1 /*
2 * Copyright (c) 2005, 2025, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "classfile/classLoaderDataGraph.hpp"
26 #include "classfile/javaClasses.inline.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "classfile/symbolTable.hpp"
29 #include "classfile/systemDictionary.hpp"
30 #include "code/codeCache.hpp"
31 #include "compiler/oopMap.hpp"
32 #include "gc/parallel/objectStartArray.inline.hpp"
33 #include "gc/parallel/parallelArguments.hpp"
34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
35 #include "gc/parallel/parMarkBitMap.inline.hpp"
36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
37 #include "gc/parallel/psCompactionManager.inline.hpp"
38 #include "gc/parallel/psOldGen.hpp"
39 #include "gc/parallel/psParallelCompact.inline.hpp"
40 #include "gc/parallel/psPromotionManager.inline.hpp"
41 #include "gc/parallel/psRootType.hpp"
42 #include "gc/parallel/psScavenge.hpp"
43 #include "gc/parallel/psStringDedup.hpp"
44 #include "gc/parallel/psYoungGen.hpp"
45 #include "gc/shared/classUnloadingContext.hpp"
46 #include "gc/shared/fullGCForwarding.inline.hpp"
47 #include "gc/shared/gcCause.hpp"
48 #include "gc/shared/gcHeapSummary.hpp"
49 #include "gc/shared/gcId.hpp"
50 #include "gc/shared/gcLocker.hpp"
51 #include "gc/shared/gcTimer.hpp"
52 #include "gc/shared/gcTrace.hpp"
53 #include "gc/shared/gcTraceTime.inline.hpp"
54 #include "gc/shared/gcVMOperations.hpp"
55 #include "gc/shared/isGCActiveMark.hpp"
56 #include "gc/shared/oopStorage.inline.hpp"
57 #include "gc/shared/oopStorageSet.inline.hpp"
58 #include "gc/shared/oopStorageSetParState.inline.hpp"
59 #include "gc/shared/preservedMarks.inline.hpp"
60 #include "gc/shared/referencePolicy.hpp"
61 #include "gc/shared/referenceProcessor.hpp"
62 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
63 #include "gc/shared/spaceDecorator.hpp"
64 #include "gc/shared/strongRootsScope.hpp"
65 #include "gc/shared/taskTerminator.hpp"
66 #include "gc/shared/weakProcessor.inline.hpp"
67 #include "gc/shared/workerPolicy.hpp"
68 #include "gc/shared/workerThread.hpp"
69 #include "gc/shared/workerUtils.hpp"
70 #include "logging/log.hpp"
71 #include "memory/iterator.inline.hpp"
72 #include "memory/memoryReserver.hpp"
73 #include "memory/metaspaceUtils.hpp"
74 #include "memory/resourceArea.hpp"
75 #include "memory/universe.hpp"
76 #include "nmt/memTracker.hpp"
77 #include "oops/access.inline.hpp"
78 #include "oops/instanceClassLoaderKlass.inline.hpp"
79 #include "oops/instanceKlass.inline.hpp"
80 #include "oops/instanceMirrorKlass.inline.hpp"
81 #include "oops/methodData.hpp"
82 #include "oops/objArrayKlass.inline.hpp"
83 #include "oops/oop.inline.hpp"
84 #include "runtime/atomic.hpp"
85 #include "runtime/handles.inline.hpp"
86 #include "runtime/java.hpp"
87 #include "runtime/safepoint.hpp"
88 #include "runtime/threads.hpp"
89 #include "runtime/vmThread.hpp"
90 #include "services/memoryService.hpp"
91 #include "utilities/align.hpp"
92 #include "utilities/debug.hpp"
93 #include "utilities/events.hpp"
94 #include "utilities/formatBuffer.hpp"
95 #include "utilities/macros.hpp"
96 #include "utilities/stack.inline.hpp"
97 #if INCLUDE_JVMCI
98 #include "jvmci/jvmci.hpp"
99 #endif
100
101 #include <math.h>
102
103 // All sizes are in HeapWords.
104 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
105 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
106 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
107 const size_t ParallelCompactData::RegionSizeBytes =
108 RegionSize << LogHeapWordSize;
109 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
110 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
111 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
112
113 const ParallelCompactData::RegionData::region_sz_t
114 ParallelCompactData::RegionData::dc_shift = 27;
115
116 const ParallelCompactData::RegionData::region_sz_t
117 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
118
119 const ParallelCompactData::RegionData::region_sz_t
120 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
121
122 const ParallelCompactData::RegionData::region_sz_t
123 ParallelCompactData::RegionData::los_mask = ~dc_mask;
124
125 const ParallelCompactData::RegionData::region_sz_t
126 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
127
128 const ParallelCompactData::RegionData::region_sz_t
129 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
130
131 bool ParallelCompactData::RegionData::is_clear() {
132 return (_destination == nullptr) &&
133 (_source_region == 0) &&
134 (_partial_obj_addr == nullptr) &&
135 (_partial_obj_size == 0) &&
136 (_dc_and_los == 0) &&
137 (_shadow_state == 0);
138 }
139
140 #ifdef ASSERT
141 void ParallelCompactData::RegionData::verify_clear() {
142 assert(_destination == nullptr, "inv");
143 assert(_source_region == 0, "inv");
144 assert(_partial_obj_addr == nullptr, "inv");
145 assert(_partial_obj_size == 0, "inv");
146 assert(_dc_and_los == 0, "inv");
147 assert(_shadow_state == 0, "inv");
148 }
149 #endif
150
151 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
152
153 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
154 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
155
156 void SplitInfo::record(size_t split_region_idx, HeapWord* split_point, size_t preceding_live_words) {
157 assert(split_region_idx != 0, "precondition");
158
159 // Obj denoted by split_point will be deferred to the next space.
160 assert(split_point != nullptr, "precondition");
161
162 const ParallelCompactData& sd = PSParallelCompact::summary_data();
163
164 PSParallelCompact::RegionData* split_region_ptr = sd.region(split_region_idx);
165 assert(preceding_live_words < split_region_ptr->data_size(), "inv");
166
167 HeapWord* preceding_destination = split_region_ptr->destination();
168 assert(preceding_destination != nullptr, "inv");
169
170 // How many regions does the preceding part occupy
171 uint preceding_destination_count;
172 if (preceding_live_words == 0) {
173 preceding_destination_count = 0;
174 } else {
175 // -1 so that the ending address doesn't fall on the region-boundary
176 if (sd.region_align_down(preceding_destination) ==
177 sd.region_align_down(preceding_destination + preceding_live_words - 1)) {
178 preceding_destination_count = 1;
179 } else {
180 preceding_destination_count = 2;
181 }
182 }
183
184 _split_region_idx = split_region_idx;
185 _split_point = split_point;
186 _preceding_live_words = preceding_live_words;
187 _preceding_destination = preceding_destination;
188 _preceding_destination_count = preceding_destination_count;
189 }
190
191 void SplitInfo::clear()
192 {
193 _split_region_idx = 0;
194 _split_point = nullptr;
195 _preceding_live_words = 0;
196 _preceding_destination = nullptr;
197 _preceding_destination_count = 0;
198 assert(!is_valid(), "sanity");
199 }
200
201 #ifdef ASSERT
202 void SplitInfo::verify_clear()
203 {
204 assert(_split_region_idx == 0, "not clear");
205 assert(_split_point == nullptr, "not clear");
206 assert(_preceding_live_words == 0, "not clear");
207 assert(_preceding_destination == nullptr, "not clear");
208 assert(_preceding_destination_count == 0, "not clear");
209 }
210 #endif // #ifdef ASSERT
211
212
213 void PSParallelCompact::print_on(outputStream* st) {
214 _mark_bitmap.print_on(st);
215 }
216
217 ParallelCompactData::ParallelCompactData() :
218 _heap_start(nullptr),
219 DEBUG_ONLY(_heap_end(nullptr) COMMA)
220 _region_vspace(nullptr),
221 _reserved_byte_size(0),
222 _region_data(nullptr),
223 _region_count(0) {}
224
225 bool ParallelCompactData::initialize(MemRegion reserved_heap)
226 {
227 _heap_start = reserved_heap.start();
228 const size_t heap_size = reserved_heap.word_size();
229 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
230
231 assert(region_align_down(_heap_start) == _heap_start,
232 "region start not aligned");
233
234 return initialize_region_data(heap_size);
235 }
236
237 PSVirtualSpace*
238 ParallelCompactData::create_vspace(size_t count, size_t element_size)
239 {
240 const size_t raw_bytes = count * element_size;
241 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
242 const size_t granularity = os::vm_allocation_granularity();
243 const size_t rs_align = MAX2(page_sz, granularity);
244
245 _reserved_byte_size = align_up(raw_bytes, rs_align);
246
247 ReservedSpace rs = MemoryReserver::reserve(_reserved_byte_size,
248 rs_align,
249 page_sz,
250 mtGC);
251
252 if (!rs.is_reserved()) {
253 // Failed to reserve memory.
254 return nullptr;
255 }
256
257 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
258 rs.size(), page_sz);
259
260 MemTracker::record_virtual_memory_tag(rs, mtGC);
261
262 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
263
264 if (!vspace->expand_by(_reserved_byte_size)) {
265 // Failed to commit memory.
266
267 delete vspace;
268
269 // Release memory reserved in the space.
270 MemoryReserver::release(rs);
271
272 return nullptr;
273 }
274
275 return vspace;
276 }
277
278 bool ParallelCompactData::initialize_region_data(size_t heap_size)
279 {
280 assert(is_aligned(heap_size, RegionSize), "precondition");
281
282 const size_t count = heap_size >> Log2RegionSize;
283 _region_vspace = create_vspace(count, sizeof(RegionData));
284 if (_region_vspace != nullptr) {
285 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
286 _region_count = count;
287 return true;
288 }
289 return false;
290 }
291
292 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
293 assert(beg_region <= _region_count, "beg_region out of range");
294 assert(end_region <= _region_count, "end_region out of range");
295
296 const size_t region_cnt = end_region - beg_region;
297 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
298 }
299
300 void
301 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
302 {
303 assert(is_region_aligned(beg), "not RegionSize aligned");
304 assert(is_region_aligned(end), "not RegionSize aligned");
305
306 size_t cur_region = addr_to_region_idx(beg);
307 const size_t end_region = addr_to_region_idx(end);
308 HeapWord* addr = beg;
309 while (cur_region < end_region) {
310 _region_data[cur_region].set_destination(addr);
311 _region_data[cur_region].set_destination_count(0);
312 _region_data[cur_region].set_source_region(cur_region);
313
314 // Update live_obj_size so the region appears completely full.
315 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
316 _region_data[cur_region].set_live_obj_size(live_size);
317
318 ++cur_region;
319 addr += RegionSize;
320 }
321 }
322
323 // The total live words on src_region would overflow the target space, so find
324 // the overflowing object and record the split point. The invariant is that an
325 // obj should not cross space boundary.
326 HeapWord* ParallelCompactData::summarize_split_space(size_t src_region,
327 SplitInfo& split_info,
328 HeapWord* const destination,
329 HeapWord* const target_end,
330 HeapWord** target_next) {
331 assert(destination <= target_end, "sanity");
332 assert(destination + _region_data[src_region].data_size() > target_end,
333 "region should not fit into target space");
334 assert(is_region_aligned(target_end), "sanity");
335
336 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
337
338 if (destination + partial_obj_size > target_end) {
339 assert(partial_obj_size > 0, "inv");
340 // The overflowing obj is from a previous region.
341 //
342 // source-regions:
343 //
344 // ***************
345 // | A|AA |
346 // ***************
347 // ^
348 // | split-point
349 //
350 // dest-region:
351 //
352 // ********
353 // |~~~~A |
354 // ********
355 // ^^
356 // || target-space-end
357 // |
358 // | destination
359 //
360 // AAA would overflow target-space.
361 //
362 HeapWord* overflowing_obj = _region_data[src_region].partial_obj_addr();
363 size_t split_region = addr_to_region_idx(overflowing_obj);
364
365 // The number of live words before the overflowing object on this split region
366 size_t preceding_live_words;
367 if (is_region_aligned(overflowing_obj)) {
368 preceding_live_words = 0;
369 } else {
370 // Words accounted by the overflowing object on the split region
371 size_t overflowing_size = pointer_delta(region_align_up(overflowing_obj), overflowing_obj);
372 preceding_live_words = region(split_region)->data_size() - overflowing_size;
373 }
374
375 split_info.record(split_region, overflowing_obj, preceding_live_words);
376
377 // The [overflowing_obj, src_region_start) part has been accounted for, so
378 // must move back the new_top, now that this overflowing obj is deferred.
379 HeapWord* new_top = destination - pointer_delta(region_to_addr(src_region), overflowing_obj);
380
381 // If the overflowing obj was relocated to its original destination,
382 // those destination regions would have their source_region set. Now that
383 // this overflowing obj is relocated somewhere else, reset the
384 // source_region.
385 {
386 size_t range_start = addr_to_region_idx(region_align_up(new_top));
387 size_t range_end = addr_to_region_idx(region_align_up(destination));
388 for (size_t i = range_start; i < range_end; ++i) {
389 region(i)->set_source_region(0);
390 }
391 }
392
393 // Update new top of target space
394 *target_next = new_top;
395
396 return overflowing_obj;
397 }
398
399 // Obj-iteration to locate the overflowing obj
400 HeapWord* region_start = region_to_addr(src_region);
401 HeapWord* region_end = region_start + RegionSize;
402 HeapWord* cur_addr = region_start + partial_obj_size;
403 size_t live_words = partial_obj_size;
404
405 while (true) {
406 assert(cur_addr < region_end, "inv");
407 cur_addr = PSParallelCompact::mark_bitmap()->find_obj_beg(cur_addr, region_end);
408 // There must be an overflowing obj in this region
409 assert(cur_addr < region_end, "inv");
410
411 oop obj = cast_to_oop(cur_addr);
412 size_t obj_size = obj->size();
413 if (destination + live_words + obj_size > target_end) {
414 // Found the overflowing obj
415 split_info.record(src_region, cur_addr, live_words);
416 *target_next = destination + live_words;
417 return cur_addr;
418 }
419
420 live_words += obj_size;
421 cur_addr += obj_size;
422 }
423 }
424
425 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
426 HeapWord** full_region_prefix_end) {
427 size_t cur_region = addr_to_region_idx(space->bottom());
428 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
429 size_t live_words = 0;
430 if (full_region_prefix_end == nullptr) {
431 for (/* empty */; cur_region < end_region; ++cur_region) {
432 live_words += _region_data[cur_region].data_size();
433 }
434 } else {
435 bool first_set = false;
436 for (/* empty */; cur_region < end_region; ++cur_region) {
437 size_t live_words_in_region = _region_data[cur_region].data_size();
438 if (!first_set && live_words_in_region < RegionSize) {
439 *full_region_prefix_end = region_to_addr(cur_region);
440 first_set = true;
441 }
442 live_words += live_words_in_region;
443 }
444 if (!first_set) {
445 // All regions are full of live objs.
446 assert(is_region_aligned(space->top()), "inv");
447 *full_region_prefix_end = space->top();
448 }
449 assert(*full_region_prefix_end != nullptr, "postcondition");
450 assert(is_region_aligned(*full_region_prefix_end), "inv");
451 assert(*full_region_prefix_end >= space->bottom(), "in-range");
452 assert(*full_region_prefix_end <= space->top(), "in-range");
453 }
454 return live_words;
455 }
456
457 bool ParallelCompactData::summarize(SplitInfo& split_info,
458 HeapWord* source_beg, HeapWord* source_end,
459 HeapWord** source_next,
460 HeapWord* target_beg, HeapWord* target_end,
461 HeapWord** target_next)
462 {
463 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
464 log_develop_trace(gc, compaction)(
465 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
466 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
467 p2i(source_beg), p2i(source_end), p2i(source_next_val),
468 p2i(target_beg), p2i(target_end), p2i(*target_next));
469
470 size_t cur_region = addr_to_region_idx(source_beg);
471 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
472
473 HeapWord *dest_addr = target_beg;
474 for (/* empty */; cur_region < end_region; cur_region++) {
475 size_t words = _region_data[cur_region].data_size();
476
477 // Skip empty ones
478 if (words == 0) {
479 continue;
480 }
481
482 if (split_info.is_split(cur_region)) {
483 assert(words > split_info.preceding_live_words(), "inv");
484 words -= split_info.preceding_live_words();
485 }
486
487 _region_data[cur_region].set_destination(dest_addr);
488
489 // If cur_region does not fit entirely into the target space, find a point
490 // at which the source space can be 'split' so that part is copied to the
491 // target space and the rest is copied elsewhere.
492 if (dest_addr + words > target_end) {
493 assert(source_next != nullptr, "source_next is null when splitting");
494 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
495 target_end, target_next);
496 return false;
497 }
498
499 uint destination_count = split_info.is_split(cur_region)
500 ? split_info.preceding_destination_count()
501 : 0;
502
503 HeapWord* const last_addr = dest_addr + words - 1;
504 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
505 const size_t dest_region_2 = addr_to_region_idx(last_addr);
506
507 // Initially assume that the destination regions will be the same and
508 // adjust the value below if necessary. Under this assumption, if
509 // cur_region == dest_region_2, then cur_region will be compacted
510 // completely into itself.
511 destination_count += cur_region == dest_region_2 ? 0 : 1;
512 if (dest_region_1 != dest_region_2) {
513 // Destination regions differ; adjust destination_count.
514 destination_count += 1;
515 // Data from cur_region will be copied to the start of dest_region_2.
516 _region_data[dest_region_2].set_source_region(cur_region);
517 } else if (is_region_aligned(dest_addr)) {
518 // Data from cur_region will be copied to the start of the destination
519 // region.
520 _region_data[dest_region_1].set_source_region(cur_region);
521 }
522
523 _region_data[cur_region].set_destination_count(destination_count);
524 dest_addr += words;
525 }
526
527 *target_next = dest_addr;
528 return true;
529 }
530
531 #ifdef ASSERT
532 void ParallelCompactData::verify_clear() {
533 for (uint cur_idx = 0; cur_idx < region_count(); ++cur_idx) {
534 if (!region(cur_idx)->is_clear()) {
535 log_warning(gc)("Uncleared Region: %u", cur_idx);
536 region(cur_idx)->verify_clear();
537 }
538 }
539 }
540 #endif // #ifdef ASSERT
541
542 STWGCTimer PSParallelCompact::_gc_timer;
543 ParallelOldTracer PSParallelCompact::_gc_tracer;
544 elapsedTimer PSParallelCompact::_accumulated_time;
545 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
546 CollectorCounters* PSParallelCompact::_counters = nullptr;
547 ParMarkBitMap PSParallelCompact::_mark_bitmap;
548 ParallelCompactData PSParallelCompact::_summary_data;
549
550 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
551
552 class PCAdjustPointerClosureNew: public BasicOopIterateClosure {
553 template <typename T>
554 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
555
556 public:
557 virtual void do_oop(oop* p) { do_oop_work(p); }
558 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
559
560 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
561 };
562
563 static PCAdjustPointerClosureNew pc_adjust_pointer_closure;
564
565 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
566
567 void PSParallelCompact::post_initialize() {
568 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
569 _span_based_discoverer.set_span(heap->reserved_region());
570 _ref_processor =
571 new ReferenceProcessor(&_span_based_discoverer,
572 ParallelGCThreads, // mt processing degree
573 ParallelGCThreads, // mt discovery degree
574 false, // concurrent_discovery
575 &_is_alive_closure); // non-header is alive closure
576
577 _counters = new CollectorCounters("Parallel full collection pauses", 1);
578
579 // Initialize static fields in ParCompactionManager.
580 ParCompactionManager::initialize(mark_bitmap());
581 }
582
583 bool PSParallelCompact::initialize_aux_data() {
584 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
585 MemRegion mr = heap->reserved_region();
586 assert(mr.byte_size() != 0, "heap should be reserved");
587
588 initialize_space_info();
589
590 if (!_mark_bitmap.initialize(mr)) {
591 vm_shutdown_during_initialization(
592 err_msg("Unable to allocate %zuKB bitmaps for parallel "
593 "garbage collection for the requested %zuKB heap.",
594 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
595 return false;
596 }
597
598 if (!_summary_data.initialize(mr)) {
599 vm_shutdown_during_initialization(
600 err_msg("Unable to allocate %zuKB card tables for parallel "
601 "garbage collection for the requested %zuKB heap.",
602 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
603 return false;
604 }
605
606 return true;
607 }
608
609 void PSParallelCompact::initialize_space_info()
610 {
611 memset(&_space_info, 0, sizeof(_space_info));
612
613 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
614 PSYoungGen* young_gen = heap->young_gen();
615
616 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
617 _space_info[eden_space_id].set_space(young_gen->eden_space());
618 _space_info[from_space_id].set_space(young_gen->from_space());
619 _space_info[to_space_id].set_space(young_gen->to_space());
620
621 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
622 }
623
624 void
625 PSParallelCompact::clear_data_covering_space(SpaceId id)
626 {
627 // At this point, top is the value before GC, new_top() is the value that will
628 // be set at the end of GC. The marking bitmap is cleared to top; nothing
629 // should be marked above top. The summary data is cleared to the larger of
630 // top & new_top.
631 MutableSpace* const space = _space_info[id].space();
632 HeapWord* const bot = space->bottom();
633 HeapWord* const top = space->top();
634 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
635
636 _mark_bitmap.clear_range(bot, top);
637
638 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
639 const size_t end_region =
640 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
641 _summary_data.clear_range(beg_region, end_region);
642
643 // Clear the data used to 'split' regions.
644 SplitInfo& split_info = _space_info[id].split_info();
645 if (split_info.is_valid()) {
646 split_info.clear();
647 }
648 DEBUG_ONLY(split_info.verify_clear();)
649 }
650
651 void PSParallelCompact::pre_compact()
652 {
653 // Update the from & to space pointers in space_info, since they are swapped
654 // at each young gen gc. Do the update unconditionally (even though a
655 // promotion failure does not swap spaces) because an unknown number of young
656 // collections will have swapped the spaces an unknown number of times.
657 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
658 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
659 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
660 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
661
662 // Increment the invocation count
663 heap->increment_total_collections(true);
664
665 CodeCache::on_gc_marking_cycle_start();
666
667 heap->print_heap_before_gc();
668 heap->trace_heap_before_gc(&_gc_tracer);
669
670 // Fill in TLABs
671 heap->ensure_parsability(true); // retire TLABs
672
673 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
674 Universe::verify("Before GC");
675 }
676
677 DEBUG_ONLY(mark_bitmap()->verify_clear();)
678 DEBUG_ONLY(summary_data().verify_clear();)
679 }
680
681 void PSParallelCompact::post_compact()
682 {
683 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
684 ParCompactionManager::remove_all_shadow_regions();
685
686 CodeCache::on_gc_marking_cycle_finish();
687 CodeCache::arm_all_nmethods();
688
689 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
690 // Clear the marking bitmap, summary data and split info.
691 clear_data_covering_space(SpaceId(id));
692 {
693 MutableSpace* space = _space_info[id].space();
694 HeapWord* top = space->top();
695 HeapWord* new_top = _space_info[id].new_top();
696 if (ZapUnusedHeapArea && new_top < top) {
697 space->mangle_region(MemRegion(new_top, top));
698 }
699 // Update top(). Must be done after clearing the bitmap and summary data.
700 space->set_top(new_top);
701 }
702 }
703
704 #ifdef ASSERT
705 {
706 mark_bitmap()->verify_clear();
707 summary_data().verify_clear();
708 }
709 #endif
710
711 ParCompactionManager::flush_all_string_dedup_requests();
712
713 MutableSpace* const eden_space = _space_info[eden_space_id].space();
714 MutableSpace* const from_space = _space_info[from_space_id].space();
715 MutableSpace* const to_space = _space_info[to_space_id].space();
716
717 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
718 bool eden_empty = eden_space->is_empty();
719
720 // Update heap occupancy information which is used as input to the soft ref
721 // clearing policy at the next gc.
722 Universe::heap()->update_capacity_and_used_at_gc();
723
724 bool young_gen_empty = eden_empty && from_space->is_empty() &&
725 to_space->is_empty();
726
727 PSCardTable* ct = heap->card_table();
728 MemRegion old_mr = heap->old_gen()->committed();
729 if (young_gen_empty) {
730 ct->clear_MemRegion(old_mr);
731 } else {
732 ct->dirty_MemRegion(old_mr);
733 }
734
735 {
736 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
737 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
738 ClassLoaderDataGraph::purge(true /* at_safepoint */);
739 DEBUG_ONLY(MetaspaceUtils::verify();)
740 }
741
742 // Need to clear claim bits for the next mark.
743 ClassLoaderDataGraph::clear_claimed_marks();
744
745 heap->prune_scavengable_nmethods();
746
747 #if COMPILER2_OR_JVMCI
748 DerivedPointerTable::update_pointers();
749 #endif
750
751 // Signal that we have completed a visit to all live objects.
752 Universe::heap()->record_whole_heap_examined_timestamp();
753 }
754
755 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
756 HeapWord* full_region_prefix_end) {
757 const size_t region_size = ParallelCompactData::RegionSize;
758 const ParallelCompactData& sd = summary_data();
759
760 // Iteration starts with the region *after* the full-region-prefix-end.
761 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
762 // If final region is not full, iteration stops before that region,
763 // because fill_dense_prefix_end assumes that prefix_end <= top.
764 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
765 assert(start_region <= end_region, "inv");
766
767 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
768 const RegionData* cur_region = start_region;
769 for (/* empty */; cur_region < end_region; ++cur_region) {
770 assert(region_size >= cur_region->data_size(), "inv");
771 size_t dead_size = region_size - cur_region->data_size();
772 if (max_waste < dead_size) {
773 break;
774 }
775 max_waste -= dead_size;
776 }
777
778 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
779 assert(sd.is_region_aligned(prefix_end), "postcondition");
780 assert(prefix_end >= full_region_prefix_end, "in-range");
781 assert(prefix_end <= old_space->top(), "in-range");
782 return prefix_end;
783 }
784
785 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
786 // Comparing two sizes to decide if filling is required:
787 //
788 // The size of the filler (min-obj-size) is 2 heap words with the default
789 // MinObjAlignment, since both markword and klass take 1 heap word.
790 // With +UseCompactObjectHeaders, the minimum filler size is only one word,
791 // because the Klass* gets encoded in the mark-word.
792 //
793 // The size of the gap (if any) right before dense-prefix-end is
794 // MinObjAlignment.
795 //
796 // Need to fill in the gap only if it's smaller than min-obj-size, and the
797 // filler obj will extend to next region.
798
799 if (MinObjAlignment >= checked_cast<int>(CollectedHeap::min_fill_size())) {
800 return;
801 }
802
803 assert(!UseCompactObjectHeaders, "Compact headers can allocate small objects");
804 assert(CollectedHeap::min_fill_size() == 2, "inv");
805 HeapWord* const dense_prefix_end = dense_prefix(id);
806 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
807 assert(dense_prefix_end <= space(id)->top(), "precondition");
808 if (dense_prefix_end == space(id)->top()) {
809 // Must not have single-word gap right before prefix-end/top.
810 return;
811 }
812 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
813
814 if (region_after_dense_prefix->partial_obj_size() != 0 ||
815 _mark_bitmap.is_marked(dense_prefix_end)) {
816 // The region after the dense prefix starts with live bytes.
817 return;
818 }
819
820 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
821 if (block_start == dense_prefix_end - 1) {
822 assert(!_mark_bitmap.is_marked(block_start), "inv");
823 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
824 // The filler object will extend into region_after_dense_prefix.
825 const size_t obj_len = 2; // min-fill-size
826 HeapWord* const obj_beg = dense_prefix_end - 1;
827 CollectedHeap::fill_with_object(obj_beg, obj_len);
828 _mark_bitmap.mark_obj(obj_beg);
829 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
830 region_after_dense_prefix->set_partial_obj_size(1);
831 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
832 assert(start_array(id) != nullptr, "sanity");
833 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
834 }
835 }
836
837 bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
838 MutableSpace* const old_space,
839 HeapWord* full_region_prefix_end) {
840
841 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
842
843 // Check System.GC
844 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
845 && GCCause::is_user_requested_gc(heap->gc_cause());
846
847 // Check if all live objs are larger than old-gen.
848 const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
849
850 // JVM flags
851 const uint total_invocations = heap->total_full_collections();
852 assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
853 const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
854 const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
855
856 // If all regions in old-gen are full
857 const bool is_region_full =
858 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
859
860 if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
861 _maximum_compaction_gc_num = total_invocations;
862 return true;
863 }
864
865 return false;
866 }
867
868 void PSParallelCompact::summary_phase()
869 {
870 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
871
872 MutableSpace* const old_space = _space_info[old_space_id].space();
873 {
874 size_t total_live_words = 0;
875 HeapWord* full_region_prefix_end = nullptr;
876 {
877 // old-gen
878 size_t live_words = _summary_data.live_words_in_space(old_space,
879 &full_region_prefix_end);
880 total_live_words += live_words;
881 }
882 // young-gen
883 for (uint i = eden_space_id; i < last_space_id; ++i) {
884 const MutableSpace* space = _space_info[i].space();
885 size_t live_words = _summary_data.live_words_in_space(space);
886 total_live_words += live_words;
887 _space_info[i].set_new_top(space->bottom() + live_words);
888 _space_info[i].set_dense_prefix(space->bottom());
889 }
890
891 bool maximum_compaction = check_maximum_compaction(total_live_words,
892 old_space,
893 full_region_prefix_end);
894 HeapWord* dense_prefix_end = maximum_compaction
895 ? full_region_prefix_end
896 : compute_dense_prefix_for_old_space(old_space,
897 full_region_prefix_end);
898 SpaceId id = old_space_id;
899 _space_info[id].set_dense_prefix(dense_prefix_end);
900
901 if (dense_prefix_end != old_space->bottom()) {
902 fill_dense_prefix_end(id);
903 _summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
904 }
905
906 // Compacting objs in [dense_prefix_end, old_space->top())
907 _summary_data.summarize(_space_info[id].split_info(),
908 dense_prefix_end, old_space->top(), nullptr,
909 dense_prefix_end, old_space->end(),
910 _space_info[id].new_top_addr());
911 }
912
913 // Summarize the remaining spaces in the young gen. The initial target space
914 // is the old gen. If a space does not fit entirely into the target, then the
915 // remainder is compacted into the space itself and that space becomes the new
916 // target.
917 SpaceId dst_space_id = old_space_id;
918 HeapWord* dst_space_end = old_space->end();
919 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
920 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
921 const MutableSpace* space = _space_info[id].space();
922 const size_t live = pointer_delta(_space_info[id].new_top(),
923 space->bottom());
924 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
925
926 if (live > 0 && live <= available) {
927 // All the live data will fit.
928 bool done = _summary_data.summarize(_space_info[id].split_info(),
929 space->bottom(), space->top(),
930 nullptr,
931 *new_top_addr, dst_space_end,
932 new_top_addr);
933 assert(done, "space must fit into old gen");
934
935 // Reset the new_top value for the space.
936 _space_info[id].set_new_top(space->bottom());
937 } else if (live > 0) {
938 // Attempt to fit part of the source space into the target space.
939 HeapWord* next_src_addr = nullptr;
940 bool done = _summary_data.summarize(_space_info[id].split_info(),
941 space->bottom(), space->top(),
942 &next_src_addr,
943 *new_top_addr, dst_space_end,
944 new_top_addr);
945 assert(!done, "space should not fit into old gen");
946 assert(next_src_addr != nullptr, "sanity");
947
948 // The source space becomes the new target, so the remainder is compacted
949 // within the space itself.
950 dst_space_id = SpaceId(id);
951 dst_space_end = space->end();
952 new_top_addr = _space_info[id].new_top_addr();
953 done = _summary_data.summarize(_space_info[id].split_info(),
954 next_src_addr, space->top(),
955 nullptr,
956 space->bottom(), dst_space_end,
957 new_top_addr);
958 assert(done, "space must fit when compacted into itself");
959 assert(*new_top_addr <= space->top(), "usage should not grow");
960 }
961 }
962 }
963
964 // This method should contain all heap-specific policy for invoking a full
965 // collection. invoke_no_policy() will only attempt to compact the heap; it
966 // will do nothing further. If we need to bail out for policy reasons, scavenge
967 // before full gc, or any other specialized behavior, it needs to be added here.
968 //
969 // Note that this method should only be called from the vm_thread while at a
970 // safepoint.
971 //
972 // Note that the all_soft_refs_clear flag in the soft ref policy
973 // may be true because this method can be called without intervening
974 // activity. For example when the heap space is tight and full measure
975 // are being taken to free space.
976 bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
977 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
978 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
979 "should be in vm thread");
980
981 SvcGCMarker sgcm(SvcGCMarker::FULL);
982 IsSTWGCActiveMark mark;
983
984 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
985 clear_all_soft_refs = clear_all_soft_refs
986 || heap->soft_ref_policy()->should_clear_all_soft_refs();
987
988 return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
989 }
990
991 // This method contains no policy. You should probably
992 // be calling invoke() instead.
993 bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
994 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
995 assert(ref_processor() != nullptr, "Sanity");
996
997 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
998
999 GCIdMark gc_id_mark;
1000 _gc_timer.register_gc_start();
1001 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1002
1003 GCCause::Cause gc_cause = heap->gc_cause();
1004 PSYoungGen* young_gen = heap->young_gen();
1005 PSOldGen* old_gen = heap->old_gen();
1006 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1007
1008 // The scope of casr should end after code that can change
1009 // SoftRefPolicy::_should_clear_all_soft_refs.
1010 ClearedAllSoftRefs casr(clear_all_soft_refs,
1011 heap->soft_ref_policy());
1012
1013 // Make sure data structures are sane, make the heap parsable, and do other
1014 // miscellaneous bookkeeping.
1015 pre_compact();
1016
1017 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1018
1019 {
1020 const uint active_workers =
1021 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
1022 ParallelScavengeHeap::heap()->workers().active_workers(),
1023 Threads::number_of_non_daemon_threads());
1024 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
1025
1026 GCTraceCPUTime tcpu(&_gc_tracer);
1027 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
1028
1029 heap->pre_full_gc_dump(&_gc_timer);
1030
1031 TraceCollectorStats tcs(counters());
1032 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
1033
1034 if (log_is_enabled(Debug, gc, heap, exit)) {
1035 accumulated_time()->start();
1036 }
1037
1038 // Let the size policy know we're starting
1039 size_policy->major_collection_begin();
1040
1041 #if COMPILER2_OR_JVMCI
1042 DerivedPointerTable::clear();
1043 #endif
1044
1045 ref_processor()->start_discovery(clear_all_soft_refs);
1046
1047 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
1048 false /* unregister_nmethods_during_purge */,
1049 false /* lock_nmethod_free_separately */);
1050
1051 marking_phase(&_gc_tracer);
1052
1053 summary_phase();
1054
1055 #if COMPILER2_OR_JVMCI
1056 assert(DerivedPointerTable::is_active(), "Sanity");
1057 DerivedPointerTable::set_active(false);
1058 #endif
1059
1060 FullGCForwarding::begin();
1061
1062 forward_to_new_addr();
1063
1064 adjust_pointers();
1065
1066 compact();
1067
1068 FullGCForwarding::end();
1069
1070 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1071
1072 ParCompactionManager::verify_all_region_stack_empty();
1073
1074 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1075 // done before resizing.
1076 post_compact();
1077
1078 // Let the size policy know we're done
1079 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1080
1081 if (UseAdaptiveSizePolicy) {
1082 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1083 log_trace(gc, ergo)("old_gen_capacity: %zu young_gen_capacity: %zu",
1084 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1085
1086 // Don't check if the size_policy is ready here. Let
1087 // the size_policy check that internally.
1088 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1089 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1090 // Swap the survivor spaces if from_space is empty. The
1091 // resize_young_gen() called below is normally used after
1092 // a successful young GC and swapping of survivor spaces;
1093 // otherwise, it will fail to resize the young gen with
1094 // the current implementation.
1095 if (young_gen->from_space()->is_empty()) {
1096 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1097 young_gen->swap_spaces();
1098 }
1099
1100 // Calculate optimal free space amounts
1101 assert(young_gen->max_gen_size() >
1102 young_gen->from_space()->capacity_in_bytes() +
1103 young_gen->to_space()->capacity_in_bytes(),
1104 "Sizes of space in young gen are out-of-bounds");
1105
1106 size_t young_live = young_gen->used_in_bytes();
1107 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1108 size_t old_live = old_gen->used_in_bytes();
1109 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1110 size_t max_old_gen_size = old_gen->max_gen_size();
1111 size_t max_eden_size = young_gen->max_gen_size() -
1112 young_gen->from_space()->capacity_in_bytes() -
1113 young_gen->to_space()->capacity_in_bytes();
1114
1115 // Used for diagnostics
1116 size_policy->clear_generation_free_space_flags();
1117
1118 size_policy->compute_generations_free_space(young_live,
1119 eden_live,
1120 old_live,
1121 cur_eden,
1122 max_old_gen_size,
1123 max_eden_size,
1124 true /* full gc*/);
1125
1126 size_policy->check_gc_overhead_limit(eden_live,
1127 max_old_gen_size,
1128 max_eden_size,
1129 true /* full gc*/,
1130 gc_cause,
1131 heap->soft_ref_policy());
1132
1133 size_policy->decay_supplemental_growth(true /* full gc*/);
1134
1135 heap->resize_old_gen(
1136 size_policy->calculated_old_free_size_in_bytes());
1137
1138 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1139 size_policy->calculated_survivor_size_in_bytes());
1140 }
1141
1142 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1143 }
1144
1145 if (UsePerfData) {
1146 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1147 counters->update_counters();
1148 counters->update_old_capacity(old_gen->capacity_in_bytes());
1149 counters->update_young_capacity(young_gen->capacity_in_bytes());
1150 }
1151
1152 heap->resize_all_tlabs();
1153
1154 // Resize the metaspace capacity after a collection
1155 MetaspaceGC::compute_new_size();
1156
1157 if (log_is_enabled(Debug, gc, heap, exit)) {
1158 accumulated_time()->stop();
1159 }
1160
1161 heap->print_heap_change(pre_gc_values);
1162
1163 // Track memory usage and detect low memory
1164 MemoryService::track_memory_usage();
1165 heap->update_counters();
1166
1167 heap->post_full_gc_dump(&_gc_timer);
1168 }
1169
1170 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1171 Universe::verify("After GC");
1172 }
1173
1174 heap->print_heap_after_gc();
1175 heap->trace_heap_after_gc(&_gc_tracer);
1176
1177 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1178
1179 _gc_timer.register_gc_end();
1180
1181 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1182 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1183
1184 return true;
1185 }
1186
1187 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1188 private:
1189 uint _worker_id;
1190
1191 public:
1192 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1193 void do_thread(Thread* thread) {
1194 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1195
1196 ResourceMark rm;
1197
1198 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1199
1200 MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
1201 !NMethodToOopClosure::FixRelocations,
1202 true /* keepalive nmethods */);
1203
1204 thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1205
1206 // Do the real work
1207 cm->follow_marking_stacks();
1208 }
1209 };
1210
1211 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1212 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1213
1214 ParCompactionManager* cm =
1215 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1216
1217 do {
1218 ScannerTask task;
1219 if (ParCompactionManager::steal(worker_id, task)) {
1220 cm->follow_contents(task, true);
1221 }
1222 cm->follow_marking_stacks();
1223 } while (!terminator.offer_termination());
1224 }
1225
1226 class MarkFromRootsTask : public WorkerTask {
1227 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
1228 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1229 TaskTerminator _terminator;
1230 uint _active_workers;
1231
1232 public:
1233 MarkFromRootsTask(uint active_workers) :
1234 WorkerTask("MarkFromRootsTask"),
1235 _strong_roots_scope(active_workers),
1236 _terminator(active_workers, ParCompactionManager::marking_stacks()),
1237 _active_workers(active_workers) {}
1238
1239 virtual void work(uint worker_id) {
1240 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1241 cm->create_marking_stats_cache();
1242 {
1243 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1244 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1245
1246 // Do the real work
1247 cm->follow_marking_stacks();
1248 }
1249
1250 {
1251 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
1252 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1253 }
1254
1255 // Mark from OopStorages
1256 {
1257 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1258 // Do the real work
1259 cm->follow_marking_stacks();
1260 }
1261
1262 if (_active_workers > 1) {
1263 steal_marking_work(_terminator, worker_id);
1264 }
1265 }
1266 };
1267
1268 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1269 TaskTerminator _terminator;
1270
1271 public:
1272 ParallelCompactRefProcProxyTask(uint max_workers)
1273 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1274 _terminator(_max_workers, ParCompactionManager::marking_stacks()) {}
1275
1276 void work(uint worker_id) override {
1277 assert(worker_id < _max_workers, "sanity");
1278 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1279 BarrierEnqueueDiscoveredFieldClosure enqueue;
1280 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1281 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1282 }
1283
1284 void prepare_run_task_hook() override {
1285 _terminator.reset_for_reuse(_queue_count);
1286 }
1287 };
1288
1289 static void flush_marking_stats_cache(const uint num_workers) {
1290 for (uint i = 0; i < num_workers; ++i) {
1291 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1292 cm->flush_and_destroy_marking_stats_cache();
1293 }
1294 }
1295
1296 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1297 // Recursively traverse all live objects and mark them
1298 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1299
1300 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1301
1302 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1303 {
1304 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1305
1306 MarkFromRootsTask task(active_gc_threads);
1307 ParallelScavengeHeap::heap()->workers().run_task(&task);
1308 }
1309
1310 // Process reference objects found during marking
1311 {
1312 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1313
1314 ReferenceProcessorStats stats;
1315 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1316
1317 ref_processor()->set_active_mt_degree(active_gc_threads);
1318 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1319 stats = ref_processor()->process_discovered_references(task, pt);
1320
1321 gc_tracer->report_gc_reference_stats(stats);
1322 pt.print_all_references();
1323 }
1324
1325 {
1326 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1327
1328 flush_marking_stats_cache(active_gc_threads);
1329 }
1330
1331 // This is the point where the entire marking should have completed.
1332 ParCompactionManager::verify_all_marking_stack_empty();
1333
1334 {
1335 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1336 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1337 is_alive_closure(),
1338 &do_nothing_cl,
1339 1);
1340 }
1341
1342 {
1343 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1344
1345 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
1346
1347 bool unloading_occurred;
1348 {
1349 CodeCache::UnlinkingScope scope(is_alive_closure());
1350
1351 // Follow system dictionary roots and unload classes.
1352 unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1353
1354 // Unload nmethods.
1355 CodeCache::do_unloading(unloading_occurred);
1356 }
1357
1358 {
1359 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1360 // Release unloaded nmethod's memory.
1361 ctx->purge_nmethods();
1362 }
1363 {
1364 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1365 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1366 }
1367 {
1368 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1369 ctx->free_nmethods();
1370 }
1371
1372 // Prune dead klasses from subklass/sibling/implementor lists.
1373 Klass::clean_weak_klass_links(unloading_occurred);
1374
1375 // Clean JVMCI metadata handles.
1376 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
1377 }
1378
1379 {
1380 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
1381 _gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
1382 }
1383 #if TASKQUEUE_STATS
1384 ParCompactionManager::print_and_reset_taskqueue_stats();
1385 #endif
1386 }
1387
1388 template<typename Func>
1389 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1390 MutableSpace* sp = PSParallelCompact::space(id);
1391 HeapWord* const bottom = sp->bottom();
1392 HeapWord* const top = sp->top();
1393 if (bottom == top) {
1394 return;
1395 }
1396
1397 const uint num_regions_per_stripe = 2;
1398 const size_t region_size = ParallelCompactData::RegionSize;
1399 const size_t stripe_size = num_regions_per_stripe * region_size;
1400
1401 while (true) {
1402 uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
1403 HeapWord* cur_stripe = bottom + counter * region_size;
1404 if (cur_stripe >= top) {
1405 break;
1406 }
1407 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1408 on_stripe(cur_stripe, stripe_end);
1409 }
1410 }
1411
1412 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1413 // Regions in old-space shouldn't be split.
1414 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1415
1416 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1417 assert(mark_bitmap()->is_marked(obj_start), "inv");
1418 oop obj = cast_to_oop(obj_start);
1419 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1420 };
1421
1422 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1423 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1424 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1425 HeapWord* obj_start;
1426 if (cur_region->partial_obj_size() != 0) {
1427 obj_start = cur_region->partial_obj_addr();
1428 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1429 } else {
1430 obj_start = stripe_start;
1431 }
1432
1433 while (obj_start < stripe_end) {
1434 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1435 if (obj_start >= stripe_end) {
1436 break;
1437 }
1438 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1439 }
1440 });
1441 }
1442
1443 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1444 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1445 HeapWord* obj_start = stripe_start;
1446 while (obj_start < stripe_end) {
1447 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1448 if (obj_start >= stripe_end) {
1449 break;
1450 }
1451 oop obj = cast_to_oop(obj_start);
1452 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1453 }
1454 });
1455 }
1456
1457 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1458 auto start_time = Ticks::now();
1459 adjust_in_old_space(&claim_counters[0]);
1460 for (uint id = eden_space_id; id < last_space_id; ++id) {
1461 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1462 }
1463 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1464 }
1465
1466 class PSAdjustTask final : public WorkerTask {
1467 SubTasksDone _sub_tasks;
1468 WeakProcessor::Task _weak_proc_task;
1469 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1470 uint _nworkers;
1471 volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1472
1473 enum PSAdjustSubTask {
1474 PSAdjustSubTask_code_cache,
1475
1476 PSAdjustSubTask_num_elements
1477 };
1478
1479 public:
1480 PSAdjustTask(uint nworkers) :
1481 WorkerTask("PSAdjust task"),
1482 _sub_tasks(PSAdjustSubTask_num_elements),
1483 _weak_proc_task(nworkers),
1484 _nworkers(nworkers) {
1485
1486 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1487 if (nworkers > 1) {
1488 Threads::change_thread_claim_token();
1489 }
1490 }
1491
1492 ~PSAdjustTask() {
1493 Threads::assert_all_threads_claimed();
1494 }
1495
1496 void work(uint worker_id) {
1497 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1498 cm->preserved_marks()->adjust_during_full_gc();
1499 {
1500 // adjust pointers in all spaces
1501 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1502 }
1503 {
1504 ResourceMark rm;
1505 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1506 }
1507 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1508 {
1509 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1510 ClassLoaderDataGraph::cld_do(&cld_closure);
1511 }
1512 {
1513 AlwaysTrueClosure always_alive;
1514 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1515 }
1516 if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
1517 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1518 CodeCache::nmethods_do(&adjust_code);
1519 }
1520 _sub_tasks.all_tasks_claimed();
1521 }
1522 };
1523
1524 void PSParallelCompact::adjust_pointers() {
1525 // Adjust the pointers to reflect the new locations
1526 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1527 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1528 PSAdjustTask task(nworkers);
1529 ParallelScavengeHeap::heap()->workers().run_task(&task);
1530 }
1531
1532 // Split [start, end) evenly for a number of workers and return the
1533 // range for worker_id.
1534 static void split_regions_for_worker(size_t start, size_t end,
1535 uint worker_id, uint num_workers,
1536 size_t* worker_start, size_t* worker_end) {
1537 assert(start < end, "precondition");
1538 assert(num_workers > 0, "precondition");
1539 assert(worker_id < num_workers, "precondition");
1540
1541 size_t num_regions = end - start;
1542 size_t num_regions_per_worker = num_regions / num_workers;
1543 size_t remainder = num_regions % num_workers;
1544 // The first few workers will get one extra.
1545 *worker_start = start + worker_id * num_regions_per_worker
1546 + MIN2(checked_cast<size_t>(worker_id), remainder);
1547 *worker_end = *worker_start + num_regions_per_worker
1548 + (worker_id < remainder ? 1 : 0);
1549 }
1550
1551 void PSParallelCompact::forward_to_new_addr() {
1552 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1553 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1554
1555 struct ForwardTask final : public WorkerTask {
1556 uint _num_workers;
1557
1558 explicit ForwardTask(uint num_workers) :
1559 WorkerTask("PSForward task"),
1560 _num_workers(num_workers) {}
1561
1562 static void forward_objs_in_range(ParCompactionManager* cm,
1563 HeapWord* start,
1564 HeapWord* end,
1565 HeapWord* destination) {
1566 HeapWord* cur_addr = start;
1567 HeapWord* new_addr = destination;
1568
1569 while (cur_addr < end) {
1570 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, end);
1571 if (cur_addr >= end) {
1572 return;
1573 }
1574 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1575 oop obj = cast_to_oop(cur_addr);
1576 if (new_addr != cur_addr) {
1577 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1578 FullGCForwarding::forward_to(obj, cast_to_oop(new_addr));
1579 }
1580 size_t obj_size = obj->size();
1581 new_addr += obj_size;
1582 cur_addr += obj_size;
1583 }
1584 }
1585
1586 void work(uint worker_id) override {
1587 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1588 for (uint id = old_space_id; id < last_space_id; ++id) {
1589 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1590 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1591 HeapWord* top = sp->top();
1592
1593 if (dense_prefix_addr == top) {
1594 continue;
1595 }
1596
1597 const SplitInfo& split_info = _space_info[SpaceId(id)].split_info();
1598
1599 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1600 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1601 size_t start_region;
1602 size_t end_region;
1603 split_regions_for_worker(dense_prefix_region, top_region,
1604 worker_id, _num_workers,
1605 &start_region, &end_region);
1606 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1607 RegionData* region_ptr = _summary_data.region(cur_region);
1608 size_t partial_obj_size = region_ptr->partial_obj_size();
1609
1610 if (partial_obj_size == ParallelCompactData::RegionSize) {
1611 // No obj-start
1612 continue;
1613 }
1614
1615 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1616 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1617
1618 if (split_info.is_split(cur_region)) {
1619 // Part 1: will be relocated to space-1
1620 HeapWord* preceding_destination = split_info.preceding_destination();
1621 HeapWord* split_point = split_info.split_point();
1622 forward_objs_in_range(cm, region_start + partial_obj_size, split_point, preceding_destination + partial_obj_size);
1623
1624 // Part 2: will be relocated to space-2
1625 HeapWord* destination = region_ptr->destination();
1626 forward_objs_in_range(cm, split_point, region_end, destination);
1627 } else {
1628 HeapWord* destination = region_ptr->destination();
1629 forward_objs_in_range(cm, region_start + partial_obj_size, region_end, destination + partial_obj_size);
1630 }
1631 }
1632 }
1633 }
1634 } task(nworkers);
1635
1636 ParallelScavengeHeap::heap()->workers().run_task(&task);
1637 DEBUG_ONLY(verify_forward();)
1638 }
1639
1640 #ifdef ASSERT
1641 void PSParallelCompact::verify_forward() {
1642 HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1643 RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
1644 HeapWord* bump_ptr = old_region->partial_obj_size() != 0
1645 ? old_dense_prefix_addr + old_region->partial_obj_size()
1646 : old_dense_prefix_addr;
1647 SpaceId bump_ptr_space = old_space_id;
1648
1649 for (uint id = old_space_id; id < last_space_id; ++id) {
1650 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1651 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1652 HeapWord* top = sp->top();
1653 HeapWord* cur_addr = dense_prefix_addr;
1654
1655 while (cur_addr < top) {
1656 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1657 if (cur_addr >= top) {
1658 break;
1659 }
1660 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1661 assert(bump_ptr <= _space_info[bump_ptr_space].new_top(), "inv");
1662 // Move to the space containing cur_addr
1663 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1664 bump_ptr = space(space_id(cur_addr))->bottom();
1665 bump_ptr_space = space_id(bump_ptr);
1666 }
1667 oop obj = cast_to_oop(cur_addr);
1668 if (cur_addr == bump_ptr) {
1669 assert(!FullGCForwarding::is_forwarded(obj), "inv");
1670 } else {
1671 assert(FullGCForwarding::forwardee(obj) == cast_to_oop(bump_ptr), "inv");
1672 }
1673 bump_ptr += obj->size();
1674 cur_addr += obj->size();
1675 }
1676 }
1677 }
1678 #endif
1679
1680 // Helper class to print 8 region numbers per line and then print the total at the end.
1681 class FillableRegionLogger : public StackObj {
1682 private:
1683 Log(gc, compaction) log;
1684 static const int LineLength = 8;
1685 size_t _regions[LineLength];
1686 int _next_index;
1687 bool _enabled;
1688 size_t _total_regions;
1689 public:
1690 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1691 ~FillableRegionLogger() {
1692 log.trace("%zu initially fillable regions", _total_regions);
1693 }
1694
1695 void print_line() {
1696 if (!_enabled || _next_index == 0) {
1697 return;
1698 }
1699 FormatBuffer<> line("Fillable: ");
1700 for (int i = 0; i < _next_index; i++) {
1701 line.append(" %7zu", _regions[i]);
1702 }
1703 log.trace("%s", line.buffer());
1704 _next_index = 0;
1705 }
1706
1707 void handle(size_t region) {
1708 if (!_enabled) {
1709 return;
1710 }
1711 _regions[_next_index++] = region;
1712 if (_next_index == LineLength) {
1713 print_line();
1714 }
1715 _total_regions++;
1716 }
1717 };
1718
1719 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1720 {
1721 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1722
1723 // Find the threads that are active
1724 uint worker_id = 0;
1725
1726 // Find all regions that are available (can be filled immediately) and
1727 // distribute them to the thread stacks. The iteration is done in reverse
1728 // order (high to low) so the regions will be removed in ascending order.
1729
1730 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1731
1732 // id + 1 is used to test termination so unsigned can
1733 // be used with an old_space_id == 0.
1734 FillableRegionLogger region_logger;
1735 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
1736 SpaceInfo* const space_info = _space_info + id;
1737 HeapWord* const new_top = space_info->new_top();
1738
1739 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1740 const size_t end_region =
1741 sd.addr_to_region_idx(sd.region_align_up(new_top));
1742
1743 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1744 if (sd.region(cur)->claim_unsafe()) {
1745 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1746 bool result = sd.region(cur)->mark_normal();
1747 assert(result, "Must succeed at this point.");
1748 cm->region_stack()->push(cur);
1749 region_logger.handle(cur);
1750 // Assign regions to tasks in round-robin fashion.
1751 if (++worker_id == parallel_gc_threads) {
1752 worker_id = 0;
1753 }
1754 }
1755 }
1756 region_logger.print_line();
1757 }
1758 }
1759
1760 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1761 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1762
1763 ParCompactionManager* cm =
1764 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1765
1766 // Drain the stacks that have been preloaded with regions
1767 // that are ready to fill.
1768
1769 cm->drain_region_stacks();
1770
1771 guarantee(cm->region_stack()->is_empty(), "Not empty");
1772
1773 size_t region_index = 0;
1774
1775 while (true) {
1776 if (ParCompactionManager::steal(worker_id, region_index)) {
1777 PSParallelCompact::fill_and_update_region(cm, region_index);
1778 cm->drain_region_stacks();
1779 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1780 // Fill and update an unavailable region with the help of a shadow region
1781 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1782 cm->drain_region_stacks();
1783 } else {
1784 if (terminator->offer_termination()) {
1785 break;
1786 }
1787 // Go around again.
1788 }
1789 }
1790 }
1791
1792 class FillDensePrefixAndCompactionTask: public WorkerTask {
1793 uint _num_workers;
1794 TaskTerminator _terminator;
1795
1796 public:
1797 FillDensePrefixAndCompactionTask(uint active_workers) :
1798 WorkerTask("FillDensePrefixAndCompactionTask"),
1799 _num_workers(active_workers),
1800 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1801 }
1802
1803 virtual void work(uint worker_id) {
1804 {
1805 auto start = Ticks::now();
1806 PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
1807 log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
1808 }
1809 compaction_with_stealing_work(&_terminator, worker_id);
1810 }
1811 };
1812
1813 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1814 #ifdef ASSERT
1815 {
1816 assert(start < end, "precondition");
1817 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1818 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1819 if (start != bottom) {
1820 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1821 HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
1822 assert(after_obj == start, "precondition");
1823 }
1824 }
1825 #endif
1826
1827 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1828 HeapWord* addr = start;
1829 do {
1830 size_t size = cast_to_oop(addr)->size();
1831 start_array(old_space_id)->update_for_block(addr, addr + size);
1832 addr += size;
1833 } while (addr < end);
1834 }
1835
1836 void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
1837 ParMarkBitMap* bitmap = mark_bitmap();
1838
1839 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1840 HeapWord* const prefix_end = dense_prefix(old_space_id);
1841
1842 if (bottom == prefix_end) {
1843 return;
1844 }
1845
1846 size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
1847 size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
1848
1849 size_t start_region;
1850 size_t end_region;
1851 split_regions_for_worker(bottom_region, prefix_end_region,
1852 worker_id, num_workers,
1853 &start_region, &end_region);
1854
1855 if (start_region == end_region) {
1856 return;
1857 }
1858
1859 HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
1860 HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
1861
1862 // Skip live partial obj (if any) from previous region.
1863 HeapWord* cur_addr;
1864 RegionData* start_region_ptr = _summary_data.region(start_region);
1865 if (start_region_ptr->partial_obj_size() != 0) {
1866 HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
1867 assert(bitmap->is_marked(partial_obj_start), "inv");
1868 cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
1869 } else {
1870 cur_addr = start_addr;
1871 }
1872
1873 // end_addr is inclusive to handle regions starting with dead space.
1874 while (cur_addr <= end_addr) {
1875 // Use prefix_end to handle trailing obj in each worker region-chunk.
1876 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
1877 if (cur_addr != live_start) {
1878 // Only worker 0 handles proceeding dead space.
1879 if (cur_addr != start_addr || worker_id == 0) {
1880 fill_range_in_dense_prefix(cur_addr, live_start);
1881 }
1882 }
1883 if (live_start >= end_addr) {
1884 break;
1885 }
1886 assert(bitmap->is_marked(live_start), "inv");
1887 cur_addr = live_start + cast_to_oop(live_start)->size();
1888 }
1889 }
1890
1891 void PSParallelCompact::compact() {
1892 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1893
1894 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1895
1896 initialize_shadow_regions(active_gc_threads);
1897 prepare_region_draining_tasks(active_gc_threads);
1898
1899 {
1900 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1901
1902 FillDensePrefixAndCompactionTask task(active_gc_threads);
1903 ParallelScavengeHeap::heap()->workers().run_task(&task);
1904
1905 #ifdef ASSERT
1906 verify_filler_in_dense_prefix();
1907
1908 // Verify that all regions have been processed.
1909 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1910 verify_complete(SpaceId(id));
1911 }
1912 #endif
1913 }
1914 }
1915
1916 #ifdef ASSERT
1917 void PSParallelCompact::verify_filler_in_dense_prefix() {
1918 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1919 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1920 HeapWord* cur_addr = bottom;
1921 while (cur_addr < dense_prefix_end) {
1922 oop obj = cast_to_oop(cur_addr);
1923 oopDesc::verify(obj);
1924 if (!mark_bitmap()->is_marked(cur_addr)) {
1925 Klass* k = cast_to_oop(cur_addr)->klass();
1926 assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
1927 }
1928 cur_addr += obj->size();
1929 }
1930 }
1931
1932 void PSParallelCompact::verify_complete(SpaceId space_id) {
1933 // All Regions served as compaction targets, from dense_prefix() to
1934 // new_top(), should be marked as filled and all Regions between new_top()
1935 // and top() should be available (i.e., should have been emptied).
1936 ParallelCompactData& sd = summary_data();
1937 SpaceInfo si = _space_info[space_id];
1938 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1939 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1940 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1941 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1942 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1943
1944 size_t cur_region;
1945 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1946 const RegionData* const c = sd.region(cur_region);
1947 assert(c->completed(), "region %zu not filled: destination_count=%u",
1948 cur_region, c->destination_count());
1949 }
1950
1951 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1952 const RegionData* const c = sd.region(cur_region);
1953 assert(c->available(), "region %zu not empty: destination_count=%u",
1954 cur_region, c->destination_count());
1955 }
1956 }
1957 #endif // #ifdef ASSERT
1958
1959 // Return the SpaceId for the space containing addr. If addr is not in the
1960 // heap, last_space_id is returned. In debug mode it expects the address to be
1961 // in the heap and asserts such.
1962 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1963 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1964
1965 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1966 if (_space_info[id].space()->contains(addr)) {
1967 return SpaceId(id);
1968 }
1969 }
1970
1971 assert(false, "no space contains the addr");
1972 return last_space_id;
1973 }
1974
1975 // Skip over count live words starting from beg, and return the address of the
1976 // next live word. Callers must also ensure that there are enough live words in
1977 // the range [beg, end) to skip.
1978 HeapWord* PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1979 {
1980 ParMarkBitMap* m = mark_bitmap();
1981 HeapWord* cur_addr = beg;
1982 while (true) {
1983 cur_addr = m->find_obj_beg(cur_addr, end);
1984 assert(cur_addr < end, "inv");
1985 size_t obj_size = cast_to_oop(cur_addr)->size();
1986 // Strictly greater-than
1987 if (obj_size > count) {
1988 return cur_addr + count;
1989 }
1990 count -= obj_size;
1991 cur_addr += obj_size;
1992 }
1993 }
1994
1995 // On starting to fill a destination region (dest-region), we need to know the
1996 // location of the word that will be at the start of the dest-region after
1997 // compaction. A dest-region can have one or more source regions, but only the
1998 // first source-region contains this location. This location is retrieved by
1999 // calling `first_src_addr` on a dest-region.
2000 // Conversely, a source-region has a dest-region which holds the destination of
2001 // the first live word on this source-region, based on which the destination
2002 // for the rest of live words can be derived.
2003 //
2004 // Note:
2005 // There is some complication due to space-boundary-fragmentation (an obj can't
2006 // cross space-boundary) -- a source-region may be split and behave like two
2007 // distinct regions with their own dest-region, as depicted below.
2008 //
2009 // source-region: region-n
2010 //
2011 // **********************
2012 // | A|A~~~~B|B |
2013 // **********************
2014 // n-1 n n+1
2015 //
2016 // AA, BB denote two live objs. ~~~~ denotes unknown number of live objs.
2017 //
2018 // Assuming the dest-region for region-n is the final region before
2019 // old-space-end and its first-live-word is the middle of AA, the heap content
2020 // will look like the following after compaction:
2021 //
2022 // ************** *************
2023 // A|A~~~~ | |BB |
2024 // ************** *************
2025 // ^ ^
2026 // | old-space-end | eden-space-start
2027 //
2028 // Therefore, in this example, region-n will have two dest-regions:
2029 // 1. the final region in old-space
2030 // 2. the first region in eden-space.
2031 // To handle this special case, we introduce the concept of split-region, whose
2032 // contents are relocated to two spaces. `SplitInfo` captures all necessary
2033 // info about the split, the first part, spliting-point, and the second part.
2034 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2035 SpaceId src_space_id,
2036 size_t src_region_idx)
2037 {
2038 const size_t RegionSize = ParallelCompactData::RegionSize;
2039 const ParallelCompactData& sd = summary_data();
2040 assert(sd.is_region_aligned(dest_addr), "precondition");
2041
2042 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2043 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2044
2045 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2046 HeapWord* const src_region_destination = src_region_ptr->destination();
2047
2048 HeapWord* const region_start = sd.region_to_addr(src_region_idx);
2049 HeapWord* const region_end = sd.region_to_addr(src_region_idx) + RegionSize;
2050
2051 // Identify the actual destination for the first live words on this region,
2052 // taking split-region into account.
2053 HeapWord* region_start_destination;
2054 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2055 if (split_info.is_split(src_region_idx)) {
2056 // The second part of this split region; use the recorded split point.
2057 if (dest_addr == src_region_destination) {
2058 return split_info.split_point();
2059 }
2060 region_start_destination = split_info.preceding_destination();
2061 } else {
2062 region_start_destination = src_region_destination;
2063 }
2064
2065 // Calculate the offset to be skipped
2066 size_t words_to_skip = pointer_delta(dest_addr, region_start_destination);
2067
2068 HeapWord* result;
2069 if (partial_obj_size > words_to_skip) {
2070 result = region_start + words_to_skip;
2071 } else {
2072 words_to_skip -= partial_obj_size;
2073 result = skip_live_words(region_start + partial_obj_size, region_end, words_to_skip);
2074 }
2075
2076 if (split_info.is_split(src_region_idx)) {
2077 assert(result < split_info.split_point(), "postcondition");
2078 } else {
2079 assert(result < region_end, "postcondition");
2080 }
2081
2082 return result;
2083 }
2084
2085 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2086 SpaceId src_space_id,
2087 size_t beg_region,
2088 HeapWord* end_addr)
2089 {
2090 ParallelCompactData& sd = summary_data();
2091
2092 #ifdef ASSERT
2093 MutableSpace* const src_space = _space_info[src_space_id].space();
2094 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2095 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2096 "src_space_id does not match beg_addr");
2097 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2098 "src_space_id does not match end_addr");
2099 #endif // #ifdef ASSERT
2100
2101 RegionData* const beg = sd.region(beg_region);
2102 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2103
2104 // Regions up to new_top() are enqueued if they become available.
2105 HeapWord* const new_top = _space_info[src_space_id].new_top();
2106 RegionData* const enqueue_end =
2107 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2108
2109 for (RegionData* cur = beg; cur < end; ++cur) {
2110 assert(cur->data_size() > 0, "region must have live data");
2111 cur->decrement_destination_count();
2112 if (cur < enqueue_end && cur->available() && cur->claim()) {
2113 if (cur->mark_normal()) {
2114 cm->push_region(sd.region(cur));
2115 } else if (cur->mark_copied()) {
2116 // Try to copy the content of the shadow region back to its corresponding
2117 // heap region if the shadow region is filled. Otherwise, the GC thread
2118 // fills the shadow region will copy the data back (see
2119 // MoveAndUpdateShadowClosure::complete_region).
2120 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2121 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2122 cur->set_completed();
2123 }
2124 }
2125 }
2126 }
2127
2128 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2129 SpaceId& src_space_id,
2130 HeapWord*& src_space_top,
2131 HeapWord* end_addr)
2132 {
2133 ParallelCompactData& sd = PSParallelCompact::summary_data();
2134
2135 size_t src_region_idx = 0;
2136
2137 // Skip empty regions (if any) up to the top of the space.
2138 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2139 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2140 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2141 const RegionData* const top_region_ptr = sd.addr_to_region_ptr(top_aligned_up);
2142
2143 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2144 ++src_region_ptr;
2145 }
2146
2147 if (src_region_ptr < top_region_ptr) {
2148 // Found the first non-empty region in the same space.
2149 src_region_idx = sd.region(src_region_ptr);
2150 closure.set_source(sd.region_to_addr(src_region_idx));
2151 return src_region_idx;
2152 }
2153
2154 // Switch to a new source space and find the first non-empty region.
2155 uint space_id = src_space_id + 1;
2156 assert(space_id < last_space_id, "not enough spaces");
2157
2158 for (/* empty */; space_id < last_space_id; ++space_id) {
2159 HeapWord* bottom = _space_info[space_id].space()->bottom();
2160 HeapWord* top = _space_info[space_id].space()->top();
2161 // Skip empty space
2162 if (bottom == top) {
2163 continue;
2164 }
2165
2166 // Identify the first region that contains live words in this space
2167 size_t cur_region = sd.addr_to_region_idx(bottom);
2168 size_t end_region = sd.addr_to_region_idx(sd.region_align_up(top));
2169
2170 for (/* empty */ ; cur_region < end_region; ++cur_region) {
2171 RegionData* cur = sd.region(cur_region);
2172 if (cur->live_obj_size() > 0) {
2173 HeapWord* region_start_addr = sd.region_to_addr(cur_region);
2174
2175 src_space_id = SpaceId(space_id);
2176 src_space_top = top;
2177 closure.set_source(region_start_addr);
2178 return cur_region;
2179 }
2180 }
2181 }
2182
2183 ShouldNotReachHere();
2184 }
2185
2186 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2187 ParallelCompactData& sd = summary_data();
2188 assert(sd.is_region_aligned(region_start_addr), "precondition");
2189
2190 // Use per-region partial_obj_size to locate the end of the obj, that extends
2191 // to region_start_addr.
2192 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2193 size_t end_region_idx = sd.region_count();
2194 size_t accumulated_size = 0;
2195 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2196 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2197 accumulated_size += cur_partial_obj_size;
2198 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2199 break;
2200 }
2201 }
2202 return region_start_addr + accumulated_size;
2203 }
2204
2205 // Use region_idx as the destination region, and evacuate all live objs on its
2206 // source regions to this destination region.
2207 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2208 {
2209 ParMarkBitMap* const bitmap = mark_bitmap();
2210 ParallelCompactData& sd = summary_data();
2211 RegionData* const region_ptr = sd.region(region_idx);
2212
2213 // Get the source region and related info.
2214 size_t src_region_idx = region_ptr->source_region();
2215 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2216 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2217 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2218
2219 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2220
2221 // Adjust src_region_idx to prepare for decrementing destination counts (the
2222 // destination count is not decremented when a region is copied to itself).
2223 if (src_region_idx == region_idx) {
2224 src_region_idx += 1;
2225 }
2226
2227 // source-region:
2228 //
2229 // **********
2230 // | ~~~ |
2231 // **********
2232 // ^
2233 // |-- closure.source() / first_src_addr
2234 //
2235 //
2236 // ~~~ : live words
2237 //
2238 // destination-region:
2239 //
2240 // **********
2241 // | |
2242 // **********
2243 // ^
2244 // |-- region-start
2245 if (bitmap->is_unmarked(closure.source())) {
2246 // An object overflows the previous destination region, so this
2247 // destination region should copy the remainder of the object or as much as
2248 // will fit.
2249 HeapWord* const old_src_addr = closure.source();
2250 {
2251 HeapWord* region_start = sd.region_align_down(closure.source());
2252 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2253 HeapWord* obj_end;
2254 if (obj_start != closure.source()) {
2255 assert(bitmap->is_marked(obj_start), "inv");
2256 // Found the actual obj-start, try to find the obj-end using either
2257 // size() if this obj is completely contained in the current region.
2258 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2259 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2260 ? nullptr
2261 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2262 // This obj extends to next region iff partial_obj_addr of the *next*
2263 // region is the same as obj-start.
2264 if (partial_obj_start == obj_start) {
2265 // This obj extends to next region.
2266 obj_end = partial_obj_end(next_region_start);
2267 } else {
2268 // Completely contained in this region; safe to use size().
2269 obj_end = obj_start + cast_to_oop(obj_start)->size();
2270 }
2271 } else {
2272 // This obj extends to current region.
2273 obj_end = partial_obj_end(region_start);
2274 }
2275 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2276 closure.copy_partial_obj(partial_obj_size);
2277 }
2278
2279 if (closure.is_full()) {
2280 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2281 closure.complete_region(dest_addr, region_ptr);
2282 return;
2283 }
2284
2285 // Finished copying without using up the current destination-region
2286 HeapWord* const end_addr = sd.region_align_down(closure.source());
2287 if (sd.region_align_down(old_src_addr) != end_addr) {
2288 assert(sd.region_align_up(old_src_addr) == end_addr, "only one region");
2289 // The partial object was copied from more than one source region.
2290 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2291
2292 // Move to the next source region, possibly switching spaces as well. All
2293 // args except end_addr may be modified.
2294 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2295 }
2296 }
2297
2298 // Handle the rest obj-by-obj, where we know obj-start.
2299 do {
2300 HeapWord* cur_addr = closure.source();
2301 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2302 src_space_top);
2303 // To handle the case where the final obj in source region extends to next region.
2304 HeapWord* final_obj_start = (end_addr == src_space_top)
2305 ? nullptr
2306 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2307 // Apply closure on objs inside [cur_addr, end_addr)
2308 do {
2309 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2310 if (cur_addr == end_addr) {
2311 break;
2312 }
2313 size_t obj_size;
2314 if (final_obj_start == cur_addr) {
2315 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2316 } else {
2317 // This obj doesn't extend into next region; size() is safe to use.
2318 obj_size = cast_to_oop(cur_addr)->size();
2319 }
2320 closure.do_addr(cur_addr, obj_size);
2321 cur_addr += obj_size;
2322 } while (cur_addr < end_addr && !closure.is_full());
2323
2324 if (closure.is_full()) {
2325 decrement_destination_counts(cm, src_space_id, src_region_idx, closure.source());
2326 closure.complete_region(dest_addr, region_ptr);
2327 return;
2328 }
2329
2330 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2331
2332 // Move to the next source region, possibly switching spaces as well. All
2333 // args except end_addr may be modified.
2334 src_region_idx = next_src_region(closure, src_space_id, src_space_top, end_addr);
2335 } while (true);
2336 }
2337
2338 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2339 {
2340 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2341 fill_region(cm, cl, region_idx);
2342 }
2343
2344 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2345 {
2346 // Get a shadow region first
2347 ParallelCompactData& sd = summary_data();
2348 RegionData* const region_ptr = sd.region(region_idx);
2349 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2350 // The InvalidShadow return value indicates the corresponding heap region is available,
2351 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2352 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2353 if (shadow_region == ParCompactionManager::InvalidShadow) {
2354 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2355 region_ptr->shadow_to_normal();
2356 return fill_region(cm, cl, region_idx);
2357 } else {
2358 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2359 return fill_region(cm, cl, region_idx);
2360 }
2361 }
2362
2363 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2364 {
2365 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2366 }
2367
2368 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2369 {
2370 size_t next = cm->next_shadow_region();
2371 ParallelCompactData& sd = summary_data();
2372 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2373 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2374
2375 while (next < old_new_top) {
2376 if (sd.region(next)->mark_shadow()) {
2377 region_idx = next;
2378 return true;
2379 }
2380 next = cm->move_next_shadow_region_by(active_gc_threads);
2381 }
2382
2383 return false;
2384 }
2385
2386 // The shadow region is an optimization to address region dependencies in full GC. The basic
2387 // idea is making more regions available by temporally storing their live objects in empty
2388 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2389 // GC threads need not wait destination regions to be available before processing sources.
2390 //
2391 // A typical workflow would be:
2392 // After draining its own stack and failing to steal from others, a GC worker would pick an
2393 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2394 // the shadow region by copying live objects from source regions of the unavailable one. Once
2395 // the unavailable region becomes available, the data in the shadow region will be copied back.
2396 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2397 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2398 {
2399 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2400
2401 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2402 SpaceInfo* const space_info = _space_info + id;
2403 MutableSpace* const space = space_info->space();
2404
2405 const size_t beg_region =
2406 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2407 const size_t end_region =
2408 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2409
2410 for (size_t cur = beg_region; cur < end_region; ++cur) {
2411 ParCompactionManager::push_shadow_region(cur);
2412 }
2413 }
2414
2415 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2416 for (uint i = 0; i < parallel_gc_threads; i++) {
2417 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2418 cm->set_next_shadow_region(beg_region + i);
2419 }
2420 }
2421
2422 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2423 {
2424 size_t words = MIN2(partial_obj_size, words_remaining());
2425
2426 // This test is necessary; if omitted, the pointer updates to a partial object
2427 // that crosses the dense prefix boundary could be overwritten.
2428 if (source() != copy_destination()) {
2429 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2430 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2431 }
2432 update_state(words);
2433 }
2434
2435 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2436 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2437 region_ptr->set_completed();
2438 }
2439
2440 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2441 assert(destination() != nullptr, "sanity");
2442 _source = addr;
2443
2444 // The start_array must be updated even if the object is not moving.
2445 if (_start_array != nullptr) {
2446 _start_array->update_for_block(destination(), destination() + words);
2447 }
2448
2449 // Avoid overflow
2450 words = MIN2(words, words_remaining());
2451 assert(words > 0, "inv");
2452
2453 if (copy_destination() != source()) {
2454 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2455 assert(source() != destination(), "inv");
2456 assert(FullGCForwarding::is_forwarded(cast_to_oop(source())), "inv");
2457 assert(FullGCForwarding::forwardee(cast_to_oop(source())) == cast_to_oop(destination()), "inv");
2458 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2459 cast_to_oop(copy_destination())->init_mark();
2460 }
2461
2462 update_state(words);
2463 }
2464
2465 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2466 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2467 // Record the shadow region index
2468 region_ptr->set_shadow_region(_shadow);
2469 // Mark the shadow region as filled to indicate the data is ready to be
2470 // copied back
2471 region_ptr->mark_filled();
2472 // Try to copy the content of the shadow region back to its corresponding
2473 // heap region if available; the GC thread that decreases the destination
2474 // count to zero will do the copying otherwise (see
2475 // PSParallelCompact::decrement_destination_counts).
2476 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2477 region_ptr->set_completed();
2478 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2479 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2480 }
2481 }