1 /*
2 * Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/javaClasses.inline.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "compiler/oopMap.hpp"
32 #include "gc/parallel/objectStartArray.inline.hpp"
33 #include "gc/parallel/parallelArguments.hpp"
34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
35 #include "gc/parallel/parMarkBitMap.inline.hpp"
36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
37 #include "gc/parallel/psCompactionManager.inline.hpp"
38 #include "gc/parallel/psOldGen.hpp"
39 #include "gc/parallel/psParallelCompact.inline.hpp"
40 #include "gc/parallel/psPromotionManager.inline.hpp"
41 #include "gc/parallel/psRootType.hpp"
42 #include "gc/parallel/psScavenge.hpp"
43 #include "gc/parallel/psStringDedup.hpp"
44 #include "gc/parallel/psYoungGen.hpp"
45 #include "gc/shared/classUnloadingContext.hpp"
46 #include "gc/shared/fullGCForwarding.inline.hpp"
47 #include "gc/shared/gcCause.hpp"
48 #include "gc/shared/gcHeapSummary.hpp"
49 #include "gc/shared/gcId.hpp"
50 #include "gc/shared/gcLocker.hpp"
51 #include "gc/shared/gcTimer.hpp"
52 #include "gc/shared/gcTrace.hpp"
53 #include "gc/shared/gcTraceTime.inline.hpp"
54 #include "gc/shared/gcVMOperations.hpp"
55 #include "gc/shared/isGCActiveMark.hpp"
56 #include "gc/shared/oopStorage.inline.hpp"
57 #include "gc/shared/oopStorageSet.inline.hpp"
58 #include "gc/shared/oopStorageSetParState.inline.hpp"
59 #include "gc/shared/preservedMarks.inline.hpp"
60 #include "gc/shared/referencePolicy.hpp"
61 #include "gc/shared/referenceProcessor.hpp"
62 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
63 #include "gc/shared/spaceDecorator.hpp"
64 #include "gc/shared/strongRootsScope.hpp"
65 #include "gc/shared/taskTerminator.hpp"
66 #include "gc/shared/weakProcessor.inline.hpp"
67 #include "gc/shared/workerPolicy.hpp"
68 #include "gc/shared/workerThread.hpp"
69 #include "gc/shared/workerUtils.hpp"
70 #include "logging/log.hpp"
71 #include "memory/iterator.inline.hpp"
72 #include "memory/memoryReserver.hpp"
73 #include "memory/metaspaceUtils.hpp"
74 #include "memory/resourceArea.hpp"
75 #include "memory/universe.hpp"
76 #include "nmt/memTracker.hpp"
77 #include "oops/access.inline.hpp"
78 #include "oops/flatArrayKlass.inline.hpp"
79 #include "oops/instanceClassLoaderKlass.inline.hpp"
80 #include "oops/instanceKlass.inline.hpp"
81 #include "oops/instanceMirrorKlass.inline.hpp"
82 #include "oops/methodData.hpp"
83 #include "oops/objArrayKlass.inline.hpp"
84 #include "oops/oop.inline.hpp"
85 #include "runtime/atomic.hpp"
86 #include "runtime/handles.inline.hpp"
87 #include "runtime/java.hpp"
88 #include "runtime/safepoint.hpp"
89 #include "runtime/threads.hpp"
90 #include "runtime/vmThread.hpp"
91 #include "services/memoryService.hpp"
92 #include "utilities/align.hpp"
93 #include "utilities/debug.hpp"
94 #include "utilities/events.hpp"
95 #include "utilities/formatBuffer.hpp"
96 #include "utilities/macros.hpp"
97 #include "utilities/stack.inline.hpp"
98 #if INCLUDE_JVMCI
99 #include "jvmci/jvmci.hpp"
100 #endif
101
102 #include <math.h>
103
104 // All sizes are in HeapWords.
105 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
106 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
107 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
108 const size_t ParallelCompactData::RegionSizeBytes =
109 RegionSize << LogHeapWordSize;
110 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
111 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
112 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
113
114 const ParallelCompactData::RegionData::region_sz_t
115 ParallelCompactData::RegionData::dc_shift = 27;
116
117 const ParallelCompactData::RegionData::region_sz_t
118 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
119
120 const ParallelCompactData::RegionData::region_sz_t
121 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
122
123 const ParallelCompactData::RegionData::region_sz_t
124 ParallelCompactData::RegionData::los_mask = ~dc_mask;
125
126 const ParallelCompactData::RegionData::region_sz_t
127 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
128
129 const ParallelCompactData::RegionData::region_sz_t
130 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
131
132 bool ParallelCompactData::RegionData::is_clear() {
133 return (_destination == nullptr) &&
134 (_source_region == 0) &&
135 (_partial_obj_addr == nullptr) &&
136 (_partial_obj_size == 0) &&
137 (_dc_and_los == 0) &&
138 (_shadow_state == 0);
139 }
140
141 #ifdef ASSERT
142 void ParallelCompactData::RegionData::verify_clear() {
143 assert(_destination == nullptr, "inv");
144 assert(_source_region == 0, "inv");
145 assert(_partial_obj_addr == nullptr, "inv");
146 assert(_partial_obj_size == 0, "inv");
147 assert(_dc_and_los == 0, "inv");
148 assert(_shadow_state == 0, "inv");
149 }
150 #endif
151
152 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
153
154 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
155 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
156
157 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
158 assert(split_region_idx != 0, "precondition");
159
160 // Obj denoted by split_point will be deferred to the next space.
161 assert(split_point != nullptr, "precondition");
162
163 const ParallelCompactData& sd = PSParallelCompact::summary_data();
164
165 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
166 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
167
168 HeapWord* preceding_destination = split_region_ptr->destination();
169 assert(preceding_destination != nullptr, "inv");
170
171 // How many regions does the preceding part occupy
172 uint preceding_destination_count;
173 if (preceding_live_words == 0) {
174 preceding_destination_count = 0;
175 } else {
176 // -1 so that the ending address doesn't fall on the region-boundary
177 if (sd.region_align_down(preceding_destination) ==
178 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
179 preceding_destination_count = 1;
180 } else {
181 preceding_destination_count = 2;
182 }
183 }
184
185 _split_region_idx = split_region_idx;
186 _split_point = split_point;
187 _preceding_live_words = preceding_live_words;
188 _preceding_destination = preceding_destination;
189 _preceding_destination_count = preceding_destination_count;
190 }
191
192 void SplitInfo::clear()
193 {
194 _split_region_idx = 0;
195 _split_point = nullptr;
196 _preceding_live_words = 0;
197 _preceding_destination = nullptr;
198 _preceding_destination_count = 0;
199 assert(!is_valid(), "sanity");
200 }
201
202 #ifdef ASSERT
203 void SplitInfo::verify_clear()
204 {
205 assert(_split_region_idx == 0, "not clear");
206 assert(_split_point == nullptr, "not clear");
207 assert(_preceding_live_words == 0, "not clear");
208 assert(_preceding_destination == nullptr, "not clear");
209 assert(_preceding_destination_count == 0, "not clear");
210 }
211 #endif // #ifdef ASSERT
212
213
214 void PSParallelCompact::print_on(outputStream* st) {
215 _mark_bitmap.print_on(st);
216 }
217
218 ParallelCompactData::ParallelCompactData() :
219 _heap_start(nullptr),
220 DEBUG_ONLY(_heap_end(nullptr) COMMA)
221 _region_vspace(nullptr),
222 _reserved_byte_size(0),
223 _region_data(nullptr),
224 _region_count(0) {}
225
226 bool ParallelCompactData::initialize(MemRegion reserved_heap)
227 {
228 _heap_start = reserved_heap.start();
229 const size_t heap_size = reserved_heap.word_size();
230 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
231
232 assert(region_align_down(_heap_start) == _heap_start,
233 "region start not aligned");
234
235 return initialize_region_data(heap_size);
236 }
237
238 PSVirtualSpace*
239 ParallelCompactData::create_vspace(size_t count, size_t element_size)
240 {
241 const size_t raw_bytes = count * element_size;
242 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
243 const size_t granularity = os::vm_allocation_granularity();
244 const size_t rs_align = MAX2(page_sz, granularity);
245
246 _reserved_byte_size = align_up(raw_bytes, rs_align);
247
248 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
249 rs_align,
250 page_sz,
251 mtGC);
252
253 if (!rs.is_reserved()) {
254 // Failed to reserve memory.
255 return nullptr;
256 }
257
258 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
259 rs.size(), page_sz);
260
261 MemTracker::record_virtual_memory_tag(rs, mtGC);
262
263 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
264
265 if (!vspace->expand_by(_reserved_byte_size)) {
266 // Failed to commit memory.
267
268 delete vspace;
269
270 // Release memory reserved in the space.
271 MemoryReserver::release(rs);
272
273 return nullptr;
274 }
275
276 return vspace;
277 }
278
279 bool ParallelCompactData::initialize_region_data(size_t heap_size)
280 {
281 assert(is_aligned(heap_size, RegionSize), "precondition");
282
283 const size_t count = heap_size >> Log2RegionSize;
284 _region_vspace = create_vspace(count, sizeof(RegionData));
285 if (_region_vspace != nullptr) {
286 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
287 _region_count = count;
288 return true;
289 }
290 return false;
291 }
292
293 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
294 assert(beg_region <= _region_count, "beg_region out of range");
295 assert(end_region <= _region_count, "end_region out of range");
296
297 const size_t region_cnt = end_region - beg_region;
298 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
299 }
300
301 void
302 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
303 {
304 assert(is_region_aligned(beg), "not RegionSize aligned");
305 assert(is_region_aligned(end), "not RegionSize aligned");
306
307 size_t cur_region = addr_to_region_idx(beg);
308 const size_t end_region = addr_to_region_idx(end);
309 HeapWord* addr = beg;
310 while (cur_region < end_region) {
311 _region_data[cur_region].set_destination(addr);
312 _region_data[cur_region].set_destination_count(0);
313 _region_data[cur_region].set_source_region(cur_region);
314
315 // Update live_obj_size so the region appears completely full.
316 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
317 _region_data[cur_region].set_live_obj_size(live_size);
318
319 ++cur_region;
320 addr += RegionSize;
321 }
322 }
323
324 // The total live words on src_region would overflow the target space, so find
325 // the overflowing object and record the split point. The invariant is that an
326 // obj should not cross space boundary.
327 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
328 SplitInfo& split_info,
329 HeapWord* const destination,
330 HeapWord* const target_end,
331 HeapWord** target_next) {
332 assert(destination <= target_end, "sanity");
333 assert(destination + _region_data[src_region].data_size() > target_end,
334 "region should not fit into target space");
335 assert(is_region_aligned(target_end), "sanity");
336
337 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
338
339 if (destination + partial_obj_size > target_end) {
340 assert(partial_obj_size > 0, "inv");
341 // The overflowing obj is from a previous region.
342 //
343 // source-regions:
344 //
345 // ***************
346 // | A|AA |
347 // ***************
348 // ^
349 // | split-point
350 //
351 // dest-region:
352 //
353 // ********
354 // |~~~~A |
355 // ********
356 // ^^
357 // || target-space-end
358 // |
359 // | destination
360 //
361 // AAA would overflow target-space.
362 //
363 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
364 size_t split_region = addr_to_region_idx(overflowing_obj);
365
366 // The number of live words before the overflowing object on this split region
367 size_t preceding_live_words;
368 if (is_region_aligned(overflowing_obj)) {
369 preceding_live_words = 0;
370 } else {
371 // Words accounted by the overflowing object on the split region
372 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
373 preceding_live_words = region(split_region)->data_size() - overflowing_size;
374 }
375
376 split_info.record(split_region, overflowing_obj, preceding_live_words);
377
378 // The [overflowing_obj, src_region_start) part has been accounted for, so
379 // must move back the new_top, now that this overflowing obj is deferred.
380 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
381
382 // If the overflowing obj was relocated to its original destination,
383 // those destination regions would have their source_region set. Now that
384 // this overflowing obj is relocated somewhere else, reset the
385 // source_region.
386 {
387 size_t range_start = addr_to_region_idx(region_align_up(new_top));
388 size_t range_end = addr_to_region_idx(region_align_up(destination));
389 for (size_t i = range_start; i < range_end; ++i) {
390 region(i)->set_source_region(0);
391 }
392 }
393
394 // Update new top of target space
395 *target_next = new_top;
396
397 return overflowing_obj;
398 }
399
400 // Obj-iteration to locate the overflowing obj
401 HeapWord* region_start = region_to_addr(src_region);
402 HeapWord* region_end = region_start + RegionSize;
403 HeapWord* cur_addr = region_start + partial_obj_size;
404 size_t live_words = partial_obj_size;
405
406 while (true) {
407 assert(cur_addr < region_end, "inv");
408 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
409 // There must be an overflowing obj in this region
410 assert(cur_addr < region_end, "inv");
411
412 oop obj = cast_to_oop(cur_addr);
413 size_t obj_size = obj->size();
414 if (destination + live_words + obj_size > target_end) {
415 // Found the overflowing obj
416 split_info.record(src_region, cur_addr, live_words);
417 *target_next = destination + live_words;
418 return cur_addr;
419 }
420
421 live_words += obj_size;
422 cur_addr += obj_size;
423 }
424 }
425
426 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
427 HeapWord** full_region_prefix_end) {
428 size_t cur_region = addr_to_region_idx(space->bottom());
429 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
430 size_t live_words = 0;
431 if (full_region_prefix_end == nullptr) {
432 for (/* empty */; cur_region < end_region; ++cur_region) {
433 live_words += _region_data[cur_region].data_size();
434 }
435 } else {
436 bool first_set = false;
437 for (/* empty */; cur_region < end_region; ++cur_region) {
438 size_t live_words_in_region = _region_data[cur_region].data_size();
439 if (!first_set && live_words_in_region < RegionSize) {
440 *full_region_prefix_end = region_to_addr(cur_region);
441 first_set = true;
442 }
443 live_words += live_words_in_region;
444 }
445 if (!first_set) {
446 // All regions are full of live objs.
447 assert(is_region_aligned(space->top()), "inv");
448 *full_region_prefix_end = space->top();
449 }
450 assert(*full_region_prefix_end != nullptr, "postcondition");
451 assert(is_region_aligned(*full_region_prefix_end), "inv");
452 assert(*full_region_prefix_end >= space->bottom(), "in-range");
453 assert(*full_region_prefix_end <= space->top(), "in-range");
454 }
455 return live_words;
456 }
457
458 bool ParallelCompactData::summarize(SplitInfo& split_info,
459 HeapWord* source_beg, HeapWord* source_end,
460 HeapWord** source_next,
461 HeapWord* target_beg, HeapWord* target_end,
462 HeapWord** target_next)
463 {
464 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
465 log_develop_trace(gc, compaction)(
466 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
467 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
468 p2i(source_beg), p2i(source_end), p2i(source_next_val),
469 p2i(target_beg), p2i(target_end), p2i(*target_next));
470
471 size_t cur_region = addr_to_region_idx(source_beg);
472 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
473
474 HeapWord *dest_addr = target_beg;
475 for (/* empty */; cur_region < end_region; cur_region++) {
476 size_t words = _region_data[cur_region].data_size();
477
478 // Skip empty ones
479 if (words == 0) {
480 continue;
481 }
482
483 if (split_info.is_split(cur_region)) {
484 assert(words > split_info.preceding_live_words(), "inv");
485 words -= split_info.preceding_live_words();
486 }
487
488 _region_data[cur_region].set_destination(dest_addr);
489
490 // If cur_region does not fit entirely into the target space, find a point
491 // at which the source space can be 'split' so that part is copied to the
492 // target space and the rest is copied elsewhere.
493 if (dest_addr + words > target_end) {
494 assert(source_next != nullptr, "source_next is null when splitting");
495 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
496 target_end, target_next);
497 return false;
498 }
499
500 uint destination_count = split_info.is_split(cur_region)
501 ? split_info.preceding_destination_count()
502 : 0;
503
504 HeapWord* const last_addr = dest_addr + words - 1;
505 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
506 const size_t dest_region_2 = addr_to_region_idx(last_addr);
507
508 // Initially assume that the destination regions will be the same and
509 // adjust the value below if necessary. Under this assumption, if
510 // cur_region == dest_region_2, then cur_region will be compacted
511 // completely into itself.
512 destination_count += cur_region == dest_region_2 ? 0 : 1;
513 if (dest_region_1 != dest_region_2) {
514 // Destination regions differ; adjust destination_count.
515 destination_count += 1;
516 // Data from cur_region will be copied to the start of dest_region_2.
517 _region_data[dest_region_2].set_source_region(cur_region);
518 } else if (is_region_aligned(dest_addr)) {
519 // Data from cur_region will be copied to the start of the destination
520 // region.
521 _region_data[dest_region_1].set_source_region(cur_region);
522 }
523
524 _region_data[cur_region].set_destination_count(destination_count);
525 dest_addr += words;
526 }
527
528 *target_next = dest_addr;
529 return true;
530 }
531
532 #ifdef ASSERT
533 void ParallelCompactData::verify_clear() {
534 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
535 if (!region(cur_idx)->is_clear()) {
536 log_warning(gc)("Uncleared Region: %u", cur_idx);
537 region(cur_idx)->verify_clear();
538 }
539 }
540 }
541 #endif // #ifdef ASSERT
542
543 STWGCTimer PSParallelCompact::_gc_timer;
544 ParallelOldTracer PSParallelCompact::_gc_tracer;
545 elapsedTimer PSParallelCompact::_accumulated_time;
546 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
547 CollectorCounters* PSParallelCompact::_counters = nullptr;
548 ParMarkBitMap PSParallelCompact::_mark_bitmap;
549 ParallelCompactData PSParallelCompact::_summary_data;
550
551 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
552
553 class PCAdjustPointerClosure: public BasicOopIterateClosure {
554 template <typename T>
555 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
556
557 public:
558 virtual void do_oop(oop* p) { do_oop_work(p); }
559 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
560
561 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
562 };
563
564 static PCAdjustPointerClosure pc_adjust_pointer_closure;
565
566 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
567
568 void PSParallelCompact::post_initialize() {
569 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
570 _span_based_discoverer.set_span(heap->reserved_region());
571 _ref_processor =
572 new ReferenceProcessor(&_span_based_discoverer,
573 ParallelGCThreads, // mt processing degree
574 ParallelGCThreads, // mt discovery degree
575 false, // concurrent_discovery
576 &_is_alive_closure); // non-header is alive closure
577
578 _counters = new CollectorCounters("Parallel full collection pauses", 1);
579
580 // Initialize static fields in ParCompactionManager.
581 ParCompactionManager::initialize(mark_bitmap());
582 }
583
584 bool PSParallelCompact::initialize_aux_data() {
585 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
586 MemRegion mr = heap->reserved_region();
587 assert(mr.byte_size() != 0, "heap should be reserved");
588
589 initialize_space_info();
590
591 if (!_mark_bitmap.initialize(mr)) {
592 vm_shutdown_during_initialization(
593 err_msg("Unable to allocate %zuKB bitmaps for parallel "
594 "garbage collection for the requested %zuKB heap.",
595 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
596 return false;
597 }
598
599 if (!_summary_data.initialize(mr)) {
600 vm_shutdown_during_initialization(
601 err_msg("Unable to allocate %zuKB card tables for parallel "
602 "garbage collection for the requested %zuKB heap.",
603 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
604 return false;
605 }
606
607 return true;
608 }
609
610 void PSParallelCompact::initialize_space_info()
611 {
612 memset(&_space_info, 0, sizeof(_space_info));
613
614 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
615 PSYoungGen* young_gen = heap->young_gen();
616
617 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
618 _space_info[eden_space_id].set_space(young_gen->eden_space());
619 _space_info[from_space_id].set_space(young_gen->from_space());
620 _space_info[to_space_id].set_space(young_gen->to_space());
621
622 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
623 }
624
625 void
626 PSParallelCompact::clear_data_covering_space(SpaceId id)
627 {
628 // At this point, top is the value before GC, new_top() is the value that will
629 // be set at the end of GC. The marking bitmap is cleared to top; nothing
630 // should be marked above top. The summary data is cleared to the larger of
631 // top & new_top.
632 MutableSpace* const space = _space_info[id].space();
633 HeapWord* const bot = space->bottom();
634 HeapWord* const top = space->top();
635 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
636
637 _mark_bitmap.clear_range(bot, top);
638
639 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
640 const size_t end_region =
641 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
642 _summary_data.clear_range(beg_region, end_region);
643
644 // Clear the data used to 'split' regions.
645 SplitInfo& split_info = _space_info[id].split_info();
646 if (split_info.is_valid()) {
647 split_info.clear();
648 }
649 DEBUG_ONLY(split_info.verify_clear();)
650 }
651
652 void PSParallelCompact::pre_compact()
653 {
654 // Update the from & to space pointers in space_info, since they are swapped
655 // at each young gen gc. Do the update unconditionally (even though a
656 // promotion failure does not swap spaces) because an unknown number of young
657 // collections will have swapped the spaces an unknown number of times.
658 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
659 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
660 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
661 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
662
663 // Increment the invocation count
664 heap->increment_total_collections(true);
665
666 CodeCache::on_gc_marking_cycle_start();
667
668 heap->print_before_gc();
669 heap->trace_heap_before_gc(&_gc_tracer);
670
671 // Fill in TLABs
672 heap->ensure_parsability(true); // retire TLABs
673
674 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
675 Universe::verify("Before GC");
676 }
677
678 DEBUG_ONLY(mark_bitmap()->verify_clear();)
679 DEBUG_ONLY(summary_data().verify_clear();)
680 }
681
682 void PSParallelCompact::post_compact()
683 {
684 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
685 ParCompactionManager::remove_all_shadow_regions();
686
687 CodeCache::on_gc_marking_cycle_finish();
688 CodeCache::arm_all_nmethods();
689
690 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
691 // Clear the marking bitmap, summary data and split info.
692 clear_data_covering_space(SpaceId(id));
693 {
694 MutableSpace* space = _space_info[id].space();
695 HeapWord* top = space->top();
696 HeapWord* new_top = _space_info[id].new_top();
697 if (ZapUnusedHeapArea && new_top < top) {
698 space->mangle_region(MemRegion(new_top, top));
699 }
700 // Update top(). Must be done after clearing the bitmap and summary data.
701 space->set_top(new_top);
702 }
703 }
704
705 #ifdef ASSERT
706 {
707 mark_bitmap()->verify_clear();
708 summary_data().verify_clear();
709 }
710 #endif
711
712 ParCompactionManager::flush_all_string_dedup_requests();
713
714 MutableSpace* const eden_space = _space_info[eden_space_id].space();
715 MutableSpace* const from_space = _space_info[from_space_id].space();
716 MutableSpace* const to_space = _space_info[to_space_id].space();
717
718 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
719 bool eden_empty = eden_space->is_empty();
720
721 // Update heap occupancy information which is used as input to the soft ref
722 // clearing policy at the next gc.
723 Universe::heap()->update_capacity_and_used_at_gc();
724
725 bool young_gen_empty = eden_empty && from_space->is_empty() &&
726 to_space->is_empty();
727
728 PSCardTable* ct = heap->card_table();
729 MemRegion old_mr = heap->old_gen()->committed();
730 if (young_gen_empty) {
731 ct->clear_MemRegion(old_mr);
732 } else {
733 ct->dirty_MemRegion(old_mr);
734 }
735
736 {
737 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
738 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
739 ClassLoaderDataGraph::purge(true /* at_safepoint */);
740 DEBUG_ONLY(MetaspaceUtils::verify();)
741 }
742
743 // Need to clear claim bits for the next mark.
744 ClassLoaderDataGraph::clear_claimed_marks();
745
746 heap->prune_scavengable_nmethods();
747
748 #if COMPILER2_OR_JVMCI
749 DerivedPointerTable::update_pointers();
750 #endif
751
752 // Signal that we have completed a visit to all live objects.
753 Universe::heap()->record_whole_heap_examined_timestamp();
754 }
755
756 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
757 HeapWord* full_region_prefix_end) {
758 const size_t region_size = ParallelCompactData::RegionSize;
759 const ParallelCompactData& sd = summary_data();
760
761 // Iteration starts with the region *after* the full-region-prefix-end.
762 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
763 // If final region is not full, iteration stops before that region,
764 // because fill_dense_prefix_end assumes that prefix_end <= top.
765 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
766 assert(start_region <= end_region, "inv");
767
768 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
769 const RegionData* cur_region = start_region;
770 for (/* empty */; cur_region < end_region; ++cur_region) {
771 assert(region_size >= cur_region->data_size(), "inv");
772 size_t dead_size = region_size - cur_region->data_size();
773 if (max_waste < dead_size) {
774 break;
775 }
776 max_waste -= dead_size;
777 }
778
779 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
780 assert(sd.is_region_aligned(prefix_end), "postcondition");
781 assert(prefix_end >= full_region_prefix_end, "in-range");
782 assert(prefix_end <= old_space->top(), "in-range");
783 return prefix_end;
784 }
785
786 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
787 // Comparing two sizes to decide if filling is required:
788 //
789 // The size of the filler (min-obj-size) is 2 heap words with the default
790 // MinObjAlignment, since both markword and klass take 1 heap word.
791 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
792 // because the Klass* gets encoded in the mark-word.
793 //
794 // The size of the gap (if any) right before dense-prefix-end is
795 // MinObjAlignment.
796 //
797 // Need to fill in the gap only if it's smaller than min-obj-size, and the
798 // filler obj will extend to next region.
799
800 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
801 return;
802 }
803
804 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
805 assert(CollectedHeap::min_fill_size() == 2, "inv");
806 HeapWord* const dense_prefix_end = dense_prefix(id);
807 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
808 assert(dense_prefix_end <= space(id)->top(), "precondition");
809 if (dense_prefix_end == space(id)->top()) {
810 // Must not have single-word gap right before prefix-end/top.
811 return;
812 }
813 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
814
815 if (region_after_dense_prefix->partial_obj_size() != 0 ||
816 _mark_bitmap.is_marked(dense_prefix_end)) {
817 // The region after the dense prefix starts with live bytes.
818 return;
819 }
820
821 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
822 if (block_start == dense_prefix_end - 1) {
823 assert(!_mark_bitmap.is_marked(block_start), "inv");
824 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
825 // The filler object will extend into region_after_dense_prefix.
826 const size_t obj_len = 2; // min-fill-size
827 HeapWord* const obj_beg = dense_prefix_end - 1;
828 CollectedHeap::fill_with_object(obj_beg, obj_len);
829 _mark_bitmap.mark_obj(obj_beg);
830 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
831 region_after_dense_prefix->set_partial_obj_size(1);
832 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
833 assert(start_array(id) != nullptr, "sanity");
834 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
835 }
836 }
837
838 bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
839 MutableSpace* const old_space,
840 HeapWord* full_region_prefix_end) {
841
842 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
843
844 // Check System.GC
845 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
846 && GCCause::is_user_requested_gc(heap->gc_cause());
847
848 // Check if all live objs are larger than old-gen.
849 const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
850
851 // JVM flags
852 const uint total_invocations = heap->total_full_collections();
853 assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
854 const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
855 const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
856
857 // If all regions in old-gen are full
858 const bool is_region_full =
859 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
860
861 if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
862 _maximum_compaction_gc_num = total_invocations;
863 return true;
864 }
865
866 return false;
867 }
868
869 void PSParallelCompact::summary_phase()
870 {
871 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
872
873 MutableSpace* const old_space = _space_info[old_space_id].space();
874 {
875 size_t total_live_words = 0;
876 HeapWord* full_region_prefix_end = nullptr;
877 {
878 // old-gen
879 size_t live_words = _summary_data.live_words_in_space(old_space,
880 &full_region_prefix_end);
881 total_live_words += live_words;
882 }
883 // young-gen
884 for (uint i = eden_space_id; i < last_space_id; ++i) {
885 const MutableSpace* space = _space_info[i].space();
886 size_t live_words = _summary_data.live_words_in_space(space);
887 total_live_words += live_words;
888 _space_info[i].set_new_top(space->bottom() + live_words);
889 _space_info[i].set_dense_prefix(space->bottom());
890 }
891
892 bool maximum_compaction = check_maximum_compaction(total_live_words,
893 old_space,
894 full_region_prefix_end);
895 HeapWord* dense_prefix_end = maximum_compaction
896 ? full_region_prefix_end
897 : compute_dense_prefix_for_old_space(old_space,
898 full_region_prefix_end);
899 SpaceId id = old_space_id;
900 _space_info[id].set_dense_prefix(dense_prefix_end);
901
902 if (dense_prefix_end != old_space->bottom()) {
903 fill_dense_prefix_end(id);
904 _summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
905 }
906
907 // Compacting objs in [dense_prefix_end, old_space->top())
908 _summary_data.summarize(_space_info[id].split_info(),
909 dense_prefix_end, old_space->top(), nullptr,
910 dense_prefix_end, old_space->end(),
911 _space_info[id].new_top_addr());
912 }
913
914 // Summarize the remaining spaces in the young gen. The initial target space
915 // is the old gen. If a space does not fit entirely into the target, then the
916 // remainder is compacted into the space itself and that space becomes the new
917 // target.
918 SpaceId dst_space_id = old_space_id;
919 HeapWord* dst_space_end = old_space->end();
920 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
921 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
922 const MutableSpace* space = _space_info[id].space();
923 const size_t live = pointer_delta(_space_info[id].new_top(),
924 space->bottom());
925 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
926
927 if (live > 0 && live <= available) {
928 // All the live data will fit.
929 bool done = _summary_data.summarize(_space_info[id].split_info(),
930 space->bottom(), space->top(),
931 nullptr,
932 *new_top_addr, dst_space_end,
933 new_top_addr);
934 assert(done, "space must fit into old gen");
935
936 // Reset the new_top value for the space.
937 _space_info[id].set_new_top(space->bottom());
938 } else if (live > 0) {
939 // Attempt to fit part of the source space into the target space.
940 HeapWord* next_src_addr = nullptr;
941 bool done = _summary_data.summarize(_space_info[id].split_info(),
942 space->bottom(), space->top(),
943 &next_src_addr,
944 *new_top_addr, dst_space_end,
945 new_top_addr);
946 assert(!done, "space should not fit into old gen");
947 assert(next_src_addr != nullptr, "sanity");
948
949 // The source space becomes the new target, so the remainder is compacted
950 // within the space itself.
951 dst_space_id = SpaceId(id);
952 dst_space_end = space->end();
953 new_top_addr = _space_info[id].new_top_addr();
954 done = _summary_data.summarize(_space_info[id].split_info(),
955 next_src_addr, space->top(),
956 nullptr,
957 space->bottom(), dst_space_end,
958 new_top_addr);
959 assert(done, "space must fit when compacted into itself");
960 assert(*new_top_addr <= space->top(), "usage should not grow");
961 }
962 }
963 }
964
965 // This method should contain all heap-specific policy for invoking a full
966 // collection. invoke_no_policy() will only attempt to compact the heap; it
967 // will do nothing further. If we need to bail out for policy reasons, scavenge
968 // before full gc, or any other specialized behavior, it needs to be added here.
969 //
970 // Note that this method should only be called from the vm_thread while at a
971 // safepoint.
972 //
973 // Note that the all_soft_refs_clear flag in the soft ref policy
974 // may be true because this method can be called without intervening
975 // activity. For example when the heap space is tight and full measure
976 // are being taken to free space.
977 bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
978 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
979 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
980 "should be in vm thread");
981
982 SvcGCMarker sgcm(SvcGCMarker::FULL);
983 IsSTWGCActiveMark mark;
984
985 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
986 clear_all_soft_refs = clear_all_soft_refs
987 || heap->soft_ref_policy()->should_clear_all_soft_refs();
988
989 return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
990 }
991
992 // This method contains no policy. You should probably
993 // be calling invoke() instead.
994 bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
995 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
996 assert(ref_processor() != nullptr, "Sanity");
997
998 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
999
1000 GCIdMark gc_id_mark;
1001 _gc_timer.register_gc_start();
1002 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1003
1004 GCCause::Cause gc_cause = heap->gc_cause();
1005 PSYoungGen* young_gen = heap->young_gen();
1006 PSOldGen* old_gen = heap->old_gen();
1007 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1008
1009 // The scope of casr should end after code that can change
1010 // SoftRefPolicy::_should_clear_all_soft_refs.
1011 ClearedAllSoftRefs casr(clear_all_soft_refs,
1012 heap->soft_ref_policy());
1013
1014 // Make sure data structures are sane, make the heap parsable, and do other
1015 // miscellaneous bookkeeping.
1016 pre_compact();
1017
1018 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1019
1020 {
1021 const uint active_workers =
1022 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
1023 ParallelScavengeHeap::heap()->workers().active_workers(),
1024 Threads::number_of_non_daemon_threads());
1025 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
1026
1027 GCTraceCPUTime tcpu(&_gc_tracer);
1028 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
1029
1030 heap->pre_full_gc_dump(&_gc_timer);
1031
1032 TraceCollectorStats tcs(counters());
1033 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
1034
1035 if (log_is_enabled(Debug, gc, heap, exit)) {
1036 accumulated_time()->start();
1037 }
1038
1039 // Let the size policy know we're starting
1040 size_policy->major_collection_begin();
1041
1042 #if COMPILER2_OR_JVMCI
1043 DerivedPointerTable::clear();
1044 #endif
1045
1046 ref_processor()->start_discovery(clear_all_soft_refs);
1047
1048 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
1049 false /* unregister_nmethods_during_purge */,
1050 false /* lock_nmethod_free_separately */);
1051
1052 marking_phase(&_gc_tracer);
1053
1054 summary_phase();
1055
1056 #if COMPILER2_OR_JVMCI
1057 assert(DerivedPointerTable::is_active(), "Sanity");
1058 DerivedPointerTable::set_active(false);
1059 #endif
1060
1061 forward_to_new_addr();
1062
1063 adjust_pointers();
1064
1065 compact();
1066
1067 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1068
1069 ParCompactionManager::verify_all_region_stack_empty();
1070
1071 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1072 // done before resizing.
1073 post_compact();
1074
1075 // Let the size policy know we're done
1076 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1077
1078 if (UseAdaptiveSizePolicy) {
1079 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1080 log_trace(gc, ergo)("old_gen_capacity: %zu young_gen_capacity: %zu",
1081 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1082
1083 // Don't check if the size_policy is ready here. Let
1084 // the size_policy check that internally.
1085 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1086 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1087 // Swap the survivor spaces if from_space is empty. The
1088 // resize_young_gen() called below is normally used after
1089 // a successful young GC and swapping of survivor spaces;
1090 // otherwise, it will fail to resize the young gen with
1091 // the current implementation.
1092 if (young_gen->from_space()->is_empty()) {
1093 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1094 young_gen->swap_spaces();
1095 }
1096
1097 // Calculate optimal free space amounts
1098 assert(young_gen->max_gen_size() >
1099 young_gen->from_space()->capacity_in_bytes() +
1100 young_gen->to_space()->capacity_in_bytes(),
1101 "Sizes of space in young gen are out-of-bounds");
1102
1103 size_t young_live = young_gen->used_in_bytes();
1104 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1105 size_t old_live = old_gen->used_in_bytes();
1106 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1107 size_t max_old_gen_size = old_gen->max_gen_size();
1108 size_t max_eden_size = young_gen->max_gen_size() -
1109 young_gen->from_space()->capacity_in_bytes() -
1110 young_gen->to_space()->capacity_in_bytes();
1111
1112 // Used for diagnostics
1113 size_policy->clear_generation_free_space_flags();
1114
1115 size_policy->compute_generations_free_space(young_live,
1116 eden_live,
1117 old_live,
1118 cur_eden,
1119 max_old_gen_size,
1120 max_eden_size,
1121 true /* full gc*/);
1122
1123 size_policy->check_gc_overhead_limit(eden_live,
1124 max_old_gen_size,
1125 max_eden_size,
1126 true /* full gc*/,
1127 gc_cause,
1128 heap->soft_ref_policy());
1129
1130 size_policy->decay_supplemental_growth(true /* full gc*/);
1131
1132 heap->resize_old_gen(
1133 size_policy->calculated_old_free_size_in_bytes());
1134
1135 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1136 size_policy->calculated_survivor_size_in_bytes());
1137 }
1138
1139 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1140 }
1141
1142 if (UsePerfData) {
1143 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1144 counters->update_counters();
1145 counters->update_old_capacity(old_gen->capacity_in_bytes());
1146 counters->update_young_capacity(young_gen->capacity_in_bytes());
1147 }
1148
1149 heap->resize_all_tlabs();
1150
1151 // Resize the metaspace capacity after a collection
1152 MetaspaceGC::compute_new_size();
1153
1154 if (log_is_enabled(Debug, gc, heap, exit)) {
1155 accumulated_time()->stop();
1156 }
1157
1158 heap->print_heap_change(pre_gc_values);
1159
1160 // Track memory usage and detect low memory
1161 MemoryService::track_memory_usage();
1162 heap->update_counters();
1163
1164 heap->post_full_gc_dump(&_gc_timer);
1165 }
1166
1167 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1168 Universe::verify("After GC");
1169 }
1170
1171 heap->print_after_gc();
1172 heap->trace_heap_after_gc(&_gc_tracer);
1173
1174 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1175
1176 _gc_timer.register_gc_end();
1177
1178 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1179 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1180
1181 return true;
1182 }
1183
1184 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1185 private:
1186 uint _worker_id;
1187
1188 public:
1189 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1190 void do_thread(Thread* thread) {
1191 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1192
1193 ResourceMark rm;
1194
1195 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1196
1197 MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
1198 !NMethodToOopClosure::FixRelocations,
1199 true /* keepalive nmethods */);
1200
1201 thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1202
1203 // Do the real work
1204 cm->follow_marking_stacks();
1205 }
1206 };
1207
1208 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1209 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1210
1211 ParCompactionManager* cm =
1212 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1213
1214 do {
1215 ScannerTask task;
1216 if (ParCompactionManager::steal(worker_id, task)) {
1217 cm->follow_contents(task, true);
1218 }
1219 cm->follow_marking_stacks();
1220 } while (!terminator.offer_termination());
1221 }
1222
1223 class MarkFromRootsTask : public WorkerTask {
1224 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
1225 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1226 TaskTerminator _terminator;
1227 uint _active_workers;
1228
1229 public:
1230 MarkFromRootsTask(uint active_workers) :
1231 WorkerTask("MarkFromRootsTask"),
1232 _strong_roots_scope(active_workers),
1233 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1234 _active_workers(active_workers) {}
1235
1236 virtual void work(uint worker_id) {
1237 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1238 cm->create_marking_stats_cache();
1239 {
1240 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1241 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1242
1243 // Do the real work
1244 cm->follow_marking_stacks();
1245 }
1246
1247 {
1248 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
1249 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1250 }
1251
1252 // Mark from OopStorages
1253 {
1254 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1255 // Do the real work
1256 cm->follow_marking_stacks();
1257 }
1258
1259 if (_active_workers > 1) {
1260 steal_marking_work(_terminator, worker_id);
1261 }
1262 }
1263 };
1264
1265 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1266 TaskTerminator _terminator;
1267
1268 public:
1269 ParallelCompactRefProcProxyTask(uint max_workers)
1270 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1271 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1272
1273 void work(uint worker_id) override {
1274 assert(worker_id < _max_workers, "sanity");
1275 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1276 BarrierEnqueueDiscoveredFieldClosure enqueue;
1277 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1278 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1279 }
1280
1281 void prepare_run_task_hook() override {
1282 _terminator.reset_for_reuse(_queue_count);
1283 }
1284 };
1285
1286 static void flush_marking_stats_cache(const uint num_workers) {
1287 for (uint i = 0; i < num_workers; ++i) {
1288 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1289 cm->flush_and_destroy_marking_stats_cache();
1290 }
1291 }
1292
1293 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1294 // Recursively traverse all live objects and mark them
1295 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1296
1297 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1298
1299 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1300 {
1301 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1302
1303 MarkFromRootsTask task(active_gc_threads);
1304 ParallelScavengeHeap::heap()->workers().run_task(&task);
1305 }
1306
1307 // Process reference objects found during marking
1308 {
1309 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1310
1311 ReferenceProcessorStats stats;
1312 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1313
1314 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1315 stats = ref_processor()->process_discovered_references(task, &ParallelScavengeHeap::heap()->workers(), pt);
1316
1317 gc_tracer->report_gc_reference_stats(stats);
1318 pt.print_all_references();
1319 }
1320
1321 {
1322 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1323
1324 flush_marking_stats_cache(active_gc_threads);
1325 }
1326
1327 // This is the point where the entire marking should have completed.
1328 ParCompactionManager::verify_all_marking_stack_empty();
1329
1330 {
1331 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1332 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1333 is_alive_closure(),
1334 &do_nothing_cl,
1335 1);
1336 }
1337
1338 {
1339 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1340
1341 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
1342
1343 bool unloading_occurred;
1344 {
1345 CodeCache::UnlinkingScope scope(is_alive_closure());
1346
1347 // Follow system dictionary roots and unload classes.
1348 unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1349
1350 // Unload nmethods.
1351 CodeCache::do_unloading(unloading_occurred);
1352 }
1353
1354 {
1355 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1356 // Release unloaded nmethod's memory.
1357 ctx->purge_nmethods();
1358 }
1359 {
1360 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1361 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1362 }
1363 {
1364 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1365 ctx->free_nmethods();
1366 }
1367
1368 // Prune dead klasses from subklass/sibling/implementor lists.
1369 Klass::clean_weak_klass_links(unloading_occurred);
1370
1371 // Clean JVMCI metadata handles.
1372 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
1373 }
1374
1375 {
1376 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
1377 _gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
1378 }
1379 #if TASKQUEUE_STATS
1380 ParCompactionManager::print_and_reset_taskqueue_stats();
1381 #endif
1382 }
1383
1384 template<typename Func>
1385 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1386 MutableSpace* sp = PSParallelCompact::space(id);
1387 HeapWord* const bottom = sp->bottom();
1388 HeapWord* const top = sp->top();
1389 if (bottom == top) {
1390 return;
1391 }
1392
1393 const uint num_regions_per_stripe = 2;
1394 const size_t region_size = ParallelCompactData::RegionSize;
1395 const size_t stripe_size = num_regions_per_stripe * region_size;
1396
1397 while (true) {
1398 uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
1399 HeapWord* cur_stripe = bottom + counter * region_size;
1400 if (cur_stripe >= top) {
1401 break;
1402 }
1403 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1404 on_stripe(cur_stripe, stripe_end);
1405 }
1406 }
1407
1408 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1409 // Regions in old-space shouldn't be split.
1410 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1411
1412 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1413 assert(mark_bitmap()->is_marked(obj_start), "inv");
1414 oop obj = cast_to_oop(obj_start);
1415 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1416 };
1417
1418 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1419 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1420 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1421 HeapWord* obj_start;
1422 if (cur_region->partial_obj_size() != 0) {
1423 obj_start = cur_region->partial_obj_addr();
1424 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1425 } else {
1426 obj_start = stripe_start;
1427 }
1428
1429 while (obj_start < stripe_end) {
1430 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1431 if (obj_start >= stripe_end) {
1432 break;
1433 }
1434 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1435 }
1436 });
1437 }
1438
1439 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1440 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1441 HeapWord* obj_start = stripe_start;
1442 while (obj_start < stripe_end) {
1443 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1444 if (obj_start >= stripe_end) {
1445 break;
1446 }
1447 oop obj = cast_to_oop(obj_start);
1448 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1449 }
1450 });
1451 }
1452
1453 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1454 auto start_time = Ticks::now();
1455 adjust_in_old_space(&claim_counters[0]);
1456 for (uint id = eden_space_id; id < last_space_id; ++id) {
1457 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1458 }
1459 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1460 }
1461
1462 class PSAdjustTask final : public WorkerTask {
1463 SubTasksDone _sub_tasks;
1464 WeakProcessor::Task _weak_proc_task;
1465 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1466 uint _nworkers;
1467 volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1468
1469 enum PSAdjustSubTask {
1470 PSAdjustSubTask_code_cache,
1471
1472 PSAdjustSubTask_num_elements
1473 };
1474
1475 public:
1476 PSAdjustTask(uint nworkers) :
1477 WorkerTask("PSAdjust task"),
1478 _sub_tasks(PSAdjustSubTask_num_elements),
1479 _weak_proc_task(nworkers),
1480 _nworkers(nworkers) {
1481
1482 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1483 if (nworkers > 1) {
1484 Threads::change_thread_claim_token();
1485 }
1486 }
1487
1488 ~PSAdjustTask() {
1489 Threads::assert_all_threads_claimed();
1490 }
1491
1492 void work(uint worker_id) {
1493 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1494 cm->preserved_marks()->adjust_during_full_gc();
1495 {
1496 // adjust pointers in all spaces
1497 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1498 }
1499 {
1500 ResourceMark rm;
1501 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1502 }
1503 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1504 {
1505 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1506 ClassLoaderDataGraph::cld_do(&cld_closure);
1507 }
1508 {
1509 AlwaysTrueClosure always_alive;
1510 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1511 }
1512 if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
1513 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1514 CodeCache::nmethods_do(&adjust_code);
1515 }
1516 _sub_tasks.all_tasks_claimed();
1517 }
1518 };
1519
1520 void PSParallelCompact::adjust_pointers() {
1521 // Adjust the pointers to reflect the new locations
1522 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1523 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1524 PSAdjustTask task(nworkers);
1525 ParallelScavengeHeap::heap()->workers().run_task(&task);
1526 }
1527
1528 // Split [start, end) evenly for a number of workers and return the
1529 // range for worker_id.
1530 static void split_regions_for_worker(size_t start, size_t end,
1531 uint worker_id, uint num_workers,
1532 size_t* worker_start, size_t* worker_end) {
1533 assert(start < end, "precondition");
1534 assert(num_workers > 0, "precondition");
1535 assert(worker_id < num_workers, "precondition");
1536
1537 size_t num_regions = end - start;
1538 size_t num_regions_per_worker = num_regions / num_workers;
1539 size_t remainder = num_regions % num_workers;
1540 // The first few workers will get one extra.
1541 *worker_start = start + worker_id * num_regions_per_worker
1542 + MIN2(checked_cast<size_t>(worker_id), remainder);
1543 *worker_end = *worker_start + num_regions_per_worker
1544 + (worker_id < remainder ? 1 : 0);
1545 }
1546
1547 void PSParallelCompact::forward_to_new_addr() {
1548 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1549 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1550
1551 struct ForwardTask final : public WorkerTask {
1552 uint _num_workers;
1553
1554 explicit ForwardTask(uint num_workers) :
1555 WorkerTask("PSForward task"),
1556 _num_workers(num_workers) {}
1557
1558 static void forward_objs_in_range(ParCompactionManager* cm,
1559 HeapWord* start,
1560 HeapWord* end,
1561 HeapWord* destination) {
1562 HeapWord* cur_addr = start;
1563 HeapWord* new_addr = destination;
1564
1565 while (cur_addr < end) {
1566 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1567 if (cur_addr >= end) {
1568 return;
1569 }
1570 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1571 oop obj = cast_to_oop(cur_addr);
1572 if (new_addr != cur_addr) {
1573 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1574 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1575 }
1576 size_t obj_size = obj->size();
1577 new_addr += obj_size;
1578 cur_addr += obj_size;
1579 }
1580 }
1581
1582 void work(uint worker_id) override {
1583 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1584 for (uint id = old_space_id; id < last_space_id; ++id) {
1585 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1586 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1587 HeapWord* top = sp->top();
1588
1589 if (dense_prefix_addr == top) {
1590 continue;
1591 }
1592
1593 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1594
1595 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1596 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1597 size_t start_region;
1598 size_t end_region;
1599 split_regions_for_worker(dense_prefix_region, top_region,
1600 worker_id, _num_workers,
1601 &start_region, &end_region);
1602 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1603 RegionData* region_ptr = _summary_data.region(cur_region);
1604 size_t partial_obj_size = region_ptr->partial_obj_size();
1605
1606 if (partial_obj_size == ParallelCompactData::RegionSize) {
1607 // No obj-start
1608 continue;
1609 }
1610
1611 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1612 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1613
1614 if (split_info.is_split(cur_region)) {
1615 // Part 1: will be relocated to space-1
1616 HeapWord* preceding_destination = split_info.preceding_destination();
1617 HeapWord* split_point = split_info.split_point();
1618 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1619
1620 // Part 2: will be relocated to space-2
1621 HeapWord* destination = region_ptr->destination();
1622 forward_objs_in_range(cm, split_point, region_end, destination);
1623 } else {
1624 HeapWord* destination = region_ptr->destination();
1625 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1626 }
1627 }
1628 }
1629 }
1630 } task(nworkers);
1631
1632 ParallelScavengeHeap::heap()->workers().run_task(&task);
1633 DEBUG_ONLY(verify_forward();)
1634 }
1635
1636 #ifdef ASSERT
1637 void PSParallelCompact::verify_forward() {
1638 HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1639 RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
1640 HeapWord* bump_ptr = old_region->partial_obj_size() != 0
1641 ? old_dense_prefix_addr + old_region->partial_obj_size()
1642 : old_dense_prefix_addr;
1643 SpaceId bump_ptr_space = old_space_id;
1644
1645 for (uint id = old_space_id; id < last_space_id; ++id) {
1646 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1647 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1648 HeapWord* top = sp->top();
1649 HeapWord* cur_addr = dense_prefix_addr;
1650
1651 while (cur_addr < top) {
1652 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1653 if (cur_addr >= top) {
1654 break;
1655 }
1656 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1657 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1658 // Move to the space containing cur_addr
1659 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1660 bump_ptr = space(space_id(cur_addr))->bottom();
1661 bump_ptr_space = space_id(bump_ptr);
1662 }
1663 oop obj = cast_to_oop(cur_addr);
1664 if (cur_addr == bump_ptr) {
1665 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1666 } else {
1667 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1668 }
1669 bump_ptr += obj->size();
1670 cur_addr += obj->size();
1671 }
1672 }
1673 }
1674 #endif
1675
1676 // Helper class to print 8 region numbers per line and then print the total at the end.
1677 class FillableRegionLogger : public StackObj {
1678 private:
1679 Log(gc, compaction) log;
1680 static const int LineLength = 8;
1681 size_t _regions[LineLength];
1682 int _next_index;
1683 bool _enabled;
1684 size_t _total_regions;
1685 public:
1686 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1687 ~FillableRegionLogger() {
1688 log.trace("%zu initially fillable regions", _total_regions);
1689 }
1690
1691 void print_line() {
1692 if (!_enabled || _next_index == 0) {
1693 return;
1694 }
1695 FormatBuffer<> line("Fillable: ");
1696 for (int i = 0; i < _next_index; i++) {
1697 line.append(" %7zu", _regions[i]);
1698 }
1699 log.trace("%s", line.buffer());
1700 _next_index = 0;
1701 }
1702
1703 void handle(size_t region) {
1704 if (!_enabled) {
1705 return;
1706 }
1707 _regions[_next_index++] = region;
1708 if (_next_index == LineLength) {
1709 print_line();
1710 }
1711 _total_regions++;
1712 }
1713 };
1714
1715 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1716 {
1717 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1718
1719 // Find the threads that are active
1720 uint worker_id = 0;
1721
1722 // Find all regions that are available (can be filled immediately) and
1723 // distribute them to the thread stacks. The iteration is done in reverse
1724 // order (high to low) so the regions will be removed in ascending order.
1725
1726 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1727
1728 // id + 1 is used to test termination so unsigned can
1729 // be used with an old_space_id == 0.
1730 FillableRegionLogger region_logger;
1731 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
1732 SpaceInfo* const space_info = _space_info + id;
1733 HeapWord* const new_top = space_info->new_top();
1734
1735 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1736 const size_t end_region =
1737 sd.addr_to_region_idx(sd.region_align_up(new_top));
1738
1739 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1740 if (sd.region(cur)->claim_unsafe()) {
1741 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1742 bool result = sd.region(cur)->mark_normal();
1743 assert(result, "Must succeed at this point.");
1744 cm->region_stack()->push(cur);
1745 region_logger.handle(cur);
1746 // Assign regions to tasks in round-robin fashion.
1747 if (++worker_id == parallel_gc_threads) {
1748 worker_id = 0;
1749 }
1750 }
1751 }
1752 region_logger.print_line();
1753 }
1754 }
1755
1756 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1757 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1758
1759 ParCompactionManager* cm =
1760 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1761
1762 // Drain the stacks that have been preloaded with regions
1763 // that are ready to fill.
1764
1765 cm->drain_region_stacks();
1766
1767 guarantee(cm->region_stack()->is_empty(), "Not empty");
1768
1769 size_t region_index = 0;
1770
1771 while (true) {
1772 if (ParCompactionManager::steal(worker_id, region_index)) {
1773 PSParallelCompact::fill_and_update_region(cm, region_index);
1774 cm->drain_region_stacks();
1775 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1776 // Fill and update an unavailable region with the help of a shadow region
1777 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1778 cm->drain_region_stacks();
1779 } else {
1780 if (terminator->offer_termination()) {
1781 break;
1782 }
1783 // Go around again.
1784 }
1785 }
1786 }
1787
1788 class FillDensePrefixAndCompactionTask: public WorkerTask {
1789 uint _num_workers;
1790 TaskTerminator _terminator;
1791
1792 public:
1793 FillDensePrefixAndCompactionTask(uint active_workers) :
1794 WorkerTask("FillDensePrefixAndCompactionTask"),
1795 _num_workers(active_workers),
1796 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1797 }
1798
1799 virtual void work(uint worker_id) {
1800 {
1801 auto start = Ticks::now();
1802 PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
1803 log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
1804 }
1805 compaction_with_stealing_work(&_terminator, worker_id);
1806 }
1807 };
1808
1809 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1810 #ifdef ASSERT
1811 {
1812 assert(start < end, "precondition");
1813 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1814 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1815 if (start != bottom) {
1816 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1817 HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
1818 assert(after_obj == start, "precondition");
1819 }
1820 }
1821 #endif
1822
1823 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1824 HeapWord* addr = start;
1825 do {
1826 size_t size = cast_to_oop(addr)->size();
1827 start_array(old_space_id)->update_for_block(addr, addr + size);
1828 addr += size;
1829 } while (addr < end);
1830 }
1831
1832 void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
1833 ParMarkBitMap* bitmap = mark_bitmap();
1834
1835 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1836 HeapWord* const prefix_end = dense_prefix(old_space_id);
1837
1838 if (bottom == prefix_end) {
1839 return;
1840 }
1841
1842 size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
1843 size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
1844
1845 size_t start_region;
1846 size_t end_region;
1847 split_regions_for_worker(bottom_region, prefix_end_region,
1848 worker_id, num_workers,
1849 &start_region, &end_region);
1850
1851 if (start_region == end_region) {
1852 return;
1853 }
1854
1855 HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
1856 HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
1857
1858 // Skip live partial obj (if any) from previous region.
1859 HeapWord* cur_addr;
1860 RegionData* start_region_ptr = _summary_data.region(start_region);
1861 if (start_region_ptr->partial_obj_size() != 0) {
1862 HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
1863 assert(bitmap->is_marked(partial_obj_start), "inv");
1864 cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
1865 } else {
1866 cur_addr = start_addr;
1867 }
1868
1869 // end_addr is inclusive to handle regions starting with dead space.
1870 while (cur_addr <= end_addr) {
1871 // Use prefix_end to handle trailing obj in each worker region-chunk.
1872 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
1873 if (cur_addr != live_start) {
1874 // Only worker 0 handles proceeding dead space.
1875 if (cur_addr != start_addr || worker_id == 0) {
1876 fill_range_in_dense_prefix(cur_addr, live_start);
1877 }
1878 }
1879 if (live_start >= end_addr) {
1880 break;
1881 }
1882 assert(bitmap->is_marked(live_start), "inv");
1883 cur_addr = live_start + cast_to_oop(live_start)->size();
1884 }
1885 }
1886
1887 void PSParallelCompact::compact() {
1888 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1889
1890 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1891
1892 initialize_shadow_regions(active_gc_threads);
1893 prepare_region_draining_tasks(active_gc_threads);
1894
1895 {
1896 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1897
1898 FillDensePrefixAndCompactionTask task(active_gc_threads);
1899 ParallelScavengeHeap::heap()->workers().run_task(&task);
1900
1901 #ifdef ASSERT
1902 verify_filler_in_dense_prefix();
1903
1904 // Verify that all regions have been processed.
1905 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1906 verify_complete(SpaceId(id));
1907 }
1908 #endif
1909 }
1910 }
1911
1912 #ifdef ASSERT
1913 void PSParallelCompact::verify_filler_in_dense_prefix() {
1914 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1915 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1916 HeapWord* cur_addr = bottom;
1917 while (cur_addr < dense_prefix_end) {
1918 oop obj = cast_to_oop(cur_addr);
1919 oopDesc::verify(obj);
1920 if (!mark_bitmap()->is_marked(cur_addr)) {
1921 Klass* k = cast_to_oop(cur_addr)->klass();
1922 assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
1923 }
1924 cur_addr += obj->size();
1925 }
1926 }
1927
1928 void PSParallelCompact::verify_complete(SpaceId space_id) {
1929 // All Regions served as compaction targets, from dense_prefix() to
1930 // new_top(), should be marked as filled and all Regions between new_top()
1931 // and top() should be available (i.e., should have been emptied).
1932 ParallelCompactData& sd = summary_data();
1933 SpaceInfo si = _space_info[space_id];
1934 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1935 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1936 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1937 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1938 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1939
1940 size_t cur_region;
1941 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1942 const RegionData* const c = sd.region(cur_region);
1943 assert(c->completed(), "region %zu not filled: destination_count=%u",
1944 cur_region, c->destination_count());
1945 }
1946
1947 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1948 const RegionData* const c = sd.region(cur_region);
1949 assert(c->available(), "region %zu not empty: destination_count=%u",
1950 cur_region, c->destination_count());
1951 }
1952 }
1953 #endif // #ifdef ASSERT
1954
1955 // Return the SpaceId for the space containing addr. If addr is not in the
1956 // heap, last_space_id is returned. In debug mode it expects the address to be
1957 // in the heap and asserts such.
1958 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1959 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1960
1961 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1962 if (_space_info[id].space()->contains(addr)) {
1963 return SpaceId(id);
1964 }
1965 }
1966
1967 assert(false, "no space contains the addr");
1968 return last_space_id;
1969 }
1970
1971 // Skip over count live words starting from beg, and return the address of the
1972 // next live word. Callers must also ensure that there are enough live words in
1973 // the range [beg, end) to skip.
1974 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1975 {
1976 ParMarkBitMap* m = mark_bitmap();
1977 HeapWord* cur_addr = beg;
1978 while (true) {
1979 cur_addr = m->find_obj_beg(cur_addr, end);
1980 assert(cur_addr < end, "inv");
1981 size_t obj_size = cast_to_oop(cur_addr)->size();
1982 // Strictly greater-than
1983 if (obj_size > count) {
1984 return cur_addr + count;
1985 }
1986 count -= obj_size;
1987 cur_addr += obj_size;
1988 }
1989 }
1990
1991 // On starting to fill a destination region (dest-region), we need to know the
1992 // location of the word that will be at the start of the dest-region after
1993 // compaction. A dest-region can have one or more source regions, but only the
1994 // first source-region contains this location. This location is retrieved by
1995 // calling `first_src_addr` on a dest-region.
1996 // Conversely, a source-region has a dest-region which holds the destination of
1997 // the first live word on this source-region, based on which the destination
1998 // for the rest of live words can be derived.
1999 //
2000 // Note:
2001 // There is some complication due to space-boundary-fragmentation (an obj can't
2002 // cross space-boundary) -- a source-region may be split and behave like two
2003 // distinct regions with their own dest-region, as depicted below.
2004 //
2005 // source-region: region-n
2006 //
2007 // **********************
2008 // | A|A~~~~B|B |
2009 // **********************
2010 // n-1 n n+1
2011 //
2012 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
2013 //
2014 // Assuming the dest-region for region-n is the final region before
2015 // old-space-end and its first-live-word is the middle of AA, the heap content
2016 // will look like the following after compaction:
2017 //
2018 // ************** *************
2019 // A|A~~~~ | |BB |
2020 // ************** *************
2021 // ^ ^
2022 // | old-space-end | eden-space-start
2023 //
2024 // Therefore, in this example, region-n will have two dest-regions:
2025 // 1. the final region in old-space
2026 // 2. the first region in eden-space.
2027 // To handle this special case, we introduce the concept of split-region, whose
2028 // contents are relocated to two spaces. `SplitInfo` captures all necessary
2029 // info about the split, the first part, spliting-point, and the second part.
2030 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2031 SpaceId src_space_id,
2032 size_t src_region_idx)
2033 {
2034 const size_t RegionSize = ParallelCompactData::RegionSize;
2035 const ParallelCompactData& sd = summary_data();
2036 assert(sd.is_region_aligned(dest_addr), "precondition");
2037
2038 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2039 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2040
2041 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2042 HeapWord* const src_region_destination = src_region_ptr->destination();
2043
2044 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
2045 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
2046
2047 // Identify the actual destination for the first live words on this region,
2048 // taking split-region into account.
2049 HeapWord* region_start_destination;
2050 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2051 if (split_info.is_split(src_region_idx)) {
2052 // The second part of this split region; use the recorded split point.
2053 if (dest_addr == src_region_destination) {
2054 return split_info.split_point();
2055 }
2056 region_start_destination = split_info.preceding_destination();
2057 } else {
2058 region_start_destination = src_region_destination;
2059 }
2060
2061 // Calculate the offset to be skipped
2062 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
2063
2064 HeapWord* result;
2065 if (partial_obj_size > words_to_skip) {
2066 result = region_start + words_to_skip;
2067 } else {
2068 words_to_skip -= partial_obj_size;
2069 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2070 }
2071
2072 if (split_info.is_split(src_region_idx)) {
2073 assert(result < split_info.split_point(), "postcondition");
2074 } else {
2075 assert(result < region_end, "postcondition");
2076 }
2077
2078 return result;
2079 }
2080
2081 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2082 SpaceId src_space_id,
2083 size_t beg_region,
2084 HeapWord* end_addr)
2085 {
2086 ParallelCompactData& sd = summary_data();
2087
2088 #ifdef ASSERT
2089 MutableSpace* const src_space = _space_info[src_space_id].space();
2090 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2091 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2092 "src_space_id does not match beg_addr");
2093 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2094 "src_space_id does not match end_addr");
2095 #endif // #ifdef ASSERT
2096
2097 RegionData* const beg = sd.region(beg_region);
2098 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2099
2100 // Regions up to new_top() are enqueued if they become available.
2101 HeapWord* const new_top = _space_info[src_space_id].new_top();
2102 RegionData* const enqueue_end =
2103 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2104
2105 for (RegionData* cur = beg; cur < end; ++cur) {
2106 assert(cur->data_size() > 0, "region must have live data");
2107 cur->decrement_destination_count();
2108 if (cur < enqueue_end && cur->available() && cur->claim()) {
2109 if (cur->mark_normal()) {
2110 cm->push_region(sd.region(cur));
2111 } else if (cur->mark_copied()) {
2112 // Try to copy the content of the shadow region back to its corresponding
2113 // heap region if the shadow region is filled. Otherwise, the GC thread
2114 // fills the shadow region will copy the data back (see
2115 // MoveAndUpdateShadowClosure::complete_region).
2116 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2117 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2118 cur->set_completed();
2119 }
2120 }
2121 }
2122 }
2123
2124 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2125 SpaceId& src_space_id,
2126 HeapWord*& src_space_top,
2127 HeapWord* end_addr)
2128 {
2129 ParallelCompactData& sd = PSParallelCompact::summary_data();
2130
2131 size_t src_region_idx = 0;
2132
2133 // Skip empty regions (if any) up to the top of the space.
2134 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2135 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2136 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2137 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2138
2139 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2140 ++src_region_ptr;
2141 }
2142
2143 if (src_region_ptr < top_region_ptr) {
2144 // Found the first non-empty region in the same space.
2145 src_region_idx = sd.region(src_region_ptr);
2146 closure.set_source(sd.region_to_addr(src_region_idx));
2147 return src_region_idx;
2148 }
2149
2150 // Switch to a new source space and find the first non-empty region.
2151 uint space_id = src_space_id + 1;
2152 assert(space_id < last_space_id, "not enough spaces");
2153
2154 for (/* empty */; space_id < last_space_id; ++space_id) {
2155 HeapWord* bottom = _space_info[space_id].space()->bottom();
2156 HeapWord* top = _space_info[space_id].space()->top();
2157 // Skip empty space
2158 if (bottom == top) {
2159 continue;
2160 }
2161
2162 // Identify the first region that contains live words in this space
2163 size_t cur_region = sd.addr_to_region_idx(bottom);
2164 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2165
2166 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2167 RegionData* cur = sd.region(cur_region);
2168 if (cur->live_obj_size() > 0) {
2169 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2170
2171 src_space_id = SpaceId(space_id);
2172 src_space_top = top;
2173 closure.set_source(region_start_addr);
2174 return cur_region;
2175 }
2176 }
2177 }
2178
2179 ShouldNotReachHere();
2180 }
2181
2182 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2183 ParallelCompactData& sd = summary_data();
2184 assert(sd.is_region_aligned(region_start_addr), "precondition");
2185
2186 // Use per-region partial_obj_size to locate the end of the obj, that extends
2187 // to region_start_addr.
2188 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2189 size_t end_region_idx = sd.region_count();
2190 size_t accumulated_size = 0;
2191 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2192 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2193 accumulated_size += cur_partial_obj_size;
2194 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2195 break;
2196 }
2197 }
2198 return region_start_addr + accumulated_size;
2199 }
2200
2201 // Use region_idx as the destination region, and evacuate all live objs on its
2202 // source regions to this destination region.
2203 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2204 {
2205 ParMarkBitMap* const bitmap = mark_bitmap();
2206 ParallelCompactData& sd = summary_data();
2207 RegionData* const region_ptr = sd.region(region_idx);
2208
2209 // Get the source region and related info.
2210 size_t src_region_idx = region_ptr->source_region();
2211 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2212 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2213 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2214
2215 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2216
2217 // Adjust src_region_idx to prepare for decrementing destination counts (the
2218 // destination count is not decremented when a region is copied to itself).
2219 if (src_region_idx == region_idx) {
2220 src_region_idx += 1;
2221 }
2222
2223 // source-region:
2224 //
2225 // **********
2226 // | ~~~ |
2227 // **********
2228 // ^
2229 // |-- closure.source() / first_src_addr
2230 //
2231 //
2232 // ~~~ : live words
2233 //
2234 // destination-region:
2235 //
2236 // **********
2237 // | |
2238 // **********
2239 // ^
2240 // |-- region-start
2241 if (bitmap->is_unmarked(closure.source())) {
2242 // An object overflows the previous destination region, so this
2243 // destination region should copy the remainder of the object or as much as
2244 // will fit.
2245 HeapWord* const old_src_addr = closure.source();
2246 {
2247 HeapWord* region_start = sd.region_align_down(closure.source());
2248 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2249 HeapWord* obj_end;
2250 if (obj_start != closure.source()) {
2251 assert(bitmap->is_marked(obj_start), "inv");
2252 // Found the actual obj-start, try to find the obj-end using either
2253 // size() if this obj is completely contained in the current region.
2254 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2255 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2256 ? nullptr
2257 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2258 // This obj extends to next region iff partial_obj_addr of the *next*
2259 // region is the same as obj-start.
2260 if (partial_obj_start == obj_start) {
2261 // This obj extends to next region.
2262 obj_end = partial_obj_end(next_region_start);
2263 } else {
2264 // Completely contained in this region; safe to use size().
2265 obj_end = obj_start + cast_to_oop(obj_start)->size();
2266 }
2267 } else {
2268 // This obj extends to current region.
2269 obj_end = partial_obj_end(region_start);
2270 }
2271 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2272 closure.copy_partial_obj(partial_obj_size);
2273 }
2274
2275 if (closure.is_full()) {
2276 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2277 closure.complete_region(dest_addr, region_ptr);
2278 return;
2279 }
2280
2281 // Finished copying without using up the current destination-region
2282 HeapWord* const end_addr = sd.region_align_down(closure.source());
2283 if (sd.region_align_down(old_src_addr) != end_addr) {
2284 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2285 // The partial object was copied from more than one source region.
2286 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2287
2288 // Move to the next source region, possibly switching spaces as well. All
2289 // args except end_addr may be modified.
2290 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2291 }
2292 }
2293
2294 // Handle the rest obj-by-obj, where we know obj-start.
2295 do {
2296 HeapWord* cur_addr = closure.source();
2297 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2298 src_space_top);
2299 // To handle the case where the final obj in source region extends to next region.
2300 HeapWord* final_obj_start = (end_addr == src_space_top)
2301 ? nullptr
2302 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2303 // Apply closure on objs inside [cur_addr, end_addr)
2304 do {
2305 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2306 if (cur_addr == end_addr) {
2307 break;
2308 }
2309 size_t obj_size;
2310 if (final_obj_start == cur_addr) {
2311 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2312 } else {
2313 // This obj doesn't extend into next region; size() is safe to use.
2314 obj_size = cast_to_oop(cur_addr)->size();
2315 }
2316 closure.do_addr(cur_addr, obj_size);
2317 cur_addr += obj_size;
2318 } while (cur_addr < end_addr && !closure.is_full());
2319
2320 if (closure.is_full()) {
2321 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2322 closure.complete_region(dest_addr, region_ptr);
2323 return;
2324 }
2325
2326 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2327
2328 // Move to the next source region, possibly switching spaces as well. All
2329 // args except end_addr may be modified.
2330 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2331 } while (true);
2332 }
2333
2334 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2335 {
2336 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2337 fill_region(cm, cl, region_idx);
2338 }
2339
2340 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2341 {
2342 // Get a shadow region first
2343 ParallelCompactData& sd = summary_data();
2344 RegionData* const region_ptr = sd.region(region_idx);
2345 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2346 // The InvalidShadow return value indicates the corresponding heap region is available,
2347 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2348 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2349 if (shadow_region == ParCompactionManager::InvalidShadow) {
2350 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2351 region_ptr->shadow_to_normal();
2352 return fill_region(cm, cl, region_idx);
2353 } else {
2354 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2355 return fill_region(cm, cl, region_idx);
2356 }
2357 }
2358
2359 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2360 {
2361 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2362 }
2363
2364 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2365 {
2366 size_t next = cm->next_shadow_region();
2367 ParallelCompactData& sd = summary_data();
2368 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2369 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2370
2371 while (next < old_new_top) {
2372 if (sd.region(next)->mark_shadow()) {
2373 region_idx = next;
2374 return true;
2375 }
2376 next = cm->move_next_shadow_region_by(active_gc_threads);
2377 }
2378
2379 return false;
2380 }
2381
2382 // The shadow region is an optimization to address region dependencies in full GC. The basic
2383 // idea is making more regions available by temporally storing their live objects in empty
2384 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2385 // GC threads need not wait destination regions to be available before processing sources.
2386 //
2387 // A typical workflow would be:
2388 // After draining its own stack and failing to steal from others, a GC worker would pick an
2389 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2390 // the shadow region by copying live objects from source regions of the unavailable one. Once
2391 // the unavailable region becomes available, the data in the shadow region will be copied back.
2392 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2393 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2394 {
2395 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2396
2397 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2398 SpaceInfo* const space_info = _space_info + id;
2399 MutableSpace* const space = space_info->space();
2400
2401 const size_t beg_region =
2402 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2403 const size_t end_region =
2404 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2405
2406 for (size_t cur = beg_region; cur < end_region; ++cur) {
2407 ParCompactionManager::push_shadow_region(cur);
2408 }
2409 }
2410
2411 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2412 for (uint i = 0; i < parallel_gc_threads; i++) {
2413 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2414 cm->set_next_shadow_region(beg_region + i);
2415 }
2416 }
2417
2418 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2419 {
2420 size_t words = MIN2(partial_obj_size, words_remaining());
2421
2422 // This test is necessary; if omitted, the pointer updates to a partial object
2423 // that crosses the dense prefix boundary could be overwritten.
2424 if (source() != copy_destination()) {
2425 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2426 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2427 }
2428 update_state(words);
2429 }
2430
2431 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2432 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2433 region_ptr->set_completed();
2434 }
2435
2436 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2437 assert(destination() != nullptr, "sanity");
2438 _source = addr;
2439
2440 // The start_array must be updated even if the object is not moving.
2441 if (_start_array != nullptr) {
2442 _start_array->update_for_block(destination(), destination() + words);
2443 }
2444
2445 // Avoid overflow
2446 words = MIN2(words, words_remaining());
2447 assert(words > 0, "inv");
2448
2449 if (copy_destination() != source()) {
2450 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2451 assert(source() != destination(), "inv");
2452 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2453 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2454 // Read the klass before the copying, since it might destroy the klass (i.e. overlapping copy)
2455 // and if partial copy, the destination klass may not be copied yet
2456 Klass* klass = cast_to_oop(source())->klass();
2457 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2458 cast_to_oop(copy_destination())->set_mark(Klass::default_prototype_header(klass));
2459 }
2460
2461 update_state(words);
2462 }
2463
2464 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2465 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2466 // Record the shadow region index
2467 region_ptr->set_shadow_region(_shadow);
2468 // Mark the shadow region as filled to indicate the data is ready to be
2469 // copied back
2470 region_ptr->mark_filled();
2471 // Try to copy the content of the shadow region back to its corresponding
2472 // heap region if available; the GC thread that decreases the destination
2473 // count to zero will do the copying otherwise (see
2474 // PSParallelCompact::decrement_destination_counts).
2475 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2476 region_ptr->set_completed();
2477 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2478 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2479 }
2480 }