1 /*
2 * Copyright (c) 2005, 2025, 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 "compiler/oopMap.hpp"
32 #include "gc/parallel/objectStartArray.inline.hpp"
33 #include "gc/parallel/parallelArguments.hpp"
34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
35 #include "gc/parallel/parMarkBitMap.inline.hpp"
36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
37 #include "gc/parallel/psCompactionManager.inline.hpp"
38 #include "gc/parallel/psOldGen.hpp"
39 #include "gc/parallel/psParallelCompact.inline.hpp"
40 #include "gc/parallel/psPromotionManager.inline.hpp"
41 #include "gc/parallel/psRootType.hpp"
42 #include "gc/parallel/psScavenge.hpp"
43 #include "gc/parallel/psStringDedup.hpp"
44 #include "gc/parallel/psYoungGen.hpp"
45 #include "gc/shared/classUnloadingContext.hpp"
46 #include "gc/shared/fullGCForwarding.inline.hpp"
47 #include "gc/shared/gcCause.hpp"
48 #include "gc/shared/gcHeapSummary.hpp"
49 #include "gc/shared/gcId.hpp"
50 #include "gc/shared/gcLocker.hpp"
51 #include "gc/shared/gcTimer.hpp"
52 #include "gc/shared/gcTrace.hpp"
53 #include "gc/shared/gcTraceTime.inline.hpp"
54 #include "gc/shared/gcVMOperations.hpp"
55 #include "gc/shared/isGCActiveMark.hpp"
56 #include "gc/shared/oopStorage.inline.hpp"
57 #include "gc/shared/oopStorageSet.inline.hpp"
58 #include "gc/shared/oopStorageSetParState.inline.hpp"
59 #include "gc/shared/preservedMarks.inline.hpp"
60 #include "gc/shared/referencePolicy.hpp"
61 #include "gc/shared/referenceProcessor.hpp"
62 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
63 #include "gc/shared/spaceDecorator.hpp"
64 #include "gc/shared/strongRootsScope.hpp"
65 #include "gc/shared/taskTerminator.hpp"
66 #include "gc/shared/weakProcessor.inline.hpp"
67 #include "gc/shared/workerPolicy.hpp"
68 #include "gc/shared/workerThread.hpp"
69 #include "gc/shared/workerUtils.hpp"
70 #include "logging/log.hpp"
71 #include "memory/iterator.inline.hpp"
72 #include "memory/memoryReserver.hpp"
73 #include "memory/metaspaceUtils.hpp"
74 #include "memory/resourceArea.hpp"
75 #include "memory/universe.hpp"
76 #include "nmt/memTracker.hpp"
77 #include "oops/access.inline.hpp"
78 #include "oops/instanceClassLoaderKlass.inline.hpp"
79 #include "oops/instanceKlass.inline.hpp"
80 #include "oops/instanceMirrorKlass.inline.hpp"
81 #include "oops/methodData.hpp"
82 #include "oops/objArrayKlass.inline.hpp"
83 #include "oops/oop.inline.hpp"
84 #include "runtime/atomic.hpp"
85 #include "runtime/handles.inline.hpp"
86 #include "runtime/java.hpp"
87 #include "runtime/safepoint.hpp"
88 #include "runtime/threads.hpp"
89 #include "runtime/vmThread.hpp"
90 #include "services/memoryService.hpp"
91 #include "utilities/align.hpp"
92 #include "utilities/debug.hpp"
93 #include "utilities/events.hpp"
94 #include "utilities/formatBuffer.hpp"
95 #include "utilities/macros.hpp"
96 #include "utilities/stack.inline.hpp"
97 #if INCLUDE_JVMCI
98 #include "jvmci/jvmci.hpp"
99 #endif
100
101 #include <math.h>
102
103 // All sizes are in HeapWords.
104 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
105 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
106 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
107 const size_t ParallelCompactData::RegionSizeBytes =
108 RegionSize << LogHeapWordSize;
109 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
110 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
111 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
112
113 const ParallelCompactData::RegionData::region_sz_t
114 ParallelCompactData::RegionData::dc_shift = 27;
115
116 const ParallelCompactData::RegionData::region_sz_t
117 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
118
119 const ParallelCompactData::RegionData::region_sz_t
120 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
121
122 const ParallelCompactData::RegionData::region_sz_t
123 ParallelCompactData::RegionData::los_mask = ~dc_mask;
124
125 const ParallelCompactData::RegionData::region_sz_t
126 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
127
128 const ParallelCompactData::RegionData::region_sz_t
129 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
130
131 bool ParallelCompactData::RegionData::is_clear() {
132 return (_destination == nullptr) &&
133 (_source_region == 0) &&
134 (_partial_obj_addr == nullptr) &&
135 (_partial_obj_size == 0) &&
136 (_dc_and_los == 0) &&
137 (_shadow_state == 0);
138 }
139
140 #ifdef ASSERT
141 void ParallelCompactData::RegionData::verify_clear() {
142 assert(_destination == nullptr, "inv");
143 assert(_source_region == 0, "inv");
144 assert(_partial_obj_addr == nullptr, "inv");
145 assert(_partial_obj_size == 0, "inv");
146 assert(_dc_and_los == 0, "inv");
147 assert(_shadow_state == 0, "inv");
148 }
149 #endif
150
151 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
152
153 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
154 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
155
156 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
157 assert(split_region_idx != 0, "precondition");
158
159 // Obj denoted by split_point will be deferred to the next space.
160 assert(split_point != nullptr, "precondition");
161
162 const ParallelCompactData& sd = PSParallelCompact::summary_data();
163
164 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
165 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
166
167 HeapWord* preceding_destination = split_region_ptr->destination();
168 assert(preceding_destination != nullptr, "inv");
169
170 // How many regions does the preceding part occupy
171 uint preceding_destination_count;
172 if (preceding_live_words == 0) {
173 preceding_destination_count = 0;
174 } else {
175 // -1 so that the ending address doesn't fall on the region-boundary
176 if (sd.region_align_down(preceding_destination) ==
177 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
178 preceding_destination_count = 1;
179 } else {
180 preceding_destination_count = 2;
181 }
182 }
183
184 _split_region_idx = split_region_idx;
185 _split_point = split_point;
186 _preceding_live_words = preceding_live_words;
187 _preceding_destination = preceding_destination;
188 _preceding_destination_count = preceding_destination_count;
189 }
190
191 void SplitInfo::clear()
192 {
193 _split_region_idx = 0;
194 _split_point = nullptr;
195 _preceding_live_words = 0;
196 _preceding_destination = nullptr;
197 _preceding_destination_count = 0;
198 assert(!is_valid(), "sanity");
199 }
200
201 #ifdef ASSERT
202 void SplitInfo::verify_clear()
203 {
204 assert(_split_region_idx == 0, "not clear");
205 assert(_split_point == nullptr, "not clear");
206 assert(_preceding_live_words == 0, "not clear");
207 assert(_preceding_destination == nullptr, "not clear");
208 assert(_preceding_destination_count == 0, "not clear");
209 }
210 #endif // #ifdef ASSERT
211
212
213 void PSParallelCompact::print_on_error(outputStream* st) {
214 _mark_bitmap.print_on_error(st);
215 }
216
217 ParallelCompactData::ParallelCompactData() :
218 _heap_start(nullptr),
219 DEBUG_ONLY(_heap_end(nullptr) COMMA)
220 _region_vspace(nullptr),
221 _reserved_byte_size(0),
222 _region_data(nullptr),
223 _region_count(0) {}
224
225 bool ParallelCompactData::initialize(MemRegion reserved_heap)
226 {
227 _heap_start = reserved_heap.start();
228 const size_t heap_size = reserved_heap.word_size();
229 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
230
231 assert(region_align_down(_heap_start) == _heap_start,
232 "region start not aligned");
233
234 return initialize_region_data(heap_size);
235 }
236
237 PSVirtualSpace*
238 ParallelCompactData::create_vspace(size_t count, size_t element_size)
239 {
240 const size_t raw_bytes = count * element_size;
241 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
242 const size_t granularity = os::vm_allocation_granularity();
243 const size_t rs_align = MAX2(page_sz, granularity);
244
245 _reserved_byte_size = align_up(raw_bytes, rs_align);
246
247 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
248 rs_align,
249 page_sz);
250
251 if (!rs.is_reserved()) {
252 // Failed to reserve memory.
253 return nullptr;
254 }
255
256 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
257 rs.size(), page_sz);
258
259 MemTracker::record_virtual_memory_tag(rs, mtGC);
260
261 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
262
263 if (!vspace->expand_by(_reserved_byte_size)) {
264 // Failed to commit memory.
265
266 delete vspace;
267
268 // Release memory reserved in the space.
269 MemoryReserver::release(rs);
270
271 return nullptr;
272 }
273
274 return vspace;
275 }
276
277 bool ParallelCompactData::initialize_region_data(size_t heap_size)
278 {
279 assert(is_aligned(heap_size, RegionSize), "precondition");
280
281 const size_t count = heap_size >> Log2RegionSize;
282 _region_vspace = create_vspace(count, sizeof(RegionData));
283 if (_region_vspace != nullptr) {
284 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
285 _region_count = count;
286 return true;
287 }
288 return false;
289 }
290
291 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
292 assert(beg_region <= _region_count, "beg_region out of range");
293 assert(end_region <= _region_count, "end_region out of range");
294
295 const size_t region_cnt = end_region - beg_region;
296 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
297 }
298
299 void
300 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
301 {
302 assert(is_region_aligned(beg), "not RegionSize aligned");
303 assert(is_region_aligned(end), "not RegionSize aligned");
304
305 size_t cur_region = addr_to_region_idx(beg);
306 const size_t end_region = addr_to_region_idx(end);
307 HeapWord* addr = beg;
308 while (cur_region < end_region) {
309 _region_data[cur_region].set_destination(addr);
310 _region_data[cur_region].set_destination_count(0);
311 _region_data[cur_region].set_source_region(cur_region);
312
313 // Update live_obj_size so the region appears completely full.
314 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
315 _region_data[cur_region].set_live_obj_size(live_size);
316
317 ++cur_region;
318 addr += RegionSize;
319 }
320 }
321
322 // The total live words on src_region would overflow the target space, so find
323 // the overflowing object and record the split point. The invariant is that an
324 // obj should not cross space boundary.
325 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
326 SplitInfo& split_info,
327 HeapWord* const destination,
328 HeapWord* const target_end,
329 HeapWord** target_next) {
330 assert(destination <= target_end, "sanity");
331 assert(destination + _region_data[src_region].data_size() > target_end,
332 "region should not fit into target space");
333 assert(is_region_aligned(target_end), "sanity");
334
335 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
336
337 if (destination + partial_obj_size > target_end) {
338 assert(partial_obj_size > 0, "inv");
339 // The overflowing obj is from a previous region.
340 //
341 // source-regions:
342 //
343 // ***************
344 // | A|AA |
345 // ***************
346 // ^
347 // | split-point
348 //
349 // dest-region:
350 //
351 // ********
352 // |~~~~A |
353 // ********
354 // ^^
355 // || target-space-end
356 // |
357 // | destination
358 //
359 // AAA would overflow target-space.
360 //
361 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
362 size_t split_region = addr_to_region_idx(overflowing_obj);
363
364 // The number of live words before the overflowing object on this split region
365 size_t preceding_live_words;
366 if (is_region_aligned(overflowing_obj)) {
367 preceding_live_words = 0;
368 } else {
369 // Words accounted by the overflowing object on the split region
370 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
371 preceding_live_words = region(split_region)->data_size() - overflowing_size;
372 }
373
374 split_info.record(split_region, overflowing_obj, preceding_live_words);
375
376 // The [overflowing_obj, src_region_start) part has been accounted for, so
377 // must move back the new_top, now that this overflowing obj is deferred.
378 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
379
380 // If the overflowing obj was relocated to its original destination,
381 // those destination regions would have their source_region set. Now that
382 // this overflowing obj is relocated somewhere else, reset the
383 // source_region.
384 {
385 size_t range_start = addr_to_region_idx(region_align_up(new_top));
386 size_t range_end = addr_to_region_idx(region_align_up(destination));
387 for (size_t i = range_start; i < range_end; ++i) {
388 region(i)->set_source_region(0);
389 }
390 }
391
392 // Update new top of target space
393 *target_next = new_top;
394
395 return overflowing_obj;
396 }
397
398 // Obj-iteration to locate the overflowing obj
399 HeapWord* region_start = region_to_addr(src_region);
400 HeapWord* region_end = region_start + RegionSize;
401 HeapWord* cur_addr = region_start + partial_obj_size;
402 size_t live_words = partial_obj_size;
403
404 while (true) {
405 assert(cur_addr < region_end, "inv");
406 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
407 // There must be an overflowing obj in this region
408 assert(cur_addr < region_end, "inv");
409
410 oop obj = cast_to_oop(cur_addr);
411 size_t obj_size = obj->size();
412 if (destination + live_words + obj_size > target_end) {
413 // Found the overflowing obj
414 split_info.record(src_region, cur_addr, live_words);
415 *target_next = destination + live_words;
416 return cur_addr;
417 }
418
419 live_words += obj_size;
420 cur_addr += obj_size;
421 }
422 }
423
424 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
425 HeapWord** full_region_prefix_end) {
426 size_t cur_region = addr_to_region_idx(space->bottom());
427 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
428 size_t live_words = 0;
429 if (full_region_prefix_end == nullptr) {
430 for (/* empty */; cur_region < end_region; ++cur_region) {
431 live_words += _region_data[cur_region].data_size();
432 }
433 } else {
434 bool first_set = false;
435 for (/* empty */; cur_region < end_region; ++cur_region) {
436 size_t live_words_in_region = _region_data[cur_region].data_size();
437 if (!first_set && live_words_in_region < RegionSize) {
438 *full_region_prefix_end = region_to_addr(cur_region);
439 first_set = true;
440 }
441 live_words += live_words_in_region;
442 }
443 if (!first_set) {
444 // All regions are full of live objs.
445 assert(is_region_aligned(space->top()), "inv");
446 *full_region_prefix_end = space->top();
447 }
448 assert(*full_region_prefix_end != nullptr, "postcondition");
449 assert(is_region_aligned(*full_region_prefix_end), "inv");
450 assert(*full_region_prefix_end >= space->bottom(), "in-range");
451 assert(*full_region_prefix_end <= space->top(), "in-range");
452 }
453 return live_words;
454 }
455
456 bool ParallelCompactData::summarize(SplitInfo& split_info,
457 HeapWord* source_beg, HeapWord* source_end,
458 HeapWord** source_next,
459 HeapWord* target_beg, HeapWord* target_end,
460 HeapWord** target_next)
461 {
462 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
463 log_develop_trace(gc, compaction)(
464 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
465 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
466 p2i(source_beg), p2i(source_end), p2i(source_next_val),
467 p2i(target_beg), p2i(target_end), p2i(*target_next));
468
469 size_t cur_region = addr_to_region_idx(source_beg);
470 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
471
472 HeapWord *dest_addr = target_beg;
473 for (/* empty */; cur_region < end_region; cur_region++) {
474 size_t words = _region_data[cur_region].data_size();
475
476 // Skip empty ones
477 if (words == 0) {
478 continue;
479 }
480
481 if (split_info.is_split(cur_region)) {
482 assert(words > split_info.preceding_live_words(), "inv");
483 words -= split_info.preceding_live_words();
484 }
485
486 _region_data[cur_region].set_destination(dest_addr);
487
488 // If cur_region does not fit entirely into the target space, find a point
489 // at which the source space can be 'split' so that part is copied to the
490 // target space and the rest is copied elsewhere.
491 if (dest_addr + words > target_end) {
492 assert(source_next != nullptr, "source_next is null when splitting");
493 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
494 target_end, target_next);
495 return false;
496 }
497
498 uint destination_count = split_info.is_split(cur_region)
499 ? split_info.preceding_destination_count()
500 : 0;
501
502 HeapWord* const last_addr = dest_addr + words - 1;
503 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
504 const size_t dest_region_2 = addr_to_region_idx(last_addr);
505
506 // Initially assume that the destination regions will be the same and
507 // adjust the value below if necessary. Under this assumption, if
508 // cur_region == dest_region_2, then cur_region will be compacted
509 // completely into itself.
510 destination_count += cur_region == dest_region_2 ? 0 : 1;
511 if (dest_region_1 != dest_region_2) {
512 // Destination regions differ; adjust destination_count.
513 destination_count += 1;
514 // Data from cur_region will be copied to the start of dest_region_2.
515 _region_data[dest_region_2].set_source_region(cur_region);
516 } else if (is_region_aligned(dest_addr)) {
517 // Data from cur_region will be copied to the start of the destination
518 // region.
519 _region_data[dest_region_1].set_source_region(cur_region);
520 }
521
522 _region_data[cur_region].set_destination_count(destination_count);
523 dest_addr += words;
524 }
525
526 *target_next = dest_addr;
527 return true;
528 }
529
530 #ifdef ASSERT
531 void ParallelCompactData::verify_clear() {
532 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
533 if (!region(cur_idx)->is_clear()) {
534 log_warning(gc)("Uncleared Region: %u", cur_idx);
535 region(cur_idx)->verify_clear();
536 }
537 }
538 }
539 #endif // #ifdef ASSERT
540
541 STWGCTimer PSParallelCompact::_gc_timer;
542 ParallelOldTracer PSParallelCompact::_gc_tracer;
543 elapsedTimer PSParallelCompact::_accumulated_time;
544 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
545 CollectorCounters* PSParallelCompact::_counters = nullptr;
546 ParMarkBitMap PSParallelCompact::_mark_bitmap;
547 ParallelCompactData PSParallelCompact::_summary_data;
548
549 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
550
551 class PCAdjustPointerClosure: public BasicOopIterateClosure {
552 template <typename T>
553 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
554
555 public:
556 virtual void do_oop(oop* p) { do_oop_work(p); }
557 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
558
559 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
560 };
561
562 static PCAdjustPointerClosure pc_adjust_pointer_closure;
563
564 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
565
566 void PSParallelCompact::post_initialize() {
567 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
568 _span_based_discoverer.set_span(heap->reserved_region());
569 _ref_processor =
570 new ReferenceProcessor(&_span_based_discoverer,
571 ParallelGCThreads, // mt processing degree
572 ParallelGCThreads, // mt discovery degree
573 false, // concurrent_discovery
574 &_is_alive_closure); // non-header is alive closure
575
576 _counters = new CollectorCounters("Parallel full collection pauses", 1);
577
578 // Initialize static fields in ParCompactionManager.
579 ParCompactionManager::initialize(mark_bitmap());
580 }
581
582 bool PSParallelCompact::initialize_aux_data() {
583 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
584 MemRegion mr = heap->reserved_region();
585 assert(mr.byte_size() != 0, "heap should be reserved");
586
587 initialize_space_info();
588
589 if (!_mark_bitmap.initialize(mr)) {
590 vm_shutdown_during_initialization(
591 err_msg("Unable to allocate %zuKB bitmaps for parallel "
592 "garbage collection for the requested %zuKB heap.",
593 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
594 return false;
595 }
596
597 if (!_summary_data.initialize(mr)) {
598 vm_shutdown_during_initialization(
599 err_msg("Unable to allocate %zuKB card tables for parallel "
600 "garbage collection for the requested %zuKB heap.",
601 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
602 return false;
603 }
604
605 return true;
606 }
607
608 void PSParallelCompact::initialize_space_info()
609 {
610 memset(&_space_info, 0, sizeof(_space_info));
611
612 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
613 PSYoungGen* young_gen = heap->young_gen();
614
615 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
616 _space_info[eden_space_id].set_space(young_gen->eden_space());
617 _space_info[from_space_id].set_space(young_gen->from_space());
618 _space_info[to_space_id].set_space(young_gen->to_space());
619
620 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
621 }
622
623 void
624 PSParallelCompact::clear_data_covering_space(SpaceId id)
625 {
626 // At this point, top is the value before GC, new_top() is the value that will
627 // be set at the end of GC. The marking bitmap is cleared to top; nothing
628 // should be marked above top. The summary data is cleared to the larger of
629 // top & new_top.
630 MutableSpace* const space = _space_info[id].space();
631 HeapWord* const bot = space->bottom();
632 HeapWord* const top = space->top();
633 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
634
635 _mark_bitmap.clear_range(bot, top);
636
637 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
638 const size_t end_region =
639 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
640 _summary_data.clear_range(beg_region, end_region);
641
642 // Clear the data used to 'split' regions.
643 SplitInfo& split_info = _space_info[id].split_info();
644 if (split_info.is_valid()) {
645 split_info.clear();
646 }
647 DEBUG_ONLY(split_info.verify_clear();)
648 }
649
650 void PSParallelCompact::pre_compact()
651 {
652 // Update the from & to space pointers in space_info, since they are swapped
653 // at each young gen gc. Do the update unconditionally (even though a
654 // promotion failure does not swap spaces) because an unknown number of young
655 // collections will have swapped the spaces an unknown number of times.
656 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
657 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
658 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
659 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
660
661 // Increment the invocation count
662 heap->increment_total_collections(true);
663
664 CodeCache::on_gc_marking_cycle_start();
665
666 heap->print_heap_before_gc();
667 heap->trace_heap_before_gc(&_gc_tracer);
668
669 // Fill in TLABs
670 heap->ensure_parsability(true); // retire TLABs
671
672 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
673 Universe::verify("Before GC");
674 }
675
676 DEBUG_ONLY(mark_bitmap()->verify_clear();)
677 DEBUG_ONLY(summary_data().verify_clear();)
678 }
679
680 void PSParallelCompact::post_compact()
681 {
682 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
683 ParCompactionManager::remove_all_shadow_regions();
684
685 CodeCache::on_gc_marking_cycle_finish();
686 CodeCache::arm_all_nmethods();
687
688 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
689 // Clear the marking bitmap, summary data and split info.
690 clear_data_covering_space(SpaceId(id));
691 {
692 MutableSpace* space = _space_info[id].space();
693 HeapWord* top = space->top();
694 HeapWord* new_top = _space_info[id].new_top();
695 if (ZapUnusedHeapArea && new_top < top) {
696 space->mangle_region(MemRegion(new_top, top));
697 }
698 // Update top(). Must be done after clearing the bitmap and summary data.
699 space->set_top(new_top);
700 }
701 }
702
703 #ifdef ASSERT
704 {
705 mark_bitmap()->verify_clear();
706 summary_data().verify_clear();
707 }
708 #endif
709
710 ParCompactionManager::flush_all_string_dedup_requests();
711
712 MutableSpace* const eden_space = _space_info[eden_space_id].space();
713 MutableSpace* const from_space = _space_info[from_space_id].space();
714 MutableSpace* const to_space = _space_info[to_space_id].space();
715
716 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
717 bool eden_empty = eden_space->is_empty();
718
719 // Update heap occupancy information which is used as input to the soft ref
720 // clearing policy at the next gc.
721 Universe::heap()->update_capacity_and_used_at_gc();
722
723 bool young_gen_empty = eden_empty && from_space->is_empty() &&
724 to_space->is_empty();
725
726 PSCardTable* ct = heap->card_table();
727 MemRegion old_mr = heap->old_gen()->committed();
728 if (young_gen_empty) {
729 ct->clear_MemRegion(old_mr);
730 } else {
731 ct->dirty_MemRegion(old_mr);
732 }
733
734 {
735 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
736 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
737 ClassLoaderDataGraph::purge(true /* at_safepoint */);
738 DEBUG_ONLY(MetaspaceUtils::verify();)
739 }
740
741 // Need to clear claim bits for the next mark.
742 ClassLoaderDataGraph::clear_claimed_marks();
743
744 heap->prune_scavengable_nmethods();
745
746 #if COMPILER2_OR_JVMCI
747 DerivedPointerTable::update_pointers();
748 #endif
749
750 // Signal that we have completed a visit to all live objects.
751 Universe::heap()->record_whole_heap_examined_timestamp();
752 }
753
754 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
755 HeapWord* full_region_prefix_end) {
756 const size_t region_size = ParallelCompactData::RegionSize;
757 const ParallelCompactData& sd = summary_data();
758
759 // Iteration starts with the region *after* the full-region-prefix-end.
760 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
761 // If final region is not full, iteration stops before that region,
762 // because fill_dense_prefix_end assumes that prefix_end <= top.
763 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
764 assert(start_region <= end_region, "inv");
765
766 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
767 const RegionData* cur_region = start_region;
768 for (/* empty */; cur_region < end_region; ++cur_region) {
769 assert(region_size >= cur_region->data_size(), "inv");
770 size_t dead_size = region_size - cur_region->data_size();
771 if (max_waste < dead_size) {
772 break;
773 }
774 max_waste -= dead_size;
775 }
776
777 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
778 assert(sd.is_region_aligned(prefix_end), "postcondition");
779 assert(prefix_end >= full_region_prefix_end, "in-range");
780 assert(prefix_end <= old_space->top(), "in-range");
781 return prefix_end;
782 }
783
784 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
785 // Comparing two sizes to decide if filling is required:
786 //
787 // The size of the filler (min-obj-size) is 2 heap words with the default
788 // MinObjAlignment, since both markword and klass take 1 heap word.
789 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
790 // because the Klass* gets encoded in the mark-word.
791 //
792 // The size of the gap (if any) right before dense-prefix-end is
793 // MinObjAlignment.
794 //
795 // Need to fill in the gap only if it's smaller than min-obj-size, and the
796 // filler obj will extend to next region.
797
798 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
799 return;
800 }
801
802 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
803 assert(CollectedHeap::min_fill_size() == 2, "inv");
804 HeapWord* const dense_prefix_end = dense_prefix(id);
805 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
806 assert(dense_prefix_end <= space(id)->top(), "precondition");
807 if (dense_prefix_end == space(id)->top()) {
808 // Must not have single-word gap right before prefix-end/top.
809 return;
810 }
811 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
812
813 if (region_after_dense_prefix->partial_obj_size() != 0 ||
814 _mark_bitmap.is_marked(dense_prefix_end)) {
815 // The region after the dense prefix starts with live bytes.
816 return;
817 }
818
819 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
820 if (block_start == dense_prefix_end - 1) {
821 assert(!_mark_bitmap.is_marked(block_start), "inv");
822 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
823 // The filler object will extend into region_after_dense_prefix.
824 const size_t obj_len = 2; // min-fill-size
825 HeapWord* const obj_beg = dense_prefix_end - 1;
826 CollectedHeap::fill_with_object(obj_beg, obj_len);
827 _mark_bitmap.mark_obj(obj_beg);
828 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
829 region_after_dense_prefix->set_partial_obj_size(1);
830 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
831 assert(start_array(id) != nullptr, "sanity");
832 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
833 }
834 }
835
836 bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
837 MutableSpace* const old_space,
838 HeapWord* full_region_prefix_end) {
839
840 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
841
842 // Check System.GC
843 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
844 && GCCause::is_user_requested_gc(heap->gc_cause());
845
846 // Check if all live objs are larger than old-gen.
847 const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
848
849 // JVM flags
850 const uint total_invocations = heap->total_full_collections();
851 assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
852 const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
853 const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
854
855 // If all regions in old-gen are full
856 const bool is_region_full =
857 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
858
859 if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
860 _maximum_compaction_gc_num = total_invocations;
861 return true;
862 }
863
864 return false;
865 }
866
867 void PSParallelCompact::summary_phase()
868 {
869 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
870
871 MutableSpace* const old_space = _space_info[old_space_id].space();
872 {
873 size_t total_live_words = 0;
874 HeapWord* full_region_prefix_end = nullptr;
875 {
876 // old-gen
877 size_t live_words = _summary_data.live_words_in_space(old_space,
878 &full_region_prefix_end);
879 total_live_words += live_words;
880 }
881 // young-gen
882 for (uint i = eden_space_id; i < last_space_id; ++i) {
883 const MutableSpace* space = _space_info[i].space();
884 size_t live_words = _summary_data.live_words_in_space(space);
885 total_live_words += live_words;
886 _space_info[i].set_new_top(space->bottom() + live_words);
887 _space_info[i].set_dense_prefix(space->bottom());
888 }
889
890 bool maximum_compaction = check_maximum_compaction(total_live_words,
891 old_space,
892 full_region_prefix_end);
893 HeapWord* dense_prefix_end = maximum_compaction
894 ? full_region_prefix_end
895 : compute_dense_prefix_for_old_space(old_space,
896 full_region_prefix_end);
897 SpaceId id = old_space_id;
898 _space_info[id].set_dense_prefix(dense_prefix_end);
899
900 if (dense_prefix_end != old_space->bottom()) {
901 fill_dense_prefix_end(id);
902 _summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
903 }
904
905 // Compacting objs in [dense_prefix_end, old_space->top())
906 _summary_data.summarize(_space_info[id].split_info(),
907 dense_prefix_end, old_space->top(), nullptr,
908 dense_prefix_end, old_space->end(),
909 _space_info[id].new_top_addr());
910 }
911
912 // Summarize the remaining spaces in the young gen. The initial target space
913 // is the old gen. If a space does not fit entirely into the target, then the
914 // remainder is compacted into the space itself and that space becomes the new
915 // target.
916 SpaceId dst_space_id = old_space_id;
917 HeapWord* dst_space_end = old_space->end();
918 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
919 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
920 const MutableSpace* space = _space_info[id].space();
921 const size_t live = pointer_delta(_space_info[id].new_top(),
922 space->bottom());
923 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
924
925 if (live > 0 && live <= available) {
926 // All the live data will fit.
927 bool done = _summary_data.summarize(_space_info[id].split_info(),
928 space->bottom(), space->top(),
929 nullptr,
930 *new_top_addr, dst_space_end,
931 new_top_addr);
932 assert(done, "space must fit into old gen");
933
934 // Reset the new_top value for the space.
935 _space_info[id].set_new_top(space->bottom());
936 } else if (live > 0) {
937 // Attempt to fit part of the source space into the target space.
938 HeapWord* next_src_addr = nullptr;
939 bool done = _summary_data.summarize(_space_info[id].split_info(),
940 space->bottom(), space->top(),
941 &next_src_addr,
942 *new_top_addr, dst_space_end,
943 new_top_addr);
944 assert(!done, "space should not fit into old gen");
945 assert(next_src_addr != nullptr, "sanity");
946
947 // The source space becomes the new target, so the remainder is compacted
948 // within the space itself.
949 dst_space_id = SpaceId(id);
950 dst_space_end = space->end();
951 new_top_addr = _space_info[id].new_top_addr();
952 done = _summary_data.summarize(_space_info[id].split_info(),
953 next_src_addr, space->top(),
954 nullptr,
955 space->bottom(), dst_space_end,
956 new_top_addr);
957 assert(done, "space must fit when compacted into itself");
958 assert(*new_top_addr <= space->top(), "usage should not grow");
959 }
960 }
961 }
962
963 // This method should contain all heap-specific policy for invoking a full
964 // collection. invoke_no_policy() will only attempt to compact the heap; it
965 // will do nothing further. If we need to bail out for policy reasons, scavenge
966 // before full gc, or any other specialized behavior, it needs to be added here.
967 //
968 // Note that this method should only be called from the vm_thread while at a
969 // safepoint.
970 //
971 // Note that the all_soft_refs_clear flag in the soft ref policy
972 // may be true because this method can be called without intervening
973 // activity. For example when the heap space is tight and full measure
974 // are being taken to free space.
975 bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
976 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
977 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
978 "should be in vm thread");
979
980 SvcGCMarker sgcm(SvcGCMarker::FULL);
981 IsSTWGCActiveMark mark;
982
983 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
984 clear_all_soft_refs = clear_all_soft_refs
985 || heap->soft_ref_policy()->should_clear_all_soft_refs();
986
987 return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
988 }
989
990 // This method contains no policy. You should probably
991 // be calling invoke() instead.
992 bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
993 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
994 assert(ref_processor() != nullptr, "Sanity");
995
996 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
997
998 GCIdMark gc_id_mark;
999 _gc_timer.register_gc_start();
1000 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1001
1002 GCCause::Cause gc_cause = heap->gc_cause();
1003 PSYoungGen* young_gen = heap->young_gen();
1004 PSOldGen* old_gen = heap->old_gen();
1005 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1006
1007 // The scope of casr should end after code that can change
1008 // SoftRefPolicy::_should_clear_all_soft_refs.
1009 ClearedAllSoftRefs casr(clear_all_soft_refs,
1010 heap->soft_ref_policy());
1011
1012 // Make sure data structures are sane, make the heap parsable, and do other
1013 // miscellaneous bookkeeping.
1014 pre_compact();
1015
1016 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1017
1018 {
1019 const uint active_workers =
1020 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
1021 ParallelScavengeHeap::heap()->workers().active_workers(),
1022 Threads::number_of_non_daemon_threads());
1023 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
1024
1025 GCTraceCPUTime tcpu(&_gc_tracer);
1026 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
1027
1028 heap->pre_full_gc_dump(&_gc_timer);
1029
1030 TraceCollectorStats tcs(counters());
1031 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
1032
1033 if (log_is_enabled(Debug, gc, heap, exit)) {
1034 accumulated_time()->start();
1035 }
1036
1037 // Let the size policy know we're starting
1038 size_policy->major_collection_begin();
1039
1040 #if COMPILER2_OR_JVMCI
1041 DerivedPointerTable::clear();
1042 #endif
1043
1044 ref_processor()->start_discovery(clear_all_soft_refs);
1045
1046 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
1047 false /* unregister_nmethods_during_purge */,
1048 false /* lock_nmethod_free_separately */);
1049
1050 marking_phase(&_gc_tracer);
1051
1052 summary_phase();
1053
1054 #if COMPILER2_OR_JVMCI
1055 assert(DerivedPointerTable::is_active(), "Sanity");
1056 DerivedPointerTable::set_active(false);
1057 #endif
1058
1059 forward_to_new_addr();
1060
1061 adjust_pointers();
1062
1063 compact();
1064
1065 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1066
1067 ParCompactionManager::verify_all_region_stack_empty();
1068
1069 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1070 // done before resizing.
1071 post_compact();
1072
1073 // Let the size policy know we're done
1074 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1075
1076 if (UseAdaptiveSizePolicy) {
1077 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1078 log_trace(gc, ergo)("old_gen_capacity: %zu young_gen_capacity: %zu",
1079 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1080
1081 // Don't check if the size_policy is ready here. Let
1082 // the size_policy check that internally.
1083 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1084 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1085 // Swap the survivor spaces if from_space is empty. The
1086 // resize_young_gen() called below is normally used after
1087 // a successful young GC and swapping of survivor spaces;
1088 // otherwise, it will fail to resize the young gen with
1089 // the current implementation.
1090 if (young_gen->from_space()->is_empty()) {
1091 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1092 young_gen->swap_spaces();
1093 }
1094
1095 // Calculate optimal free space amounts
1096 assert(young_gen->max_gen_size() >
1097 young_gen->from_space()->capacity_in_bytes() +
1098 young_gen->to_space()->capacity_in_bytes(),
1099 "Sizes of space in young gen are out-of-bounds");
1100
1101 size_t young_live = young_gen->used_in_bytes();
1102 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1103 size_t old_live = old_gen->used_in_bytes();
1104 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1105 size_t max_old_gen_size = old_gen->max_gen_size();
1106 size_t max_eden_size = young_gen->max_gen_size() -
1107 young_gen->from_space()->capacity_in_bytes() -
1108 young_gen->to_space()->capacity_in_bytes();
1109
1110 // Used for diagnostics
1111 size_policy->clear_generation_free_space_flags();
1112
1113 size_policy->compute_generations_free_space(young_live,
1114 eden_live,
1115 old_live,
1116 cur_eden,
1117 max_old_gen_size,
1118 max_eden_size,
1119 true /* full gc*/);
1120
1121 size_policy->check_gc_overhead_limit(eden_live,
1122 max_old_gen_size,
1123 max_eden_size,
1124 true /* full gc*/,
1125 gc_cause,
1126 heap->soft_ref_policy());
1127
1128 size_policy->decay_supplemental_growth(true /* full gc*/);
1129
1130 heap->resize_old_gen(
1131 size_policy->calculated_old_free_size_in_bytes());
1132
1133 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1134 size_policy->calculated_survivor_size_in_bytes());
1135 }
1136
1137 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1138 }
1139
1140 if (UsePerfData) {
1141 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1142 counters->update_counters();
1143 counters->update_old_capacity(old_gen->capacity_in_bytes());
1144 counters->update_young_capacity(young_gen->capacity_in_bytes());
1145 }
1146
1147 heap->resize_all_tlabs();
1148
1149 // Resize the metaspace capacity after a collection
1150 MetaspaceGC::compute_new_size();
1151
1152 if (log_is_enabled(Debug, gc, heap, exit)) {
1153 accumulated_time()->stop();
1154 }
1155
1156 heap->print_heap_change(pre_gc_values);
1157
1158 // Track memory usage and detect low memory
1159 MemoryService::track_memory_usage();
1160 heap->update_counters();
1161
1162 heap->post_full_gc_dump(&_gc_timer);
1163 }
1164
1165 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1166 Universe::verify("After GC");
1167 }
1168
1169 heap->print_heap_after_gc();
1170 heap->trace_heap_after_gc(&_gc_tracer);
1171
1172 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1173
1174 _gc_timer.register_gc_end();
1175
1176 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1177 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1178
1179 return true;
1180 }
1181
1182 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1183 private:
1184 uint _worker_id;
1185
1186 public:
1187 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1188 void do_thread(Thread* thread) {
1189 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1190
1191 ResourceMark rm;
1192
1193 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1194
1195 MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
1196 !NMethodToOopClosure::FixRelocations,
1197 true /* keepalive nmethods */);
1198
1199 thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1200
1201 // Do the real work
1202 cm->follow_marking_stacks();
1203 }
1204 };
1205
1206 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1207 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1208
1209 ParCompactionManager* cm =
1210 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1211
1212 do {
1213 ScannerTask task;
1214 if (ParCompactionManager::steal(worker_id, task)) {
1215 cm->follow_contents(task, true);
1216 }
1217 cm->follow_marking_stacks();
1218 } while (!terminator.offer_termination());
1219 }
1220
1221 class MarkFromRootsTask : public WorkerTask {
1222 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
1223 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1224 TaskTerminator _terminator;
1225 uint _active_workers;
1226
1227 public:
1228 MarkFromRootsTask(uint active_workers) :
1229 WorkerTask("MarkFromRootsTask"),
1230 _strong_roots_scope(active_workers),
1231 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1232 _active_workers(active_workers) {}
1233
1234 virtual void work(uint worker_id) {
1235 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1236 cm->create_marking_stats_cache();
1237 {
1238 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1239 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1240
1241 // Do the real work
1242 cm->follow_marking_stacks();
1243 }
1244
1245 {
1246 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
1247 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1248 }
1249
1250 // Mark from OopStorages
1251 {
1252 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1253 // Do the real work
1254 cm->follow_marking_stacks();
1255 }
1256
1257 if (_active_workers > 1) {
1258 steal_marking_work(_terminator, worker_id);
1259 }
1260 }
1261 };
1262
1263 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1264 TaskTerminator _terminator;
1265
1266 public:
1267 ParallelCompactRefProcProxyTask(uint max_workers)
1268 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1269 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1270
1271 void work(uint worker_id) override {
1272 assert(worker_id < _max_workers, "sanity");
1273 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1274 BarrierEnqueueDiscoveredFieldClosure enqueue;
1275 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1276 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1277 }
1278
1279 void prepare_run_task_hook() override {
1280 _terminator.reset_for_reuse(_queue_count);
1281 }
1282 };
1283
1284 static void flush_marking_stats_cache(const uint num_workers) {
1285 for (uint i = 0; i < num_workers; ++i) {
1286 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1287 cm->flush_and_destroy_marking_stats_cache();
1288 }
1289 }
1290
1291 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1292 // Recursively traverse all live objects and mark them
1293 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1294
1295 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1296
1297 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1298 {
1299 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1300
1301 MarkFromRootsTask task(active_gc_threads);
1302 ParallelScavengeHeap::heap()->workers().run_task(&task);
1303 }
1304
1305 // Process reference objects found during marking
1306 {
1307 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1308
1309 ReferenceProcessorStats stats;
1310 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1311
1312 ref_processor()->set_active_mt_degree(active_gc_threads);
1313 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1314 stats = ref_processor()->process_discovered_references(task, pt);
1315
1316 gc_tracer->report_gc_reference_stats(stats);
1317 pt.print_all_references();
1318 }
1319
1320 {
1321 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1322
1323 flush_marking_stats_cache(active_gc_threads);
1324 }
1325
1326 // This is the point where the entire marking should have completed.
1327 ParCompactionManager::verify_all_marking_stack_empty();
1328
1329 {
1330 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1331 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1332 is_alive_closure(),
1333 &do_nothing_cl,
1334 1);
1335 }
1336
1337 {
1338 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1339
1340 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
1341
1342 bool unloading_occurred;
1343 {
1344 CodeCache::UnlinkingScope scope(is_alive_closure());
1345
1346 // Follow system dictionary roots and unload classes.
1347 unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1348
1349 // Unload nmethods.
1350 CodeCache::do_unloading(unloading_occurred);
1351 }
1352
1353 {
1354 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1355 // Release unloaded nmethod's memory.
1356 ctx->purge_nmethods();
1357 }
1358 {
1359 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1360 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1361 }
1362 {
1363 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1364 ctx->free_nmethods();
1365 }
1366
1367 // Prune dead klasses from subklass/sibling/implementor lists.
1368 Klass::clean_weak_klass_links(unloading_occurred);
1369
1370 // Clean JVMCI metadata handles.
1371 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
1372 }
1373
1374 {
1375 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
1376 _gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
1377 }
1378 #if TASKQUEUE_STATS
1379 ParCompactionManager::print_and_reset_taskqueue_stats();
1380 #endif
1381 }
1382
1383 template<typename Func>
1384 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1385 MutableSpace* sp = PSParallelCompact::space(id);
1386 HeapWord* const bottom = sp->bottom();
1387 HeapWord* const top = sp->top();
1388 if (bottom == top) {
1389 return;
1390 }
1391
1392 const uint num_regions_per_stripe = 2;
1393 const size_t region_size = ParallelCompactData::RegionSize;
1394 const size_t stripe_size = num_regions_per_stripe * region_size;
1395
1396 while (true) {
1397 uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
1398 HeapWord* cur_stripe = bottom + counter * region_size;
1399 if (cur_stripe >= top) {
1400 break;
1401 }
1402 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1403 on_stripe(cur_stripe, stripe_end);
1404 }
1405 }
1406
1407 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1408 // Regions in old-space shouldn't be split.
1409 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1410
1411 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1412 assert(mark_bitmap()->is_marked(obj_start), "inv");
1413 oop obj = cast_to_oop(obj_start);
1414 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1415 };
1416
1417 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1418 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1419 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1420 HeapWord* obj_start;
1421 if (cur_region->partial_obj_size() != 0) {
1422 obj_start = cur_region->partial_obj_addr();
1423 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1424 } else {
1425 obj_start = stripe_start;
1426 }
1427
1428 while (obj_start < stripe_end) {
1429 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1430 if (obj_start >= stripe_end) {
1431 break;
1432 }
1433 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1434 }
1435 });
1436 }
1437
1438 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1439 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1440 HeapWord* obj_start = stripe_start;
1441 while (obj_start < stripe_end) {
1442 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1443 if (obj_start >= stripe_end) {
1444 break;
1445 }
1446 oop obj = cast_to_oop(obj_start);
1447 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1448 }
1449 });
1450 }
1451
1452 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1453 auto start_time = Ticks::now();
1454 adjust_in_old_space(&claim_counters[0]);
1455 for (uint id = eden_space_id; id < last_space_id; ++id) {
1456 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1457 }
1458 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1459 }
1460
1461 class PSAdjustTask final : public WorkerTask {
1462 SubTasksDone _sub_tasks;
1463 WeakProcessor::Task _weak_proc_task;
1464 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1465 uint _nworkers;
1466 volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1467
1468 enum PSAdjustSubTask {
1469 PSAdjustSubTask_code_cache,
1470
1471 PSAdjustSubTask_num_elements
1472 };
1473
1474 public:
1475 PSAdjustTask(uint nworkers) :
1476 WorkerTask("PSAdjust task"),
1477 _sub_tasks(PSAdjustSubTask_num_elements),
1478 _weak_proc_task(nworkers),
1479 _nworkers(nworkers) {
1480
1481 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1482 if (nworkers > 1) {
1483 Threads::change_thread_claim_token();
1484 }
1485 }
1486
1487 ~PSAdjustTask() {
1488 Threads::assert_all_threads_claimed();
1489 }
1490
1491 void work(uint worker_id) {
1492 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1493 cm->preserved_marks()->adjust_during_full_gc();
1494 {
1495 // adjust pointers in all spaces
1496 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1497 }
1498 {
1499 ResourceMark rm;
1500 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1501 }
1502 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1503 {
1504 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1505 ClassLoaderDataGraph::cld_do(&cld_closure);
1506 }
1507 {
1508 AlwaysTrueClosure always_alive;
1509 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1510 }
1511 if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
1512 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1513 CodeCache::nmethods_do(&adjust_code);
1514 }
1515 _sub_tasks.all_tasks_claimed();
1516 }
1517 };
1518
1519 void PSParallelCompact::adjust_pointers() {
1520 // Adjust the pointers to reflect the new locations
1521 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1522 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1523 PSAdjustTask task(nworkers);
1524 ParallelScavengeHeap::heap()->workers().run_task(&task);
1525 }
1526
1527 // Split [start, end) evenly for a number of workers and return the
1528 // range for worker_id.
1529 static void split_regions_for_worker(size_t start, size_t end,
1530 uint worker_id, uint num_workers,
1531 size_t* worker_start, size_t* worker_end) {
1532 assert(start < end, "precondition");
1533 assert(num_workers > 0, "precondition");
1534 assert(worker_id < num_workers, "precondition");
1535
1536 size_t num_regions = end - start;
1537 size_t num_regions_per_worker = num_regions / num_workers;
1538 size_t remainder = num_regions % num_workers;
1539 // The first few workers will get one extra.
1540 *worker_start = start + worker_id * num_regions_per_worker
1541 + MIN2(checked_cast<size_t>(worker_id), remainder);
1542 *worker_end = *worker_start + num_regions_per_worker
1543 + (worker_id < remainder ? 1 : 0);
1544 }
1545
1546 void PSParallelCompact::forward_to_new_addr() {
1547 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1548 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1549
1550 struct ForwardTask final : public WorkerTask {
1551 uint _num_workers;
1552
1553 explicit ForwardTask(uint num_workers) :
1554 WorkerTask("PSForward task"),
1555 _num_workers(num_workers) {}
1556
1557 static void forward_objs_in_range(ParCompactionManager* cm,
1558 HeapWord* start,
1559 HeapWord* end,
1560 HeapWord* destination) {
1561 HeapWord* cur_addr = start;
1562 HeapWord* new_addr = destination;
1563
1564 while (cur_addr < end) {
1565 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1566 if (cur_addr >= end) {
1567 return;
1568 }
1569 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1570 oop obj = cast_to_oop(cur_addr);
1571 if (new_addr != cur_addr) {
1572 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1573 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1574 }
1575 size_t obj_size = obj->size();
1576 new_addr += obj_size;
1577 cur_addr += obj_size;
1578 }
1579 }
1580
1581 void work(uint worker_id) override {
1582 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1583 for (uint id = old_space_id; id < last_space_id; ++id) {
1584 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1585 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1586 HeapWord* top = sp->top();
1587
1588 if (dense_prefix_addr == top) {
1589 continue;
1590 }
1591
1592 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1593
1594 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1595 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1596 size_t start_region;
1597 size_t end_region;
1598 split_regions_for_worker(dense_prefix_region, top_region,
1599 worker_id, _num_workers,
1600 &start_region, &end_region);
1601 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1602 RegionData* region_ptr = _summary_data.region(cur_region);
1603 size_t partial_obj_size = region_ptr->partial_obj_size();
1604
1605 if (partial_obj_size == ParallelCompactData::RegionSize) {
1606 // No obj-start
1607 continue;
1608 }
1609
1610 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1611 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1612
1613 if (split_info.is_split(cur_region)) {
1614 // Part 1: will be relocated to space-1
1615 HeapWord* preceding_destination = split_info.preceding_destination();
1616 HeapWord* split_point = split_info.split_point();
1617 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1618
1619 // Part 2: will be relocated to space-2
1620 HeapWord* destination = region_ptr->destination();
1621 forward_objs_in_range(cm, split_point, region_end, destination);
1622 } else {
1623 HeapWord* destination = region_ptr->destination();
1624 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1625 }
1626 }
1627 }
1628 }
1629 } task(nworkers);
1630
1631 ParallelScavengeHeap::heap()->workers().run_task(&task);
1632 debug_only(verify_forward();)
1633 }
1634
1635 #ifdef ASSERT
1636 void PSParallelCompact::verify_forward() {
1637 HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1638 RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
1639 HeapWord* bump_ptr = old_region->partial_obj_size() != 0
1640 ? old_dense_prefix_addr + old_region->partial_obj_size()
1641 : old_dense_prefix_addr;
1642 SpaceId bump_ptr_space = old_space_id;
1643
1644 for (uint id = old_space_id; id < last_space_id; ++id) {
1645 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1646 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1647 HeapWord* top = sp->top();
1648 HeapWord* cur_addr = dense_prefix_addr;
1649
1650 while (cur_addr < top) {
1651 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1652 if (cur_addr >= top) {
1653 break;
1654 }
1655 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1656 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1657 // Move to the space containing cur_addr
1658 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1659 bump_ptr = space(space_id(cur_addr))->bottom();
1660 bump_ptr_space = space_id(bump_ptr);
1661 }
1662 oop obj = cast_to_oop(cur_addr);
1663 if (cur_addr == bump_ptr) {
1664 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1665 } else {
1666 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1667 }
1668 bump_ptr += obj->size();
1669 cur_addr += obj->size();
1670 }
1671 }
1672 }
1673 #endif
1674
1675 // Helper class to print 8 region numbers per line and then print the total at the end.
1676 class FillableRegionLogger : public StackObj {
1677 private:
1678 Log(gc, compaction) log;
1679 static const int LineLength = 8;
1680 size_t _regions[LineLength];
1681 int _next_index;
1682 bool _enabled;
1683 size_t _total_regions;
1684 public:
1685 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1686 ~FillableRegionLogger() {
1687 log.trace("%zu initially fillable regions", _total_regions);
1688 }
1689
1690 void print_line() {
1691 if (!_enabled || _next_index == 0) {
1692 return;
1693 }
1694 FormatBuffer<> line("Fillable: ");
1695 for (int i = 0; i < _next_index; i++) {
1696 line.append(" %7zu", _regions[i]);
1697 }
1698 log.trace("%s", line.buffer());
1699 _next_index = 0;
1700 }
1701
1702 void handle(size_t region) {
1703 if (!_enabled) {
1704 return;
1705 }
1706 _regions[_next_index++] = region;
1707 if (_next_index == LineLength) {
1708 print_line();
1709 }
1710 _total_regions++;
1711 }
1712 };
1713
1714 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1715 {
1716 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1717
1718 // Find the threads that are active
1719 uint worker_id = 0;
1720
1721 // Find all regions that are available (can be filled immediately) and
1722 // distribute them to the thread stacks. The iteration is done in reverse
1723 // order (high to low) so the regions will be removed in ascending order.
1724
1725 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1726
1727 // id + 1 is used to test termination so unsigned can
1728 // be used with an old_space_id == 0.
1729 FillableRegionLogger region_logger;
1730 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
1731 SpaceInfo* const space_info = _space_info + id;
1732 HeapWord* const new_top = space_info->new_top();
1733
1734 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1735 const size_t end_region =
1736 sd.addr_to_region_idx(sd.region_align_up(new_top));
1737
1738 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1739 if (sd.region(cur)->claim_unsafe()) {
1740 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1741 bool result = sd.region(cur)->mark_normal();
1742 assert(result, "Must succeed at this point.");
1743 cm->region_stack()->push(cur);
1744 region_logger.handle(cur);
1745 // Assign regions to tasks in round-robin fashion.
1746 if (++worker_id == parallel_gc_threads) {
1747 worker_id = 0;
1748 }
1749 }
1750 }
1751 region_logger.print_line();
1752 }
1753 }
1754
1755 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1756 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1757
1758 ParCompactionManager* cm =
1759 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1760
1761 // Drain the stacks that have been preloaded with regions
1762 // that are ready to fill.
1763
1764 cm->drain_region_stacks();
1765
1766 guarantee(cm->region_stack()->is_empty(), "Not empty");
1767
1768 size_t region_index = 0;
1769
1770 while (true) {
1771 if (ParCompactionManager::steal(worker_id, region_index)) {
1772 PSParallelCompact::fill_and_update_region(cm, region_index);
1773 cm->drain_region_stacks();
1774 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1775 // Fill and update an unavailable region with the help of a shadow region
1776 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1777 cm->drain_region_stacks();
1778 } else {
1779 if (terminator->offer_termination()) {
1780 break;
1781 }
1782 // Go around again.
1783 }
1784 }
1785 }
1786
1787 class FillDensePrefixAndCompactionTask: public WorkerTask {
1788 uint _num_workers;
1789 TaskTerminator _terminator;
1790
1791 public:
1792 FillDensePrefixAndCompactionTask(uint active_workers) :
1793 WorkerTask("FillDensePrefixAndCompactionTask"),
1794 _num_workers(active_workers),
1795 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1796 }
1797
1798 virtual void work(uint worker_id) {
1799 {
1800 auto start = Ticks::now();
1801 PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
1802 log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
1803 }
1804 compaction_with_stealing_work(&_terminator, worker_id);
1805 }
1806 };
1807
1808 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1809 #ifdef ASSERT
1810 {
1811 assert(start < end, "precondition");
1812 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1813 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1814 if (start != bottom) {
1815 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1816 HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
1817 assert(after_obj == start, "precondition");
1818 }
1819 }
1820 #endif
1821
1822 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1823 HeapWord* addr = start;
1824 do {
1825 size_t size = cast_to_oop(addr)->size();
1826 start_array(old_space_id)->update_for_block(addr, addr + size);
1827 addr += size;
1828 } while (addr < end);
1829 }
1830
1831 void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
1832 ParMarkBitMap* bitmap = mark_bitmap();
1833
1834 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1835 HeapWord* const prefix_end = dense_prefix(old_space_id);
1836
1837 if (bottom == prefix_end) {
1838 return;
1839 }
1840
1841 size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
1842 size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
1843
1844 size_t start_region;
1845 size_t end_region;
1846 split_regions_for_worker(bottom_region, prefix_end_region,
1847 worker_id, num_workers,
1848 &start_region, &end_region);
1849
1850 if (start_region == end_region) {
1851 return;
1852 }
1853
1854 HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
1855 HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
1856
1857 // Skip live partial obj (if any) from previous region.
1858 HeapWord* cur_addr;
1859 RegionData* start_region_ptr = _summary_data.region(start_region);
1860 if (start_region_ptr->partial_obj_size() != 0) {
1861 HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
1862 assert(bitmap->is_marked(partial_obj_start), "inv");
1863 cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
1864 } else {
1865 cur_addr = start_addr;
1866 }
1867
1868 // end_addr is inclusive to handle regions starting with dead space.
1869 while (cur_addr <= end_addr) {
1870 // Use prefix_end to handle trailing obj in each worker region-chunk.
1871 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
1872 if (cur_addr != live_start) {
1873 // Only worker 0 handles proceeding dead space.
1874 if (cur_addr != start_addr || worker_id == 0) {
1875 fill_range_in_dense_prefix(cur_addr, live_start);
1876 }
1877 }
1878 if (live_start >= end_addr) {
1879 break;
1880 }
1881 assert(bitmap->is_marked(live_start), "inv");
1882 cur_addr = live_start + cast_to_oop(live_start)->size();
1883 }
1884 }
1885
1886 void PSParallelCompact::compact() {
1887 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1888
1889 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1890
1891 initialize_shadow_regions(active_gc_threads);
1892 prepare_region_draining_tasks(active_gc_threads);
1893
1894 {
1895 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1896
1897 FillDensePrefixAndCompactionTask task(active_gc_threads);
1898 ParallelScavengeHeap::heap()->workers().run_task(&task);
1899
1900 #ifdef ASSERT
1901 verify_filler_in_dense_prefix();
1902
1903 // Verify that all regions have been processed.
1904 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1905 verify_complete(SpaceId(id));
1906 }
1907 #endif
1908 }
1909 }
1910
1911 #ifdef ASSERT
1912 void PSParallelCompact::verify_filler_in_dense_prefix() {
1913 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1914 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1915 HeapWord* cur_addr = bottom;
1916 while (cur_addr < dense_prefix_end) {
1917 oop obj = cast_to_oop(cur_addr);
1918 oopDesc::verify(obj);
1919 if (!mark_bitmap()->is_marked(cur_addr)) {
1920 Klass* k = cast_to_oop(cur_addr)->klass();
1921 assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
1922 }
1923 cur_addr += obj->size();
1924 }
1925 }
1926
1927 void PSParallelCompact::verify_complete(SpaceId space_id) {
1928 // All Regions served as compaction targets, from dense_prefix() to
1929 // new_top(), should be marked as filled and all Regions between new_top()
1930 // and top() should be available (i.e., should have been emptied).
1931 ParallelCompactData& sd = summary_data();
1932 SpaceInfo si = _space_info[space_id];
1933 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1934 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1935 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1936 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1937 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1938
1939 size_t cur_region;
1940 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1941 const RegionData* const c = sd.region(cur_region);
1942 assert(c->completed(), "region %zu not filled: destination_count=%u",
1943 cur_region, c->destination_count());
1944 }
1945
1946 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1947 const RegionData* const c = sd.region(cur_region);
1948 assert(c->available(), "region %zu not empty: destination_count=%u",
1949 cur_region, c->destination_count());
1950 }
1951 }
1952 #endif // #ifdef ASSERT
1953
1954 // Return the SpaceId for the space containing addr. If addr is not in the
1955 // heap, last_space_id is returned. In debug mode it expects the address to be
1956 // in the heap and asserts such.
1957 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1958 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1959
1960 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1961 if (_space_info[id].space()->contains(addr)) {
1962 return SpaceId(id);
1963 }
1964 }
1965
1966 assert(false, "no space contains the addr");
1967 return last_space_id;
1968 }
1969
1970 // Skip over count live words starting from beg, and return the address of the
1971 // next live word. Callers must also ensure that there are enough live words in
1972 // the range [beg, end) to skip.
1973 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1974 {
1975 ParMarkBitMap* m = mark_bitmap();
1976 HeapWord* cur_addr = beg;
1977 while (true) {
1978 cur_addr = m->find_obj_beg(cur_addr, end);
1979 assert(cur_addr < end, "inv");
1980 size_t obj_size = cast_to_oop(cur_addr)->size();
1981 // Strictly greater-than
1982 if (obj_size > count) {
1983 return cur_addr + count;
1984 }
1985 count -= obj_size;
1986 cur_addr += obj_size;
1987 }
1988 }
1989
1990 // On starting to fill a destination region (dest-region), we need to know the
1991 // location of the word that will be at the start of the dest-region after
1992 // compaction. A dest-region can have one or more source regions, but only the
1993 // first source-region contains this location. This location is retrieved by
1994 // calling `first_src_addr` on a dest-region.
1995 // Conversely, a source-region has a dest-region which holds the destination of
1996 // the first live word on this source-region, based on which the destination
1997 // for the rest of live words can be derived.
1998 //
1999 // Note:
2000 // There is some complication due to space-boundary-fragmentation (an obj can't
2001 // cross space-boundary) -- a source-region may be split and behave like two
2002 // distinct regions with their own dest-region, as depicted below.
2003 //
2004 // source-region: region-n
2005 //
2006 // **********************
2007 // | A|A~~~~B|B |
2008 // **********************
2009 // n-1 n n+1
2010 //
2011 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
2012 //
2013 // Assuming the dest-region for region-n is the final region before
2014 // old-space-end and its first-live-word is the middle of AA, the heap content
2015 // will look like the following after compaction:
2016 //
2017 // ************** *************
2018 // A|A~~~~ | |BB |
2019 // ************** *************
2020 // ^ ^
2021 // | old-space-end | eden-space-start
2022 //
2023 // Therefore, in this example, region-n will have two dest-regions:
2024 // 1. the final region in old-space
2025 // 2. the first region in eden-space.
2026 // To handle this special case, we introduce the concept of split-region, whose
2027 // contents are relocated to two spaces. `SplitInfo` captures all necessary
2028 // info about the split, the first part, spliting-point, and the second part.
2029 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2030 SpaceId src_space_id,
2031 size_t src_region_idx)
2032 {
2033 const size_t RegionSize = ParallelCompactData::RegionSize;
2034 const ParallelCompactData& sd = summary_data();
2035 assert(sd.is_region_aligned(dest_addr), "precondition");
2036
2037 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2038 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2039
2040 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2041 HeapWord* const src_region_destination = src_region_ptr->destination();
2042
2043 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
2044 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
2045
2046 // Identify the actual destination for the first live words on this region,
2047 // taking split-region into account.
2048 HeapWord* region_start_destination;
2049 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2050 if (split_info.is_split(src_region_idx)) {
2051 // The second part of this split region; use the recorded split point.
2052 if (dest_addr == src_region_destination) {
2053 return split_info.split_point();
2054 }
2055 region_start_destination = split_info.preceding_destination();
2056 } else {
2057 region_start_destination = src_region_destination;
2058 }
2059
2060 // Calculate the offset to be skipped
2061 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
2062
2063 HeapWord* result;
2064 if (partial_obj_size > words_to_skip) {
2065 result = region_start + words_to_skip;
2066 } else {
2067 words_to_skip -= partial_obj_size;
2068 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2069 }
2070
2071 if (split_info.is_split(src_region_idx)) {
2072 assert(result < split_info.split_point(), "postcondition");
2073 } else {
2074 assert(result < region_end, "postcondition");
2075 }
2076
2077 return result;
2078 }
2079
2080 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2081 SpaceId src_space_id,
2082 size_t beg_region,
2083 HeapWord* end_addr)
2084 {
2085 ParallelCompactData& sd = summary_data();
2086
2087 #ifdef ASSERT
2088 MutableSpace* const src_space = _space_info[src_space_id].space();
2089 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2090 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2091 "src_space_id does not match beg_addr");
2092 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2093 "src_space_id does not match end_addr");
2094 #endif // #ifdef ASSERT
2095
2096 RegionData* const beg = sd.region(beg_region);
2097 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2098
2099 // Regions up to new_top() are enqueued if they become available.
2100 HeapWord* const new_top = _space_info[src_space_id].new_top();
2101 RegionData* const enqueue_end =
2102 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2103
2104 for (RegionData* cur = beg; cur < end; ++cur) {
2105 assert(cur->data_size() > 0, "region must have live data");
2106 cur->decrement_destination_count();
2107 if (cur < enqueue_end && cur->available() && cur->claim()) {
2108 if (cur->mark_normal()) {
2109 cm->push_region(sd.region(cur));
2110 } else if (cur->mark_copied()) {
2111 // Try to copy the content of the shadow region back to its corresponding
2112 // heap region if the shadow region is filled. Otherwise, the GC thread
2113 // fills the shadow region will copy the data back (see
2114 // MoveAndUpdateShadowClosure::complete_region).
2115 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2116 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2117 cur->set_completed();
2118 }
2119 }
2120 }
2121 }
2122
2123 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2124 SpaceId& src_space_id,
2125 HeapWord*& src_space_top,
2126 HeapWord* end_addr)
2127 {
2128 ParallelCompactData& sd = PSParallelCompact::summary_data();
2129
2130 size_t src_region_idx = 0;
2131
2132 // Skip empty regions (if any) up to the top of the space.
2133 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2134 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2135 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2136 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2137
2138 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2139 ++src_region_ptr;
2140 }
2141
2142 if (src_region_ptr < top_region_ptr) {
2143 // Found the first non-empty region in the same space.
2144 src_region_idx = sd.region(src_region_ptr);
2145 closure.set_source(sd.region_to_addr(src_region_idx));
2146 return src_region_idx;
2147 }
2148
2149 // Switch to a new source space and find the first non-empty region.
2150 uint space_id = src_space_id + 1;
2151 assert(space_id < last_space_id, "not enough spaces");
2152
2153 for (/* empty */; space_id < last_space_id; ++space_id) {
2154 HeapWord* bottom = _space_info[space_id].space()->bottom();
2155 HeapWord* top = _space_info[space_id].space()->top();
2156 // Skip empty space
2157 if (bottom == top) {
2158 continue;
2159 }
2160
2161 // Identify the first region that contains live words in this space
2162 size_t cur_region = sd.addr_to_region_idx(bottom);
2163 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2164
2165 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2166 RegionData* cur = sd.region(cur_region);
2167 if (cur->live_obj_size() > 0) {
2168 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2169
2170 src_space_id = SpaceId(space_id);
2171 src_space_top = top;
2172 closure.set_source(region_start_addr);
2173 return cur_region;
2174 }
2175 }
2176 }
2177
2178 ShouldNotReachHere();
2179 }
2180
2181 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2182 ParallelCompactData& sd = summary_data();
2183 assert(sd.is_region_aligned(region_start_addr), "precondition");
2184
2185 // Use per-region partial_obj_size to locate the end of the obj, that extends
2186 // to region_start_addr.
2187 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2188 size_t end_region_idx = sd.region_count();
2189 size_t accumulated_size = 0;
2190 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2191 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2192 accumulated_size += cur_partial_obj_size;
2193 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2194 break;
2195 }
2196 }
2197 return region_start_addr + accumulated_size;
2198 }
2199
2200 // Use region_idx as the destination region, and evacuate all live objs on its
2201 // source regions to this destination region.
2202 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2203 {
2204 ParMarkBitMap* const bitmap = mark_bitmap();
2205 ParallelCompactData& sd = summary_data();
2206 RegionData* const region_ptr = sd.region(region_idx);
2207
2208 // Get the source region and related info.
2209 size_t src_region_idx = region_ptr->source_region();
2210 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2211 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2212 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2213
2214 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2215
2216 // Adjust src_region_idx to prepare for decrementing destination counts (the
2217 // destination count is not decremented when a region is copied to itself).
2218 if (src_region_idx == region_idx) {
2219 src_region_idx += 1;
2220 }
2221
2222 // source-region:
2223 //
2224 // **********
2225 // | ~~~ |
2226 // **********
2227 // ^
2228 // |-- closure.source() / first_src_addr
2229 //
2230 //
2231 // ~~~ : live words
2232 //
2233 // destination-region:
2234 //
2235 // **********
2236 // | |
2237 // **********
2238 // ^
2239 // |-- region-start
2240 if (bitmap->is_unmarked(closure.source())) {
2241 // An object overflows the previous destination region, so this
2242 // destination region should copy the remainder of the object or as much as
2243 // will fit.
2244 HeapWord* const old_src_addr = closure.source();
2245 {
2246 HeapWord* region_start = sd.region_align_down(closure.source());
2247 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2248 HeapWord* obj_end;
2249 if (obj_start != closure.source()) {
2250 assert(bitmap->is_marked(obj_start), "inv");
2251 // Found the actual obj-start, try to find the obj-end using either
2252 // size() if this obj is completely contained in the current region.
2253 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2254 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2255 ? nullptr
2256 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2257 // This obj extends to next region iff partial_obj_addr of the *next*
2258 // region is the same as obj-start.
2259 if (partial_obj_start == obj_start) {
2260 // This obj extends to next region.
2261 obj_end = partial_obj_end(next_region_start);
2262 } else {
2263 // Completely contained in this region; safe to use size().
2264 obj_end = obj_start + cast_to_oop(obj_start)->size();
2265 }
2266 } else {
2267 // This obj extends to current region.
2268 obj_end = partial_obj_end(region_start);
2269 }
2270 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2271 closure.copy_partial_obj(partial_obj_size);
2272 }
2273
2274 if (closure.is_full()) {
2275 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2276 closure.complete_region(dest_addr, region_ptr);
2277 return;
2278 }
2279
2280 // Finished copying without using up the current destination-region
2281 HeapWord* const end_addr = sd.region_align_down(closure.source());
2282 if (sd.region_align_down(old_src_addr) != end_addr) {
2283 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2284 // The partial object was copied from more than one source region.
2285 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2286
2287 // Move to the next source region, possibly switching spaces as well. All
2288 // args except end_addr may be modified.
2289 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2290 }
2291 }
2292
2293 // Handle the rest obj-by-obj, where we know obj-start.
2294 do {
2295 HeapWord* cur_addr = closure.source();
2296 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2297 src_space_top);
2298 // To handle the case where the final obj in source region extends to next region.
2299 HeapWord* final_obj_start = (end_addr == src_space_top)
2300 ? nullptr
2301 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2302 // Apply closure on objs inside [cur_addr, end_addr)
2303 do {
2304 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2305 if (cur_addr == end_addr) {
2306 break;
2307 }
2308 size_t obj_size;
2309 if (final_obj_start == cur_addr) {
2310 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2311 } else {
2312 // This obj doesn't extend into next region; size() is safe to use.
2313 obj_size = cast_to_oop(cur_addr)->size();
2314 }
2315 closure.do_addr(cur_addr, obj_size);
2316 cur_addr += obj_size;
2317 } while (cur_addr < end_addr && !closure.is_full());
2318
2319 if (closure.is_full()) {
2320 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2321 closure.complete_region(dest_addr, region_ptr);
2322 return;
2323 }
2324
2325 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2326
2327 // Move to the next source region, possibly switching spaces as well. All
2328 // args except end_addr may be modified.
2329 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2330 } while (true);
2331 }
2332
2333 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2334 {
2335 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2336 fill_region(cm, cl, region_idx);
2337 }
2338
2339 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2340 {
2341 // Get a shadow region first
2342 ParallelCompactData& sd = summary_data();
2343 RegionData* const region_ptr = sd.region(region_idx);
2344 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2345 // The InvalidShadow return value indicates the corresponding heap region is available,
2346 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2347 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2348 if (shadow_region == ParCompactionManager::InvalidShadow) {
2349 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2350 region_ptr->shadow_to_normal();
2351 return fill_region(cm, cl, region_idx);
2352 } else {
2353 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2354 return fill_region(cm, cl, region_idx);
2355 }
2356 }
2357
2358 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2359 {
2360 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2361 }
2362
2363 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2364 {
2365 size_t next = cm->next_shadow_region();
2366 ParallelCompactData& sd = summary_data();
2367 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2368 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2369
2370 while (next < old_new_top) {
2371 if (sd.region(next)->mark_shadow()) {
2372 region_idx = next;
2373 return true;
2374 }
2375 next = cm->move_next_shadow_region_by(active_gc_threads);
2376 }
2377
2378 return false;
2379 }
2380
2381 // The shadow region is an optimization to address region dependencies in full GC. The basic
2382 // idea is making more regions available by temporally storing their live objects in empty
2383 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2384 // GC threads need not wait destination regions to be available before processing sources.
2385 //
2386 // A typical workflow would be:
2387 // After draining its own stack and failing to steal from others, a GC worker would pick an
2388 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2389 // the shadow region by copying live objects from source regions of the unavailable one. Once
2390 // the unavailable region becomes available, the data in the shadow region will be copied back.
2391 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2392 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2393 {
2394 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2395
2396 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2397 SpaceInfo* const space_info = _space_info + id;
2398 MutableSpace* const space = space_info->space();
2399
2400 const size_t beg_region =
2401 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2402 const size_t end_region =
2403 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2404
2405 for (size_t cur = beg_region; cur < end_region; ++cur) {
2406 ParCompactionManager::push_shadow_region(cur);
2407 }
2408 }
2409
2410 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2411 for (uint i = 0; i < parallel_gc_threads; i++) {
2412 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2413 cm->set_next_shadow_region(beg_region + i);
2414 }
2415 }
2416
2417 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2418 {
2419 size_t words = MIN2(partial_obj_size, words_remaining());
2420
2421 // This test is necessary; if omitted, the pointer updates to a partial object
2422 // that crosses the dense prefix boundary could be overwritten.
2423 if (source() != copy_destination()) {
2424 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2425 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2426 }
2427 update_state(words);
2428 }
2429
2430 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2431 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2432 region_ptr->set_completed();
2433 }
2434
2435 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2436 assert(destination() != nullptr, "sanity");
2437 _source = addr;
2438
2439 // The start_array must be updated even if the object is not moving.
2440 if (_start_array != nullptr) {
2441 _start_array->update_for_block(destination(), destination() + words);
2442 }
2443
2444 // Avoid overflow
2445 words = MIN2(words, words_remaining());
2446 assert(words > 0, "inv");
2447
2448 if (copy_destination() != source()) {
2449 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2450 assert(source() != destination(), "inv");
2451 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2452 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2453 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2454 cast_to_oop(copy_destination())->init_mark();
2455 }
2456
2457 update_state(words);
2458 }
2459
2460 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2461 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2462 // Record the shadow region index
2463 region_ptr->set_shadow_region(_shadow);
2464 // Mark the shadow region as filled to indicate the data is ready to be
2465 // copied back
2466 region_ptr->mark_filled();
2467 // Try to copy the content of the shadow region back to its corresponding
2468 // heap region if available; the GC thread that decreases the destination
2469 // count to zero will do the copying otherwise (see
2470 // PSParallelCompact::decrement_destination_counts).
2471 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2472 region_ptr->set_completed();
2473 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2474 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2475 }
2476 }