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