clear");
210 assert(_preceding_destination == nullptr, "not clear");
211 assert(_preceding_destination_count == 0, "not clear");
212 }
213 #endif // #ifdef ASSERT
214
215
216 void PSParallelCompact::print_on(outputStream* st) {
217 _mark_bitmap.print_on(st);
218 }
219
220 ParallelCompactData::ParallelCompactData() :
221 _heap_start(nullptr),
222 DEBUG_ONLY(_heap_end(nullptr) COMMA)
223 _region_vspace(nullptr),
224 _reserved_byte_size(0),
225 _region_data(nullptr),
226 _region_count(0) {}
227
228 bool ParallelCompactData::initialize(MemRegion reserved_heap)
229 {
230 _heap_start = reserved_heap.start();
231 const size_t heap_size = reserved_heap.word_size();
232 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
233
234 assert(region_align_down(_heap_start) == _heap_start,
235 "region start not aligned");
236
237 return initialize_region_data(heap_size);
238 }
239
240 PSVirtualSpace*
241 ParallelCompactData::create_vspace(size_t count, size_t element_size)
242 {
243 const size_t raw_bytes = count * element_size;
244 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
245 const size_t granularity = os::vm_allocation_granularity();
246 const size_t rs_align = MAX2(page_sz, granularity);
247
248 _reserved_byte_size = align_up(raw_bytes, rs_align);
249
250 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
251 rs_align,
252 page_sz,
253 mtGC);
254
255 if (!rs.is_reserved()) {
256 // Failed to reserve memory.
257 return nullptr;
258 }
259
260 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
261 rs.size(), page_sz);
262
263 MemTracker::record_virtual_memory_tag(rs, mtGC);
264
265 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
266
267 if (!vspace->expand_by(_reserved_byte_size)) {
268 // Failed to commit memory.
269
270 delete vspace;
271
272 // Release memory reserved in the space.
273 MemoryReserver::release(rs);
274
275 return nullptr;
276 }
277
278 return vspace;
279 }
280
281 bool ParallelCompactData::initialize_region_data(size_t heap_size)
282 {
283 assert(is_aligned(heap_size, RegionSize), "precondition");
284
285 const size_t count = heap_size >> Log2RegionSize;
286 _region_vspace = create_vspace(count, sizeof(RegionData));
287 if (_region_vspace != nullptr) {
288 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
289 _region_count = count;
290 return true;
291 }
292 return false;
293 }
294
295 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
296 assert(beg_region <= _region_count, "beg_region out of range");
297 assert(end_region <= _region_count, "end_region out of range");
298
299 const size_t region_cnt = end_region - beg_region;
300 for (size_t i = beg_region; i < end_region; i++) {
301 ::new (&_region_data[i]) RegionData{};
302 }
303 }
304
305 // The total live words on src_region would overflow the target space, so find
306 // the overflowing object and record the split point. The invariant is that an
307 // obj should not cross space boundary.
308 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
309 SplitInfo& split_info,
310 HeapWord* const destination,
311 HeapWord* const target_end,
312 HeapWord** target_next) {
313 assert(destination <= target_end, "sanity");
314 assert(destination + _region_data[src_region].data_size() > target_end,
315 "region should not fit into target space");
316 assert(is_region_aligned(target_end), "sanity");
317
318 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
319
320 if (destination + partial_obj_size > target_end) {
321 assert(partial_obj_size > 0, "inv");
322 // The overflowing obj is from a previous region.
323 //
324 // source-regions:
325 //
326 // ***************
327 // | A|AA |
328 // ***************
329 // ^
330 // | split-point
331 //
332 // dest-region:
333 //
334 // ********
335 // |~~~~A |
336 // ********
337 // ^^
338 // || target-space-end
339 // |
340 // | destination
341 //
342 // AAA would overflow target-space.
343 //
344 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
345 size_t split_region = addr_to_region_idx(overflowing_obj);
346
347 // The number of live words before the overflowing object on this split region
348 size_t preceding_live_words;
349 if (is_region_aligned(overflowing_obj)) {
350 preceding_live_words = 0;
351 } else {
352 // Words accounted by the overflowing object on the split region
353 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
354 preceding_live_words = region(split_region)->data_size() - overflowing_size;
355 }
356
357 split_info.record(split_region, overflowing_obj, preceding_live_words);
358
359 // The [overflowing_obj, src_region_start) part has been accounted for, so
360 // must move back the new_top, now that this overflowing obj is deferred.
361 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
362
363 // If the overflowing obj was relocated to its original destination,
364 // those destination regions would have their source_region set. Now that
365 // this overflowing obj is relocated somewhere else, reset the
366 // source_region.
367 {
368 size_t range_start = addr_to_region_idx(region_align_up(new_top));
369 size_t range_end = addr_to_region_idx(region_align_up(destination));
370 for (size_t i = range_start; i < range_end; ++i) {
371 region(i)->set_source_region(0);
372 }
373 }
374
375 // Update new top of target space
376 *target_next = new_top;
377
378 return overflowing_obj;
379 }
380
381 // Obj-iteration to locate the overflowing obj
382 HeapWord* region_start = region_to_addr(src_region);
383 HeapWord* region_end = region_start + RegionSize;
384 HeapWord* cur_addr = region_start + partial_obj_size;
385 size_t live_words = partial_obj_size;
386
387 while (true) {
388 assert(cur_addr < region_end, "inv");
389 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
390 // There must be an overflowing obj in this region
391 assert(cur_addr < region_end, "inv");
392
393 oop obj = cast_to_oop(cur_addr);
394 size_t obj_size = obj->size();
395 if (destination + live_words + obj_size > target_end) {
396 // Found the overflowing obj
397 split_info.record(src_region, cur_addr, live_words);
398 *target_next = destination + live_words;
399 return cur_addr;
400 }
401
402 live_words += obj_size;
403 cur_addr += obj_size;
404 }
405 }
406
407 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
408 HeapWord** full_region_prefix_end) {
409 size_t cur_region = addr_to_region_idx(space->bottom());
410 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
411 size_t live_words = 0;
412 if (full_region_prefix_end == nullptr) {
413 for (/* empty */; cur_region < end_region; ++cur_region) {
414 live_words += _region_data[cur_region].data_size();
415 }
416 } else {
417 bool first_set = false;
418 for (/* empty */; cur_region < end_region; ++cur_region) {
419 size_t live_words_in_region = _region_data[cur_region].data_size();
420 if (!first_set && live_words_in_region < RegionSize) {
421 *full_region_prefix_end = region_to_addr(cur_region);
422 first_set = true;
423 }
424 live_words += live_words_in_region;
425 }
426 if (!first_set) {
427 // All regions are full of live objs.
428 assert(is_region_aligned(space->top()), "inv");
429 *full_region_prefix_end = space->top();
430 }
431 assert(*full_region_prefix_end != nullptr, "postcondition");
432 assert(is_region_aligned(*full_region_prefix_end), "inv");
433 assert(*full_region_prefix_end >= space->bottom(), "in-range");
434 assert(*full_region_prefix_end <= space->top(), "in-range");
435 }
436 return live_words;
437 }
438
439 bool ParallelCompactData::summarize(SplitInfo& split_info,
440 HeapWord* source_beg, HeapWord* source_end,
441 HeapWord** source_next,
442 HeapWord* target_beg, HeapWord* target_end,
443 HeapWord** target_next)
444 {
445 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
446 log_develop_trace(gc, compaction)(
447 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
448 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
449 p2i(source_beg), p2i(source_end), p2i(source_next_val),
450 p2i(target_beg), p2i(target_end), p2i(*target_next));
451
452 size_t cur_region = addr_to_region_idx(source_beg);
453 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
454
455 HeapWord *dest_addr = target_beg;
456 for (/* empty */; cur_region < end_region; cur_region++) {
457 size_t words = _region_data[cur_region].data_size();
458
459 // Skip empty ones
460 if (words == 0) {
461 continue;
462 }
463
464 if (split_info.is_split(cur_region)) {
465 assert(words > split_info.preceding_live_words(), "inv");
466 words -= split_info.preceding_live_words();
467 }
468
469 _region_data[cur_region].set_destination(dest_addr);
470
471 // If cur_region does not fit entirely into the target space, find a point
472 // at which the source space can be 'split' so that part is copied to the
473 // target space and the rest is copied elsewhere.
474 if (dest_addr + words > target_end) {
475 assert(source_next != nullptr, "source_next is null when splitting");
476 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
477 target_end, target_next);
478 return false;
479 }
480
481 uint destination_count = split_info.is_split(cur_region)
482 ? split_info.preceding_destination_count()
483 : 0;
484
485 HeapWord* const last_addr = dest_addr + words - 1;
486 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
487 const size_t dest_region_2 = addr_to_region_idx(last_addr);
488
489 // Initially assume that the destination regions will be the same and
490 // adjust the value below if necessary. Under this assumption, if
491 // cur_region == dest_region_2, then cur_region will be compacted
492 // completely into itself.
493 destination_count += cur_region == dest_region_2 ? 0 : 1;
494 if (dest_region_1 != dest_region_2) {
495 // Destination regions differ; adjust destination_count.
496 destination_count += 1;
497 // Data from cur_region will be copied to the start of dest_region_2.
498 _region_data[dest_region_2].set_source_region(cur_region);
499 } else if (is_region_aligned(dest_addr)) {
500 // Data from cur_region will be copied to the start of the destination
501 // region.
502 _region_data[dest_region_1].set_source_region(cur_region);
503 }
504
505 _region_data[cur_region].set_destination_count(destination_count);
506 dest_addr += words;
507 }
508
509 *target_next = dest_addr;
510 return true;
511 }
512
513 #ifdef ASSERT
514 void ParallelCompactData::verify_clear() {
515 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
516 if (!region(cur_idx)->is_clear()) {
517 log_warning(gc)("Uncleared Region: %u", cur_idx);
518 region(cur_idx)->verify_clear();
519 }
520 }
521 }
522 #endif // #ifdef ASSERT
523
524 STWGCTimer PSParallelCompact::_gc_timer;
525 ParallelOldTracer PSParallelCompact::_gc_tracer;
526 elapsedTimer PSParallelCompact::_accumulated_time;
527 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
528 CollectorCounters* PSParallelCompact::_counters = nullptr;
529 ParMarkBitMap PSParallelCompact::_mark_bitmap;
530 ParallelCompactData PSParallelCompact::_summary_data;
531
532 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
533
534 class PCAdjustPointerClosure: public BasicOopIterateClosure {
535 template <typename T>
536 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
537
538 public:
539 virtual void do_oop(oop* p) { do_oop_work(p); }
540 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
541
542 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
543 };
544
545 static PCAdjustPointerClosure pc_adjust_pointer_closure;
546
547 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
548
549 void PSParallelCompact::post_initialize() {
550 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
551 _span_based_discoverer.set_span(heap->reserved_region());
552 _ref_processor =
553 new ReferenceProcessor(&_span_based_discoverer,
554 ParallelGCThreads, // mt processing degree
555 ParallelGCThreads, // mt discovery degree
556 false, // concurrent_discovery
557 &_is_alive_closure); // non-header is alive closure
558
559 _counters = new CollectorCounters("Parallel full collection pauses", 1);
560
561 // Initialize static fields in ParCompactionManager.
562 ParCompactionManager::initialize(mark_bitmap());
563 }
564
565 bool PSParallelCompact::initialize_aux_data() {
566 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
567 MemRegion mr = heap->reserved_region();
568 assert(mr.byte_size() != 0, "heap should be reserved");
569
570 initialize_space_info();
571
572 if (!_mark_bitmap.initialize(mr)) {
573 vm_shutdown_during_initialization(
574 err_msg("Unable to allocate %zuKB bitmaps for parallel "
575 "garbage collection for the requested %zuKB heap.",
576 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
577 return false;
578 }
579
580 if (!_summary_data.initialize(mr)) {
581 vm_shutdown_during_initialization(
582 err_msg("Unable to allocate %zuKB card tables for parallel "
583 "garbage collection for the requested %zuKB heap.",
584 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
585 return false;
586 }
587
588 return true;
589 }
590
591 void PSParallelCompact::initialize_space_info()
592 {
593 memset(&_space_info, 0, sizeof(_space_info));
594
595 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
596 PSYoungGen* young_gen = heap->young_gen();
597
598 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
599 _space_info[eden_space_id].set_space(young_gen->eden_space());
600 _space_info[from_space_id].set_space(young_gen->from_space());
601 _space_info[to_space_id].set_space(young_gen->to_space());
602
603 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
604 }
605
606 void
607 PSParallelCompact::clear_data_covering_space(SpaceId id)
608 {
609 // At this point, top is the value before GC, new_top() is the value that will
610 // be set at the end of GC. The marking bitmap is cleared to top; nothing
611 // should be marked above top. The summary data is cleared to the larger of
612 // top & new_top.
613 MutableSpace* const space = _space_info[id].space();
614 HeapWord* const bot = space->bottom();
615 HeapWord* const top = space->top();
616 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
617
618 _mark_bitmap.clear_range(bot, top);
619
620 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
621 const size_t end_region =
622 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
623 _summary_data.clear_range(beg_region, end_region);
624
625 // Clear the data used to 'split' regions.
626 SplitInfo& split_info = _space_info[id].split_info();
627 if (split_info.is_valid()) {
628 split_info.clear();
629 }
630 DEBUG_ONLY(split_info.verify_clear();)
631 }
632
633 void PSParallelCompact::pre_compact()
634 {
635 // Update the from & to space pointers in space_info, since they are swapped
636 // at each young gen gc. Do the update unconditionally (even though a
637 // promotion failure does not swap spaces) because an unknown number of young
638 // collections will have swapped the spaces an unknown number of times.
639 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
640 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
641 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
642 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
643
644 heap->increment_total_collections(true);
645
646 CodeCache::on_gc_marking_cycle_start();
647
648 heap->print_before_gc();
649 heap->trace_heap_before_gc(&_gc_tracer);
650
651 // Fill in TLABs
652 heap->ensure_parsability(true); // retire TLABs
653
654 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
655 Universe::verify("Before GC");
656 }
657
658 DEBUG_ONLY(mark_bitmap()->verify_clear();)
659 DEBUG_ONLY(summary_data().verify_clear();)
660 }
661
662 void PSParallelCompact::post_compact()
663 {
664 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
665 ParCompactionManager::remove_all_shadow_regions();
666
667 CodeCache::on_gc_marking_cycle_finish();
668 CodeCache::arm_all_nmethods();
669
670 // Need to clear claim bits for the next full-gc (marking and adjust-pointers).
671 ClassLoaderDataGraph::clear_claimed_marks();
672
673 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
674 // Clear the marking bitmap, summary data and split info.
675 clear_data_covering_space(SpaceId(id));
676 {
677 MutableSpace* space = _space_info[id].space();
678 HeapWord* top = space->top();
679 HeapWord* new_top = _space_info[id].new_top();
680 if (ZapUnusedHeapArea && new_top < top) {
681 space->mangle_region(MemRegion(new_top, top));
682 }
683 // Update top(). Must be done after clearing the bitmap and summary data.
684 space->set_top(new_top);
685 }
686 }
687
688 #ifdef ASSERT
689 {
690 mark_bitmap()->verify_clear();
691 summary_data().verify_clear();
692 }
693 #endif
694
695 ParCompactionManager::flush_all_string_dedup_requests();
696
697 MutableSpace* const eden_space = _space_info[eden_space_id].space();
698 MutableSpace* const from_space = _space_info[from_space_id].space();
699 MutableSpace* const to_space = _space_info[to_space_id].space();
700
701 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
702 bool eden_empty = eden_space->is_empty();
703
704 // Update heap occupancy information which is used as input to the soft ref
705 // clearing policy at the next gc.
706 Universe::heap()->update_capacity_and_used_at_gc();
707
708 bool young_gen_empty = eden_empty && from_space->is_empty() &&
709 to_space->is_empty();
710
711 PSCardTable* ct = heap->card_table();
712 MemRegion old_mr = heap->old_gen()->committed();
713 if (young_gen_empty) {
714 ct->clear_MemRegion(old_mr);
715 } else {
716 ct->dirty_MemRegion(old_mr);
717 }
718
719 heap->prune_scavengable_nmethods();
720
721 #if COMPILER2_OR_JVMCI
722 DerivedPointerTable::update_pointers();
723 #endif
724
725 // Signal that we have completed a visit to all live objects.
726 Universe::heap()->record_whole_heap_examined_timestamp();
727 }
728
729 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
730 HeapWord* full_region_prefix_end) {
731 const size_t region_size = ParallelCompactData::RegionSize;
732 const ParallelCompactData& sd = summary_data();
733
734 // Iteration starts with the region *after* the full-region-prefix-end.
735 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
736 // If final region is not full, iteration stops before that region,
737 // because fill_dense_prefix_end assumes that prefix_end <= top.
738 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
739 assert(start_region <= end_region, "inv");
740
741 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
742 const RegionData* cur_region = start_region;
743 for (/* empty */; cur_region < end_region; ++cur_region) {
744 assert(region_size >= cur_region->data_size(), "inv");
745 size_t dead_size = region_size - cur_region->data_size();
746 if (max_waste < dead_size) {
747 break;
748 }
749 max_waste -= dead_size;
750 }
751
752 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
753 assert(sd.is_region_aligned(prefix_end), "postcondition");
754 assert(prefix_end >= full_region_prefix_end, "in-range");
755 assert(prefix_end <= old_space->top(), "in-range");
756 return prefix_end;
757 }
758
759 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
760 // Comparing two sizes to decide if filling is required:
761 //
762 // The size of the filler (min-obj-size) is 2 heap words with the default
763 // MinObjAlignment, since both markword and klass take 1 heap word.
764 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
765 // because the Klass* gets encoded in the mark-word.
766 //
767 // The size of the gap (if any) right before dense-prefix-end is
768 // MinObjAlignment.
769 //
770 // Need to fill in the gap only if it's smaller than min-obj-size, and the
771 // filler obj will extend to next region.
772
773 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
774 return;
775 }
776
777 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
778 assert(CollectedHeap::min_fill_size() == 2, "inv");
779 HeapWord* const dense_prefix_end = dense_prefix(id);
780 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
781 assert(dense_prefix_end <= space(id)->top(), "precondition");
782 if (dense_prefix_end == space(id)->top()) {
783 // Must not have single-word gap right before prefix-end/top.
784 return;
785 }
786 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
787
788 if (region_after_dense_prefix->partial_obj_size() != 0 ||
789 _mark_bitmap.is_marked(dense_prefix_end)) {
790 // The region after the dense prefix starts with live bytes.
791 return;
792 }
793
794 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
795 if (block_start == dense_prefix_end - 1) {
796 assert(!_mark_bitmap.is_marked(block_start), "inv");
797 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
798 // The filler object will extend into region_after_dense_prefix.
799 const size_t obj_len = 2; // min-fill-size
800 HeapWord* const obj_beg = dense_prefix_end - 1;
801 CollectedHeap::fill_with_object(obj_beg, obj_len);
802 _mark_bitmap.mark_obj(obj_beg);
803 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
804 region_after_dense_prefix->set_partial_obj_size(1);
805 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
806 assert(start_array(id) != nullptr, "sanity");
807 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
808 }
809 }
810
811 bool PSParallelCompact::check_maximum_compaction(bool should_do_max_compaction,
812 size_t total_live_words,
813 MutableSpace* const old_space,
814 HeapWord* full_region_prefix_end) {
815
816 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
817
818 // Check System.GC
819 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
820 && GCCause::is_user_requested_gc(heap->gc_cause());
821
822 // Check if all live objs are too much for old-gen.
823 const bool is_old_gen_too_full = (total_live_words >= old_space->capacity_in_words());
824
825 // If all regions in old-gen are full
826 const bool is_region_full =
827 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
828
829 return should_do_max_compaction
830 || is_max_on_system_gc
831 || is_old_gen_too_full
832 || is_region_full;
833 }
834
835 void PSParallelCompact::summary_phase(bool should_do_max_compaction)
836 {
837 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
838
839 MutableSpace* const old_space = _space_info[old_space_id].space();
840 {
841 size_t total_live_words = 0;
842 HeapWord* full_region_prefix_end = nullptr;
843 {
844 // old-gen
845 size_t live_words = _summary_data.live_words_in_space(old_space,
846 &full_region_prefix_end);
847 total_live_words += live_words;
848 }
849 // young-gen
850 for (uint i = eden_space_id; i < last_space_id; ++i) {
851 const MutableSpace* space = _space_info[i].space();
852 size_t live_words = _summary_data.live_words_in_space(space);
853 total_live_words += live_words;
854 _space_info[i].set_new_top(space->bottom() + live_words);
855 _space_info[i].set_dense_prefix(space->bottom());
856 }
857
858 should_do_max_compaction = check_maximum_compaction(should_do_max_compaction,
859 total_live_words,
860 old_space,
861 full_region_prefix_end);
862 {
863 GCTraceTime(Info, gc, phases) tm("Summary Phase: expand", &_gc_timer);
864 // Try to expand old-gen in order to fit all live objs and waste.
865 size_t target_capacity_bytes = total_live_words * HeapWordSize
866 + old_space->capacity_in_bytes() * (MarkSweepDeadRatio / 100);
867 ParallelScavengeHeap::heap()->old_gen()->try_expand_till_size(target_capacity_bytes);
868 }
869
870 HeapWord* dense_prefix_end = should_do_max_compaction
871 ? full_region_prefix_end
872 : compute_dense_prefix_for_old_space(old_space,
873 full_region_prefix_end);
874 SpaceId id = old_space_id;
875 _space_info[id].set_dense_prefix(dense_prefix_end);
876
877 if (dense_prefix_end != old_space->bottom()) {
878 fill_dense_prefix_end(id);
879 }
880
881 // Compacting objs in [dense_prefix_end, old_space->top())
882 _summary_data.summarize(_space_info[id].split_info(),
883 dense_prefix_end, old_space->top(), nullptr,
884 dense_prefix_end, old_space->end(),
885 _space_info[id].new_top_addr());
886 }
887
888 // Summarize the remaining spaces in the young gen. The initial target space
889 // is the old gen. If a space does not fit entirely into the target, then the
890 // remainder is compacted into the space itself and that space becomes the new
891 // target.
892 SpaceId dst_space_id = old_space_id;
893 HeapWord* dst_space_end = old_space->end();
894 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
895 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
896 const MutableSpace* space = _space_info[id].space();
897 const size_t live = pointer_delta(_space_info[id].new_top(),
898 space->bottom());
899 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
900
901 if (live > 0 && live <= available) {
902 // All the live data will fit.
903 bool done = _summary_data.summarize(_space_info[id].split_info(),
904 space->bottom(), space->top(),
905 nullptr,
906 *new_top_addr, dst_space_end,
907 new_top_addr);
908 assert(done, "space must fit into old gen");
909
910 // Reset the new_top value for the space.
911 _space_info[id].set_new_top(space->bottom());
912 } else if (live > 0) {
913 // Attempt to fit part of the source space into the target space.
914 HeapWord* next_src_addr = nullptr;
915 bool done = _summary_data.summarize(_space_info[id].split_info(),
916 space->bottom(), space->top(),
917 &next_src_addr,
918 *new_top_addr, dst_space_end,
919 new_top_addr);
920 assert(!done, "space should not fit into old gen");
921 assert(next_src_addr != nullptr, "sanity");
922
923 // The source space becomes the new target, so the remainder is compacted
924 // within the space itself.
925 dst_space_id = SpaceId(id);
926 dst_space_end = space->end();
927 new_top_addr = _space_info[id].new_top_addr();
928 done = _summary_data.summarize(_space_info[id].split_info(),
929 next_src_addr, space->top(),
930 nullptr,
931 space->bottom(), dst_space_end,
932 new_top_addr);
933 assert(done, "space must fit when compacted into itself");
934 assert(*new_top_addr <= space->top(), "usage should not grow");
935 }
936 }
937 }
938
939 void PSParallelCompact::report_object_count_after_gc() {
940 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
941 // The heap is compacted, all objects are iterable. However there may be
942 // filler objects in the heap which we should ignore.
943 class SkipFillerObjectClosure : public BoolObjectClosure {
944 public:
945 bool do_object_b(oop obj) override { return !CollectedHeap::is_filler_object(obj); }
946 } cl;
947 _gc_tracer.report_object_count_after_gc(&cl, &ParallelScavengeHeap::heap()->workers());
948 }
949
950 bool PSParallelCompact::invoke(bool clear_all_soft_refs, bool should_do_max_compaction) {
951 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
952 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
953 "should be in vm thread");
954 assert(ref_processor() != nullptr, "Sanity");
955
956 SvcGCMarker sgcm(SvcGCMarker::FULL);
957 IsSTWGCActiveMark mark;
958
959 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
960
961 GCIdMark gc_id_mark;
962 _gc_timer.register_gc_start();
963 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
964
965 GCCause::Cause gc_cause = heap->gc_cause();
966 PSOldGen* old_gen = heap->old_gen();
967 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
968
969 // Make sure data structures are sane, make the heap parsable, and do other
970 // miscellaneous bookkeeping.
971 pre_compact();
972
973 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
974
975 {
976 const uint active_workers =
977 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
978 ParallelScavengeHeap::heap()->workers().active_workers(),
979 Threads::number_of_non_daemon_threads());
980 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
981
982 GCTraceCPUTime tcpu(&_gc_tracer);
983 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
984
985 heap->pre_full_gc_dump(&_gc_timer);
986
987 TraceCollectorStats tcs(counters());
988 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
989
990 if (log_is_enabled(Debug, gc, heap, exit)) {
991 accumulated_time()->start();
992 }
993
994 // Let the size policy know we're starting
995 size_policy->major_collection_begin();
996
997 #if COMPILER2_OR_JVMCI
998 DerivedPointerTable::clear();
999 #endif
1000
1001 ref_processor()->start_discovery(clear_all_soft_refs);
1002
1003 marking_phase(&_gc_tracer);
1004
1005 summary_phase(should_do_max_compaction);
1006
1007 #if COMPILER2_OR_JVMCI
1008 assert(DerivedPointerTable::is_active(), "Sanity");
1009 DerivedPointerTable::set_active(false);
1010 #endif
1011
1012 forward_to_new_addr();
1013
1014 adjust_pointers();
1015
1016 compact();
1017
1018 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1019
1020 ParCompactionManager::verify_all_region_stack_empty();
1021
1022 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1023 // done before resizing.
1024 post_compact();
1025
1026 size_policy->major_collection_end();
1027
1028 size_policy->sample_old_gen_used_bytes(MAX2(pre_gc_values.old_gen_used(), old_gen->used_in_bytes()));
1029
1030 if (UseAdaptiveSizePolicy) {
1031 heap->resize_after_full_gc();
1032 }
1033
1034 heap->resize_all_tlabs();
1035
1036 // Resize the metaspace capacity after a collection
1037 MetaspaceGC::compute_new_size();
1038
1039 if (log_is_enabled(Debug, gc, heap, exit)) {
1040 accumulated_time()->stop();
1041 }
1042
1043 heap->print_heap_change(pre_gc_values);
1044
1045 report_object_count_after_gc();
1046
1047 // Track memory usage and detect low memory
1048 MemoryService::track_memory_usage();
1049 heap->update_counters();
1050
1051 heap->post_full_gc_dump(&_gc_timer);
1052
1053 size_policy->record_gc_pause_end_instant();
1054 }
1055
1056 heap->gc_epilogue(true);
1057
1058 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1059 Universe::verify("After GC");
1060 }
1061
1062 heap->print_after_gc();
1063 heap->trace_heap_after_gc(&_gc_tracer);
1064
1065 _gc_timer.register_gc_end();
1066
1067 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1068 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1069
1070 return true;
1071 }
1072
1073 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1074 ParCompactionManager* _cm;
1075
1076 public:
1077 PCAddThreadRootsMarkingTaskClosure(ParCompactionManager* cm) : _cm(cm) { }
1078 void do_thread(Thread* thread) {
1079 ResourceMark rm;
1080
1081 MarkingNMethodClosure mark_and_push_in_blobs(&_cm->_mark_and_push_closure);
1082
1083 thread->oops_do(&_cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1084
1085 // Do the real work
1086 _cm->follow_marking_stacks();
1087 }
1088 };
1089
1090 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1091 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1092
1093 ParCompactionManager* cm =
1094 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1095
1096 do {
1097 ScannerTask task;
1098 if (ParCompactionManager::steal(worker_id, task)) {
1099 cm->follow_contents(task, true);
1100 }
1101 cm->follow_marking_stacks();
1102 } while (!terminator.offer_termination());
1103 }
1104
1105 class MarkFromRootsTask : public WorkerTask {
1106 NMethodMarkingScope _nmethod_marking_scope;
1107 ThreadsClaimTokenScope _threads_claim_token_scope;
1108 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1109 TaskTerminator _terminator;
1110 uint _active_workers;
1111
1112 public:
1113 MarkFromRootsTask(uint active_workers) :
1114 WorkerTask("MarkFromRootsTask"),
1115 _nmethod_marking_scope(),
1116 _threads_claim_token_scope(),
1117 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1118 _active_workers(active_workers) {}
1119
1120 virtual void work(uint worker_id) {
1121 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1122 cm->create_marking_stats_cache();
1123 {
1124 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1125 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1126
1127 // Do the real work
1128 cm->follow_marking_stacks();
1129 }
1130
1131 {
1132 PCAddThreadRootsMarkingTaskClosure closure(cm);
1133 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1134 }
1135
1136 // Mark from OopStorages
1137 {
1138 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1139 // Do the real work
1140 cm->follow_marking_stacks();
1141 }
1142
1143 if (_active_workers > 1) {
1144 steal_marking_work(_terminator, worker_id);
1145 }
1146 }
1147 };
1148
1149 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1150 TaskTerminator _terminator;
1151
1152 public:
1153 ParallelCompactRefProcProxyTask(uint max_workers)
1154 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1155 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1156
1157 void work(uint worker_id) override {
1158 assert(worker_id < _max_workers, "sanity");
1159 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1160 BarrierEnqueueDiscoveredFieldClosure enqueue;
1161 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1162 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1163 }
1164
1165 void prepare_run_task_hook() override {
1166 _terminator.reset_for_reuse(_queue_count);
1167 }
1168 };
1169
1170 static void flush_marking_stats_cache(const uint num_workers) {
1171 for (uint i = 0; i < num_workers; ++i) {
1172 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1173 cm->flush_and_destroy_marking_stats_cache();
1174 }
1175 }
1176
1177 class PSParallelCleaningTask : public WorkerTask {
1178 bool _unloading_occurred;
1179 CodeCacheUnloadingTask _code_cache_task;
1180 // Prune dead klasses from subklass/sibling/implementor lists.
1181 KlassCleaningTask _klass_cleaning_task;
1182
1183 public:
1184 PSParallelCleaningTask(bool unloading_occurred) :
1185 WorkerTask("PS Parallel Cleaning"),
1186 _unloading_occurred(unloading_occurred),
1187 _code_cache_task(unloading_occurred),
1188 _klass_cleaning_task() {}
1189
1190 void work(uint worker_id) {
1191 #if INCLUDE_JVMCI
1192 if (EnableJVMCI && worker_id == 0) {
1193 // Serial work; only first worker.
1194 // Clean JVMCI metadata handles.
1195 JVMCI::do_unloading(_unloading_occurred);
1196 }
1197 #endif
1198
1199 // Do first pass of code cache cleaning.
1200 _code_cache_task.work(worker_id);
1201
1202 // Clean all klasses that were not unloaded.
1203 // The weak metadata in klass doesn't need to be
1204 // processed if there was no unloading.
1205 if (_unloading_occurred) {
1206 _klass_cleaning_task.work();
1207 }
1208 }
1209 };
1210
1211 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1212 // Recursively traverse all live objects and mark them
1213 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1214
1215 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1216
1217 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1218 {
1219 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1220
1221 MarkFromRootsTask task(active_gc_threads);
1222 ParallelScavengeHeap::heap()->workers().run_task(&task);
1223 }
1224
1225 // Process reference objects found during marking
1226 {
1227 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1228
1229 ReferenceProcessorStats stats;
1230 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1231
1232 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1233 stats = ref_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
1234
1235 gc_tracer->report_gc_reference_stats(stats);
1236 pt.print_all_references();
1237 }
1238
1239 {
1240 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1241
1242 flush_marking_stats_cache(active_gc_threads);
1243 }
1244
1245 // This is the point where the entire marking should have completed.
1246 ParCompactionManager::verify_all_marking_stack_empty();
1247
1248 {
1249 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1250 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1251 is_alive_closure(),
1252 &do_nothing_cl,
1253 1);
1254 }
1255
1256 {
1257 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1258
1259 ClassUnloadingContext ctx(active_gc_threads /* num_nmethod_unlink_workers */,
1260 false /* unregister_nmethods_during_purge */,
1261 false /* lock_nmethod_free_separately */);
1262
1263 {
1264 CodeCache::UnlinkingScope scope(is_alive_closure());
1265
1266 // Follow system dictionary roots and unload classes.
1267 bool unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1268
1269 PSParallelCleaningTask task{unloading_occurred};
1270 ParallelScavengeHeap::heap()->workers().run_task(&task);
1271 }
1272
1273 {
1274 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1275 // Release unloaded nmethod's memory.
1276 ctx.purge_nmethods();
1277 }
1278 {
1279 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1280 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1281 }
1282 {
1283 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1284 ctx.free_nmethods();
1285 }
1286 {
1287 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1288 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
1289 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1290 DEBUG_ONLY(MetaspaceUtils::verify();)
1291 }
1292 }
1293
1294 #if TASKQUEUE_STATS
1295 ParCompactionManager::print_and_reset_taskqueue_stats();
1296 #endif
1297 }
1298
1299 template<typename Func>
1300 void PSParallelCompact::adjust_in_space_helper(SpaceId id, Atomic<uint>* claim_counter, Func&& on_stripe) {
1301 MutableSpace* sp = PSParallelCompact::space(id);
1302 HeapWord* const bottom = sp->bottom();
1303 HeapWord* const top = sp->top();
1304 if (bottom == top) {
1305 return;
1306 }
1307
1308 const uint num_regions_per_stripe = 2;
1309 const size_t region_size = ParallelCompactData::RegionSize;
1310 const size_t stripe_size = num_regions_per_stripe * region_size;
1311
1312 while (true) {
1313 uint counter = claim_counter->fetch_then_add(num_regions_per_stripe);
1314 HeapWord* cur_stripe = bottom + counter * region_size;
1315 if (cur_stripe >= top) {
1316 break;
1317 }
1318 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1319 on_stripe(cur_stripe, stripe_end);
1320 }
1321 }
1322
1323 void PSParallelCompact::adjust_in_old_space(Atomic<uint>* claim_counter) {
1324 // Regions in old-space shouldn't be split.
1325 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1326
1327 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1328 assert(mark_bitmap()->is_marked(obj_start), "inv");
1329 oop obj = cast_to_oop(obj_start);
1330 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1331 };
1332
1333 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1334 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1335 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1336 HeapWord* obj_start;
1337 if (cur_region->partial_obj_size() != 0) {
1338 obj_start = cur_region->partial_obj_addr();
1339 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1340 } else {
1341 obj_start = stripe_start;
1342 }
1343
1344 while (obj_start < stripe_end) {
1345 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1346 if (obj_start >= stripe_end) {
1347 break;
1348 }
1349 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1350 }
1351 });
1352 }
1353
1354 void PSParallelCompact::adjust_in_young_space(SpaceId id, Atomic<uint>* claim_counter) {
1355 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1356 HeapWord* obj_start = stripe_start;
1357 while (obj_start < stripe_end) {
1358 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1359 if (obj_start >= stripe_end) {
1360 break;
1361 }
1362 oop obj = cast_to_oop(obj_start);
1363 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1364 }
1365 });
1366 }
1367
1368 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, Atomic<uint>* claim_counters) {
1369 auto start_time = Ticks::now();
1370 adjust_in_old_space(&claim_counters[0]);
1371 for (uint id = eden_space_id; id < last_space_id; ++id) {
1372 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1373 }
1374 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1375 }
1376
1377 class PSAdjustTask final : public WorkerTask {
1378 ThreadsClaimTokenScope _threads_claim_token_scope;
1379 WeakProcessor::Task _weak_proc_task;
1380 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1381 uint _nworkers;
1382 Atomic<bool> _code_cache_claimed;
1383 Atomic<uint> _claim_counters[PSParallelCompact::last_space_id];
1384
1385 bool try_claim_code_cache_task() {
1386 return _code_cache_claimed.load_relaxed() == false
1387 && _code_cache_claimed.compare_set(false, true);
1388 }
1389
1390 public:
1391 PSAdjustTask(uint nworkers) :
1392 WorkerTask("PSAdjust task"),
1393 _threads_claim_token_scope(),
1394 _weak_proc_task(nworkers),
1395 _oop_storage_iter(),
1396 _nworkers(nworkers),
1397 _code_cache_claimed(false) {
1398
1399 for (unsigned int i = PSParallelCompact::old_space_id; i < PSParallelCompact::last_space_id; ++i) {
1400 ::new (&_claim_counters[i]) Atomic<uint>{};
1401 }
1402 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1403 }
1404
1405 void work(uint worker_id) {
1406 {
1407 // Pointers in heap.
1408 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1409 cm->preserved_marks()->adjust_during_full_gc();
1410
1411 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1412 }
1413
1414 {
1415 // All (strong and weak) CLDs.
1416 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1417 ClassLoaderDataGraph::cld_do(&cld_closure);
1418 }
1419
1420 {
1421 // Threads stack frames. No need to visit on-stack nmethods, because all
1422 // nmethods are visited in one go via CodeCache::nmethods_do.
1423 ResourceMark rm;
1424 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1425 if (try_claim_code_cache_task()) {
1426 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1427 CodeCache::nmethods_do(&adjust_code);
1428 }
1429 }
1430
1431 {
1432 // VM internal strong and weak roots.
1433 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1434 AlwaysTrueClosure always_alive;
1435 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1436 }
1437 }
1438 };
1439
1440 void PSParallelCompact::adjust_pointers() {
1441 // Adjust the pointers to reflect the new locations
1442 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1443 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1444 PSAdjustTask task(nworkers);
1445 ParallelScavengeHeap::heap()->workers().run_task(&task);
1446 }
1447
1448 // Split [start, end) evenly for a number of workers and return the
1449 // range for worker_id.
1450 static void split_regions_for_worker(size_t start, size_t end,
1451 uint worker_id, uint num_workers,
1452 size_t* worker_start, size_t* worker_end) {
1453 assert(start < end, "precondition");
1454 assert(num_workers > 0, "precondition");
1455 assert(worker_id < num_workers, "precondition");
1456
1457 size_t num_regions = end - start;
1458 size_t num_regions_per_worker = num_regions / num_workers;
1459 size_t remainder = num_regions % num_workers;
1460 // The first few workers will get one extra.
1461 *worker_start = start + worker_id * num_regions_per_worker
1462 + MIN2(checked_cast<size_t>(worker_id), remainder);
1463 *worker_end = *worker_start + num_regions_per_worker
1464 + (worker_id < remainder ? 1 : 0);
1465 }
1466
1467 void PSParallelCompact::forward_to_new_addr() {
1468 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1469 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1470
1471 struct ForwardTask final : public WorkerTask {
1472 uint _num_workers;
1473
1474 explicit ForwardTask(uint num_workers) :
1475 WorkerTask("PSForward task"),
1476 _num_workers(num_workers) {}
1477
1478 static void forward_objs_in_range(ParCompactionManager* cm,
1479 HeapWord* start,
1480 HeapWord* end,
1481 HeapWord* destination) {
1482 HeapWord* cur_addr = start;
1483 HeapWord* new_addr = destination;
1484
1485 while (cur_addr < end) {
1486 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1487 if (cur_addr >= end) {
1488 return;
1489 }
1490 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1491 oop obj = cast_to_oop(cur_addr);
1492 if (new_addr != cur_addr) {
1493 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1494 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1495 }
1496 size_t obj_size = obj->size();
1497 new_addr += obj_size;
1498 cur_addr += obj_size;
1499 }
1500 }
1501
1502 void work(uint worker_id) override {
1503 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1504 for (uint id = old_space_id; id < last_space_id; ++id) {
1505 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1506 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1507 HeapWord* top = sp->top();
1508
1509 if (dense_prefix_addr == top) {
1510 // Empty space
1511 continue;
1512 }
1513
1514 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1515 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1516 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1517 size_t start_region;
1518 size_t end_region;
1519 split_regions_for_worker(dense_prefix_region, top_region,
1520 worker_id, _num_workers,
1521 &start_region, &end_region);
1522 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1523 RegionData* region_ptr = _summary_data.region(cur_region);
1524 size_t partial_obj_size = region_ptr->partial_obj_size();
1525
1526 if (partial_obj_size == ParallelCompactData::RegionSize) {
1527 // No obj-start
1528 continue;
1529 }
1530
1531 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1532 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1533
1534 if (split_info.is_split(cur_region)) {
1535 // Part 1: will be relocated to space-1
1536 HeapWord* preceding_destination = split_info.preceding_destination();
1537 HeapWord* split_point = split_info.split_point();
1538 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1539
1540 // Part 2: will be relocated to space-2
1541 HeapWord* destination = region_ptr->destination();
1542 forward_objs_in_range(cm, split_point, region_end, destination);
1543 } else {
1544 HeapWord* destination = region_ptr->destination();
1545 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1546 }
1547 }
1548 }
1549 }
1550 } task(nworkers);
1551
1552 ParallelScavengeHeap::heap()->workers().run_task(&task);
1553 DEBUG_ONLY(verify_forward();)
1554 }
1555
1556 #ifdef ASSERT
1557 void PSParallelCompact::verify_forward() {
1558 HeapWord* const old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1559 // The destination addr for the first live obj after dense-prefix.
1560 HeapWord* bump_ptr = old_dense_prefix_addr
1561 + _summary_data.addr_to_region_ptr(old_dense_prefix_addr)->partial_obj_size();
1562 SpaceId bump_ptr_space = old_space_id;
1563
1564 for (uint id = old_space_id; id < last_space_id; ++id) {
1565 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1566 // Only verify objs after dense-prefix, because those before dense-prefix are not moved (forwarded).
1567 HeapWord* cur_addr = dense_prefix(SpaceId(id));
1568 HeapWord* top = sp->top();
1569
1570 while (cur_addr < top) {
1571 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1572 if (cur_addr >= top) {
1573 break;
1574 }
1575 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1576 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1577 // Move to the space containing cur_addr
1578 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1579 bump_ptr = space(space_id(cur_addr))->bottom();
1580 bump_ptr_space = space_id(bump_ptr);
1581 }
1582 oop obj = cast_to_oop(cur_addr);
1583 if (cur_addr == bump_ptr) {
1584 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1585 } else {
1586 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1587 }
1588 bump_ptr += obj->size();
1589 cur_addr += obj->size();
1590 }
1591 }
1592 }
1593 #endif
1594
1595 // Helper class to print 8 region numbers per line and then print the total at the end.
1596 class FillableRegionLogger : public StackObj {
1597 private:
1598 Log(gc, compaction) log;
1599 static const int LineLength = 8;
1600 size_t _regions[LineLength];
1601 int _next_index;
1602 bool _enabled;
1603 size_t _total_regions;
1604 public:
1605 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1606 ~FillableRegionLogger() {
1607 log.trace("%zu initially fillable regions", _total_regions);
1608 }
1609
1610 void print_line() {
1611 if (!_enabled || _next_index == 0) {
1612 return;
1613 }
1614 FormatBuffer<> line("Fillable: ");
1615 for (int i = 0; i < _next_index; i++) {
1616 line.append(" %7zu", _regions[i]);
1617 }
1618 log.trace("%s", line.buffer());
1619 _next_index = 0;
1620 }
1621
1622 void handle(size_t region) {
1623 if (!_enabled) {
1624 return;
1625 }
1626 _regions[_next_index++] = region;
1627 if (_next_index == LineLength) {
1628 print_line();
1629 }
1630 _total_regions++;
1631 }
1632 };
1633
1634 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1635 {
1636 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1637
1638 // Find the threads that are active
1639 uint worker_id = 0;
1640
1641 // Find all regions that are available (can be filled immediately) and
1642 // distribute them to the thread stacks. The iteration is done in reverse
1643 // order (high to low) so the regions will be removed in ascending order.
1644
1645 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1646
1647 // id + 1 is used to test termination so unsigned can
1648 // be used with an old_space_id == 0.
1649 FillableRegionLogger region_logger;
1650 for (unsigned int id = last_space_id - 1; id + 1 > old_space_id; --id) {
1651 SpaceInfo* const space_info = _space_info + id;
1652 HeapWord* const new_top = space_info->new_top();
1653
1654 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1655 const size_t end_region =
1656 sd.addr_to_region_idx(sd.region_align_up(new_top));
1657
1658 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1659 if (sd.region(cur)->claim_unsafe()) {
1660 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1661 bool result = sd.region(cur)->mark_normal();
1662 assert(result, "Must succeed at this point.");
1663 cm->region_stack()->push(cur);
1664 region_logger.handle(cur);
1665 // Assign regions to tasks in round-robin fashion.
1666 if (++worker_id == parallel_gc_threads) {
1667 worker_id = 0;
1668 }
1669 }
1670 }
1671 region_logger.print_line();
1672 }
1673 }
1674
1675 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1676 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1677
1678 ParCompactionManager* cm =
1679 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1680
1681 // Drain the stacks that have been preloaded with regions
1682 // that are ready to fill.
1683
1684 cm->drain_region_stacks();
1685
1686 guarantee(cm->region_stack()->is_empty(), "Not empty");
1687
1688 size_t region_index = 0;
1689
1690 while (true) {
1691 if (ParCompactionManager::steal(worker_id, region_index)) {
1692 PSParallelCompact::fill_and_update_region(cm, region_index);
1693 cm->drain_region_stacks();
1694 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1695 // Fill and update an unavailable region with the help of a shadow region
1696 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1697 cm->drain_region_stacks();
1698 } else {
1699 if (terminator->offer_termination()) {
1700 break;
1701 }
1702 // Go around again.
1703 }
1704 }
1705 }
1706
1707 class FillDensePrefixAndCompactionTask: public WorkerTask {
1708 TaskTerminator _terminator;
1709
1710 public:
1711 FillDensePrefixAndCompactionTask(uint active_workers) :
1712 WorkerTask("FillDensePrefixAndCompactionTask"),
1713 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1714 }
1715
1716 virtual void work(uint worker_id) {
1717 if (worker_id == 0) {
1718 auto start = Ticks::now();
1719 PSParallelCompact::fill_dead_objs_in_dense_prefix();
1720 log_trace(gc, phases)("Fill dense prefix by worker 0: %.3f ms", (Ticks::now() - start).seconds() * 1000);
1721 }
1722 compaction_with_stealing_work(&_terminator, worker_id);
1723 }
1724 };
1725
1726 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1727 #ifdef ASSERT
1728 {
1729 assert(start < end, "precondition");
1730 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1731 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1732 if (start != bottom) {
1733 // The preceding live obj.
1734 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1735 HeapWord* obj_end = obj_start + cast_to_oop(obj_start)->size();
1736 assert(obj_end == start, "precondition");
1737 }
1738 }
1739 #endif
1740
1741 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1742 HeapWord* addr = start;
1743 do {
1744 size_t size = cast_to_oop(addr)->size();
1745 start_array(old_space_id)->update_for_block(addr, addr + size);
1746 addr += size;
1747 } while (addr < end);
1748 }
1749
1750 void PSParallelCompact::fill_dead_objs_in_dense_prefix() {
1751 ParMarkBitMap* bitmap = mark_bitmap();
1752
1753 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1754 HeapWord* const prefix_end = dense_prefix(old_space_id);
1755
1756 const size_t region_size = ParallelCompactData::RegionSize;
1757
1758 // Fill dead space in [start_addr, end_addr)
1759 HeapWord* const start_addr = bottom;
1760 HeapWord* const end_addr = prefix_end;
1761
1762 for (HeapWord* cur_addr = start_addr; cur_addr < end_addr; /* empty */) {
1763 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1764 if (cur_region_ptr->data_size() == region_size) {
1765 // Full; no dead space. Next region.
1766 if (_summary_data.is_region_aligned(cur_addr)) {
1767 cur_addr += region_size;
1768 } else {
1769 cur_addr = _summary_data.region_align_up(cur_addr);
1770 }
1771 continue;
1772 }
1773
1774 // Fill dead space inside cur_region.
1775 if (_summary_data.is_region_aligned(cur_addr)) {
1776 cur_addr += cur_region_ptr->partial_obj_size();
1777 }
1778
1779 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1780 assert(region_end_addr <= end_addr, "inv");
1781 while (cur_addr < region_end_addr) {
1782 // Use end_addr to allow filler-obj to cross region boundary.
1783 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, end_addr);
1784 if (cur_addr != live_start) {
1785 // Found dead space [cur_addr, live_start).
1786 fill_range_in_dense_prefix(cur_addr, live_start);
1787 }
1788 if (live_start >= region_end_addr) {
1789 cur_addr = live_start;
1790 break;
1791 }
1792 assert(bitmap->is_marked(live_start), "inv");
1793 cur_addr = live_start + cast_to_oop(live_start)->size();
1794 }
1795 }
1796 }
1797
1798 void PSParallelCompact::compact() {
1799 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1800
1801 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1802
1803 initialize_shadow_regions(active_gc_threads);
1804 prepare_region_draining_tasks(active_gc_threads);
1805
1806 {
1807 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1808
1809 FillDensePrefixAndCompactionTask task(active_gc_threads);
1810 ParallelScavengeHeap::heap()->workers().run_task(&task);
1811
1812 #ifdef ASSERT
1813 verify_filler_in_dense_prefix();
1814
1815 // Verify that all regions have been processed.
1816 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1817 verify_complete(SpaceId(id));
1818 }
1819 #endif
1820 }
1821 }
1822
1823 #ifdef ASSERT
1824 void PSParallelCompact::verify_filler_in_dense_prefix() {
1825 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1826 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1827
1828 const size_t region_size = ParallelCompactData::RegionSize;
1829
1830 for (HeapWord* cur_addr = bottom; cur_addr < dense_prefix_end; /* empty */) {
1831 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1832 if (cur_region_ptr->data_size() == region_size) {
1833 // Full; no dead space. Next region.
1834 if (_summary_data.is_region_aligned(cur_addr)) {
1835 cur_addr += region_size;
1836 } else {
1837 cur_addr = _summary_data.region_align_up(cur_addr);
1838 }
1839 continue;
1840 }
1841
1842 // This region contains filler objs.
1843 if (_summary_data.is_region_aligned(cur_addr)) {
1844 cur_addr += cur_region_ptr->partial_obj_size();
1845 }
1846
1847 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1848 assert(region_end_addr <= dense_prefix_end, "inv");
1849
1850 while (cur_addr < region_end_addr) {
1851 oop obj = cast_to_oop(cur_addr);
1852 oopDesc::verify(obj);
1853 if (!mark_bitmap()->is_marked(cur_addr)) {
1854 assert(CollectedHeap::is_filler_object(cast_to_oop(cur_addr)), "inv");
1855 }
1856 cur_addr += obj->size();
1857 }
1858 }
1859 }
1860
1861 void PSParallelCompact::verify_complete(SpaceId space_id) {
1862 // All Regions served as compaction targets, from dense_prefix() to
1863 // new_top(), should be marked as filled and all Regions between new_top()
1864 // and top() should be available (i.e., should have been emptied).
1865 ParallelCompactData& sd = summary_data();
1866 SpaceInfo si = _space_info[space_id];
1867 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1868 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1869 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1870 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1871 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1872
1873 size_t cur_region;
1874 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1875 const RegionData* const c = sd.region(cur_region);
1876 assert(c->completed(), "region %zu not filled: destination_count=%u",
1877 cur_region, c->destination_count());
1878 }
1879
1880 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1881 const RegionData* const c = sd.region(cur_region);
1882 assert(c->available(), "region %zu not empty: destination_count=%u",
1883 cur_region, c->destination_count());
1884 }
1885 }
1886 #endif // #ifdef ASSERT
1887
1888 // Return the SpaceId for the space containing addr. If addr is not in the
1889 // heap, last_space_id is returned. In debug mode it expects the address to be
1890 // in the heap and asserts such.
1891 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1892 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1893
1894 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1895 if (_space_info[id].space()->contains(addr)) {
1896 return SpaceId(id);
1897 }
1898 }
1899
1900 assert(false, "no space contains the addr");
1901 return last_space_id;
1902 }
1903
1904 // Skip over count live words starting from beg, and return the address of the
1905 // next live word. Callers must also ensure that there are enough live words in
1906 // the range [beg, end) to skip.
1907 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1908 {
1909 ParMarkBitMap* m = mark_bitmap();
1910 HeapWord* cur_addr = beg;
1911 while (true) {
1912 cur_addr = m->find_obj_beg(cur_addr, end);
1913 assert(cur_addr < end, "inv");
1914 size_t obj_size = cast_to_oop(cur_addr)->size();
1915 // Strictly greater-than
1916 if (obj_size > count) {
1917 return cur_addr + count;
1918 }
1919 count -= obj_size;
1920 cur_addr += obj_size;
1921 }
1922 }
1923
1924 // On starting to fill a destination region (dest-region), we need to know the
1925 // location of the word that will be at the start of the dest-region after
1926 // compaction. A dest-region can have one or more source regions, but only the
1927 // first source-region contains this location. This location is retrieved by
1928 // calling `first_src_addr` on a dest-region.
1929 // Conversely, a source-region has a dest-region which holds the destination of
1930 // the first live word on this source-region, based on which the destination
1931 // for the rest of live words can be derived.
1932 //
1933 // Note:
1934 // There is some complication due to space-boundary-fragmentation (an obj can't
1935 // cross space-boundary) -- a source-region may be split and behave like two
1936 // distinct regions with their own dest-region, as depicted below.
1937 //
1938 // source-region: region-n
1939 //
1940 // **********************
1941 // | A|A~~~~B|B |
1942 // **********************
1943 // n-1 n n+1
1944 //
1945 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
1946 //
1947 // Assuming the dest-region for region-n is the final region before
1948 // old-space-end and its first-live-word is the middle of AA, the heap content
1949 // will look like the following after compaction:
1950 //
1951 // ************** *************
1952 // A|A~~~~ | |BB |
1953 // ************** *************
1954 // ^ ^
1955 // | old-space-end | eden-space-start
1956 //
1957 // Therefore, in this example, region-n will have two dest-regions:
1958 // 1. the final region in old-space
1959 // 2. the first region in eden-space.
1960 // To handle this special case, we introduce the concept of split-region, whose
1961 // contents are relocated to two spaces. `SplitInfo` captures all necessary
1962 // info about the split, the first part, spliting-point, and the second part.
1963 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
1964 SpaceId src_space_id,
1965 size_t src_region_idx)
1966 {
1967 const size_t RegionSize = ParallelCompactData::RegionSize;
1968 const ParallelCompactData& sd = summary_data();
1969 assert(sd.is_region_aligned(dest_addr), "precondition");
1970
1971 const RegionData* const src_region_ptr = sd.region(src_region_idx);
1972 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
1973
1974 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
1975 HeapWord* const src_region_destination = src_region_ptr->destination();
1976
1977 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
1978 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
1979
1980 // Identify the actual destination for the first live words on this region,
1981 // taking split-region into account.
1982 HeapWord* region_start_destination;
1983 const SplitInfo& split_info = _space_info[src_space_id].split_info();
1984 if (split_info.is_split(src_region_idx)) {
1985 // The second part of this split region; use the recorded split point.
1986 if (dest_addr == src_region_destination) {
1987 return split_info.split_point();
1988 }
1989 region_start_destination = split_info.preceding_destination();
1990 } else {
1991 region_start_destination = src_region_destination;
1992 }
1993
1994 // Calculate the offset to be skipped
1995 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
1996
1997 HeapWord* result;
1998 if (partial_obj_size > words_to_skip) {
1999 result = region_start + words_to_skip;
2000 } else {
2001 words_to_skip -= partial_obj_size;
2002 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2003 }
2004
2005 if (split_info.is_split(src_region_idx)) {
2006 assert(result < split_info.split_point(), "postcondition");
2007 } else {
2008 assert(result < region_end, "postcondition");
2009 }
2010
2011 return result;
2012 }
2013
2014 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2015 SpaceId src_space_id,
2016 size_t beg_region,
2017 HeapWord* end_addr)
2018 {
2019 ParallelCompactData& sd = summary_data();
2020
2021 #ifdef ASSERT
2022 MutableSpace* const src_space = _space_info[src_space_id].space();
2023 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2024 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2025 "src_space_id does not match beg_addr");
2026 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2027 "src_space_id does not match end_addr");
2028 #endif // #ifdef ASSERT
2029
2030 RegionData* const beg = sd.region(beg_region);
2031 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2032
2033 // Regions up to new_top() are enqueued if they become available.
2034 HeapWord* const new_top = _space_info[src_space_id].new_top();
2035 RegionData* const enqueue_end =
2036 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2037
2038 for (RegionData* cur = beg; cur < end; ++cur) {
2039 assert(cur->data_size() > 0, "region must have live data");
2040 cur->decrement_destination_count();
2041 if (cur < enqueue_end && cur->available() && cur->claim()) {
2042 if (cur->mark_normal()) {
2043 cm->push_region(sd.region(cur));
2044 } else if (cur->mark_copied()) {
2045 // Try to copy the content of the shadow region back to its corresponding
2046 // heap region if the shadow region is filled. Otherwise, the GC thread
2047 // fills the shadow region will copy the data back (see
2048 // MoveAndUpdateShadowClosure::complete_region).
2049 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2050 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2051 cur->set_completed();
2052 }
2053 }
2054 }
2055 }
2056
2057 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2058 SpaceId& src_space_id,
2059 HeapWord*& src_space_top,
2060 HeapWord* end_addr)
2061 {
2062 ParallelCompactData& sd = PSParallelCompact::summary_data();
2063
2064 size_t src_region_idx = 0;
2065
2066 // Skip empty regions (if any) up to the top of the space.
2067 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2068 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2069 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2070 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2071
2072 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2073 ++src_region_ptr;
2074 }
2075
2076 if (src_region_ptr < top_region_ptr) {
2077 // Found the first non-empty region in the same space.
2078 src_region_idx = sd.region(src_region_ptr);
2079 closure.set_source(sd.region_to_addr(src_region_idx));
2080 return src_region_idx;
2081 }
2082
2083 // Switch to a new source space and find the first non-empty region.
2084 uint space_id = src_space_id + 1;
2085 assert(space_id < last_space_id, "not enough spaces");
2086
2087 for (/* empty */; space_id < last_space_id; ++space_id) {
2088 HeapWord* bottom = _space_info[space_id].space()->bottom();
2089 HeapWord* top = _space_info[space_id].space()->top();
2090 // Skip empty space
2091 if (bottom == top) {
2092 continue;
2093 }
2094
2095 // Identify the first region that contains live words in this space
2096 size_t cur_region = sd.addr_to_region_idx(bottom);
2097 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2098
2099 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2100 RegionData* cur = sd.region(cur_region);
2101 if (cur->live_obj_size() > 0) {
2102 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2103
2104 src_space_id = SpaceId(space_id);
2105 src_space_top = top;
2106 closure.set_source(region_start_addr);
2107 return cur_region;
2108 }
2109 }
2110 }
2111
2112 ShouldNotReachHere();
2113 }
2114
2115 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2116 ParallelCompactData& sd = summary_data();
2117 assert(sd.is_region_aligned(region_start_addr), "precondition");
2118
2119 // Use per-region partial_obj_size to locate the end of the obj, that extends
2120 // to region_start_addr.
2121 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2122 size_t end_region_idx = sd.region_count();
2123 size_t accumulated_size = 0;
2124 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2125 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2126 accumulated_size += cur_partial_obj_size;
2127 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2128 break;
2129 }
2130 }
2131 return region_start_addr + accumulated_size;
2132 }
2133
2134 // Use region_idx as the destination region, and evacuate all live objs on its
2135 // source regions to this destination region.
2136 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2137 {
2138 ParMarkBitMap* const bitmap = mark_bitmap();
2139 ParallelCompactData& sd = summary_data();
2140 RegionData* const region_ptr = sd.region(region_idx);
2141
2142 // Get the source region and related info.
2143 size_t src_region_idx = region_ptr->source_region();
2144 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2145 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2146 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2147
2148 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2149
2150 // Adjust src_region_idx to prepare for decrementing destination counts (the
2151 // destination count is not decremented when a region is copied to itself).
2152 if (src_region_idx == region_idx) {
2153 src_region_idx += 1;
2154 }
2155
2156 // source-region:
2157 //
2158 // **********
2159 // | ~~~ |
2160 // **********
2161 // ^
2162 // |-- closure.source() / first_src_addr
2163 //
2164 //
2165 // ~~~ : live words
2166 //
2167 // destination-region:
2168 //
2169 // **********
2170 // | |
2171 // **********
2172 // ^
2173 // |-- region-start
2174 if (bitmap->is_unmarked(closure.source())) {
2175 // An object overflows the previous destination region, so this
2176 // destination region should copy the remainder of the object or as much as
2177 // will fit.
2178 HeapWord* const old_src_addr = closure.source();
2179 {
2180 HeapWord* region_start = sd.region_align_down(closure.source());
2181 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2182 HeapWord* obj_end;
2183 if (obj_start != closure.source()) {
2184 assert(bitmap->is_marked(obj_start), "inv");
2185 // Found the actual obj-start, try to find the obj-end using either
2186 // size() if this obj is completely contained in the current region.
2187 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2188 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2189 ? nullptr
2190 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2191 // This obj extends to next region iff partial_obj_addr of the *next*
2192 // region is the same as obj-start.
2193 if (partial_obj_start == obj_start) {
2194 // This obj extends to next region.
2195 obj_end = partial_obj_end(next_region_start);
2196 } else {
2197 // Completely contained in this region; safe to use size().
2198 obj_end = obj_start + cast_to_oop(obj_start)->size();
2199 }
2200 } else {
2201 // This obj extends to current region.
2202 obj_end = partial_obj_end(region_start);
2203 }
2204 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2205 closure.copy_partial_obj(partial_obj_size);
2206 }
2207
2208 if (closure.is_full()) {
2209 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2210 closure.complete_region(dest_addr, region_ptr);
2211 return;
2212 }
2213
2214 // Finished copying without using up the current destination-region
2215 HeapWord* const end_addr = sd.region_align_down(closure.source());
2216 if (sd.region_align_down(old_src_addr) != end_addr) {
2217 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2218 // The partial object was copied from more than one source region.
2219 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2220
2221 // Move to the next source region, possibly switching spaces as well. All
2222 // args except end_addr may be modified.
2223 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2224 }
2225 }
2226
2227 // Handle the rest obj-by-obj, where we know obj-start.
2228 do {
2229 HeapWord* cur_addr = closure.source();
2230 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2231 src_space_top);
2232 // To handle the case where the final obj in source region extends to next region.
2233 HeapWord* final_obj_start = (end_addr == src_space_top)
2234 ? nullptr
2235 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2236 // Apply closure on objs inside [cur_addr, end_addr)
2237 do {
2238 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2239 if (cur_addr == end_addr) {
2240 break;
2241 }
2242 size_t obj_size;
2243 if (final_obj_start == cur_addr) {
2244 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2245 } else {
2246 // This obj doesn't extend into next region; size() is safe to use.
2247 obj_size = cast_to_oop(cur_addr)->size();
2248 }
2249 closure.do_addr(cur_addr, obj_size);
2250 cur_addr += obj_size;
2251 } while (cur_addr < end_addr && !closure.is_full());
2252
2253 if (closure.is_full()) {
2254 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2255 closure.complete_region(dest_addr, region_ptr);
2256 return;
2257 }
2258
2259 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2260
2261 // Move to the next source region, possibly switching spaces as well. All
2262 // args except end_addr may be modified.
2263 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2264 } while (true);
2265 }
2266
2267 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2268 {
2269 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2270 fill_region(cm, cl, region_idx);
2271 }
2272
2273 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2274 {
2275 // Get a shadow region first
2276 ParallelCompactData& sd = summary_data();
2277 RegionData* const region_ptr = sd.region(region_idx);
2278 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2279 // The InvalidShadow return value indicates the corresponding heap region is available,
2280 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2281 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2282 if (shadow_region == ParCompactionManager::InvalidShadow) {
2283 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2284 region_ptr->shadow_to_normal();
2285 return fill_region(cm, cl, region_idx);
2286 } else {
2287 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2288 return fill_region(cm, cl, region_idx);
2289 }
2290 }
2291
2292 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2293 {
2294 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2295 }
2296
2297 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2298 {
2299 size_t next = cm->next_shadow_region();
2300 ParallelCompactData& sd = summary_data();
2301 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2302 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2303
2304 while (next < old_new_top) {
2305 if (sd.region(next)->mark_shadow()) {
2306 region_idx = next;
2307 return true;
2308 }
2309 next = cm->move_next_shadow_region_by(active_gc_threads);
2310 }
2311
2312 return false;
2313 }
2314
2315 // The shadow region is an optimization to address region dependencies in full GC. The basic
2316 // idea is making more regions available by temporally storing their live objects in empty
2317 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2318 // GC threads need not wait destination regions to be available before processing sources.
2319 //
2320 // A typical workflow would be:
2321 // After draining its own stack and failing to steal from others, a GC worker would pick an
2322 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2323 // the shadow region by copying live objects from source regions of the unavailable one. Once
2324 // the unavailable region becomes available, the data in the shadow region will be copied back.
2325 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2326 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2327 {
2328 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2329
2330 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2331 SpaceInfo* const space_info = _space_info + id;
2332 MutableSpace* const space = space_info->space();
2333
2334 const size_t beg_region =
2335 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2336 const size_t end_region =
2337 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2338
2339 for (size_t cur = beg_region; cur < end_region; ++cur) {
2340 ParCompactionManager::push_shadow_region(cur);
2341 }
2342 }
2343
2344 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2345 for (uint i = 0; i < parallel_gc_threads; i++) {
2346 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2347 cm->set_next_shadow_region(beg_region + i);
2348 }
2349 }
2350
2351 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2352 {
2353 size_t words = MIN2(partial_obj_size, words_remaining());
2354
2355 // This test is necessary; if omitted, the pointer updates to a partial object
2356 // that crosses the dense prefix boundary could be overwritten.
2357 if (source() != copy_destination()) {
2358 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2359 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2360 }
2361 update_state(words);
2362 }
2363
2364 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2365 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2366 region_ptr->set_completed();
2367 }
2368
2369 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2370 assert(destination() != nullptr, "sanity");
2371 _source = addr;
2372
2373 // The start_array must be updated even if the object is not moving.
2374 if (_start_array != nullptr) {
2375 _start_array->update_for_block(destination(), destination() + words);
2376 }
2377
2378 // Avoid overflow
2379 words = MIN2(words, words_remaining());
2380 assert(words > 0, "inv");
2381
2382 if (copy_destination() != source()) {
2383 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2384 assert(source() != destination(), "inv");
2385 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2386 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2387 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2388 cast_to_oop(copy_destination())->init_mark();
2389 }
2390
2391 update_state(words);
2392 }
2393
2394 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2395 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2396 // Record the shadow region index
2397 region_ptr->set_shadow_region(_shadow);
2398 // Mark the shadow region as filled to indicate the data is ready to be
2399 // copied back
2400 region_ptr->mark_filled();
2401 // Try to copy the content of the shadow region back to its corresponding
2402 // heap region if available; the GC thread that decreases the destination
2403 // count to zero will do the copying otherwise (see
2404 // PSParallelCompact::decrement_destination_counts).
2405 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2406 region_ptr->set_completed();
2407 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2408 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2409 }
2410 }