1 /*
2 * Copyright (c) 2005, 2024, 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 "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "classfile/javaClasses.inline.hpp"
28 #include "classfile/stringTable.hpp"
29 #include "classfile/symbolTable.hpp"
30 #include "classfile/systemDictionary.hpp"
31 #include "code/codeCache.hpp"
32 #include "compiler/oopMap.hpp"
33 #include "gc/parallel/objectStartArray.inline.hpp"
34 #include "gc/parallel/parallelArguments.hpp"
35 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
36 #include "gc/parallel/parMarkBitMap.inline.hpp"
37 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
38 #include "gc/parallel/psCompactionManager.inline.hpp"
39 #include "gc/parallel/psOldGen.hpp"
40 #include "gc/parallel/psParallelCompact.inline.hpp"
41 #include "gc/parallel/psPromotionManager.inline.hpp"
42 #include "gc/parallel/psRootType.hpp"
43 #include "gc/parallel/psScavenge.hpp"
44 #include "gc/parallel/psStringDedup.hpp"
45 #include "gc/parallel/psYoungGen.hpp"
46 #include "gc/shared/classUnloadingContext.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/metaspaceUtils.hpp"
73 #include "memory/resourceArea.hpp"
74 #include "memory/universe.hpp"
75 #include "nmt/memTracker.hpp"
76 #include "oops/access.inline.hpp"
77 #include "oops/instanceClassLoaderKlass.inline.hpp"
78 #include "oops/instanceKlass.inline.hpp"
79 #include "oops/instanceMirrorKlass.inline.hpp"
80 #include "oops/methodData.hpp"
81 #include "oops/objArrayKlass.inline.hpp"
82 #include "oops/oop.inline.hpp"
83 #include "runtime/atomic.hpp"
84 #include "runtime/handles.inline.hpp"
85 #include "runtime/java.hpp"
86 #include "runtime/safepoint.hpp"
87 #include "runtime/threads.hpp"
88 #include "runtime/vmThread.hpp"
89 #include "services/memoryService.hpp"
90 #include "utilities/align.hpp"
91 #include "utilities/debug.hpp"
92 #include "utilities/events.hpp"
93 #include "utilities/formatBuffer.hpp"
94 #include "utilities/macros.hpp"
95 #include "utilities/stack.inline.hpp"
96 #if INCLUDE_JVMCI
97 #include "jvmci/jvmci.hpp"
98 #endif
99
100 #include <math.h>
101
102 // All sizes are in HeapWords.
103 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
104 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
105 static_assert(ParallelCompactData::RegionSize >= BitsPerWord, "region-start bit word-aligned");
106 const size_t ParallelCompactData::RegionSizeBytes =
107 RegionSize << LogHeapWordSize;
108 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
109 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
110 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
111
112 const ParallelCompactData::RegionData::region_sz_t
113 ParallelCompactData::RegionData::dc_shift = 27;
114
115 const ParallelCompactData::RegionData::region_sz_t
116 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
117
118 const ParallelCompactData::RegionData::region_sz_t
119 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
120
121 const ParallelCompactData::RegionData::region_sz_t
122 ParallelCompactData::RegionData::los_mask = ~dc_mask;
123
124 const ParallelCompactData::RegionData::region_sz_t
125 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
126
127 const ParallelCompactData::RegionData::region_sz_t
128 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
129
130 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
131
132 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
133 ReferenceProcessor* PSParallelCompact::_ref_processor = nullptr;
134
135 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
136 HeapWord* destination)
137 {
138 assert(src_region_idx != 0, "invalid src_region_idx");
139 assert(partial_obj_size != 0, "invalid partial_obj_size argument");
140 assert(destination != nullptr, "invalid destination argument");
141
142 _src_region_idx = src_region_idx;
143 _partial_obj_size = partial_obj_size;
144 _destination = destination;
145
146 // These fields may not be updated below, so make sure they're clear.
147 assert(_dest_region_addr == nullptr, "should have been cleared");
148 assert(_first_src_addr == nullptr, "should have been cleared");
149
150 // Determine the number of destination regions for the partial object.
151 HeapWord* const last_word = destination + partial_obj_size - 1;
152 const ParallelCompactData& sd = PSParallelCompact::summary_data();
153 HeapWord* const beg_region_addr = sd.region_align_down(destination);
154 HeapWord* const end_region_addr = sd.region_align_down(last_word);
155
156 if (beg_region_addr == end_region_addr) {
157 // One destination region.
158 _destination_count = 1;
159 if (end_region_addr == destination) {
160 // The destination falls on a region boundary, thus the first word of the
161 // partial object will be the first word copied to the destination region.
162 _dest_region_addr = end_region_addr;
163 _first_src_addr = sd.region_to_addr(src_region_idx);
164 }
165 } else {
166 // Two destination regions. When copied, the partial object will cross a
167 // destination region boundary, so a word somewhere within the partial
168 // object will be the first word copied to the second destination region.
169 _destination_count = 2;
170 _dest_region_addr = end_region_addr;
171 const size_t ofs = pointer_delta(end_region_addr, destination);
172 assert(ofs < _partial_obj_size, "sanity");
173 _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
174 }
175 }
176
177 void SplitInfo::clear()
178 {
179 _src_region_idx = 0;
180 _partial_obj_size = 0;
181 _destination = nullptr;
182 _destination_count = 0;
183 _dest_region_addr = nullptr;
184 _first_src_addr = nullptr;
185 assert(!is_valid(), "sanity");
186 }
187
188 #ifdef ASSERT
189 void SplitInfo::verify_clear()
190 {
191 assert(_src_region_idx == 0, "not clear");
192 assert(_partial_obj_size == 0, "not clear");
193 assert(_destination == nullptr, "not clear");
194 assert(_destination_count == 0, "not clear");
195 assert(_dest_region_addr == nullptr, "not clear");
196 assert(_first_src_addr == nullptr, "not clear");
197 }
198 #endif // #ifdef ASSERT
199
200
201 void PSParallelCompact::print_on_error(outputStream* st) {
202 _mark_bitmap.print_on_error(st);
203 }
204
205 ParallelCompactData::ParallelCompactData() :
206 _heap_start(nullptr),
207 DEBUG_ONLY(_heap_end(nullptr) COMMA)
208 _region_vspace(nullptr),
209 _reserved_byte_size(0),
210 _region_data(nullptr),
211 _region_count(0) {}
212
213 bool ParallelCompactData::initialize(MemRegion reserved_heap)
214 {
215 _heap_start = reserved_heap.start();
216 const size_t heap_size = reserved_heap.word_size();
217 DEBUG_ONLY(_heap_end = _heap_start + heap_size;)
218
219 assert(region_align_down(_heap_start) == _heap_start,
220 "region start not aligned");
221
222 return initialize_region_data(heap_size);
223 }
224
225 PSVirtualSpace*
226 ParallelCompactData::create_vspace(size_t count, size_t element_size)
227 {
228 const size_t raw_bytes = count * element_size;
229 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
230 const size_t granularity = os::vm_allocation_granularity();
231 _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
232
233 const size_t rs_align = page_sz == os::vm_page_size() ? 0 :
234 MAX2(page_sz, granularity);
235 ReservedSpace rs(_reserved_byte_size, rs_align, page_sz);
236 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, rs.base(),
237 rs.size(), page_sz);
238
239 MemTracker::record_virtual_memory_tag((address)rs.base(), mtGC);
240
241 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
242 if (vspace != nullptr) {
243 if (vspace->expand_by(_reserved_byte_size)) {
244 return vspace;
245 }
246 delete vspace;
247 // Release memory reserved in the space.
248 rs.release();
249 }
250
251 return nullptr;
252 }
253
254 bool ParallelCompactData::initialize_region_data(size_t heap_size)
255 {
256 assert(is_aligned(heap_size, RegionSize), "precondition");
257
258 const size_t count = heap_size >> Log2RegionSize;
259 _region_vspace = create_vspace(count, sizeof(RegionData));
260 if (_region_vspace != nullptr) {
261 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
262 _region_count = count;
263 return true;
264 }
265 return false;
266 }
267
268 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
269 assert(beg_region <= _region_count, "beg_region out of range");
270 assert(end_region <= _region_count, "end_region out of range");
271
272 const size_t region_cnt = end_region - beg_region;
273 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
274 }
275
276 void
277 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
278 {
279 assert(is_region_aligned(beg), "not RegionSize aligned");
280 assert(is_region_aligned(end), "not RegionSize aligned");
281
282 size_t cur_region = addr_to_region_idx(beg);
283 const size_t end_region = addr_to_region_idx(end);
284 HeapWord* addr = beg;
285 while (cur_region < end_region) {
286 _region_data[cur_region].set_destination(addr);
287 _region_data[cur_region].set_destination_count(0);
288 _region_data[cur_region].set_source_region(cur_region);
289
290 // Update live_obj_size so the region appears completely full.
291 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
292 _region_data[cur_region].set_live_obj_size(live_size);
293
294 ++cur_region;
295 addr += RegionSize;
296 }
297 }
298
299 // Find the point at which a space can be split and, if necessary, record the
300 // split point.
301 //
302 // If the current src region (which overflowed the destination space) doesn't
303 // have a partial object, the split point is at the beginning of the current src
304 // region (an "easy" split, no extra bookkeeping required).
305 //
306 // If the current src region has a partial object, the split point is in the
307 // region where that partial object starts (call it the split_region). If
308 // split_region has a partial object, then the split point is just after that
309 // partial object (a "hard" split where we have to record the split data and
310 // zero the partial_obj_size field). With a "hard" split, we know that the
311 // partial_obj ends within split_region because the partial object that caused
312 // the overflow starts in split_region. If split_region doesn't have a partial
313 // obj, then the split is at the beginning of split_region (another "easy"
314 // split).
315 HeapWord*
316 ParallelCompactData::summarize_split_space(size_t src_region,
317 SplitInfo& split_info,
318 HeapWord* destination,
319 HeapWord* target_end,
320 HeapWord** target_next)
321 {
322 assert(destination <= target_end, "sanity");
323 assert(destination + _region_data[src_region].data_size() > target_end,
324 "region should not fit into target space");
325 assert(is_region_aligned(target_end), "sanity");
326
327 size_t split_region = src_region;
328 HeapWord* split_destination = destination;
329 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
330
331 if (destination + partial_obj_size > target_end) {
332 // The split point is just after the partial object (if any) in the
333 // src_region that contains the start of the object that overflowed the
334 // destination space.
335 //
336 // Find the start of the "overflow" object and set split_region to the
337 // region containing it.
338 HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
339 split_region = addr_to_region_idx(overflow_obj);
340
341 // Clear the source_region field of all destination regions whose first word
342 // came from data after the split point (a non-null source_region field
343 // implies a region must be filled).
344 //
345 // An alternative to the simple loop below: clear during post_compact(),
346 // which uses memcpy instead of individual stores, and is easy to
347 // parallelize. (The downside is that it clears the entire RegionData
348 // object as opposed to just one field.)
349 //
350 // post_compact() would have to clear the summary data up to the highest
351 // address that was written during the summary phase, which would be
352 //
353 // max(top, max(new_top, clear_top))
354 //
355 // where clear_top is a new field in SpaceInfo. Would have to set clear_top
356 // to target_end.
357 const RegionData* const sr = region(split_region);
358 const size_t beg_idx =
359 addr_to_region_idx(region_align_up(sr->destination() +
360 sr->partial_obj_size()));
361 const size_t end_idx = addr_to_region_idx(target_end);
362
363 log_develop_trace(gc, compaction)("split: clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
364 for (size_t idx = beg_idx; idx < end_idx; ++idx) {
365 _region_data[idx].set_source_region(0);
366 }
367
368 // Set split_destination and partial_obj_size to reflect the split region.
369 split_destination = sr->destination();
370 partial_obj_size = sr->partial_obj_size();
371 }
372
373 // The split is recorded only if a partial object extends onto the region.
374 if (partial_obj_size != 0) {
375 _region_data[split_region].set_partial_obj_size(0);
376 split_info.record(split_region, partial_obj_size, split_destination);
377 }
378
379 // Setup the continuation addresses.
380 *target_next = split_destination + partial_obj_size;
381 HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
382
383 if (log_develop_is_enabled(Trace, gc, compaction)) {
384 const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
385 log_develop_trace(gc, compaction)("%s split: src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
386 split_type, p2i(source_next), split_region, partial_obj_size);
387 log_develop_trace(gc, compaction)("%s split: dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
388 split_type, p2i(split_destination),
389 addr_to_region_idx(split_destination),
390 p2i(*target_next));
391
392 if (partial_obj_size != 0) {
393 HeapWord* const po_beg = split_info.destination();
394 HeapWord* const po_end = po_beg + split_info.partial_obj_size();
395 log_develop_trace(gc, compaction)("%s split: po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
396 split_type,
397 p2i(po_beg), addr_to_region_idx(po_beg),
398 p2i(po_end), addr_to_region_idx(po_end));
399 }
400 }
401
402 return source_next;
403 }
404
405 size_t ParallelCompactData::live_words_in_space(const MutableSpace* space,
406 HeapWord** full_region_prefix_end) {
407 size_t cur_region = addr_to_region_idx(space->bottom());
408 const size_t end_region = addr_to_region_idx(region_align_up(space->top()));
409 size_t live_words = 0;
410 if (full_region_prefix_end == nullptr) {
411 for (/* empty */; cur_region < end_region; ++cur_region) {
412 live_words += _region_data[cur_region].data_size();
413 }
414 } else {
415 bool first_set = false;
416 for (/* empty */; cur_region < end_region; ++cur_region) {
417 size_t live_words_in_region = _region_data[cur_region].data_size();
418 if (!first_set && live_words_in_region < RegionSize) {
419 *full_region_prefix_end = region_to_addr(cur_region);
420 first_set = true;
421 }
422 live_words += live_words_in_region;
423 }
424 if (!first_set) {
425 // All regions are full of live objs.
426 assert(is_region_aligned(space->top()), "inv");
427 *full_region_prefix_end = space->top();
428 }
429 assert(*full_region_prefix_end != nullptr, "postcondition");
430 assert(is_region_aligned(*full_region_prefix_end), "inv");
431 assert(*full_region_prefix_end >= space->bottom(), "in-range");
432 assert(*full_region_prefix_end <= space->top(), "in-range");
433 }
434 return live_words;
435 }
436
437 bool ParallelCompactData::summarize(SplitInfo& split_info,
438 HeapWord* source_beg, HeapWord* source_end,
439 HeapWord** source_next,
440 HeapWord* target_beg, HeapWord* target_end,
441 HeapWord** target_next)
442 {
443 HeapWord* const source_next_val = source_next == nullptr ? nullptr : *source_next;
444 log_develop_trace(gc, compaction)(
445 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
446 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
447 p2i(source_beg), p2i(source_end), p2i(source_next_val),
448 p2i(target_beg), p2i(target_end), p2i(*target_next));
449
450 size_t cur_region = addr_to_region_idx(source_beg);
451 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
452
453 HeapWord *dest_addr = target_beg;
454 while (cur_region < end_region) {
455 // The destination must be set even if the region has no data.
456 _region_data[cur_region].set_destination(dest_addr);
457
458 size_t words = _region_data[cur_region].data_size();
459 if (words > 0) {
460 // If cur_region does not fit entirely into the target space, find a point
461 // at which the source space can be 'split' so that part is copied to the
462 // target space and the rest is copied elsewhere.
463 if (dest_addr + words > target_end) {
464 assert(source_next != nullptr, "source_next is null when splitting");
465 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
466 target_end, target_next);
467 return false;
468 }
469
470 // Compute the destination_count for cur_region, and if necessary, update
471 // source_region for a destination region. The source_region field is
472 // updated if cur_region is the first (left-most) region to be copied to a
473 // destination region.
474 //
475 // The destination_count calculation is a bit subtle. A region that has
476 // data that compacts into itself does not count itself as a destination.
477 // This maintains the invariant that a zero count means the region is
478 // available and can be claimed and then filled.
479 uint destination_count = 0;
480 if (split_info.is_split(cur_region)) {
481 // The current region has been split: the partial object will be copied
482 // to one destination space and the remaining data will be copied to
483 // another destination space. Adjust the initial destination_count and,
484 // if necessary, set the source_region field if the partial object will
485 // cross a destination region boundary.
486 destination_count = split_info.destination_count();
487 if (destination_count == 2) {
488 size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
489 _region_data[dest_idx].set_source_region(cur_region);
490 }
491 }
492
493 HeapWord* const last_addr = dest_addr + words - 1;
494 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
495 const size_t dest_region_2 = addr_to_region_idx(last_addr);
496
497 // Initially assume that the destination regions will be the same and
498 // adjust the value below if necessary. Under this assumption, if
499 // cur_region == dest_region_2, then cur_region will be compacted
500 // completely into itself.
501 destination_count += cur_region == dest_region_2 ? 0 : 1;
502 if (dest_region_1 != dest_region_2) {
503 // Destination regions differ; adjust destination_count.
504 destination_count += 1;
505 // Data from cur_region will be copied to the start of dest_region_2.
506 _region_data[dest_region_2].set_source_region(cur_region);
507 } else if (is_region_aligned(dest_addr)) {
508 // Data from cur_region will be copied to the start of the destination
509 // region.
510 _region_data[dest_region_1].set_source_region(cur_region);
511 }
512
513 _region_data[cur_region].set_destination_count(destination_count);
514 dest_addr += words;
515 }
516
517 ++cur_region;
518 }
519
520 *target_next = dest_addr;
521 return true;
522 }
523
524 #ifdef ASSERT
525 void ParallelCompactData::verify_clear()
526 {
527 const size_t* const beg = (const size_t*) _region_vspace->committed_low_addr();
528 const size_t* const end = (const size_t*) _region_vspace->committed_high_addr();
529 for (const size_t* p = beg; p < end; ++p) {
530 assert(*p == 0, "not zero");
531 }
532 }
533 #endif // #ifdef ASSERT
534
535 STWGCTimer PSParallelCompact::_gc_timer;
536 ParallelOldTracer PSParallelCompact::_gc_tracer;
537 elapsedTimer PSParallelCompact::_accumulated_time;
538 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
539 CollectorCounters* PSParallelCompact::_counters = nullptr;
540 ParMarkBitMap PSParallelCompact::_mark_bitmap;
541 ParallelCompactData PSParallelCompact::_summary_data;
542
543 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
544
545 class PCAdjustPointerClosure: public BasicOopIterateClosure {
546 template <typename T>
547 void do_oop_work(T* p) { PSParallelCompact::adjust_pointer(p); }
548
549 public:
550 virtual void do_oop(oop* p) { do_oop_work(p); }
551 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
552
553 virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
554 };
555
556 static PCAdjustPointerClosure pc_adjust_pointer_closure;
557
558 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
559
560 void PSParallelCompact::post_initialize() {
561 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
562 _span_based_discoverer.set_span(heap->reserved_region());
563 _ref_processor =
564 new ReferenceProcessor(&_span_based_discoverer,
565 ParallelGCThreads, // mt processing degree
566 ParallelGCThreads, // mt discovery degree
567 false, // concurrent_discovery
568 &_is_alive_closure); // non-header is alive closure
569
570 _counters = new CollectorCounters("Parallel full collection pauses", 1);
571
572 // Initialize static fields in ParCompactionManager.
573 ParCompactionManager::initialize(mark_bitmap());
574 }
575
576 bool PSParallelCompact::initialize_aux_data() {
577 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
578 MemRegion mr = heap->reserved_region();
579 assert(mr.byte_size() != 0, "heap should be reserved");
580
581 initialize_space_info();
582
583 if (!_mark_bitmap.initialize(mr)) {
584 vm_shutdown_during_initialization(
585 err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
586 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
587 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
588 return false;
589 }
590
591 if (!_summary_data.initialize(mr)) {
592 vm_shutdown_during_initialization(
593 err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
594 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
595 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
596 return false;
597 }
598
599 return true;
600 }
601
602 void PSParallelCompact::initialize_space_info()
603 {
604 memset(&_space_info, 0, sizeof(_space_info));
605
606 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
607 PSYoungGen* young_gen = heap->young_gen();
608
609 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
610 _space_info[eden_space_id].set_space(young_gen->eden_space());
611 _space_info[from_space_id].set_space(young_gen->from_space());
612 _space_info[to_space_id].set_space(young_gen->to_space());
613
614 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
615 }
616
617 void
618 PSParallelCompact::clear_data_covering_space(SpaceId id)
619 {
620 // At this point, top is the value before GC, new_top() is the value that will
621 // be set at the end of GC. The marking bitmap is cleared to top; nothing
622 // should be marked above top. The summary data is cleared to the larger of
623 // top & new_top.
624 MutableSpace* const space = _space_info[id].space();
625 HeapWord* const bot = space->bottom();
626 HeapWord* const top = space->top();
627 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
628
629 _mark_bitmap.clear_range(bot, top);
630
631 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
632 const size_t end_region =
633 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
634 _summary_data.clear_range(beg_region, end_region);
635
636 // Clear the data used to 'split' regions.
637 SplitInfo& split_info = _space_info[id].split_info();
638 if (split_info.is_valid()) {
639 split_info.clear();
640 }
641 DEBUG_ONLY(split_info.verify_clear();)
642 }
643
644 void PSParallelCompact::pre_compact()
645 {
646 // Update the from & to space pointers in space_info, since they are swapped
647 // at each young gen gc. Do the update unconditionally (even though a
648 // promotion failure does not swap spaces) because an unknown number of young
649 // collections will have swapped the spaces an unknown number of times.
650 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
651 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
652 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
653 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
654
655 // Increment the invocation count
656 heap->increment_total_collections(true);
657
658 CodeCache::on_gc_marking_cycle_start();
659
660 heap->print_heap_before_gc();
661 heap->trace_heap_before_gc(&_gc_tracer);
662
663 // Fill in TLABs
664 heap->ensure_parsability(true); // retire TLABs
665
666 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
667 Universe::verify("Before GC");
668 }
669
670 DEBUG_ONLY(mark_bitmap()->verify_clear();)
671 DEBUG_ONLY(summary_data().verify_clear();)
672 }
673
674 void PSParallelCompact::post_compact()
675 {
676 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
677 ParCompactionManager::remove_all_shadow_regions();
678
679 CodeCache::on_gc_marking_cycle_finish();
680 CodeCache::arm_all_nmethods();
681
682 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
683 // Clear the marking bitmap, summary data and split info.
684 clear_data_covering_space(SpaceId(id));
685 {
686 MutableSpace* space = _space_info[id].space();
687 HeapWord* top = space->top();
688 HeapWord* new_top = _space_info[id].new_top();
689 if (ZapUnusedHeapArea && new_top < top) {
690 space->mangle_region(MemRegion(new_top, top));
691 }
692 // Update top(). Must be done after clearing the bitmap and summary data.
693 space->set_top(new_top);
694 }
695 }
696
697 ParCompactionManager::flush_all_string_dedup_requests();
698
699 MutableSpace* const eden_space = _space_info[eden_space_id].space();
700 MutableSpace* const from_space = _space_info[from_space_id].space();
701 MutableSpace* const to_space = _space_info[to_space_id].space();
702
703 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
704 bool eden_empty = eden_space->is_empty();
705
706 // Update heap occupancy information which is used as input to the soft ref
707 // clearing policy at the next gc.
708 Universe::heap()->update_capacity_and_used_at_gc();
709
710 bool young_gen_empty = eden_empty && from_space->is_empty() &&
711 to_space->is_empty();
712
713 PSCardTable* ct = heap->card_table();
714 MemRegion old_mr = heap->old_gen()->committed();
715 if (young_gen_empty) {
716 ct->clear_MemRegion(old_mr);
717 } else {
718 ct->dirty_MemRegion(old_mr);
719 }
720
721 {
722 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
723 GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", gc_timer());
724 ClassLoaderDataGraph::purge(true /* at_safepoint */);
725 DEBUG_ONLY(MetaspaceUtils::verify();)
726 }
727
728 // Need to clear claim bits for the next mark.
729 ClassLoaderDataGraph::clear_claimed_marks();
730
731 heap->prune_scavengable_nmethods();
732
733 #if COMPILER2_OR_JVMCI
734 DerivedPointerTable::update_pointers();
735 #endif
736
737 // Signal that we have completed a visit to all live objects.
738 Universe::heap()->record_whole_heap_examined_timestamp();
739 }
740
741 HeapWord* PSParallelCompact::compute_dense_prefix_for_old_space(MutableSpace* old_space,
742 HeapWord* full_region_prefix_end) {
743 const size_t region_size = ParallelCompactData::RegionSize;
744 const ParallelCompactData& sd = summary_data();
745
746 // Iteration starts with the region *after* the full-region-prefix-end.
747 const RegionData* const start_region = sd.addr_to_region_ptr(full_region_prefix_end);
748 // If final region is not full, iteration stops before that region,
749 // because fill_dense_prefix_end assumes that prefix_end <= top.
750 const RegionData* const end_region = sd.addr_to_region_ptr(old_space->top());
751 assert(start_region <= end_region, "inv");
752
753 size_t max_waste = old_space->capacity_in_words() * (MarkSweepDeadRatio / 100.0);
754 const RegionData* cur_region = start_region;
755 for (/* empty */; cur_region < end_region; ++cur_region) {
756 assert(region_size >= cur_region->data_size(), "inv");
757 size_t dead_size = region_size - cur_region->data_size();
758 if (max_waste < dead_size) {
759 break;
760 }
761 max_waste -= dead_size;
762 }
763
764 HeapWord* const prefix_end = sd.region_to_addr(cur_region);
765 assert(sd.is_region_aligned(prefix_end), "postcondition");
766 assert(prefix_end >= full_region_prefix_end, "in-range");
767 assert(prefix_end <= old_space->top(), "in-range");
768 return prefix_end;
769 }
770
771 void PSParallelCompact::fill_dense_prefix_end(SpaceId id) {
772 // Comparing two sizes to decide if filling is required:
773 //
774 // The size of the filler (min-obj-size) is 2 heap words with the default
775 // MinObjAlignment, since both markword and klass take 1 heap word.
776 //
777 // The size of the gap (if any) right before dense-prefix-end is
778 // MinObjAlignment.
779 //
780 // Need to fill in the gap only if it's smaller than min-obj-size, and the
781 // filler obj will extend to next region.
782
783 // Note: If min-fill-size decreases to 1, this whole method becomes redundant.
784 assert(CollectedHeap::min_fill_size() >= 2, "inv");
785 #ifndef _LP64
786 // In 32-bit system, each heap word is 4 bytes, so MinObjAlignment == 2.
787 // The gap is always equal to min-fill-size, so nothing to do.
788 return;
789 #endif
790 if (MinObjAlignment > 1) {
791 return;
792 }
793 assert(CollectedHeap::min_fill_size() == 2, "inv");
794 HeapWord* const dense_prefix_end = dense_prefix(id);
795 assert(_summary_data.is_region_aligned(dense_prefix_end), "precondition");
796 assert(dense_prefix_end <= space(id)->top(), "precondition");
797 if (dense_prefix_end == space(id)->top()) {
798 // Must not have single-word gap right before prefix-end/top.
799 return;
800 }
801 RegionData* const region_after_dense_prefix = _summary_data.addr_to_region_ptr(dense_prefix_end);
802
803 if (region_after_dense_prefix->partial_obj_size() != 0 ||
804 _mark_bitmap.is_marked(dense_prefix_end)) {
805 // The region after the dense prefix starts with live bytes.
806 return;
807 }
808
809 HeapWord* block_start = start_array(id)->block_start_reaching_into_card(dense_prefix_end);
810 if (block_start == dense_prefix_end - 1) {
811 assert(!_mark_bitmap.is_marked(block_start), "inv");
812 // There is exactly one heap word gap right before the dense prefix end, so we need a filler object.
813 // The filler object will extend into region_after_dense_prefix.
814 const size_t obj_len = 2; // min-fill-size
815 HeapWord* const obj_beg = dense_prefix_end - 1;
816 CollectedHeap::fill_with_object(obj_beg, obj_len);
817 _mark_bitmap.mark_obj(obj_beg);
818 _summary_data.addr_to_region_ptr(obj_beg)->add_live_obj(1);
819 region_after_dense_prefix->set_partial_obj_size(1);
820 region_after_dense_prefix->set_partial_obj_addr(obj_beg);
821 assert(start_array(id) != nullptr, "sanity");
822 start_array(id)->update_for_block(obj_beg, obj_beg + obj_len);
823 }
824 }
825
826 bool PSParallelCompact::check_maximum_compaction(size_t total_live_words,
827 MutableSpace* const old_space,
828 HeapWord* full_region_prefix_end) {
829
830 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
831
832 // Check System.GC
833 bool is_max_on_system_gc = UseMaximumCompactionOnSystemGC
834 && GCCause::is_user_requested_gc(heap->gc_cause());
835
836 // Check if all live objs are larger than old-gen.
837 const bool is_old_gen_overflowing = (total_live_words > old_space->capacity_in_words());
838
839 // JVM flags
840 const uint total_invocations = heap->total_full_collections();
841 assert(total_invocations >= _maximum_compaction_gc_num, "sanity");
842 const size_t gcs_since_max = total_invocations - _maximum_compaction_gc_num;
843 const bool is_interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
844
845 // If all regions in old-gen are full
846 const bool is_region_full =
847 full_region_prefix_end >= _summary_data.region_align_down(old_space->top());
848
849 if (is_max_on_system_gc || is_old_gen_overflowing || is_interval_ended || is_region_full) {
850 _maximum_compaction_gc_num = total_invocations;
851 return true;
852 }
853
854 return false;
855 }
856
857 void PSParallelCompact::summary_phase()
858 {
859 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
860
861 MutableSpace* const old_space = _space_info[old_space_id].space();
862 {
863 size_t total_live_words = 0;
864 HeapWord* full_region_prefix_end = nullptr;
865 {
866 // old-gen
867 size_t live_words = _summary_data.live_words_in_space(old_space,
868 &full_region_prefix_end);
869 total_live_words += live_words;
870 }
871 // young-gen
872 for (uint i = eden_space_id; i < last_space_id; ++i) {
873 const MutableSpace* space = _space_info[i].space();
874 size_t live_words = _summary_data.live_words_in_space(space);
875 total_live_words += live_words;
876 _space_info[i].set_new_top(space->bottom() + live_words);
877 _space_info[i].set_dense_prefix(space->bottom());
878 }
879
880 bool maximum_compaction = check_maximum_compaction(total_live_words,
881 old_space,
882 full_region_prefix_end);
883 HeapWord* dense_prefix_end =
884 maximum_compaction ? full_region_prefix_end
885 : compute_dense_prefix_for_old_space(old_space,
886 full_region_prefix_end);
887 SpaceId id = old_space_id;
888 _space_info[id].set_dense_prefix(dense_prefix_end);
889
890 if (dense_prefix_end != old_space->bottom()) {
891 fill_dense_prefix_end(id);
892 _summary_data.summarize_dense_prefix(old_space->bottom(), dense_prefix_end);
893 }
894 _summary_data.summarize(_space_info[id].split_info(),
895 dense_prefix_end, old_space->top(), nullptr,
896 dense_prefix_end, old_space->end(),
897 _space_info[id].new_top_addr());
898 }
899
900 // Summarize the remaining spaces in the young gen. The initial target space
901 // is the old gen. If a space does not fit entirely into the target, then the
902 // remainder is compacted into the space itself and that space becomes the new
903 // target.
904 SpaceId dst_space_id = old_space_id;
905 HeapWord* dst_space_end = old_space->end();
906 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
907 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
908 const MutableSpace* space = _space_info[id].space();
909 const size_t live = pointer_delta(_space_info[id].new_top(),
910 space->bottom());
911 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
912
913 if (live > 0 && live <= available) {
914 // All the live data will fit.
915 bool done = _summary_data.summarize(_space_info[id].split_info(),
916 space->bottom(), space->top(),
917 nullptr,
918 *new_top_addr, dst_space_end,
919 new_top_addr);
920 assert(done, "space must fit into old gen");
921
922 // Reset the new_top value for the space.
923 _space_info[id].set_new_top(space->bottom());
924 } else if (live > 0) {
925 // Attempt to fit part of the source space into the target space.
926 HeapWord* next_src_addr = nullptr;
927 bool done = _summary_data.summarize(_space_info[id].split_info(),
928 space->bottom(), space->top(),
929 &next_src_addr,
930 *new_top_addr, dst_space_end,
931 new_top_addr);
932 assert(!done, "space should not fit into old gen");
933 assert(next_src_addr != nullptr, "sanity");
934
935 // The source space becomes the new target, so the remainder is compacted
936 // within the space itself.
937 dst_space_id = SpaceId(id);
938 dst_space_end = space->end();
939 new_top_addr = _space_info[id].new_top_addr();
940 done = _summary_data.summarize(_space_info[id].split_info(),
941 next_src_addr, space->top(),
942 nullptr,
943 space->bottom(), dst_space_end,
944 new_top_addr);
945 assert(done, "space must fit when compacted into itself");
946 assert(*new_top_addr <= space->top(), "usage should not grow");
947 }
948 }
949 }
950
951 // This method should contain all heap-specific policy for invoking a full
952 // collection. invoke_no_policy() will only attempt to compact the heap; it
953 // will do nothing further. If we need to bail out for policy reasons, scavenge
954 // before full gc, or any other specialized behavior, it needs to be added here.
955 //
956 // Note that this method should only be called from the vm_thread while at a
957 // safepoint.
958 //
959 // Note that the all_soft_refs_clear flag in the soft ref policy
960 // may be true because this method can be called without intervening
961 // activity. For example when the heap space is tight and full measure
962 // are being taken to free space.
963 bool PSParallelCompact::invoke(bool clear_all_soft_refs) {
964 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
965 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
966 "should be in vm thread");
967
968 SvcGCMarker sgcm(SvcGCMarker::FULL);
969 IsSTWGCActiveMark mark;
970
971 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
972 clear_all_soft_refs = clear_all_soft_refs
973 || heap->soft_ref_policy()->should_clear_all_soft_refs();
974
975 return PSParallelCompact::invoke_no_policy(clear_all_soft_refs);
976 }
977
978 // This method contains no policy. You should probably
979 // be calling invoke() instead.
980 bool PSParallelCompact::invoke_no_policy(bool clear_all_soft_refs) {
981 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
982 assert(ref_processor() != nullptr, "Sanity");
983
984 if (GCLocker::check_active_before_gc()) {
985 return false;
986 }
987
988 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
989
990 GCIdMark gc_id_mark;
991 _gc_timer.register_gc_start();
992 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
993
994 GCCause::Cause gc_cause = heap->gc_cause();
995 PSYoungGen* young_gen = heap->young_gen();
996 PSOldGen* old_gen = heap->old_gen();
997 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
998
999 // The scope of casr should end after code that can change
1000 // SoftRefPolicy::_should_clear_all_soft_refs.
1001 ClearedAllSoftRefs casr(clear_all_soft_refs,
1002 heap->soft_ref_policy());
1003
1004 // Make sure data structures are sane, make the heap parsable, and do other
1005 // miscellaneous bookkeeping.
1006 pre_compact();
1007
1008 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1009
1010 {
1011 const uint active_workers =
1012 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().max_workers(),
1013 ParallelScavengeHeap::heap()->workers().active_workers(),
1014 Threads::number_of_non_daemon_threads());
1015 ParallelScavengeHeap::heap()->workers().set_active_workers(active_workers);
1016
1017 GCTraceCPUTime tcpu(&_gc_tracer);
1018 GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause, true);
1019
1020 heap->pre_full_gc_dump(&_gc_timer);
1021
1022 TraceCollectorStats tcs(counters());
1023 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause, "end of major GC");
1024
1025 if (log_is_enabled(Debug, gc, heap, exit)) {
1026 accumulated_time()->start();
1027 }
1028
1029 // Let the size policy know we're starting
1030 size_policy->major_collection_begin();
1031
1032 #if COMPILER2_OR_JVMCI
1033 DerivedPointerTable::clear();
1034 #endif
1035
1036 ref_processor()->start_discovery(clear_all_soft_refs);
1037
1038 ClassUnloadingContext ctx(1 /* num_nmethod_unlink_workers */,
1039 false /* unregister_nmethods_during_purge */,
1040 false /* lock_nmethod_free_separately */);
1041
1042 marking_phase(&_gc_tracer);
1043
1044 summary_phase();
1045
1046 #if COMPILER2_OR_JVMCI
1047 assert(DerivedPointerTable::is_active(), "Sanity");
1048 DerivedPointerTable::set_active(false);
1049 #endif
1050
1051 forward_to_new_addr();
1052
1053 adjust_pointers();
1054
1055 compact();
1056
1057 ParCompactionManager::_preserved_marks_set->restore(&ParallelScavengeHeap::heap()->workers());
1058
1059 ParCompactionManager::verify_all_region_stack_empty();
1060
1061 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1062 // done before resizing.
1063 post_compact();
1064
1065 // Let the size policy know we're done
1066 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1067
1068 if (UseAdaptiveSizePolicy) {
1069 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1070 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1071 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1072
1073 // Don't check if the size_policy is ready here. Let
1074 // the size_policy check that internally.
1075 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1076 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1077 // Swap the survivor spaces if from_space is empty. The
1078 // resize_young_gen() called below is normally used after
1079 // a successful young GC and swapping of survivor spaces;
1080 // otherwise, it will fail to resize the young gen with
1081 // the current implementation.
1082 if (young_gen->from_space()->is_empty()) {
1083 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1084 young_gen->swap_spaces();
1085 }
1086
1087 // Calculate optimal free space amounts
1088 assert(young_gen->max_gen_size() >
1089 young_gen->from_space()->capacity_in_bytes() +
1090 young_gen->to_space()->capacity_in_bytes(),
1091 "Sizes of space in young gen are out-of-bounds");
1092
1093 size_t young_live = young_gen->used_in_bytes();
1094 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1095 size_t old_live = old_gen->used_in_bytes();
1096 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1097 size_t max_old_gen_size = old_gen->max_gen_size();
1098 size_t max_eden_size = young_gen->max_gen_size() -
1099 young_gen->from_space()->capacity_in_bytes() -
1100 young_gen->to_space()->capacity_in_bytes();
1101
1102 // Used for diagnostics
1103 size_policy->clear_generation_free_space_flags();
1104
1105 size_policy->compute_generations_free_space(young_live,
1106 eden_live,
1107 old_live,
1108 cur_eden,
1109 max_old_gen_size,
1110 max_eden_size,
1111 true /* full gc*/);
1112
1113 size_policy->check_gc_overhead_limit(eden_live,
1114 max_old_gen_size,
1115 max_eden_size,
1116 true /* full gc*/,
1117 gc_cause,
1118 heap->soft_ref_policy());
1119
1120 size_policy->decay_supplemental_growth(true /* full gc*/);
1121
1122 heap->resize_old_gen(
1123 size_policy->calculated_old_free_size_in_bytes());
1124
1125 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1126 size_policy->calculated_survivor_size_in_bytes());
1127 }
1128
1129 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1130 }
1131
1132 if (UsePerfData) {
1133 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1134 counters->update_counters();
1135 counters->update_old_capacity(old_gen->capacity_in_bytes());
1136 counters->update_young_capacity(young_gen->capacity_in_bytes());
1137 }
1138
1139 heap->resize_all_tlabs();
1140
1141 // Resize the metaspace capacity after a collection
1142 MetaspaceGC::compute_new_size();
1143
1144 if (log_is_enabled(Debug, gc, heap, exit)) {
1145 accumulated_time()->stop();
1146 }
1147
1148 heap->print_heap_change(pre_gc_values);
1149
1150 // Track memory usage and detect low memory
1151 MemoryService::track_memory_usage();
1152 heap->update_counters();
1153
1154 heap->post_full_gc_dump(&_gc_timer);
1155 }
1156
1157 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1158 Universe::verify("After GC");
1159 }
1160
1161 heap->print_heap_after_gc();
1162 heap->trace_heap_after_gc(&_gc_tracer);
1163
1164 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1165
1166 _gc_timer.register_gc_end();
1167
1168 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1169 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1170
1171 return true;
1172 }
1173
1174 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1175 private:
1176 uint _worker_id;
1177
1178 public:
1179 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1180 void do_thread(Thread* thread) {
1181 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1182
1183 ResourceMark rm;
1184
1185 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1186
1187 MarkingNMethodClosure mark_and_push_in_blobs(&cm->_mark_and_push_closure,
1188 !NMethodToOopClosure::FixRelocations,
1189 true /* keepalive nmethods */);
1190
1191 thread->oops_do(&cm->_mark_and_push_closure, &mark_and_push_in_blobs);
1192
1193 // Do the real work
1194 cm->follow_marking_stacks();
1195 }
1196 };
1197
1198 void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
1199 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1200
1201 ParCompactionManager* cm =
1202 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1203
1204 do {
1205 oop obj = nullptr;
1206 ObjArrayTask task;
1207 if (ParCompactionManager::steal_objarray(worker_id, task)) {
1208 cm->follow_array((objArrayOop)task.obj(), task.index());
1209 } else if (ParCompactionManager::steal(worker_id, obj)) {
1210 cm->follow_contents(obj);
1211 }
1212 cm->follow_marking_stacks();
1213 } while (!terminator.offer_termination());
1214 }
1215
1216 class MarkFromRootsTask : public WorkerTask {
1217 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
1218 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
1219 TaskTerminator _terminator;
1220 uint _active_workers;
1221
1222 public:
1223 MarkFromRootsTask(uint active_workers) :
1224 WorkerTask("MarkFromRootsTask"),
1225 _strong_roots_scope(active_workers),
1226 _terminator(active_workers, ParCompactionManager::oop_task_queues()),
1227 _active_workers(active_workers) {}
1228
1229 virtual void work(uint worker_id) {
1230 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1231 cm->create_marking_stats_cache();
1232 {
1233 CLDToOopClosure cld_closure(&cm->_mark_and_push_closure, ClassLoaderData::_claim_stw_fullgc_mark);
1234 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
1235
1236 // Do the real work
1237 cm->follow_marking_stacks();
1238 }
1239
1240 {
1241 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
1242 Threads::possibly_parallel_threads_do(_active_workers > 1 /* is_par */, &closure);
1243 }
1244
1245 // Mark from OopStorages
1246 {
1247 _oop_storage_set_par_state.oops_do(&cm->_mark_and_push_closure);
1248 // Do the real work
1249 cm->follow_marking_stacks();
1250 }
1251
1252 if (_active_workers > 1) {
1253 steal_marking_work(_terminator, worker_id);
1254 }
1255 }
1256 };
1257
1258 class ParallelCompactRefProcProxyTask : public RefProcProxyTask {
1259 TaskTerminator _terminator;
1260
1261 public:
1262 ParallelCompactRefProcProxyTask(uint max_workers)
1263 : RefProcProxyTask("ParallelCompactRefProcProxyTask", max_workers),
1264 _terminator(_max_workers, ParCompactionManager::oop_task_queues()) {}
1265
1266 void work(uint worker_id) override {
1267 assert(worker_id < _max_workers, "sanity");
1268 ParCompactionManager* cm = (_tm == RefProcThreadModel::Single) ? ParCompactionManager::get_vmthread_cm() : ParCompactionManager::gc_thread_compaction_manager(worker_id);
1269 BarrierEnqueueDiscoveredFieldClosure enqueue;
1270 ParCompactionManager::FollowStackClosure complete_gc(cm, (_tm == RefProcThreadModel::Single) ? nullptr : &_terminator, worker_id);
1271 _rp_task->rp_work(worker_id, PSParallelCompact::is_alive_closure(), &cm->_mark_and_push_closure, &enqueue, &complete_gc);
1272 }
1273
1274 void prepare_run_task_hook() override {
1275 _terminator.reset_for_reuse(_queue_count);
1276 }
1277 };
1278
1279 static void flush_marking_stats_cache(const uint num_workers) {
1280 for (uint i = 0; i < num_workers; ++i) {
1281 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(i);
1282 cm->flush_and_destroy_marking_stats_cache();
1283 }
1284 }
1285
1286 void PSParallelCompact::marking_phase(ParallelOldTracer *gc_tracer) {
1287 // Recursively traverse all live objects and mark them
1288 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
1289
1290 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1291
1292 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_mark);
1293 {
1294 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
1295
1296 MarkFromRootsTask task(active_gc_threads);
1297 ParallelScavengeHeap::heap()->workers().run_task(&task);
1298 }
1299
1300 // Process reference objects found during marking
1301 {
1302 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
1303
1304 ReferenceProcessorStats stats;
1305 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
1306
1307 ref_processor()->set_active_mt_degree(active_gc_threads);
1308 ParallelCompactRefProcProxyTask task(ref_processor()->max_num_queues());
1309 stats = ref_processor()->process_discovered_references(task, pt);
1310
1311 gc_tracer->report_gc_reference_stats(stats);
1312 pt.print_all_references();
1313 }
1314
1315 {
1316 GCTraceTime(Debug, gc, phases) tm("Flush Marking Stats", &_gc_timer);
1317
1318 flush_marking_stats_cache(active_gc_threads);
1319 }
1320
1321 // This is the point where the entire marking should have completed.
1322 ParCompactionManager::verify_all_marking_stack_empty();
1323
1324 {
1325 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
1326 WeakProcessor::weak_oops_do(&ParallelScavengeHeap::heap()->workers(),
1327 is_alive_closure(),
1328 &do_nothing_cl,
1329 1);
1330 }
1331
1332 {
1333 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
1334
1335 ClassUnloadingContext* ctx = ClassUnloadingContext::context();
1336
1337 bool unloading_occurred;
1338 {
1339 CodeCache::UnlinkingScope scope(is_alive_closure());
1340
1341 // Follow system dictionary roots and unload classes.
1342 unloading_occurred = SystemDictionary::do_unloading(&_gc_timer);
1343
1344 // Unload nmethods.
1345 CodeCache::do_unloading(unloading_occurred);
1346 }
1347
1348 {
1349 GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", gc_timer());
1350 // Release unloaded nmethod's memory.
1351 ctx->purge_nmethods();
1352 }
1353 {
1354 GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", &_gc_timer);
1355 ParallelScavengeHeap::heap()->prune_unlinked_nmethods();
1356 }
1357 {
1358 GCTraceTime(Debug, gc, phases) t("Free Code Blobs", gc_timer());
1359 ctx->free_nmethods();
1360 }
1361
1362 // Prune dead klasses from subklass/sibling/implementor lists.
1363 Klass::clean_weak_klass_links(unloading_occurred);
1364
1365 // Clean JVMCI metadata handles.
1366 JVMCI_ONLY(JVMCI::do_unloading(unloading_occurred));
1367 }
1368
1369 {
1370 GCTraceTime(Debug, gc, phases) tm("Report Object Count", &_gc_timer);
1371 _gc_tracer.report_object_count_after_gc(is_alive_closure(), &ParallelScavengeHeap::heap()->workers());
1372 }
1373 #if TASKQUEUE_STATS
1374 ParCompactionManager::oop_task_queues()->print_and_reset_taskqueue_stats("Oop Queue");
1375 ParCompactionManager::_objarray_task_queues->print_and_reset_taskqueue_stats("ObjArrayOop Queue");
1376 #endif
1377 }
1378
1379 template<typename Func>
1380 void PSParallelCompact::adjust_in_space_helper(SpaceId id, volatile uint* claim_counter, Func&& on_stripe) {
1381 MutableSpace* sp = PSParallelCompact::space(id);
1382 HeapWord* const bottom = sp->bottom();
1383 HeapWord* const top = sp->top();
1384 if (bottom == top) {
1385 return;
1386 }
1387
1388 const uint num_regions_per_stripe = 2;
1389 const size_t region_size = ParallelCompactData::RegionSize;
1390 const size_t stripe_size = num_regions_per_stripe * region_size;
1391
1392 while (true) {
1393 uint counter = Atomic::fetch_then_add(claim_counter, num_regions_per_stripe);
1394 HeapWord* cur_stripe = bottom + counter * region_size;
1395 if (cur_stripe >= top) {
1396 break;
1397 }
1398 HeapWord* stripe_end = MIN2(cur_stripe + stripe_size, top);
1399 on_stripe(cur_stripe, stripe_end);
1400 }
1401 }
1402
1403 void PSParallelCompact::adjust_in_old_space(volatile uint* claim_counter) {
1404 // Regions in old-space shouldn't be split.
1405 assert(!_space_info[old_space_id].split_info().is_valid(), "inv");
1406
1407 auto scan_obj_with_limit = [&] (HeapWord* obj_start, HeapWord* left, HeapWord* right) {
1408 assert(mark_bitmap()->is_marked(obj_start), "inv");
1409 oop obj = cast_to_oop(obj_start);
1410 return obj->oop_iterate_size(&pc_adjust_pointer_closure, MemRegion(left, right));
1411 };
1412
1413 adjust_in_space_helper(old_space_id, claim_counter, [&] (HeapWord* stripe_start, HeapWord* stripe_end) {
1414 assert(_summary_data.is_region_aligned(stripe_start), "inv");
1415 RegionData* cur_region = _summary_data.addr_to_region_ptr(stripe_start);
1416 HeapWord* obj_start;
1417 if (cur_region->partial_obj_size() != 0) {
1418 obj_start = cur_region->partial_obj_addr();
1419 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1420 } else {
1421 obj_start = stripe_start;
1422 }
1423
1424 while (obj_start < stripe_end) {
1425 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1426 if (obj_start >= stripe_end) {
1427 break;
1428 }
1429 obj_start += scan_obj_with_limit(obj_start, stripe_start, stripe_end);
1430 }
1431 });
1432 }
1433
1434 void PSParallelCompact::adjust_in_young_space(SpaceId id, volatile uint* claim_counter) {
1435 adjust_in_space_helper(id, claim_counter, [](HeapWord* stripe_start, HeapWord* stripe_end) {
1436 HeapWord* obj_start = stripe_start;
1437 while (obj_start < stripe_end) {
1438 obj_start = mark_bitmap()->find_obj_beg(obj_start, stripe_end);
1439 if (obj_start >= stripe_end) {
1440 break;
1441 }
1442 oop obj = cast_to_oop(obj_start);
1443 obj_start += obj->oop_iterate_size(&pc_adjust_pointer_closure);
1444 }
1445 });
1446 }
1447
1448 void PSParallelCompact::adjust_pointers_in_spaces(uint worker_id, volatile uint* claim_counters) {
1449 auto start_time = Ticks::now();
1450 adjust_in_old_space(&claim_counters[0]);
1451 for (uint id = eden_space_id; id < last_space_id; ++id) {
1452 adjust_in_young_space(SpaceId(id), &claim_counters[id]);
1453 }
1454 log_trace(gc, phases)("adjust_pointers_in_spaces worker %u: %.3f ms", worker_id, (Ticks::now() - start_time).seconds() * 1000);
1455 }
1456
1457 class PSAdjustTask final : public WorkerTask {
1458 SubTasksDone _sub_tasks;
1459 WeakProcessor::Task _weak_proc_task;
1460 OopStorageSetStrongParState<false, false> _oop_storage_iter;
1461 uint _nworkers;
1462 volatile uint _claim_counters[PSParallelCompact::last_space_id] = {};
1463
1464 enum PSAdjustSubTask {
1465 PSAdjustSubTask_code_cache,
1466
1467 PSAdjustSubTask_num_elements
1468 };
1469
1470 public:
1471 PSAdjustTask(uint nworkers) :
1472 WorkerTask("PSAdjust task"),
1473 _sub_tasks(PSAdjustSubTask_num_elements),
1474 _weak_proc_task(nworkers),
1475 _nworkers(nworkers) {
1476
1477 ClassLoaderDataGraph::verify_claimed_marks_cleared(ClassLoaderData::_claim_stw_fullgc_adjust);
1478 if (nworkers > 1) {
1479 Threads::change_thread_claim_token();
1480 }
1481 }
1482
1483 ~PSAdjustTask() {
1484 Threads::assert_all_threads_claimed();
1485 }
1486
1487 void work(uint worker_id) {
1488 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1489 cm->preserved_marks()->adjust_during_full_gc();
1490 {
1491 // adjust pointers in all spaces
1492 PSParallelCompact::adjust_pointers_in_spaces(worker_id, _claim_counters);
1493 }
1494 {
1495 ResourceMark rm;
1496 Threads::possibly_parallel_oops_do(_nworkers > 1, &pc_adjust_pointer_closure, nullptr);
1497 }
1498 _oop_storage_iter.oops_do(&pc_adjust_pointer_closure);
1499 {
1500 CLDToOopClosure cld_closure(&pc_adjust_pointer_closure, ClassLoaderData::_claim_stw_fullgc_adjust);
1501 ClassLoaderDataGraph::cld_do(&cld_closure);
1502 }
1503 {
1504 AlwaysTrueClosure always_alive;
1505 _weak_proc_task.work(worker_id, &always_alive, &pc_adjust_pointer_closure);
1506 }
1507 if (_sub_tasks.try_claim_task(PSAdjustSubTask_code_cache)) {
1508 NMethodToOopClosure adjust_code(&pc_adjust_pointer_closure, NMethodToOopClosure::FixRelocations);
1509 CodeCache::nmethods_do(&adjust_code);
1510 }
1511 _sub_tasks.all_tasks_claimed();
1512 }
1513 };
1514
1515 void PSParallelCompact::adjust_pointers() {
1516 // Adjust the pointers to reflect the new locations
1517 GCTraceTime(Info, gc, phases) tm("Adjust Pointers", &_gc_timer);
1518 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1519 PSAdjustTask task(nworkers);
1520 ParallelScavengeHeap::heap()->workers().run_task(&task);
1521 }
1522
1523 // Split [start, end) evenly for a number of workers and return the
1524 // range for worker_id.
1525 static void split_regions_for_worker(size_t start, size_t end,
1526 uint worker_id, uint num_workers,
1527 size_t* worker_start, size_t* worker_end) {
1528 assert(start < end, "precondition");
1529 assert(num_workers > 0, "precondition");
1530 assert(worker_id < num_workers, "precondition");
1531
1532 size_t num_regions = end - start;
1533 size_t num_regions_per_worker = num_regions / num_workers;
1534 size_t remainder = num_regions % num_workers;
1535 // The first few workers will get one extra.
1536 *worker_start = start + worker_id * num_regions_per_worker
1537 + MIN2(checked_cast<size_t>(worker_id), remainder);
1538 *worker_end = *worker_start + num_regions_per_worker
1539 + (worker_id < remainder ? 1 : 0);
1540 }
1541
1542 void PSParallelCompact::forward_to_new_addr() {
1543 GCTraceTime(Info, gc, phases) tm("Forward", &_gc_timer);
1544 uint nworkers = ParallelScavengeHeap::heap()->workers().active_workers();
1545
1546 struct ForwardTask final : public WorkerTask {
1547 uint _num_workers;
1548
1549 explicit ForwardTask(uint num_workers) :
1550 WorkerTask("PSForward task"),
1551 _num_workers(num_workers) {}
1552
1553 void work(uint worker_id) override {
1554 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1555 for (uint id = old_space_id; id < last_space_id; ++id) {
1556 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1557 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1558 HeapWord* top = sp->top();
1559
1560 if (dense_prefix_addr == top) {
1561 continue;
1562 }
1563
1564 size_t dense_prefix_region = _summary_data.addr_to_region_idx(dense_prefix_addr);
1565 size_t top_region = _summary_data.addr_to_region_idx(_summary_data.region_align_up(top));
1566 size_t start_region;
1567 size_t end_region;
1568 split_regions_for_worker(dense_prefix_region, top_region,
1569 worker_id, _num_workers,
1570 &start_region, &end_region);
1571 for (size_t cur_region = start_region; cur_region < end_region; ++cur_region) {
1572 RegionData* region_ptr = _summary_data.region(cur_region);
1573 size_t live_words = region_ptr->partial_obj_size();
1574
1575 if (live_words == ParallelCompactData::RegionSize) {
1576 // No obj-start
1577 continue;
1578 }
1579
1580 HeapWord* region_start = _summary_data.region_to_addr(cur_region);
1581 HeapWord* region_end = region_start + ParallelCompactData::RegionSize;
1582
1583 HeapWord* cur_addr = region_start + live_words;
1584
1585 HeapWord* destination = region_ptr->destination();
1586 while (cur_addr < region_end) {
1587 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, region_end);
1588 if (cur_addr >= region_end) {
1589 break;
1590 }
1591 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1592 HeapWord* new_addr = destination + live_words;
1593 oop obj = cast_to_oop(cur_addr);
1594 if (new_addr != cur_addr) {
1595 cm->preserved_marks()->push_if_necessary(obj, obj->mark());
1596 obj->forward_to(cast_to_oop(new_addr));
1597 }
1598 size_t obj_size = obj->size();
1599 live_words += obj_size;
1600 cur_addr += obj_size;
1601 }
1602 }
1603 }
1604 }
1605 } task(nworkers);
1606
1607 ParallelScavengeHeap::heap()->workers().run_task(&task);
1608 debug_only(verify_forward();)
1609 }
1610
1611 #ifdef ASSERT
1612 void PSParallelCompact::verify_forward() {
1613 HeapWord* old_dense_prefix_addr = dense_prefix(SpaceId(old_space_id));
1614 RegionData* old_region = _summary_data.region(_summary_data.addr_to_region_idx(old_dense_prefix_addr));
1615 HeapWord* bump_ptr = old_region->partial_obj_size() != 0
1616 ? old_dense_prefix_addr + old_region->partial_obj_size()
1617 : old_dense_prefix_addr;
1618 SpaceId bump_ptr_space = old_space_id;
1619
1620 for (uint id = old_space_id; id < last_space_id; ++id) {
1621 MutableSpace* sp = PSParallelCompact::space(SpaceId(id));
1622 HeapWord* dense_prefix_addr = dense_prefix(SpaceId(id));
1623 HeapWord* top = sp->top();
1624 HeapWord* cur_addr = dense_prefix_addr;
1625
1626 while (cur_addr < top) {
1627 cur_addr = mark_bitmap()->find_obj_beg(cur_addr, top);
1628 if (cur_addr >= top) {
1629 break;
1630 }
1631 assert(mark_bitmap()->is_marked(cur_addr), "inv");
1632 // Move to the space containing cur_addr
1633 if (bump_ptr == _space_info[bump_ptr_space].new_top()) {
1634 bump_ptr = space(space_id(cur_addr))->bottom();
1635 bump_ptr_space = space_id(bump_ptr);
1636 }
1637 oop obj = cast_to_oop(cur_addr);
1638 if (cur_addr != bump_ptr) {
1639 assert(obj->forwardee() == cast_to_oop(bump_ptr), "inv");
1640 }
1641 bump_ptr += obj->size();
1642 cur_addr += obj->size();
1643 }
1644 }
1645 }
1646 #endif
1647
1648 // Helper class to print 8 region numbers per line and then print the total at the end.
1649 class FillableRegionLogger : public StackObj {
1650 private:
1651 Log(gc, compaction) log;
1652 static const int LineLength = 8;
1653 size_t _regions[LineLength];
1654 int _next_index;
1655 bool _enabled;
1656 size_t _total_regions;
1657 public:
1658 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
1659 ~FillableRegionLogger() {
1660 log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
1661 }
1662
1663 void print_line() {
1664 if (!_enabled || _next_index == 0) {
1665 return;
1666 }
1667 FormatBuffer<> line("Fillable: ");
1668 for (int i = 0; i < _next_index; i++) {
1669 line.append(" " SIZE_FORMAT_W(7), _regions[i]);
1670 }
1671 log.trace("%s", line.buffer());
1672 _next_index = 0;
1673 }
1674
1675 void handle(size_t region) {
1676 if (!_enabled) {
1677 return;
1678 }
1679 _regions[_next_index++] = region;
1680 if (_next_index == LineLength) {
1681 print_line();
1682 }
1683 _total_regions++;
1684 }
1685 };
1686
1687 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
1688 {
1689 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
1690
1691 // Find the threads that are active
1692 uint worker_id = 0;
1693
1694 // Find all regions that are available (can be filled immediately) and
1695 // distribute them to the thread stacks. The iteration is done in reverse
1696 // order (high to low) so the regions will be removed in ascending order.
1697
1698 const ParallelCompactData& sd = PSParallelCompact::summary_data();
1699
1700 // id + 1 is used to test termination so unsigned can
1701 // be used with an old_space_id == 0.
1702 FillableRegionLogger region_logger;
1703 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
1704 SpaceInfo* const space_info = _space_info + id;
1705 HeapWord* const new_top = space_info->new_top();
1706
1707 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
1708 const size_t end_region =
1709 sd.addr_to_region_idx(sd.region_align_up(new_top));
1710
1711 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
1712 if (sd.region(cur)->claim_unsafe()) {
1713 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
1714 bool result = sd.region(cur)->mark_normal();
1715 assert(result, "Must succeed at this point.");
1716 cm->region_stack()->push(cur);
1717 region_logger.handle(cur);
1718 // Assign regions to tasks in round-robin fashion.
1719 if (++worker_id == parallel_gc_threads) {
1720 worker_id = 0;
1721 }
1722 }
1723 }
1724 region_logger.print_line();
1725 }
1726 }
1727
1728 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
1729 assert(ParallelScavengeHeap::heap()->is_stw_gc_active(), "called outside gc");
1730
1731 ParCompactionManager* cm =
1732 ParCompactionManager::gc_thread_compaction_manager(worker_id);
1733
1734 // Drain the stacks that have been preloaded with regions
1735 // that are ready to fill.
1736
1737 cm->drain_region_stacks();
1738
1739 guarantee(cm->region_stack()->is_empty(), "Not empty");
1740
1741 size_t region_index = 0;
1742
1743 while (true) {
1744 if (ParCompactionManager::steal(worker_id, region_index)) {
1745 PSParallelCompact::fill_and_update_region(cm, region_index);
1746 cm->drain_region_stacks();
1747 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
1748 // Fill and update an unavailable region with the help of a shadow region
1749 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
1750 cm->drain_region_stacks();
1751 } else {
1752 if (terminator->offer_termination()) {
1753 break;
1754 }
1755 // Go around again.
1756 }
1757 }
1758 }
1759
1760 class FillDensePrefixAndCompactionTask: public WorkerTask {
1761 uint _num_workers;
1762 TaskTerminator _terminator;
1763
1764 public:
1765 FillDensePrefixAndCompactionTask(uint active_workers) :
1766 WorkerTask("FillDensePrefixAndCompactionTask"),
1767 _num_workers(active_workers),
1768 _terminator(active_workers, ParCompactionManager::region_task_queues()) {
1769 }
1770
1771 virtual void work(uint worker_id) {
1772 {
1773 auto start = Ticks::now();
1774 PSParallelCompact::fill_dead_objs_in_dense_prefix(worker_id, _num_workers);
1775 log_trace(gc, phases)("Fill dense prefix by worker %u: %.3f ms", worker_id, (Ticks::now() - start).seconds() * 1000);
1776 }
1777 compaction_with_stealing_work(&_terminator, worker_id);
1778 }
1779 };
1780
1781 void PSParallelCompact::fill_range_in_dense_prefix(HeapWord* start, HeapWord* end) {
1782 #ifdef ASSERT
1783 {
1784 assert(start < end, "precondition");
1785 assert(mark_bitmap()->find_obj_beg(start, end) == end, "precondition");
1786 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1787 if (start != bottom) {
1788 HeapWord* obj_start = mark_bitmap()->find_obj_beg_reverse(bottom, start);
1789 HeapWord* after_obj = obj_start + cast_to_oop(obj_start)->size();
1790 assert(after_obj == start, "precondition");
1791 }
1792 }
1793 #endif
1794
1795 CollectedHeap::fill_with_objects(start, pointer_delta(end, start));
1796 HeapWord* addr = start;
1797 do {
1798 size_t size = cast_to_oop(addr)->size();
1799 start_array(old_space_id)->update_for_block(addr, addr + size);
1800 addr += size;
1801 } while (addr < end);
1802 }
1803
1804 void PSParallelCompact::fill_dead_objs_in_dense_prefix(uint worker_id, uint num_workers) {
1805 ParMarkBitMap* bitmap = mark_bitmap();
1806
1807 HeapWord* const bottom = _space_info[old_space_id].space()->bottom();
1808 HeapWord* const prefix_end = dense_prefix(old_space_id);
1809
1810 if (bottom == prefix_end) {
1811 return;
1812 }
1813
1814 size_t bottom_region = _summary_data.addr_to_region_idx(bottom);
1815 size_t prefix_end_region = _summary_data.addr_to_region_idx(prefix_end);
1816
1817 size_t start_region;
1818 size_t end_region;
1819 split_regions_for_worker(bottom_region, prefix_end_region,
1820 worker_id, num_workers,
1821 &start_region, &end_region);
1822
1823 if (start_region == end_region) {
1824 return;
1825 }
1826
1827 HeapWord* const start_addr = _summary_data.region_to_addr(start_region);
1828 HeapWord* const end_addr = _summary_data.region_to_addr(end_region);
1829
1830 // Skip live partial obj (if any) from previous region.
1831 HeapWord* cur_addr;
1832 RegionData* start_region_ptr = _summary_data.region(start_region);
1833 if (start_region_ptr->partial_obj_size() != 0) {
1834 HeapWord* partial_obj_start = start_region_ptr->partial_obj_addr();
1835 assert(bitmap->is_marked(partial_obj_start), "inv");
1836 cur_addr = partial_obj_start + cast_to_oop(partial_obj_start)->size();
1837 } else {
1838 cur_addr = start_addr;
1839 }
1840
1841 // end_addr is inclusive to handle regions starting with dead space.
1842 while (cur_addr <= end_addr) {
1843 // Use prefix_end to handle trailing obj in each worker region-chunk.
1844 HeapWord* live_start = bitmap->find_obj_beg(cur_addr, prefix_end);
1845 if (cur_addr != live_start) {
1846 // Only worker 0 handles proceeding dead space.
1847 if (cur_addr != start_addr || worker_id == 0) {
1848 fill_range_in_dense_prefix(cur_addr, live_start);
1849 }
1850 }
1851 if (live_start >= end_addr) {
1852 break;
1853 }
1854 assert(bitmap->is_marked(live_start), "inv");
1855 cur_addr = live_start + cast_to_oop(live_start)->size();
1856 }
1857 }
1858
1859 void PSParallelCompact::compact() {
1860 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
1861
1862 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
1863
1864 initialize_shadow_regions(active_gc_threads);
1865 prepare_region_draining_tasks(active_gc_threads);
1866
1867 {
1868 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
1869
1870 FillDensePrefixAndCompactionTask task(active_gc_threads);
1871 ParallelScavengeHeap::heap()->workers().run_task(&task);
1872
1873 #ifdef ASSERT
1874 verify_filler_in_dense_prefix();
1875
1876 // Verify that all regions have been processed.
1877 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1878 verify_complete(SpaceId(id));
1879 }
1880 #endif
1881 }
1882 }
1883
1884 #ifdef ASSERT
1885 void PSParallelCompact::verify_filler_in_dense_prefix() {
1886 HeapWord* bottom = _space_info[old_space_id].space()->bottom();
1887 HeapWord* dense_prefix_end = dense_prefix(old_space_id);
1888 HeapWord* cur_addr = bottom;
1889 while (cur_addr < dense_prefix_end) {
1890 oop obj = cast_to_oop(cur_addr);
1891 oopDesc::verify(obj);
1892 if (!mark_bitmap()->is_marked(cur_addr)) {
1893 Klass* k = cast_to_oop(cur_addr)->klass_without_asserts();
1894 assert(k == Universe::fillerArrayKlass() || k == vmClasses::FillerObject_klass(), "inv");
1895 }
1896 cur_addr += obj->size();
1897 }
1898 }
1899
1900 void PSParallelCompact::verify_complete(SpaceId space_id) {
1901 // All Regions served as compaction targets, from dense_prefix() to
1902 // new_top(), should be marked as filled and all Regions between new_top()
1903 // and top() should be available (i.e., should have been emptied).
1904 ParallelCompactData& sd = summary_data();
1905 SpaceInfo si = _space_info[space_id];
1906 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
1907 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
1908 const size_t beg_region = sd.addr_to_region_idx(si.dense_prefix());
1909 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
1910 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
1911
1912 size_t cur_region;
1913 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
1914 const RegionData* const c = sd.region(cur_region);
1915 assert(c->completed(), "region %zu not filled: destination_count=%u",
1916 cur_region, c->destination_count());
1917 }
1918
1919 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
1920 const RegionData* const c = sd.region(cur_region);
1921 assert(c->available(), "region %zu not empty: destination_count=%u",
1922 cur_region, c->destination_count());
1923 }
1924 }
1925 #endif // #ifdef ASSERT
1926
1927 // Return the SpaceId for the space containing addr. If addr is not in the
1928 // heap, last_space_id is returned. In debug mode it expects the address to be
1929 // in the heap and asserts such.
1930 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
1931 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
1932
1933 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1934 if (_space_info[id].space()->contains(addr)) {
1935 return SpaceId(id);
1936 }
1937 }
1938
1939 assert(false, "no space contains the addr");
1940 return last_space_id;
1941 }
1942
1943 // Skip over count live words starting from beg, and return the address of the
1944 // next live word. Unless marked, the word corresponding to beg is assumed to
1945 // be dead. Callers must either ensure beg does not correspond to the middle of
1946 // an object, or account for those live words in some other way. Callers must
1947 // also ensure that there are enough live words in the range [beg, end) to skip.
1948 HeapWord*
1949 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
1950 {
1951 assert(count > 0, "sanity");
1952
1953 ParMarkBitMap* m = mark_bitmap();
1954 HeapWord* cur_addr = beg;
1955 while (true) {
1956 cur_addr = m->find_obj_beg(cur_addr, end);
1957 assert(cur_addr < end, "inv");
1958 size_t obj_size = cast_to_oop(cur_addr)->size();
1959 // Strictly greater-than
1960 if (obj_size > count) {
1961 return cur_addr + count;
1962 }
1963 count -= obj_size;
1964 cur_addr += obj_size;
1965 }
1966 }
1967
1968 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
1969 SpaceId src_space_id,
1970 size_t src_region_idx)
1971 {
1972 assert(summary_data().is_region_aligned(dest_addr), "not aligned");
1973
1974 const SplitInfo& split_info = _space_info[src_space_id].split_info();
1975 if (split_info.dest_region_addr() == dest_addr) {
1976 // The partial object ending at the split point contains the first word to
1977 // be copied to dest_addr.
1978 return split_info.first_src_addr();
1979 }
1980
1981 const ParallelCompactData& sd = summary_data();
1982 ParMarkBitMap* const bitmap = mark_bitmap();
1983 const size_t RegionSize = ParallelCompactData::RegionSize;
1984
1985 assert(sd.is_region_aligned(dest_addr), "not aligned");
1986 const RegionData* const src_region_ptr = sd.region(src_region_idx);
1987 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
1988 HeapWord* const src_region_destination = src_region_ptr->destination();
1989
1990 assert(dest_addr >= src_region_destination, "wrong src region");
1991 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
1992
1993 HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
1994 HeapWord* const src_region_end = src_region_beg + RegionSize;
1995
1996 HeapWord* addr = src_region_beg;
1997 if (dest_addr == src_region_destination) {
1998 // Return the first live word in the source region.
1999 if (partial_obj_size == 0) {
2000 addr = bitmap->find_obj_beg(addr, src_region_end);
2001 assert(addr < src_region_end, "no objects start in src region");
2002 }
2003 return addr;
2004 }
2005
2006 // Must skip some live data.
2007 size_t words_to_skip = dest_addr - src_region_destination;
2008 assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2009
2010 if (partial_obj_size >= words_to_skip) {
2011 // All the live words to skip are part of the partial object.
2012 addr += words_to_skip;
2013 if (partial_obj_size == words_to_skip) {
2014 // Find the first live word past the partial object.
2015 addr = bitmap->find_obj_beg(addr, src_region_end);
2016 assert(addr < src_region_end, "wrong src region");
2017 }
2018 return addr;
2019 }
2020
2021 // Skip over the partial object (if any).
2022 if (partial_obj_size != 0) {
2023 words_to_skip -= partial_obj_size;
2024 addr += partial_obj_size;
2025 }
2026
2027 // Skip over live words due to objects that start in the region.
2028 addr = skip_live_words(addr, src_region_end, words_to_skip);
2029 assert(addr < src_region_end, "wrong src region");
2030 return addr;
2031 }
2032
2033 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2034 SpaceId src_space_id,
2035 size_t beg_region,
2036 HeapWord* end_addr)
2037 {
2038 ParallelCompactData& sd = summary_data();
2039
2040 #ifdef ASSERT
2041 MutableSpace* const src_space = _space_info[src_space_id].space();
2042 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2043 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2044 "src_space_id does not match beg_addr");
2045 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2046 "src_space_id does not match end_addr");
2047 #endif // #ifdef ASSERT
2048
2049 RegionData* const beg = sd.region(beg_region);
2050 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2051
2052 // Regions up to new_top() are enqueued if they become available.
2053 HeapWord* const new_top = _space_info[src_space_id].new_top();
2054 RegionData* const enqueue_end =
2055 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2056
2057 for (RegionData* cur = beg; cur < end; ++cur) {
2058 assert(cur->data_size() > 0, "region must have live data");
2059 cur->decrement_destination_count();
2060 if (cur < enqueue_end && cur->available() && cur->claim()) {
2061 if (cur->mark_normal()) {
2062 cm->push_region(sd.region(cur));
2063 } else if (cur->mark_copied()) {
2064 // Try to copy the content of the shadow region back to its corresponding
2065 // heap region if the shadow region is filled. Otherwise, the GC thread
2066 // fills the shadow region will copy the data back (see
2067 // MoveAndUpdateShadowClosure::complete_region).
2068 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2069 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2070 cur->set_completed();
2071 }
2072 }
2073 }
2074 }
2075
2076 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2077 SpaceId& src_space_id,
2078 HeapWord*& src_space_top,
2079 HeapWord* end_addr)
2080 {
2081 typedef ParallelCompactData::RegionData RegionData;
2082
2083 ParallelCompactData& sd = PSParallelCompact::summary_data();
2084 const size_t region_size = ParallelCompactData::RegionSize;
2085
2086 size_t src_region_idx = 0;
2087
2088 // Skip empty regions (if any) up to the top of the space.
2089 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2090 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2091 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2092 const RegionData* const top_region_ptr =
2093 sd.addr_to_region_ptr(top_aligned_up);
2094 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2095 ++src_region_ptr;
2096 }
2097
2098 if (src_region_ptr < top_region_ptr) {
2099 // The next source region is in the current space. Update src_region_idx
2100 // and the source address to match src_region_ptr.
2101 src_region_idx = sd.region(src_region_ptr);
2102 HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2103 if (src_region_addr > closure.source()) {
2104 closure.set_source(src_region_addr);
2105 }
2106 return src_region_idx;
2107 }
2108
2109 // Switch to a new source space and find the first non-empty region.
2110 unsigned int space_id = src_space_id + 1;
2111 assert(space_id < last_space_id, "not enough spaces");
2112
2113 HeapWord* const destination = closure.destination();
2114
2115 do {
2116 MutableSpace* space = _space_info[space_id].space();
2117 HeapWord* const bottom = space->bottom();
2118 const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2119
2120 // Iterate over the spaces that do not compact into themselves.
2121 if (bottom_cp->destination() != bottom) {
2122 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2123 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2124
2125 for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2126 if (src_cp->live_obj_size() > 0) {
2127 // Found it.
2128 assert(src_cp->destination() == destination,
2129 "first live obj in the space must match the destination");
2130 assert(src_cp->partial_obj_size() == 0,
2131 "a space cannot begin with a partial obj");
2132
2133 src_space_id = SpaceId(space_id);
2134 src_space_top = space->top();
2135 const size_t src_region_idx = sd.region(src_cp);
2136 closure.set_source(sd.region_to_addr(src_region_idx));
2137 return src_region_idx;
2138 } else {
2139 assert(src_cp->data_size() == 0, "sanity");
2140 }
2141 }
2142 }
2143 } while (++space_id < last_space_id);
2144
2145 assert(false, "no source region was found");
2146 return 0;
2147 }
2148
2149 HeapWord* PSParallelCompact::partial_obj_end(HeapWord* region_start_addr) {
2150 ParallelCompactData& sd = summary_data();
2151 assert(sd.is_region_aligned(region_start_addr), "precondition");
2152
2153 // Use per-region partial_obj_size to locate the end of the obj, that extends to region_start_addr.
2154 SplitInfo& split_info = _space_info[space_id(region_start_addr)].split_info();
2155 size_t start_region_idx = sd.addr_to_region_idx(region_start_addr);
2156 size_t end_region_idx = sd.region_count();
2157 size_t accumulated_size = 0;
2158 for (size_t region_idx = start_region_idx; region_idx < end_region_idx; ++region_idx) {
2159 if (split_info.is_split(region_idx)) {
2160 accumulated_size += split_info.partial_obj_size();
2161 break;
2162 }
2163 size_t cur_partial_obj_size = sd.region(region_idx)->partial_obj_size();
2164 accumulated_size += cur_partial_obj_size;
2165 if (cur_partial_obj_size != ParallelCompactData::RegionSize) {
2166 break;
2167 }
2168 }
2169 return region_start_addr + accumulated_size;
2170 }
2171
2172 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2173 {
2174 ParMarkBitMap* const bitmap = mark_bitmap();
2175 ParallelCompactData& sd = summary_data();
2176 RegionData* const region_ptr = sd.region(region_idx);
2177
2178 // Get the source region and related info.
2179 size_t src_region_idx = region_ptr->source_region();
2180 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2181 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2182 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2183
2184 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2185
2186 // Adjust src_region_idx to prepare for decrementing destination counts (the
2187 // destination count is not decremented when a region is copied to itself).
2188 if (src_region_idx == region_idx) {
2189 src_region_idx += 1;
2190 }
2191
2192 if (bitmap->is_unmarked(closure.source())) {
2193 // The first source word is in the middle of an object; copy the remainder
2194 // of the object or as much as will fit. The fact that pointer updates were
2195 // deferred will be noted when the object header is processed.
2196 HeapWord* const old_src_addr = closure.source();
2197 {
2198 HeapWord* region_start = sd.region_align_down(closure.source());
2199 HeapWord* obj_start = bitmap->find_obj_beg_reverse(region_start, closure.source());
2200 HeapWord* obj_end;
2201 if (bitmap->is_marked(obj_start)) {
2202 HeapWord* next_region_start = region_start + ParallelCompactData::RegionSize;
2203 HeapWord* partial_obj_start = (next_region_start >= src_space_top)
2204 ? nullptr
2205 : sd.addr_to_region_ptr(next_region_start)->partial_obj_addr();
2206 if (partial_obj_start == obj_start) {
2207 // This obj extends to next region.
2208 obj_end = partial_obj_end(next_region_start);
2209 } else {
2210 // Completely contained in this region; safe to use size().
2211 obj_end = obj_start + cast_to_oop(obj_start)->size();
2212 }
2213 } else {
2214 // This obj extends to current region.
2215 obj_end = partial_obj_end(region_start);
2216 }
2217 size_t partial_obj_size = pointer_delta(obj_end, closure.source());
2218 closure.copy_partial_obj(partial_obj_size);
2219 }
2220
2221 if (closure.is_full()) {
2222 decrement_destination_counts(cm, src_space_id, src_region_idx,
2223 closure.source());
2224 closure.complete_region(dest_addr, region_ptr);
2225 return;
2226 }
2227
2228 HeapWord* const end_addr = sd.region_align_down(closure.source());
2229 if (sd.region_align_down(old_src_addr) != end_addr) {
2230 // The partial object was copied from more than one source region.
2231 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2232
2233 // Move to the next source region, possibly switching spaces as well. All
2234 // args except end_addr may be modified.
2235 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2236 end_addr);
2237 }
2238 }
2239
2240 do {
2241 HeapWord* cur_addr = closure.source();
2242 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
2243 src_space_top);
2244 HeapWord* partial_obj_start = (end_addr == src_space_top)
2245 ? nullptr
2246 : sd.addr_to_region_ptr(end_addr)->partial_obj_addr();
2247 // apply closure on objs inside [cur_addr, end_addr)
2248 do {
2249 cur_addr = bitmap->find_obj_beg(cur_addr, end_addr);
2250 if (cur_addr == end_addr) {
2251 break;
2252 }
2253 size_t obj_size;
2254 if (partial_obj_start == cur_addr) {
2255 obj_size = pointer_delta(partial_obj_end(end_addr), cur_addr);
2256 } else {
2257 // This obj doesn't extend into next region; size() is safe to use.
2258 obj_size = cast_to_oop(cur_addr)->size();
2259 }
2260 closure.do_addr(cur_addr, obj_size);
2261 cur_addr += obj_size;
2262 } while (cur_addr < end_addr && !closure.is_full());
2263
2264 if (closure.is_full()) {
2265 decrement_destination_counts(cm, src_space_id, src_region_idx,
2266 closure.source());
2267 closure.complete_region(dest_addr, region_ptr);
2268 return;
2269 }
2270
2271 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2272
2273 // Move to the next source region, possibly switching spaces as well. All
2274 // args except end_addr may be modified.
2275 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2276 end_addr);
2277 } while (true);
2278 }
2279
2280 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
2281 {
2282 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2283 fill_region(cm, cl, region_idx);
2284 }
2285
2286 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
2287 {
2288 // Get a shadow region first
2289 ParallelCompactData& sd = summary_data();
2290 RegionData* const region_ptr = sd.region(region_idx);
2291 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
2292 // The InvalidShadow return value indicates the corresponding heap region is available,
2293 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
2294 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
2295 if (shadow_region == ParCompactionManager::InvalidShadow) {
2296 MoveAndUpdateClosure cl(mark_bitmap(), region_idx);
2297 region_ptr->shadow_to_normal();
2298 return fill_region(cm, cl, region_idx);
2299 } else {
2300 MoveAndUpdateShadowClosure cl(mark_bitmap(), region_idx, shadow_region);
2301 return fill_region(cm, cl, region_idx);
2302 }
2303 }
2304
2305 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
2306 {
2307 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
2308 }
2309
2310 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
2311 {
2312 size_t next = cm->next_shadow_region();
2313 ParallelCompactData& sd = summary_data();
2314 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
2315 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2316
2317 while (next < old_new_top) {
2318 if (sd.region(next)->mark_shadow()) {
2319 region_idx = next;
2320 return true;
2321 }
2322 next = cm->move_next_shadow_region_by(active_gc_threads);
2323 }
2324
2325 return false;
2326 }
2327
2328 // The shadow region is an optimization to address region dependencies in full GC. The basic
2329 // idea is making more regions available by temporally storing their live objects in empty
2330 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
2331 // GC threads need not wait destination regions to be available before processing sources.
2332 //
2333 // A typical workflow would be:
2334 // After draining its own stack and failing to steal from others, a GC worker would pick an
2335 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
2336 // the shadow region by copying live objects from source regions of the unavailable one. Once
2337 // the unavailable region becomes available, the data in the shadow region will be copied back.
2338 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
2339 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
2340 {
2341 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2342
2343 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2344 SpaceInfo* const space_info = _space_info + id;
2345 MutableSpace* const space = space_info->space();
2346
2347 const size_t beg_region =
2348 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
2349 const size_t end_region =
2350 sd.addr_to_region_idx(sd.region_align_down(space->end()));
2351
2352 for (size_t cur = beg_region; cur < end_region; ++cur) {
2353 ParCompactionManager::push_shadow_region(cur);
2354 }
2355 }
2356
2357 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
2358 for (uint i = 0; i < parallel_gc_threads; i++) {
2359 ParCompactionManager *cm = ParCompactionManager::gc_thread_compaction_manager(i);
2360 cm->set_next_shadow_region(beg_region + i);
2361 }
2362 }
2363
2364 void MoveAndUpdateClosure::copy_partial_obj(size_t partial_obj_size)
2365 {
2366 size_t words = MIN2(partial_obj_size, words_remaining());
2367
2368 // This test is necessary; if omitted, the pointer updates to a partial object
2369 // that crosses the dense prefix boundary could be overwritten.
2370 if (source() != copy_destination()) {
2371 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2372 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2373 }
2374 update_state(words);
2375 }
2376
2377 void MoveAndUpdateClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2378 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
2379 region_ptr->set_completed();
2380 }
2381
2382 void MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
2383 assert(destination() != nullptr, "sanity");
2384 _source = addr;
2385
2386 // The start_array must be updated even if the object is not moving.
2387 if (_start_array != nullptr) {
2388 _start_array->update_for_block(destination(), destination() + words);
2389 }
2390
2391 // Avoid overflow
2392 words = MIN2(words, words_remaining());
2393 assert(words > 0, "inv");
2394
2395 if (copy_destination() != source()) {
2396 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
2397 assert(source() != destination(), "inv");
2398 assert(cast_to_oop(source())->is_forwarded(), "inv");
2399 assert(cast_to_oop(source())->forwardee() == cast_to_oop(destination()), "inv");
2400 Copy::aligned_conjoint_words(source(), copy_destination(), words);
2401 cast_to_oop(copy_destination())->init_mark();
2402 }
2403
2404 update_state(words);
2405 }
2406
2407 void MoveAndUpdateShadowClosure::complete_region(HeapWord* dest_addr, PSParallelCompact::RegionData* region_ptr) {
2408 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
2409 // Record the shadow region index
2410 region_ptr->set_shadow_region(_shadow);
2411 // Mark the shadow region as filled to indicate the data is ready to be
2412 // copied back
2413 region_ptr->mark_filled();
2414 // Try to copy the content of the shadow region back to its corresponding
2415 // heap region if available; the GC thread that decreases the destination
2416 // count to zero will do the copying otherwise (see
2417 // PSParallelCompact::decrement_destination_counts).
2418 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
2419 region_ptr->set_completed();
2420 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
2421 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
2422 }
2423 }
2424