1 /*
2 * Copyright (c) 2005, 2026, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/javaClasses.inline.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/nmethod.hpp"
32 #include "compiler/oopMap.hpp"
33 #include "cppstdlib/new.hpp"
34 #include "gc/parallel/objectStartArray.inline.hpp"
35 #include "gc/parallel/parallelArguments.hpp"
36 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
37 #include "gc/parallel/parMarkBitMap.inline.hpp"
38 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
39 #include "gc/parallel/psCompactionManager.inline.hpp"
40 #include "gc/parallel/psOldGen.hpp"
41 #include "gc/parallel/psParallelCompact.inline.hpp"
42 #include "gc/parallel/psPromotionManager.inline.hpp"
43 #include "gc/parallel/psRootType.hpp"
44 #include "gc/parallel/psScavenge.hpp"
45 #include "gc/parallel/psStringDedup.hpp"
46 #include "gc/parallel/psYoungGen.hpp"
47 #include "gc/shared/classUnloadingContext.hpp"
48 #include "gc/shared/collectedHeap.inline.hpp"
49 #include "gc/shared/fullGCForwarding.inline.hpp"
50 #include "gc/shared/gcCause.hpp"
51 #include "gc/shared/gcHeapSummary.hpp"
52 #include "gc/shared/gcId.hpp"
53 #include "gc/shared/gcLocker.hpp"
54 #include "gc/shared/gcTimer.hpp"
55 #include "gc/shared/gcTrace.hpp"
56 #include "gc/shared/gcTraceTime.inline.hpp"
57 #include "gc/shared/gcVMOperations.hpp"
58 #include "gc/shared/isGCActiveMark.hpp"
59 #include "gc/shared/oopStorage.inline.hpp"
60 #include "gc/shared/oopStorageSet.inline.hpp"
61 #include "gc/shared/oopStorageSetParState.inline.hpp"
62 #include "gc/shared/parallelCleaning.hpp"
63 #include "gc/shared/preservedMarks.inline.hpp"
64 #include "gc/shared/referencePolicy.hpp"
65 #include "gc/shared/referenceProcessor.hpp"
66 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
67 #include "gc/shared/spaceDecorator.hpp"
68 #include "gc/shared/taskTerminator.hpp"
69 #include "gc/shared/weakProcessor.inline.hpp"
70 #include "gc/shared/workerPolicy.hpp"
71 #include "gc/shared/workerThread.hpp"
72 #include "gc/shared/workerUtils.hpp"
73 #include "logging/log.hpp"
74 #include "memory/iterator.inline.hpp"
75 #include "memory/memoryReserver.hpp"
76 #include "memory/metaspaceUtils.hpp"
77 #include "memory/resourceArea.hpp"
78 #include "memory/universe.hpp"
79 #include "nmt/memTracker.hpp"
80 #include "oops/access.inline.hpp"
81 #include "oops/flatArrayKlass.inline.hpp"
82 #include "oops/instanceClassLoaderKlass.inline.hpp"
83 #include "oops/instanceKlass.inline.hpp"
84 #include "oops/instanceMirrorKlass.inline.hpp"
85 #include "oops/methodData.hpp"
86 #include "oops/objArrayKlass.inline.hpp"
87 #include "oops/oop.inline.hpp"
88 #include "runtime/arguments.hpp"
89 #include "runtime/handles.inline.hpp"
90 #include "runtime/java.hpp"
91 #include "runtime/safepoint.hpp"
92 #include "runtime/threads.hpp"
93 #include "runtime/vmThread.hpp"
94 #include "services/memoryService.hpp"
95 #include "utilities/align.hpp"
96 #include "utilities/debug.hpp"
97 #include "utilities/events.hpp"
98 #include "utilities/formatBuffer.hpp"
99 #include "utilities/macros.hpp"
100 #include "utilities/stack.inline.hpp"
101 #if INCLUDE_JVMCI
102 #include "jvmci/jvmci.hpp"
103 #endif
104
105 #include <math.h>
106
107 // All sizes are in HeapWords.
108 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
109 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
110 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
111 const size_t ParallelCompactData::RegionSizeBytes =
112 RegionSize << LogHeapWordSize;
113 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
114 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
115 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
116
117 const ParallelCompactData::RegionData::region_sz_t
118 ParallelCompactData::RegionData::dc_shift = 27;
119
120 const ParallelCompactData::RegionData::region_sz_t
121 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
122
123 const ParallelCompactData::RegionData::region_sz_t
124 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
125
126 const ParallelCompactData::RegionData::region_sz_t
127 ParallelCompactData::RegionData::los_mask = ~dc_mask;
128
129 const ParallelCompactData::RegionData::region_sz_t
130 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
131
132 const ParallelCompactData::RegionData::region_sz_t
133 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
134
135 bool ParallelCompactData::RegionData::is_clear() {
136 return (_destination == nullptr) &&
137 (_source_region == 0) &&
138 (_partial_obj_addr == nullptr) &&
139 (_partial_obj_size == 0) &&
140 (dc_and_los() == 0) &&
141 (shadow_state() == 0);
142 }
143
144 #ifdef ASSERT
145 void ParallelCompactData::RegionData::verify_clear() {
146 assert(_destination == nullptr, "inv");
147 assert(_source_region == 0, "inv");
148 assert(_partial_obj_addr == nullptr, "inv");
149 assert(_partial_obj_size == 0, "inv");
150 assert(dc_and_los() == 0, "inv");
151 assert(shadow_state() == 0, "inv");
152 }
153 #endif
154
155 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
156
157 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
158 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
159
160 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
161 assert(split_region_idx != 0, "precondition");
162
163 // Obj denoted by split_point will be deferred to the next space.
164 assert(split_point != nullptr, "precondition");
165
166 const ParallelCompactData& sd = PSParallelCompact::summary_data();
167
168 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
169 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
170
171 HeapWord* preceding_destination = split_region_ptr->destination();
172 assert(preceding_destination != nullptr, "inv");
173
174 // How many regions does the preceding part occupy
175 uint preceding_destination_count;
176 if (preceding_live_words == 0) {
177 preceding_destination_count = 0;
178 } else {
179 // -1 so that the ending address doesn't fall on the region-boundary
180 if (sd.region_align_down(preceding_destination) ==
181 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
182 preceding_destination_count = 1;
183 } else {
184 preceding_destination_count = 2;
185 }
186 }
187
188 _split_region_idx = split_region_idx;
189 _split_point = split_point;
190 _preceding_live_words = preceding_live_words;
191 _preceding_destination = preceding_destination;
192 _preceding_destination_count = preceding_destination_count;
193 }
194
195 void SplitInfo::clear()
196 {
197 _split_region_idx = 0;
198 _split_point = nullptr;
199 _preceding_live_words = 0;
200 _preceding_destination = nullptr;
201 _preceding_destination_count = 0;
202 assert(!is_valid(), "sanity");
203 }
204
205 #ifdef ASSERT
206 void SplitInfo::verify_clear()
207 {
208 assert(_split_region_idx == 0, "not clear");
209 assert(_split_point == nullptr, "not clear");
210 assert(_preceding_live_words == 0, "not clear");
211 assert(_preceding_destination == nullptr, "not clear");
212 assert(_preceding_destination_count == 0, "not clear");
213 }
214 #endif // #ifdef ASSERT
215
216
217 void PSParallelCompact::print_on(outputStream* st) {
218 _mark_bitmap.print_on(st);
219 }
220
221 ParallelCompactData::ParallelCompactData() :
222 _heap_start(nullptr),
223 DEBUG_ONLY(_heap_end(nullptr) COMMA)
224 _region_vspace(nullptr),
225 _reserved_byte_size(0),
226 _region_data(nullptr),
227 _region_count(0) {}
228
229 bool ParallelCompactData::initialize(MemRegion reserved_heap)
230 {
231 _heap_start = reserved_heap.start();
232 const size_t heap_size = reserved_heap.word_size();
233 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
234
235 assert(region_align_down(_heap_start) == _heap_start,
236 "region start not aligned");
237 assert(is_aligned(heap_size, RegionSize), "precondition");
238
239 const size_t count = heap_size >> Log2RegionSize;
240 const size_t raw_bytes = count * sizeof(RegionData);
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 mtGC);
251
252 if (!rs.is_reserved()) {
253 // Failed to reserve memory.
254 return false;
255 }
256
257 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
258 rs.size(), page_sz);
259
260 MemTracker::record_virtual_memory_tag(rs, mtGC);
261
262 PSVirtualSpace* region_vspace = new PSVirtualSpace(rs, page_sz);
263
264 if (!region_vspace->expand_by(_reserved_byte_size)) {
265 // Failed to commit memory.
266
267 delete region_vspace;
268
269 // Release memory reserved in the space.
270 MemoryReserver::release(rs);
271
272 return false;
273 }
274
275 _region_vspace = region_vspace;
276 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
277 _region_count = count;
278 return true;
279 }
280
281 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
282 assert(beg_region <= _region_count, "beg_region out of range");
283 assert(end_region <= _region_count, "end_region out of range");
284
285 for (size_t i = beg_region; i < end_region; i++) {
286 ::new (&_region_data[i]) RegionData{};
287 }
288 }
289
290 // The total live words on src_region would overflow the target space, so find
291 // the overflowing object and record the split point. The invariant is that an
292 // obj should not cross space boundary.
293 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
294 SplitInfo& split_info,
295 HeapWord* const destination,
296 HeapWord* const target_end,
297 HeapWord** target_next) {
298 assert(destination <= target_end, "sanity");
299 assert(destination + _region_data[src_region].data_size() > target_end,
300 "region should not fit into target space");
301 assert(is_region_aligned(target_end), "sanity");
302
303 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
304
305 if (destination + partial_obj_size > target_end) {
306 assert(partial_obj_size > 0, "inv");
307 // The overflowing obj is from a previous region.
308 //
309 // source-regions:
310 //
311 // ***************
312 // | A|AA |
313 // ***************
314 // ^
315 // | split-point
316 //
317 // dest-region:
318 //
319 // ********
320 // |~~~~A |
321 // ********
322 // ^^
323 // || target-space-end
324 // |
325 // | destination
326 //
327 // AAA would overflow target-space.
328 //
329 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
330 size_t split_region = addr_to_region_idx(overflowing_obj);
331
332 // The number of live words before the overflowing object on this split region
333 size_t preceding_live_words;
334 if (is_region_aligned(overflowing_obj)) {
335 preceding_live_words = 0;
336 } else {
337 // Words accounted by the overflowing object on the split region
338 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
339 preceding_live_words = region(split_region)->data_size() - overflowing_size;
340 }
341
342 split_info.record(split_region, overflowing_obj, preceding_live_words);
343
344 // The [overflowing_obj, src_region_start) part has been accounted for, so
345 // must move back the new_top, now that this overflowing obj is deferred.
346 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
347
348 // If the overflowing obj was relocated to its original destination,
349 // those destination regions would have their source_region set. Now that
350 // this overflowing obj is relocated somewhere else, reset the
351 // source_region.
352 {
353 size_t range_start = addr_to_region_idx(region_align_up(new_top));
354 size_t range_end = addr_to_region_idx(region_align_up(destination));
355 for (size_t i = range_start; i < range_end; ++i) {
356 region(i)->set_source_region(0);
357 }
358 }
359
360 // Update new top of target space
361 *target_next = new_top;
362
363 return overflowing_obj;
364 }
365
366 // Obj-iteration to locate the overflowing obj
367 HeapWord* region_start = region_to_addr(src_region);
368 HeapWord* region_end = region_start + RegionSize;
369 HeapWord* cur_addr = region_start + partial_obj_size;
370 size_t live_words = partial_obj_size;
371
372 while (true) {
373 assert(cur_addr < region_end, "inv");
374 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
375 // There must be an overflowing obj in this region
376 assert(cur_addr < region_end, "inv");
377
378 oop obj = cast_to_oop(cur_addr);
379 size_t obj_size = obj->size();
380 if (destination + live_words + obj_size > target_end) {
381 // Found the overflowing obj
382 split_info.record(src_region, cur_addr, live_words);
383 *target_next = destination + live_words;
384 return cur_addr;
385 }
386
387 live_words += obj_size;
388 cur_addr += obj_size;
389 }
390 }
391
392 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
393 HeapWord** full_region_prefix_end) {
394 size_t cur_region = addr_to_region_idx(space->bottom());
395 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
396 size_t live_words = 0;
397 if (full_region_prefix_end == nullptr) {
398 for (/* empty */; cur_region < end_region; ++cur_region) {
399 live_words += _region_data[cur_region].data_size();
400 }
401 } else {
402 bool first_set = false;
403 for (/* empty */; cur_region < end_region; ++cur_region) {
404 size_t live_words_in_region = _region_data[cur_region].data_size();
405 if (!first_set && live_words_in_region < RegionSize) {
406 *full_region_prefix_end = region_to_addr(cur_region);
407 first_set = true;
408 }
409 live_words += live_words_in_region;
410 }
411 if (!first_set) {
412 // All regions are full of live objs.
413 assert(is_region_aligned(space->top()), "inv");
414 *full_region_prefix_end = space->top();
415 }
416 assert(*full_region_prefix_end != nullptr, "postcondition");
417 assert(is_region_aligned(*full_region_prefix_end), "inv");
418 assert(*full_region_prefix_end >= space->bottom(), "in-range");
419 assert(*full_region_prefix_end <= space->top(), "in-range");
420 }
421 return live_words;
422 }
423
424 bool ParallelCompactData::summarize(SplitInfo& split_info,
425 HeapWord* source_beg, HeapWord* source_end,
426 HeapWord** source_next,
427 HeapWord* target_beg, HeapWord* target_end,
428 HeapWord** target_next)
429 {
430 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
431 log_develop_trace(gc, compaction)(
432 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
433 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
434 p2i(source_beg), p2i(source_end), p2i(source_next_val),
435 p2i(target_beg), p2i(target_end), p2i(*target_next));
436
437 size_t cur_region = addr_to_region_idx(source_beg);
438 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
439
440 HeapWord *dest_addr = target_beg;
441 for (/* empty */; cur_region < end_region; cur_region++) {
442 size_t words = _region_data[cur_region].data_size();
443
444 // Skip empty ones
445 if (words == 0) {
446 continue;
447 }
448
449 if (split_info.is_split(cur_region)) {
450 assert(words > split_info.preceding_live_words(), "inv");
451 words -= split_info.preceding_live_words();
452 }
453
454 _region_data[cur_region].set_destination(dest_addr);
455
456 // If cur_region does not fit entirely into the target space, find a point
457 // at which the source space can be 'split' so that part is copied to the
458 // target space and the rest is copied elsewhere.
459 if (dest_addr + words > target_end) {
460 assert(source_next != nullptr, "source_next is null when splitting");
461 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
462 target_end, target_next);
463 return false;
464 }
465
466 uint destination_count = split_info.is_split(cur_region)
467 ? split_info.preceding_destination_count()
468 : 0;
469
470 HeapWord* const last_addr = dest_addr + words - 1;
471 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
472 const size_t dest_region_2 = addr_to_region_idx(last_addr);
473
474 // Initially assume that the destination regions will be the same and
475 // adjust the value below if necessary. Under this assumption, if
476 // cur_region == dest_region_2, then cur_region will be compacted
477 // completely into itself.
478 destination_count += cur_region == dest_region_2 ? 0 : 1;
479 if (dest_region_1 != dest_region_2) {
480 // Destination regions differ; adjust destination_count.
481 destination_count += 1;
482 // Data from cur_region will be copied to the start of dest_region_2.
483 _region_data[dest_region_2].set_source_region(cur_region);
484 } else if (is_region_aligned(dest_addr)) {
485 // Data from cur_region will be copied to the start of the destination
486 // region.
487 _region_data[dest_region_1].set_source_region(cur_region);
488 }
489
490 _region_data[cur_region].set_destination_count(destination_count);
491 dest_addr += words;
492 }
493
494 *target_next = dest_addr;
495 return true;
496 }
497
498 #ifdef ASSERT
499 void ParallelCompactData::verify_clear() {
500 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
501 if (!region(cur_idx)->is_clear()) {
502 log_warning(gc)("Uncleared Region: %u", cur_idx);
503 region(cur_idx)->verify_clear();
504 }
505 }
506 }
507 #endif // #ifdef ASSERT
508
509 STWGCTimer PSParallelCompact::_gc_timer;
510 ParallelOldTracer PSParallelCompact::_gc_tracer;
511 elapsedTimer PSParallelCompact::_accumulated_time;
512 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
513 CollectorCounters* PSParallelCompact::_counters = nullptr;
514 ParMarkBitMap PSParallelCompact::_mark_bitmap;
515 ParallelCompactData PSParallelCompact::_summary_data;
516
517 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
518
519 class PCAdjustPointerClosure: public BasicOopIterateClosure {
520 template <typename T>
521 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
522
523 public:
524 virtual void do_oop(oop* p) { do_oop_work(p); }
525 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
526
527 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
528 };
529
530 static PCAdjustPointerClosure pc_adjust_pointer_closure;
531
532 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
533
534 void PSParallelCompact::post_initialize() {
535 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
536 _span_based_discoverer.set_span(heap->reserved_region());
537 _ref_processor =
538 new ReferenceProcessor(&_span_based_discoverer,
539 ParallelGCThreads, // mt processing degree
540 ParallelGCThreads, // mt discovery degree
541 false, // concurrent_discovery
542 &_is_alive_closure); // non-header is alive closure
543
544 _counters = new CollectorCounters("Parallel full collection pauses", 1);
545
546 // Initialize static fields in ParCompactionManager.
547 ParCompactionManager::initialize(mark_bitmap());
548 }
549
550 bool PSParallelCompact::initialize_aux_data() {
551 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
552 MemRegion mr = heap->reserved_region();
553 assert(mr.byte_size() != 0, "heap should be reserved");
554
555 initialize_space_info();
556
557 if (!_mark_bitmap.initialize(mr)) {
558 vm_shutdown_during_initialization(
559 err_msg("Unable to allocate %zuKB bitmaps for parallel "
560 "garbage collection for the requested %zuKB heap.",
561 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
562 return false;
563 }
564
565 if (!_summary_data.initialize(mr)) {
566 vm_shutdown_during_initialization(
567 err_msg("Unable to allocate %zuKB card tables for parallel "
568 "garbage collection for the requested %zuKB heap.",
569 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
570 return false;
571 }
572
573 return true;
574 }
575
576 void PSParallelCompact::initialize_space_info()
577 {
578 memset(&_space_info, 0, sizeof(_space_info));
579
580 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
581 PSYoungGen* young_gen = heap->young_gen();
582
583 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
584 _space_info[eden_space_id].set_space(young_gen->eden_space());
585 _space_info[from_space_id].set_space(young_gen->from_space());
586 _space_info[to_space_id].set_space(young_gen->to_space());
587
588 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
589 }
590
591 void
592 PSParallelCompact::clear_data_covering_space(SpaceId id)
593 {
594 // At this point, top is the value before GC, new_top() is the value that will
595 // be set at the end of GC. The marking bitmap is cleared to top; nothing
596 // should be marked above top. The summary data is cleared to the larger of
597 // top & new_top.
598 MutableSpace* const space = _space_info[id].space();
599 HeapWord* const bot = space->bottom();
600 HeapWord* const top = space->top();
601 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
602
603 _mark_bitmap.clear_range(bot, top);
604
605 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
606 const size_t end_region =
607 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
608 _summary_data.clear_range(beg_region, end_region);
609
610 // Clear the data used to 'split' regions.
611 SplitInfo& split_info = _space_info[id].split_info();
612 if (split_info.is_valid()) {
613 split_info.clear();
614 }
615 DEBUG_ONLY(split_info.verify_clear();)
616 }
617
618 void PSParallelCompact::pre_compact()
619 {
620 // Update the from & to space pointers in space_info, since they are swapped
621 // at each young gen gc. Do the update unconditionally (even though a
622 // promotion failure does not swap spaces) because an unknown number of young
623 // collections will have swapped the spaces an unknown number of times.
624 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
625 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
626 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
627 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
628
629 heap->increment_total_collections(true);
630
631 CodeCache::on_gc_marking_cycle_start();
632
633 heap->print_before_gc();
634 heap->trace_heap_before_gc(&_gc_tracer);
635
636 // Fill in TLABs
637 heap->ensure_parsability(true); // retire TLABs
638
639 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
640 Universe::verify("Before GC");
641 }
642
643 DEBUG_ONLY(mark_bitmap()->verify_clear();)
644 DEBUG_ONLY(summary_data().verify_clear();)
645 }
646
647 void PSParallelCompact::post_compact()
648 {
649 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
650 ParCompactionManager::remove_all_shadow_regions();
651
652 CodeCache::on_gc_marking_cycle_finish();
653 CodeCache::arm_all_nmethods();
654
655 // Need to clear claim bits for the next full-gc (marking and adjust-pointers).
656 ClassLoaderDataGraph::clear_claimed_marks();
657
658 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
659 // Clear the marking bitmap, summary data and split info.
660 clear_data_covering_space(SpaceId(id));
661 {
662 MutableSpace* space = _space_info[id].space();
663 HeapWord* top = space->top();
664 HeapWord* new_top = _space_info[id].new_top();
665 if (ZapUnusedHeapArea && new_top < top) {
666 space->mangle_region(MemRegion(new_top, top));
667 }
668 // Update top(). Must be done after clearing the bitmap and summary data.
669 space->set_top(new_top);
670 }
671 }
672
673 #ifdef ASSERT
674 {
675 mark_bitmap()->verify_clear();
676 summary_data().verify_clear();
677 }
678 #endif
679
680 ParCompactionManager::flush_all_string_dedup_requests();
681
682 MutableSpace* const eden_space = _space_info[eden_space_id].space();
683 MutableSpace* const from_space = _space_info[from_space_id].space();
684 MutableSpace* const to_space = _space_info[to_space_id].space();
685
686 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
687 bool eden_empty = eden_space->is_empty();
688
689 // Update heap occupancy information which is used as input to the soft ref
690 // clearing policy at the next gc.
691 Universe::heap()->update_capacity_and_used_at_gc();
692
693 bool young_gen_empty = eden_empty && from_space->is_empty() &&
694 to_space->is_empty();
695
696 PSCardTable* ct = heap->card_table();
697 MemRegion old_mr = heap->old_gen()->committed();
698 if (young_gen_empty) {
699 ct->clear_MemRegion(old_mr);
700 } else {
701 ct->dirty_MemRegion(old_mr);
702 }
703
704 heap->prune_scavengable_nmethods();
705
706 #if COMPILER2_OR_JVMCI
707 DerivedPointerTable::update_pointers();
708 #endif
709
710 // Signal that we have completed a visit to all live objects.
711 Universe::heap()->record_whole_heap_examined_timestamp();
712 }
713
714 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
715 HeapWord* full_region_prefix_end) {
716 const size_t region_size = ParallelCompactData::RegionSize;
717 const ParallelCompactData& sd = summary_data();
718
719 // Iteration starts with the region *after* the full-region-prefix-end.
720 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
721 // If final region is not full, iteration stops before that region,
722 // because fill_dense_prefix_end assumes that prefix_end <= top.
723 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
724 assert(start_region <= end_region, "inv");
725
726 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
727 const RegionData* cur_region = start_region;
728 for (/* empty */; cur_region < end_region; ++cur_region) {
729 assert(region_size >= cur_region->data_size(), "inv");
730 size_t dead_size = region_size - cur_region->data_size();
731 if (max_waste < dead_size) {
732 break;
733 }
734 max_waste -= dead_size;
735 }
736
737 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
738 assert(sd.is_region_aligned(prefix_end), "postcondition");
739 assert(prefix_end >= full_region_prefix_end, "in-range");
740 assert(prefix_end <= old_space->top(), "in-range");
741 return prefix_end;
742 }
743
744 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
745 // Comparing two sizes to decide if filling is required:
746 //
747 // The size of the filler (min-obj-size) is 2 heap words with the default
748 // MinObjAlignment, since both markword and klass take 1 heap word.
749 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
750 // because the Klass* gets encoded in the mark-word.
751 //
752 // The size of the gap (if any) right before dense-prefix-end is
753 // MinObjAlignment.
754 //
755 // Need to fill in the gap only if it's smaller than min-obj-size, and the
756 // filler obj will extend to next region.
757
758 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
759 return;
760 }
761
762 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
763 assert(CollectedHeap::min_fill_size() == 2, "inv");
764 HeapWord* const dense_prefix_end = dense_prefix(id);
765 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
766 assert(dense_prefix_end <= space(id)->top(), "precondition");
767 if (dense_prefix_end == space(id)->top()) {
768 // Must not have single-word gap right before prefix-end/top.
769 return;
770 }
771 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
772
773 if (region_after_dense_prefix->partial_obj_size() != 0 ||
774 _mark_bitmap.is_marked(dense_prefix_end)) {
775 // The region after the dense prefix starts with live bytes.
776 return;
777 }
778
779 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
780 if (block_start == dense_prefix_end - 1) {
781 assert(!_mark_bitmap.is_marked(block_start), "inv");
782 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
783 // The filler object will extend into region_after_dense_prefix.
784 const size_t obj_len = 2; // min-fill-size
785 HeapWord* const obj_beg = dense_prefix_end - 1;
786 CollectedHeap::fill_with_object(obj_beg, obj_len);
787 _mark_bitmap.mark_obj(obj_beg);
788 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
789 region_after_dense_prefix->set_partial_obj_size(1);
790 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
791 assert(start_array(id) != nullptr, "sanity");
792 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
793 }
794 }
795
796 bool PSParallelCompact::check_maximum_compaction(bool should_do_max_compaction,
797 size_t total_live_words,
798 MutableSpace* const old_space,
799 HeapWord* full_region_prefix_end) {
800
801 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
802
803 // Check System.GC
804 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
805 && GCCause::is_user_requested_gc(heap->gc_cause());
806
807 // Check if all live objs are too much for old-gen.
808 const bool is_old_gen_too_full = (total_live_words >= old_space->capacity_in_words());
809
810 // If all regions in old-gen are full
811 const bool is_region_full =
812 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
813
814 return should_do_max_compaction
815 || is_max_on_system_gc
816 || is_old_gen_too_full
817 || is_region_full;
818 }
819
820 void PSParallelCompact::summary_phase(bool should_do_max_compaction)
821 {
822 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
823
824 MutableSpace* const old_space = _space_info[old_space_id].space();
825 {
826 size_t total_live_words = 0;
827 HeapWord* full_region_prefix_end = nullptr;
828 {
829 // old-gen
830 size_t live_words = _summary_data.live_words_in_space(old_space,
831 &full_region_prefix_end);
832 total_live_words += live_words;
833 }
834 // young-gen
835 for (uint i = eden_space_id; i < last_space_id; ++i) {
836 const MutableSpace* space = _space_info[i].space();
837 size_t live_words = _summary_data.live_words_in_space(space);
838 total_live_words += live_words;
839 _space_info[i].set_new_top(space->bottom() + live_words);
840 _space_info[i].set_dense_prefix(space->bottom());
841 }
842
843 should_do_max_compaction = check_maximum_compaction(should_do_max_compaction,
844 total_live_words,
845 old_space,
846 full_region_prefix_end);
847 {
848 GCTraceTime(Info, gc, phases) tm("Summary Phase: expand", &_gc_timer);
849 // Try to expand old-gen in order to fit all live objs and waste.
850 size_t target_capacity_bytes = total_live_words * HeapWordSize
851 + old_space->capacity_in_bytes() * (MarkSweepDeadRatio / 100);
852 ParallelScavengeHeap::heap()->old_gen()->try_expand_till_size(target_capacity_bytes);
853 }
854
855 HeapWord* dense_prefix_end = should_do_max_compaction
856 ? full_region_prefix_end
857 : compute_dense_prefix_for_old_space(old_space,
858 full_region_prefix_end);
859 SpaceId id = old_space_id;
860 _space_info[id].set_dense_prefix(dense_prefix_end);
861
862 if (dense_prefix_end != old_space->bottom()) {
863 fill_dense_prefix_end(id);
864 }
865
866 // Compacting objs in [dense_prefix_end, old_space->top())
867 _summary_data.summarize(_space_info[id].split_info(),
868 dense_prefix_end, old_space->top(), nullptr,
869 dense_prefix_end, old_space->end(),
870 _space_info[id].new_top_addr());
871 }
872
873 // Summarize the remaining spaces in the young gen. The initial target space
874 // is the old gen. If a space does not fit entirely into the target, then the
875 // remainder is compacted into the space itself and that space becomes the new
876 // target.
877 SpaceId dst_space_id = old_space_id;
878 HeapWord* dst_space_end = old_space->end();
879 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
880 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
881 const MutableSpace* space = _space_info[id].space();
882 const size_t live = pointer_delta(_space_info[id].new_top(),
883 space->bottom());
884 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
885
886 if (live > 0 && live <= available) {
887 // All the live data will fit.
888 bool done = _summary_data.summarize(_space_info[id].split_info(),
889 space->bottom(), space->top(),
890 nullptr,
891 *new_top_addr, dst_space_end,
892 new_top_addr);
893 assert(done, "space must fit into old gen");
894
895 // Reset the new_top value for the space.
896 _space_info[id].set_new_top(space->bottom());
897 } else if (live > 0) {
898 // Attempt to fit part of the source space into the target space.
899 HeapWord* next_src_addr = nullptr;
900 bool done = _summary_data.summarize(_space_info[id].split_info(),
901 space->bottom(), space->top(),
902 &next_src_addr,
903 *new_top_addr, dst_space_end,
904 new_top_addr);
905 assert(!done, "space should not fit into old gen");
906 assert(next_src_addr != nullptr, "sanity");
907
908 // The source space becomes the new target, so the remainder is compacted
909 // within the space itself.
910 dst_space_id = SpaceId(id);
911 dst_space_end = space->end();
912 new_top_addr = _space_info[id].new_top_addr();
913 done = _summary_data.summarize(_space_info[id].split_info(),
914 next_src_addr, space->top(),
915 nullptr,
916 space->bottom(), dst_space_end,
917 new_top_addr);
918 assert(done, "space must fit when compacted into itself");
919 assert(*new_top_addr <= space->top(), "usage should not grow");
920 }
921 }
922 }
923
924 void PSParallelCompact::report_object_count_after_gc() {
925 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
926 // The heap is compacted, all objects are iterable. However there may be
927 // filler objects in the heap which we should ignore.
928 class SkipFillerObjectClosure : public BoolObjectClosure {
929 public:
930 bool do_object_b(oop obj) override { return !CollectedHeap::is_filler_object(obj); }
931 } cl;
932 _gc_tracer.report_object_count_after_gc(&cl, &ParallelScavengeHeap::heap()->workers());
933 }
934
935 bool PSParallelCompact::invoke(bool clear_all_soft_refs, bool should_do_max_compaction) {
936 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
937 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
938 "should be in vm thread");
939 assert(ref_processor() != nullptr, "Sanity");
940
941 SvcGCMarker sgcm(SvcGCMarker::FULL);
942 IsSTWGCActiveMark mark;
943
944 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
945
946 GCIdMark gc_id_mark;
947 _gc_timer.register_gc_start();
948 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
949
950 GCCause::Cause gc_cause = heap->gc_cause();
951 PSOldGen* old_gen = heap->old_gen();
952 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
953
954 // Make sure data structures are sane, make the heap parsable, and do other
955 // miscellaneous bookkeeping.
956 pre_compact();
957
958 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
959
960 {
961 const uint active_workers =
962 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
963 ParallelScavengeHeap::heap()->workers().active_workers(),
964 Threads::number_of_non_daemon_threads());
965 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
966
967 GCTraceCPUTime tcpu(&_gc_tracer);
968 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
969
970 heap->pre_full_gc_dump(&_gc_timer);
971
972 TraceCollectorStats tcs(counters());
973 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
974
975 if (log_is_enabled(Debug, gc, heap, exit)) {
976 accumulated_time()->start();
977 }
978
979 // Let the size policy know we're starting
980 size_policy->major_collection_begin();
981
982 #if COMPILER2_OR_JVMCI
983 DerivedPointerTable::clear();
984 #endif
985
986 ref_processor()->start_discovery(clear_all_soft_refs);
987
988 marking_phase(&_gc_tracer);
989
990 summary_phase(should_do_max_compaction);
991
992 #if COMPILER2_OR_JVMCI
993 assert(DerivedPointerTable::is_active(), "Sanity");
994 DerivedPointerTable::set_active(false);
995 #endif
996
997 forward_to_new_addr();
998
999 adjust_pointers();
1000
1001 compact();
1002
1003 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1004
1005 ParCompactionManager::verify_all_region_stack_empty();
1006
1007 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1008 // done before resizing.
1009 post_compact();
1010
1011 size_policy->major_collection_end();
1012
1013 size_policy->sample_old_gen_used_bytes(MAX2(pre_gc_values.old_gen_used(), old_gen->used_in_bytes()));
1014
1015 if (UseAdaptiveSizePolicy) {
1016 heap->resize_after_full_gc();
1017 }
1018
1019 heap->resize_all_tlabs();
1020
1021 // Resize the metaspace capacity after a collection
1022 MetaspaceGC::compute_new_size();
1023
1024 if (log_is_enabled(Debug, gc, heap, exit)) {
1025 accumulated_time()->stop();
1026 }
1027
1028 heap->print_heap_change(pre_gc_values);
1029
1030 report_object_count_after_gc();
1031
1032 // Track memory usage and detect low memory
1033 MemoryService::track_memory_usage();
1034 heap->update_counters();
1035
1036 heap->post_full_gc_dump(&_gc_timer);
1037
1038 size_policy->record_gc_pause_end_instant();
1039 }
1040
1041 heap->gc_epilogue(true);
1042
1043 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1044 Universe::verify("After GC");
1045 }
1046
1047 heap->print_after_gc();
1048 heap->trace_heap_after_gc(&_gc_tracer);
1049
1050 _gc_timer.register_gc_end();
1051
1052 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1053 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1054
1055 return true;
1056 }
1057
1058 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1059 ParCompactionManager* _cm;
1060
1061 public:
1062 PCAddThreadRootsMarkingTaskClosure(ParCompactionManager* cm) : _cm(cm) { }
1063 void do_thread(Thread* thread) {
1064 ResourceMark rm;
1065
1066 MarkingNMethodClosure mark_and_push_in_blobs(&_cm->_mark_and_push_closure);
1067
1068 thread->oops_do(&_cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1069
1070 // Do the real work
1071 _cm->follow_marking_stacks();
1072 }
1073 };
1074
1075 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1076 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1077
1078 ParCompactionManager* cm =
1079 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1080
1081 do {
1082 ScannerTask task;
1083 if (ParCompactionManager::steal(worker_id, task)) {
1084 cm->follow_contents(task, true);
1085 }
1086 cm->follow_marking_stacks();
1087 } while (!terminator.offer_termination());
1088 }
1089
1090 class MarkFromRootsTask : public WorkerTask {
1091 NMethodMarkingScope _nmethod_marking_scope;
1092 ThreadsClaimTokenScope _threads_claim_token_scope;
1093 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1094 TaskTerminator _terminator;
1095 uint _active_workers;
1096
1097 public:
1098 MarkFromRootsTask(uint active_workers) :
1099 WorkerTask("MarkFromRootsTask"),
1100 _nmethod_marking_scope(),
1101 _threads_claim_token_scope(),
1102 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1103 _active_workers(active_workers) {}
1104
1105 virtual void work(uint worker_id) {
1106 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1107 cm->create_marking_stats_cache();
1108 {
1109 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1110 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1111
1112 // Do the real work
1113 cm->follow_marking_stacks();
1114 }
1115
1116 {
1117 PCAddThreadRootsMarkingTaskClosure closure(cm);
1118 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1119 }
1120
1121 // Mark from OopStorages
1122 {
1123 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1124 // Do the real work
1125 cm->follow_marking_stacks();
1126 }
1127
1128 if (_active_workers > 1) {
1129 steal_marking_work(_terminator, worker_id);
1130 }
1131 }
1132 };
1133
1134 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1135 TaskTerminator _terminator;
1136
1137 public:
1138 ParallelCompactRefProcProxyTask(uint max_workers)
1139 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1140 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1141
1142 void work(uint worker_id) override {
1143 assert(worker_id < _max_workers, "sanity");
1144 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1145 BarrierEnqueueDiscoveredFieldClosure enqueue;
1146 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1147 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1148 }
1149
1150 void prepare_run_task_hook() override {
1151 _terminator.reset_for_reuse(_queue_count);
1152 }
1153 };
1154
1155 static void flush_marking_stats_cache(const uint num_workers) {
1156 for (uint i = 0; i < num_workers; ++i) {
1157 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1158 cm->flush_and_destroy_marking_stats_cache();
1159 }
1160 }
1161
1162 class PSParallelCleaningTask : public WorkerTask {
1163 bool _unloading_occurred;
1164 CodeCacheUnloadingTask _code_cache_task;
1165 // Prune dead klasses from subklass/sibling/implementor lists.
1166 KlassCleaningTask _klass_cleaning_task;
1167
1168 public:
1169 PSParallelCleaningTask(bool unloading_occurred) :
1170 WorkerTask("PS Parallel Cleaning"),
1171 _unloading_occurred(unloading_occurred),
1172 _code_cache_task(unloading_occurred),
1173 _klass_cleaning_task() {}
1174
1175 void work(uint worker_id) {
1176 #if INCLUDE_JVMCI
1177 if (EnableJVMCI && worker_id == 0) {
1178 // Serial work; only first worker.
1179 // Clean JVMCI metadata handles.
1180 JVMCI::do_unloading(_unloading_occurred);
1181 }
1182 #endif
1183
1184 // Do first pass of code cache cleaning.
1185 _code_cache_task.work(worker_id);
1186
1187 // Clean all klasses that were not unloaded.
1188 // The weak metadata in klass doesn't need to be
1189 // processed if there was no unloading.
1190 if (_unloading_occurred) {
1191 _klass_cleaning_task.work();
1192 }
1193 }
1194 };
1195
1196 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1197 // Recursively traverse all live objects and mark them
1198 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1199
1200 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1201
1202 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1203 {
1204 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1205
1206 MarkFromRootsTask task(active_gc_threads);
1207 ParallelScavengeHeap::heap()->workers().run_task(&task);
1208 }
1209
1210 // Process reference objects found during marking
1211 {
1212 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1213
1214 ReferenceProcessorStats stats;
1215 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1216
1217 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1218 stats = ref_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
1219
1220 gc_tracer->report_gc_reference_stats(stats);
1221 pt.print_all_references();
1222 }
1223
1224 {
1225 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1226
1227 flush_marking_stats_cache(active_gc_threads);
1228 }
1229
1230 // This is the point where the entire marking should have completed.
1231 ParCompactionManager::verify_all_marking_stack_empty();
1232
1233 {
1234 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1235 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1236 is_alive_closure(),
1237 &do_nothing_cl,
1238 1);
1239 }
1240
1241 {
1242 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1243
1244 ClassUnloadingContext ctx(active_gc_threads /* num_nmethod_unlink_workers */,
1245 false /* unregister_nmethods_during_purge */,
1246 false /* lock_nmethod_free_separately */);
1247
1248 {
1249 CodeCache::UnlinkingScope scope(is_alive_closure());
1250
1251 // Follow system dictionary roots and unload classes.
1252 bool unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1253
1254 PSParallelCleaningTask task{unloading_occurred};
1255 ParallelScavengeHeap::heap()->workers().run_task(&task);
1256 }
1257
1258 {
1259 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1260 // Release unloaded nmethod's memory.
1261 ctx.purge_nmethods();
1262 }
1263 {
1264 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1265 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1266 }
1267 {
1268 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1269 ctx.free_nmethods();
1270 }
1271 {
1272 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1273 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
1274 ClassLoaderDataGraph::purge(true /* at_safepoint */);
1275 DEBUG_ONLY(MetaspaceUtils::verify();)
1276 }
1277 }
1278
1279 #if TASKQUEUE_STATS
1280 ParCompactionManager::print_and_reset_taskqueue_stats();
1281 #endif
1282 }
1283
1284 template<typename Func>
1285 void PSParallelCompact::adjust_in_space_helper(SpaceId id, Atomic<uint>* claim_counter, Func&& on_stripe) {
1286 MutableSpace* sp = PSParallelCompact::space(id);
1287 HeapWord* const bottom = sp->bottom();
1288 HeapWord* const top = sp->top();
1289 if (bottom == top) {
1290 return;
1291 }
1292
1293 const uint num_regions_per_stripe = 2;
1294 const size_t region_size = ParallelCompactData::RegionSize;
1295 const size_t stripe_size = num_regions_per_stripe * region_size;
1296
1297 while (true) {
1298 uint counter = claim_counter->fetch_then_add(num_regions_per_stripe);
1299 HeapWord* cur_stripe = bottom + counter * region_size;
1300 if (cur_stripe >= top) {
1301 break;
1302 }
1303 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1304 on_stripe(cur_stripe, stripe_end);
1305 }
1306 }
1307
1308 void PSParallelCompact::adjust_in_old_space(Atomic<uint>* claim_counter) {
1309 // Regions in old-space shouldn't be split.
1310 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1311
1312 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1313 assert(mark_bitmap()->is_marked(obj_start), "inv");
1314 oop obj = cast_to_oop(obj_start);
1315 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1316 };
1317
1318 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1319 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1320 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1321 HeapWord* obj_start;
1322 if (cur_region->partial_obj_size() != 0) {
1323 obj_start = cur_region->partial_obj_addr();
1324 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1325 } else {
1326 obj_start = stripe_start;
1327 }
1328
1329 while (obj_start < stripe_end) {
1330 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1331 if (obj_start >= stripe_end) {
1332 break;
1333 }
1334 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1335 }
1336 });
1337 }
1338
1339 void PSParallelCompact::adjust_in_young_space(SpaceId id, Atomic<uint>* claim_counter) {
1340 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1341 HeapWord* obj_start = stripe_start;
1342 while (obj_start < stripe_end) {
1343 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1344 if (obj_start >= stripe_end) {
1345 break;
1346 }
1347 oop obj = cast_to_oop(obj_start);
1348 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1349 }
1350 });
1351 }
1352
1353 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, Atomic<uint>* claim_counters) {
1354 auto start_time = Ticks::now();
1355 adjust_in_old_space(&claim_counters[0]);
1356 for (uint id = eden_space_id; id < last_space_id; ++id) {
1357 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1358 }
1359 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1360 }
1361
1362 class PSAdjustTask final : public WorkerTask {
1363 ThreadsClaimTokenScope _threads_claim_token_scope;
1364 WeakProcessor::Task _weak_proc_task;
1365 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1366 uint _nworkers;
1367 Atomic<bool> _code_cache_claimed;
1368 Atomic<uint> _claim_counters[PSParallelCompact::last_space_id];
1369
1370 bool try_claim_code_cache_task() {
1371 return _code_cache_claimed.load_relaxed() == false
1372 && _code_cache_claimed.compare_set(false, true);
1373 }
1374
1375 public:
1376 PSAdjustTask(uint nworkers) :
1377 WorkerTask("PSAdjust task"),
1378 _threads_claim_token_scope(),
1379 _weak_proc_task(nworkers),
1380 _oop_storage_iter(),
1381 _nworkers(nworkers),
1382 _code_cache_claimed(false),
1383 _claim_counters{} {
1384
1385 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1386 }
1387
1388 void work(uint worker_id) {
1389 {
1390 // Pointers in heap.
1391 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1392 cm->preserved_marks()->adjust_during_full_gc();
1393
1394 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1395 }
1396
1397 {
1398 // All (strong and weak) CLDs.
1399 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1400 ClassLoaderDataGraph::cld_do(&cld_closure);
1401 }
1402
1403 {
1404 // Threads stack frames. No need to visit on-stack nmethods, because all
1405 // nmethods are visited in one go via CodeCache::nmethods_do.
1406 ResourceMark rm;
1407 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1408 if (try_claim_code_cache_task()) {
1409 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1410 CodeCache::nmethods_do(&adjust_code);
1411 }
1412 }
1413
1414 {
1415 // VM internal strong and weak roots.
1416 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1417 AlwaysTrueClosure always_alive;
1418 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1419 }
1420 }
1421 };
1422
1423 void PSParallelCompact::adjust_pointers() {
1424 // Adjust the pointers to reflect the new locations
1425 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1426 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1427 PSAdjustTask task(nworkers);
1428 ParallelScavengeHeap::heap()->workers().run_task(&task);
1429 }
1430
1431 // Split [start, end) evenly for a number of workers and return the
1432 // range for worker_id.
1433 static void split_regions_for_worker(size_t start, size_t end,
1434 uint worker_id, uint num_workers,
1435 size_t* worker_start, size_t* worker_end) {
1436 assert(start < end, "precondition");
1437 assert(num_workers > 0, "precondition");
1438 assert(worker_id < num_workers, "precondition");
1439
1440 size_t num_regions = end - start;
1441 size_t num_regions_per_worker = num_regions / num_workers;
1442 size_t remainder = num_regions % num_workers;
1443 // The first few workers will get one extra.
1444 *worker_start = start + worker_id * num_regions_per_worker
1445 + MIN2(checked_cast<size_t>(worker_id), remainder);
1446 *worker_end = *worker_start + num_regions_per_worker
1447 + (worker_id < remainder ? 1 : 0);
1448 }
1449
1450 static bool safe_to_read_header(size_t words) {
1451 precond(words > 0);
1452
1453 // Safe to read if we have enough words for the full header, i.e., both
1454 // markWord and Klass pointer.
1455 const bool safe = words >= (size_t)oopDesc::header_size();
1456
1457 // If using Compact Object Headers, the full header is inside the markWord,
1458 // so will always be safe to read
1459 assert(!UseCompactObjectHeaders || safe, "Compact Object Headers should always be safe");
1460
1461 return safe;
1462 }
1463
1464 void PSParallelCompact::forward_to_new_addr() {
1465 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1466 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1467
1468 struct ForwardTask final : public WorkerTask {
1469 uint _num_workers;
1470
1471 explicit ForwardTask(uint num_workers) :
1472 WorkerTask("PSForward task"),
1473 _num_workers(num_workers) {}
1474
1475 static bool should_preserve_mark(oop obj, HeapWord* end_addr) {
1476 size_t remaining_words = pointer_delta(end_addr, cast_from_oop<HeapWord*>(obj));
1477
1478 if (Arguments::is_valhalla_enabled() && !safe_to_read_header(remaining_words)) {
1479 // When using Valhalla, it might be necessary to preserve the Valhalla-
1480 // specific bits in the markWord. If the entire object header is
1481 // copied, the correct markWord (with the appropriate Valhalla bits)
1482 // can be safely read from the Klass. However, if the full header is
1483 // not copied, we cannot safely read the Klass to obtain this information.
1484 // In such cases, we always preserve the markWord to ensure that all
1485 // relevant bits, including Valhalla-specific ones, are retained.
1486 return true;
1487 } else {
1488 return obj->mark().must_be_preserved();
1489 }
1490 }
1491
1492 static void forward_objs_in_range(ParCompactionManager* cm,
1493 HeapWord* start,
1494 HeapWord* end,
1495 HeapWord* destination) {
1496 HeapWord* cur_addr = start;
1497 HeapWord* new_addr = destination;
1498
1499 while (cur_addr < end) {
1500 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1501 if (cur_addr >= end) {
1502 return;
1503 }
1504 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1505 oop obj = cast_to_oop(cur_addr);
1506
1507 if (new_addr != cur_addr) {
1508 if (should_preserve_mark(obj, end)) {
1509 cm->preserved_marks()->push_always(obj, obj->mark());
1510 }
1511
1512 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1513 }
1514 size_t obj_size = obj->size();
1515 new_addr += obj_size;
1516 cur_addr += obj_size;
1517 }
1518 }
1519
1520 void work(uint worker_id) override {
1521 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1522 for (uint id = old_space_id; id < last_space_id; ++id) {
1523 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1524 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1525 HeapWord* top = sp->top();
1526
1527 if (dense_prefix_addr == top) {
1528 // Empty space
1529 continue;
1530 }
1531
1532 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1533 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1534 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1535 size_t start_region;
1536 size_t end_region;
1537 split_regions_for_worker(dense_prefix_region, top_region,
1538 worker_id, _num_workers,
1539 &start_region, &end_region);
1540 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1541 RegionData* region_ptr = _summary_data.region(cur_region);
1542 size_t partial_obj_size = region_ptr->partial_obj_size();
1543
1544 if (partial_obj_size == ParallelCompactData::RegionSize) {
1545 // No obj-start
1546 continue;
1547 }
1548
1549 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1550 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1551
1552 if (split_info.is_split(cur_region)) {
1553 // Part 1: will be relocated to space-1
1554 HeapWord* preceding_destination = split_info.preceding_destination();
1555 HeapWord* split_point = split_info.split_point();
1556 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1557
1558 // Part 2: will be relocated to space-2
1559 HeapWord* destination = region_ptr->destination();
1560 forward_objs_in_range(cm, split_point, region_end, destination);
1561 } else {
1562 HeapWord* destination = region_ptr->destination();
1563 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1564 }
1565 }
1566 }
1567 }
1568 } task(nworkers);
1569
1570 ParallelScavengeHeap::heap()->workers().run_task(&task);
1571 DEBUG_ONLY(verify_forward();)
1572 }
1573
1574 #ifdef ASSERT
1575 void PSParallelCompact::verify_forward() {
1576 HeapWord* const old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1577 // The destination addr for the first live obj after dense-prefix.
1578 HeapWord* bump_ptr = old_dense_prefix_addr
1579 + _summary_data.addr_to_region_ptr(old_dense_prefix_addr)->partial_obj_size();
1580 SpaceId bump_ptr_space = old_space_id;
1581
1582 for (uint id = old_space_id; id < last_space_id; ++id) {
1583 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1584 // Only verify objs after dense-prefix, because those before dense-prefix are not moved (forwarded).
1585 HeapWord* cur_addr = dense_prefix(SpaceId(id));
1586 HeapWord* top = sp->top();
1587
1588 while (cur_addr < top) {
1589 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1590 if (cur_addr >= top) {
1591 break;
1592 }
1593 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1594 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1595 // Move to the space containing cur_addr
1596 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1597 bump_ptr = space(space_id(cur_addr))->bottom();
1598 bump_ptr_space = space_id(bump_ptr);
1599 }
1600 oop obj = cast_to_oop(cur_addr);
1601 if (cur_addr == bump_ptr) {
1602 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1603 } else {
1604 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1605 }
1606 bump_ptr += obj->size();
1607 cur_addr += obj->size();
1608 }
1609 }
1610 }
1611 #endif
1612
1613 // Helper class to print 8 region numbers per line and then print the total at the end.
1614 class FillableRegionLogger : public StackObj {
1615 private:
1616 Log(gc, compaction) log;
1617 static const int LineLength = 8;
1618 size_t _regions[LineLength];
1619 int _next_index;
1620 bool _enabled;
1621 size_t _total_regions;
1622 public:
1623 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1624 ~FillableRegionLogger() {
1625 log.trace("%zu initially fillable regions", _total_regions);
1626 }
1627
1628 void print_line() {
1629 if (!_enabled || _next_index == 0) {
1630 return;
1631 }
1632 FormatBuffer<> line("Fillable: ");
1633 for (int i = 0; i < _next_index; i++) {
1634 line.append(" %7zu", _regions[i]);
1635 }
1636 log.trace("%s", line.buffer());
1637 _next_index = 0;
1638 }
1639
1640 void handle(size_t region) {
1641 if (!_enabled) {
1642 return;
1643 }
1644 _regions[_next_index++] = region;
1645 if (_next_index == LineLength) {
1646 print_line();
1647 }
1648 _total_regions++;
1649 }
1650 };
1651
1652 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1653 {
1654 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1655
1656 // Find the threads that are active
1657 uint worker_id = 0;
1658
1659 // Find all regions that are available (can be filled immediately) and
1660 // distribute them to the thread stacks. The iteration is done in reverse
1661 // order (high to low) so the regions will be removed in ascending order.
1662
1663 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1664
1665 // id + 1 is used to test termination so unsigned can
1666 // be used with an old_space_id == 0.
1667 FillableRegionLogger region_logger;
1668 for (unsigned int id = last_space_id - 1; id + 1 > old_space_id; --id) {
1669 SpaceInfo* const space_info = _space_info + id;
1670 HeapWord* const new_top = space_info->new_top();
1671
1672 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1673 const size_t end_region =
1674 sd.addr_to_region_idx(sd.region_align_up(new_top));
1675
1676 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1677 if (sd.region(cur)->claim_unsafe()) {
1678 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1679 bool result = sd.region(cur)->mark_normal();
1680 assert(result, "Must succeed at this point.");
1681 cm->region_stack()->push(cur);
1682 region_logger.handle(cur);
1683 // Assign regions to tasks in round-robin fashion.
1684 if (++worker_id == parallel_gc_threads) {
1685 worker_id = 0;
1686 }
1687 }
1688 }
1689 region_logger.print_line();
1690 }
1691 }
1692
1693 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1694 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1695
1696 ParCompactionManager* cm =
1697 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1698
1699 // Drain the stacks that have been preloaded with regions
1700 // that are ready to fill.
1701
1702 cm->drain_region_stacks();
1703
1704 guarantee(cm->region_stack()->is_empty(), "Not empty");
1705
1706 size_t region_index = 0;
1707
1708 while (true) {
1709 if (ParCompactionManager::steal(worker_id, region_index)) {
1710 PSParallelCompact::fill_and_update_region(cm, region_index);
1711 cm->drain_region_stacks();
1712 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1713 // Fill and update an unavailable region with the help of a shadow region
1714 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1715 cm->drain_region_stacks();
1716 } else {
1717 if (terminator->offer_termination()) {
1718 break;
1719 }
1720 // Go around again.
1721 }
1722 }
1723 }
1724
1725 class FillDensePrefixAndCompactionTask: public WorkerTask {
1726 TaskTerminator _terminator;
1727
1728 public:
1729 FillDensePrefixAndCompactionTask(uint active_workers) :
1730 WorkerTask("FillDensePrefixAndCompactionTask"),
1731 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1732 }
1733
1734 virtual void work(uint worker_id) {
1735 if (worker_id == 0) {
1736 auto start = Ticks::now();
1737 PSParallelCompact::fill_dead_objs_in_dense_prefix();
1738 log_trace(gc, phases)("Fill dense prefix by worker 0: %.3f ms", (Ticks::now() - start).seconds() * 1000);
1739 }
1740 compaction_with_stealing_work(&_terminator, worker_id);
1741 }
1742 };
1743
1744 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1745 #ifdef ASSERT
1746 {
1747 assert(start < end, "precondition");
1748 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1749 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1750 if (start != bottom) {
1751 // The preceding live obj.
1752 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1753 HeapWord* obj_end = obj_start + cast_to_oop(obj_start)->size();
1754 assert(obj_end == start, "precondition");
1755 }
1756 }
1757 #endif
1758
1759 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1760 HeapWord* addr = start;
1761 do {
1762 size_t size = cast_to_oop(addr)->size();
1763 start_array(old_space_id)->update_for_block(addr, addr + size);
1764 addr += size;
1765 } while (addr < end);
1766 }
1767
1768 void PSParallelCompact::fill_dead_objs_in_dense_prefix() {
1769 ParMarkBitMap* bitmap = mark_bitmap();
1770
1771 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1772 HeapWord* const prefix_end = dense_prefix(old_space_id);
1773
1774 const size_t region_size = ParallelCompactData::RegionSize;
1775
1776 // Fill dead space in [start_addr, end_addr)
1777 HeapWord* const start_addr = bottom;
1778 HeapWord* const end_addr = prefix_end;
1779
1780 for (HeapWord* cur_addr = start_addr; cur_addr < end_addr; /* empty */) {
1781 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1782 if (cur_region_ptr->data_size() == region_size) {
1783 // Full; no dead space. Next region.
1784 if (_summary_data.is_region_aligned(cur_addr)) {
1785 cur_addr += region_size;
1786 } else {
1787 cur_addr = _summary_data.region_align_up(cur_addr);
1788 }
1789 continue;
1790 }
1791
1792 // Fill dead space inside cur_region.
1793 if (_summary_data.is_region_aligned(cur_addr)) {
1794 cur_addr += cur_region_ptr->partial_obj_size();
1795 }
1796
1797 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1798 assert(region_end_addr <= end_addr, "inv");
1799 while (cur_addr < region_end_addr) {
1800 // Use end_addr to allow filler-obj to cross region boundary.
1801 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, end_addr);
1802 if (cur_addr != live_start) {
1803 // Found dead space [cur_addr, live_start).
1804 fill_range_in_dense_prefix(cur_addr, live_start);
1805 }
1806 if (live_start >= region_end_addr) {
1807 cur_addr = live_start;
1808 break;
1809 }
1810 assert(bitmap->is_marked(live_start), "inv");
1811 cur_addr = live_start + cast_to_oop(live_start)->size();
1812 }
1813 }
1814 }
1815
1816 void PSParallelCompact::compact() {
1817 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1818
1819 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1820
1821 initialize_shadow_regions(active_gc_threads);
1822 prepare_region_draining_tasks(active_gc_threads);
1823
1824 {
1825 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1826
1827 FillDensePrefixAndCompactionTask task(active_gc_threads);
1828 ParallelScavengeHeap::heap()->workers().run_task(&task);
1829
1830 #ifdef ASSERT
1831 verify_filler_in_dense_prefix();
1832
1833 // Verify that all regions have been processed.
1834 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1835 verify_complete(SpaceId(id));
1836 }
1837 #endif
1838 }
1839 }
1840
1841 #ifdef ASSERT
1842 void PSParallelCompact::verify_filler_in_dense_prefix() {
1843 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1844 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1845
1846 const size_t region_size = ParallelCompactData::RegionSize;
1847
1848 for (HeapWord* cur_addr = bottom; cur_addr < dense_prefix_end; /* empty */) {
1849 RegionData* cur_region_ptr = _summary_data.addr_to_region_ptr(cur_addr);
1850 if (cur_region_ptr->data_size() == region_size) {
1851 // Full; no dead space. Next region.
1852 if (_summary_data.is_region_aligned(cur_addr)) {
1853 cur_addr += region_size;
1854 } else {
1855 cur_addr = _summary_data.region_align_up(cur_addr);
1856 }
1857 continue;
1858 }
1859
1860 // This region contains filler objs.
1861 if (_summary_data.is_region_aligned(cur_addr)) {
1862 cur_addr += cur_region_ptr->partial_obj_size();
1863 }
1864
1865 HeapWord* region_end_addr = _summary_data.region_align_up(cur_addr + 1);
1866 assert(region_end_addr <= dense_prefix_end, "inv");
1867
1868 while (cur_addr < region_end_addr) {
1869 oop obj = cast_to_oop(cur_addr);
1870 oopDesc::verify(obj);
1871 if (!mark_bitmap()->is_marked(cur_addr)) {
1872 assert(CollectedHeap::is_filler_object(cast_to_oop(cur_addr)), "inv");
1873 }
1874 cur_addr += obj->size();
1875 }
1876 }
1877 }
1878
1879 void PSParallelCompact::verify_complete(SpaceId space_id) {
1880 // All Regions served as compaction targets, from dense_prefix() to
1881 // new_top(), should be marked as filled and all Regions between new_top()
1882 // and top() should be available (i.e., should have been emptied).
1883 ParallelCompactData& sd = summary_data();
1884 SpaceInfo si = _space_info[space_id];
1885 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1886 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1887 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1888 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1889 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1890
1891 size_t cur_region;
1892 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1893 const RegionData* const c = sd.region(cur_region);
1894 assert(c->completed(), "region %zu not filled: destination_count=%u",
1895 cur_region, c->destination_count());
1896 }
1897
1898 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1899 const RegionData* const c = sd.region(cur_region);
1900 assert(c->available(), "region %zu not empty: destination_count=%u",
1901 cur_region, c->destination_count());
1902 }
1903 }
1904 #endif // #ifdef ASSERT
1905
1906 // Return the SpaceId for the space containing addr. If addr is not in the
1907 // heap, last_space_id is returned. In debug mode it expects the address to be
1908 // in the heap and asserts such.
1909 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1910 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1911
1912 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1913 if (_space_info[id].space()->contains(addr)) {
1914 return SpaceId(id);
1915 }
1916 }
1917
1918 assert(false, "no space contains the addr");
1919 return last_space_id;
1920 }
1921
1922 // Skip over count live words starting from beg, and return the address of the
1923 // next live word. Callers must also ensure that there are enough live words in
1924 // the range [beg, end) to skip.
1925 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1926 {
1927 ParMarkBitMap* m = mark_bitmap();
1928 HeapWord* cur_addr = beg;
1929 while (true) {
1930 cur_addr = m->find_obj_beg(cur_addr, end);
1931 assert(cur_addr < end, "inv");
1932 size_t obj_size = cast_to_oop(cur_addr)->size();
1933 // Strictly greater-than
1934 if (obj_size > count) {
1935 return cur_addr + count;
1936 }
1937 count -= obj_size;
1938 cur_addr += obj_size;
1939 }
1940 }
1941
1942 // On starting to fill a destination region (dest-region), we need to know the
1943 // location of the word that will be at the start of the dest-region after
1944 // compaction. A dest-region can have one or more source regions, but only the
1945 // first source-region contains this location. This location is retrieved by
1946 // calling `first_src_addr` on a dest-region.
1947 // Conversely, a source-region has a dest-region which holds the destination of
1948 // the first live word on this source-region, based on which the destination
1949 // for the rest of live words can be derived.
1950 //
1951 // Note:
1952 // There is some complication due to space-boundary-fragmentation (an obj can't
1953 // cross space-boundary) -- a source-region may be split and behave like two
1954 // distinct regions with their own dest-region, as depicted below.
1955 //
1956 // source-region: region-n
1957 //
1958 // **********************
1959 // | A|A~~~~B|B |
1960 // **********************
1961 // n-1 n n+1
1962 //
1963 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
1964 //
1965 // Assuming the dest-region for region-n is the final region before
1966 // old-space-end and its first-live-word is the middle of AA, the heap content
1967 // will look like the following after compaction:
1968 //
1969 // ************** *************
1970 // A|A~~~~ | |BB |
1971 // ************** *************
1972 // ^ ^
1973 // | old-space-end | eden-space-start
1974 //
1975 // Therefore, in this example, region-n will have two dest-regions:
1976 // 1. the final region in old-space
1977 // 2. the first region in eden-space.
1978 // To handle this special case, we introduce the concept of split-region, whose
1979 // contents are relocated to two spaces. `SplitInfo` captures all necessary
1980 // info about the split, the first part, spliting-point, and the second part.
1981 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
1982 SpaceId src_space_id,
1983 size_t src_region_idx)
1984 {
1985 const size_t RegionSize = ParallelCompactData::RegionSize;
1986 const ParallelCompactData& sd = summary_data();
1987 assert(sd.is_region_aligned(dest_addr), "precondition");
1988
1989 const RegionData* const src_region_ptr = sd.region(src_region_idx);
1990 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
1991
1992 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
1993 HeapWord* const src_region_destination = src_region_ptr->destination();
1994
1995 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
1996 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
1997
1998 // Identify the actual destination for the first live words on this region,
1999 // taking split-region into account.
2000 HeapWord* region_start_destination;
2001 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2002 if (split_info.is_split(src_region_idx)) {
2003 // The second part of this split region; use the recorded split point.
2004 if (dest_addr == src_region_destination) {
2005 return split_info.split_point();
2006 }
2007 region_start_destination = split_info.preceding_destination();
2008 } else {
2009 region_start_destination = src_region_destination;
2010 }
2011
2012 // Calculate the offset to be skipped
2013 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
2014
2015 HeapWord* result;
2016 if (partial_obj_size > words_to_skip) {
2017 result = region_start + words_to_skip;
2018 } else {
2019 words_to_skip -= partial_obj_size;
2020 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2021 }
2022
2023 if (split_info.is_split(src_region_idx)) {
2024 assert(result < split_info.split_point(), "postcondition");
2025 } else {
2026 assert(result < region_end, "postcondition");
2027 }
2028
2029 return result;
2030 }
2031
2032 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2033 SpaceId src_space_id,
2034 size_t beg_region,
2035 HeapWord* end_addr)
2036 {
2037 ParallelCompactData& sd = summary_data();
2038
2039 #ifdef ASSERT
2040 MutableSpace* const src_space = _space_info[src_space_id].space();
2041 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2042 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2043 "src_space_id does not match beg_addr");
2044 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2045 "src_space_id does not match end_addr");
2046 #endif // #ifdef ASSERT
2047
2048 RegionData* const beg = sd.region(beg_region);
2049 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2050
2051 // Regions up to new_top() are enqueued if they become available.
2052 HeapWord* const new_top = _space_info[src_space_id].new_top();
2053 RegionData* const enqueue_end =
2054 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2055
2056 for (RegionData* cur = beg; cur < end; ++cur) {
2057 assert(cur->data_size() > 0, "region must have live data");
2058 cur->decrement_destination_count();
2059 if (cur < enqueue_end && cur->available() && cur->claim()) {
2060 if (cur->mark_normal()) {
2061 cm->push_region(sd.region(cur));
2062 } else if (cur->mark_copied()) {
2063 // Try to copy the content of the shadow region back to its corresponding
2064 // heap region if the shadow region is filled. Otherwise, the GC thread
2065 // fills the shadow region will copy the data back (see
2066 // MoveAndUpdateShadowClosure::complete_region).
2067 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2068 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2069 cur->set_completed();
2070 }
2071 }
2072 }
2073 }
2074
2075 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2076 SpaceId& src_space_id,
2077 HeapWord*& src_space_top,
2078 HeapWord* end_addr)
2079 {
2080 ParallelCompactData& sd = PSParallelCompact::summary_data();
2081
2082 size_t src_region_idx = 0;
2083
2084 // Skip empty regions (if any) up to the top of the space.
2085 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2086 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2087 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2088 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2089
2090 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2091 ++src_region_ptr;
2092 }
2093
2094 if (src_region_ptr < top_region_ptr) {
2095 // Found the first non-empty region in the same space.
2096 src_region_idx = sd.region(src_region_ptr);
2097 closure.set_source(sd.region_to_addr(src_region_idx));
2098 return src_region_idx;
2099 }
2100
2101 // Switch to a new source space and find the first non-empty region.
2102 uint space_id = src_space_id + 1;
2103 assert(space_id < last_space_id, "not enough spaces");
2104
2105 for (/* empty */; space_id < last_space_id; ++space_id) {
2106 HeapWord* bottom = _space_info[space_id].space()->bottom();
2107 HeapWord* top = _space_info[space_id].space()->top();
2108 // Skip empty space
2109 if (bottom == top) {
2110 continue;
2111 }
2112
2113 // Identify the first region that contains live words in this space
2114 size_t cur_region = sd.addr_to_region_idx(bottom);
2115 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2116
2117 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2118 RegionData* cur = sd.region(cur_region);
2119 if (cur->live_obj_size() > 0) {
2120 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2121
2122 src_space_id = SpaceId(space_id);
2123 src_space_top = top;
2124 closure.set_source(region_start_addr);
2125 return cur_region;
2126 }
2127 }
2128 }
2129
2130 ShouldNotReachHere();
2131 }
2132
2133 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2134 ParallelCompactData& sd = summary_data();
2135 assert(sd.is_region_aligned(region_start_addr), "precondition");
2136
2137 // Use per-region partial_obj_size to locate the end of the obj, that extends
2138 // to region_start_addr.
2139 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2140 size_t end_region_idx = sd.region_count();
2141 size_t accumulated_size = 0;
2142 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2143 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2144 accumulated_size += cur_partial_obj_size;
2145 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2146 break;
2147 }
2148 }
2149 return region_start_addr + accumulated_size;
2150 }
2151
2152 static markWord safe_mark_word_prototype(HeapWord* cur_addr, HeapWord* end_addr) {
2153 // If the original markWord contains bits that cannot be reconstructed because
2154 // the header cannot be safely read, a placeholder is used. In this case,
2155 // the correct markWord is preserved before compaction and restored after
2156 // compaction completes.
2157 size_t remaining_words = pointer_delta(end_addr, cur_addr);
2158
2159 if (UseCompactObjectHeaders || (Arguments::is_valhalla_enabled() && safe_to_read_header(remaining_words))) {
2160 return cast_to_oop(cur_addr)->klass()->prototype_header();
2161 } else {
2162 return markWord::prototype();
2163 }
2164 }
2165
2166 // Use region_idx as the destination region, and evacuate all live objs on its
2167 // source regions to this destination region.
2168 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2169 {
2170 ParMarkBitMap* const bitmap = mark_bitmap();
2171 ParallelCompactData& sd = summary_data();
2172 RegionData* const region_ptr = sd.region(region_idx);
2173
2174 // Get the source region and related info.
2175 size_t src_region_idx = region_ptr->source_region();
2176 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2177 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2178 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2179
2180 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2181
2182 // Adjust src_region_idx to prepare for decrementing destination counts (the
2183 // destination count is not decremented when a region is copied to itself).
2184 if (src_region_idx == region_idx) {
2185 src_region_idx += 1;
2186 }
2187
2188 // source-region:
2189 //
2190 // **********
2191 // | ~~~ |
2192 // **********
2193 // ^
2194 // |-- closure.source() / first_src_addr
2195 //
2196 //
2197 // ~~~ : live words
2198 //
2199 // destination-region:
2200 //
2201 // **********
2202 // | |
2203 // **********
2204 // ^
2205 // |-- region-start
2206 if (bitmap->is_unmarked(closure.source())) {
2207 // An object overflows the previous destination region, so this
2208 // destination region should copy the remainder of the object or as much as
2209 // will fit.
2210 HeapWord* const old_src_addr = closure.source();
2211 {
2212 HeapWord* region_start = sd.region_align_down(closure.source());
2213 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2214 HeapWord* obj_end;
2215 if (obj_start != closure.source()) {
2216 assert(bitmap->is_marked(obj_start), "inv");
2217 // Found the actual obj-start, try to find the obj-end using either
2218 // size() if this obj is completely contained in the current region.
2219 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2220 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2221 ? nullptr
2222 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2223 // This obj extends to next region iff partial_obj_addr of the *next*
2224 // region is the same as obj-start.
2225 if (partial_obj_start == obj_start) {
2226 // This obj extends to next region.
2227 obj_end = partial_obj_end(next_region_start);
2228 } else {
2229 // Completely contained in this region; safe to use size().
2230 obj_end = obj_start + cast_to_oop(obj_start)->size();
2231 }
2232 } else {
2233 // This obj extends to current region.
2234 obj_end = partial_obj_end(region_start);
2235 }
2236 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2237 closure.copy_partial_obj(partial_obj_size);
2238 }
2239
2240 if (closure.is_full()) {
2241 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2242 closure.complete_region(dest_addr, region_ptr);
2243 return;
2244 }
2245
2246 // Finished copying without using up the current destination-region
2247 HeapWord* const end_addr = sd.region_align_down(closure.source());
2248 if (sd.region_align_down(old_src_addr) != end_addr) {
2249 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2250 // The partial object was copied from more than one source region.
2251 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2252
2253 // Move to the next source region, possibly switching spaces as well. All
2254 // args except end_addr may be modified.
2255 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2256 }
2257 }
2258
2259 // Handle the rest obj-by-obj, where we know obj-start.
2260 do {
2261 HeapWord* cur_addr = closure.source();
2262 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2263 src_space_top);
2264 // To handle the case where the final obj in source region extends to next region.
2265 HeapWord* final_obj_start = (end_addr == src_space_top)
2266 ? nullptr
2267 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2268 // Apply closure on objs inside [cur_addr, end_addr)
2269 do {
2270 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2271 if (cur_addr == end_addr) {
2272 break;
2273 }
2274 size_t obj_size;
2275 if (final_obj_start == cur_addr) {
2276 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2277 } else {
2278 // This obj doesn't extend into next region; size() is safe to use.
2279 obj_size = cast_to_oop(cur_addr)->size();
2280 }
2281
2282 markWord mark = safe_mark_word_prototype(cur_addr, end_addr);
2283
2284 // Perform the move and update of the object
2285 closure.do_addr(cur_addr, obj_size, mark);
2286
2287 cur_addr += obj_size;
2288 } while (cur_addr < end_addr && !closure.is_full());
2289
2290 if (closure.is_full()) {
2291 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2292 closure.complete_region(dest_addr, region_ptr);
2293 return;
2294 }
2295
2296 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2297
2298 // Move to the next source region, possibly switching spaces as well. All
2299 // args except end_addr may be modified.
2300 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2301 } while (true);
2302 }
2303
2304 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2305 {
2306 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2307 fill_region(cm, cl, region_idx);
2308 }
2309
2310 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2311 {
2312 // Get a shadow region first
2313 ParallelCompactData& sd = summary_data();
2314 RegionData* const region_ptr = sd.region(region_idx);
2315 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2316 // The InvalidShadow return value indicates the corresponding heap region is available,
2317 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2318 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2319 if (shadow_region == ParCompactionManager::InvalidShadow) {
2320 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2321 region_ptr->shadow_to_normal();
2322 return fill_region(cm, cl, region_idx);
2323 } else {
2324 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2325 return fill_region(cm, cl, region_idx);
2326 }
2327 }
2328
2329 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2330 {
2331 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2332 }
2333
2334 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2335 {
2336 size_t next = cm->next_shadow_region();
2337 ParallelCompactData& sd = summary_data();
2338 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2339 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2340
2341 while (next < old_new_top) {
2342 if (sd.region(next)->mark_shadow()) {
2343 region_idx = next;
2344 return true;
2345 }
2346 next = cm->move_next_shadow_region_by(active_gc_threads);
2347 }
2348
2349 return false;
2350 }
2351
2352 // The shadow region is an optimization to address region dependencies in full GC. The basic
2353 // idea is making more regions available by temporally storing their live objects in empty
2354 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2355 // GC threads need not wait destination regions to be available before processing sources.
2356 //
2357 // A typical workflow would be:
2358 // After draining its own stack and failing to steal from others, a GC worker would pick an
2359 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2360 // the shadow region by copying live objects from source regions of the unavailable one. Once
2361 // the unavailable region becomes available, the data in the shadow region will be copied back.
2362 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2363 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2364 {
2365 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2366
2367 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2368 SpaceInfo* const space_info = _space_info + id;
2369 MutableSpace* const space = space_info->space();
2370
2371 const size_t beg_region =
2372 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2373 const size_t end_region =
2374 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2375
2376 for (size_t cur = beg_region; cur < end_region; ++cur) {
2377 ParCompactionManager::push_shadow_region(cur);
2378 }
2379 }
2380
2381 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2382 for (uint i = 0; i < parallel_gc_threads; i++) {
2383 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2384 cm->set_next_shadow_region(beg_region + i);
2385 }
2386 }
2387
2388 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2389 {
2390 size_t words = MIN2(partial_obj_size, words_remaining());
2391
2392 // This test is necessary; if omitted, the pointer updates to a partial object
2393 // that crosses the dense prefix boundary could be overwritten.
2394 if (source() != copy_destination()) {
2395 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2396 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2397 }
2398 update_state(words);
2399 }
2400
2401 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2402 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2403 region_ptr->set_completed();
2404 }
2405
2406 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words, markWord mark) {
2407 assert(destination() != nullptr, "sanity");
2408 _source = addr;
2409
2410 // The start_array must be updated even if the object is not moving.
2411 if (_start_array != nullptr) {
2412 _start_array->update_for_block(destination(), destination() + words);
2413 }
2414
2415 // Avoid overflow
2416 words = MIN2(words, words_remaining());
2417 assert(words > 0, "inv");
2418
2419 if (copy_destination() != source()) {
2420 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2421 assert(source() != destination(), "inv");
2422 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2423 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2424 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2425 cast_to_oop(copy_destination())->set_mark(mark);
2426 }
2427
2428 update_state(words);
2429 }
2430
2431 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2432 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2433 // Record the shadow region index
2434 region_ptr->set_shadow_region(_shadow);
2435 // Mark the shadow region as filled to indicate the data is ready to be
2436 // copied back
2437 region_ptr->mark_filled();
2438 // Try to copy the content of the shadow region back to its corresponding
2439 // heap region if available; the GC thread that decreases the destination
2440 // count to zero will do the copying otherwise (see
2441 // PSParallelCompact::decrement_destination_counts).
2442 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2443 region_ptr->set_completed();
2444 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2445 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2446 }
2447 }