1 /*
2 * Copyright (c) 2005, 2020, 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 "aot/aotLoader.hpp"
27 #include "classfile/classLoaderDataGraph.hpp"
28 #include "classfile/javaClasses.inline.hpp"
29 #include "classfile/stringTable.hpp"
30 #include "classfile/symbolTable.hpp"
31 #include "classfile/systemDictionary.hpp"
32 #include "code/codeCache.hpp"
33 #include "gc/parallel/parallelArguments.hpp"
34 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
35 #include "gc/parallel/parMarkBitMap.inline.hpp"
36 #include "gc/parallel/psAdaptiveSizePolicy.hpp"
37 #include "gc/parallel/psCompactionManager.inline.hpp"
38 #include "gc/parallel/psOldGen.hpp"
39 #include "gc/parallel/psParallelCompact.inline.hpp"
40 #include "gc/parallel/psPromotionManager.inline.hpp"
41 #include "gc/parallel/psRootType.hpp"
42 #include "gc/parallel/psScavenge.hpp"
43 #include "gc/parallel/psYoungGen.hpp"
44 #include "gc/shared/gcCause.hpp"
45 #include "gc/shared/gcHeapSummary.hpp"
46 #include "gc/shared/gcId.hpp"
47 #include "gc/shared/gcLocker.hpp"
48 #include "gc/shared/gcTimer.hpp"
49 #include "gc/shared/gcTrace.hpp"
50 #include "gc/shared/gcTraceTime.inline.hpp"
51 #include "gc/shared/isGCActiveMark.hpp"
52 #include "gc/shared/oopStorage.inline.hpp"
53 #include "gc/shared/oopStorageSet.inline.hpp"
54 #include "gc/shared/oopStorageSetParState.inline.hpp"
55 #include "gc/shared/referencePolicy.hpp"
56 #include "gc/shared/referenceProcessor.hpp"
57 #include "gc/shared/referenceProcessorPhaseTimes.hpp"
58 #include "gc/shared/spaceDecorator.inline.hpp"
59 #include "gc/shared/taskTerminator.hpp"
60 #include "gc/shared/weakProcessor.hpp"
61 #include "gc/shared/workerPolicy.hpp"
62 #include "gc/shared/workgroup.hpp"
63 #include "logging/log.hpp"
64 #include "memory/iterator.inline.hpp"
65 #include "memory/resourceArea.hpp"
66 #include "memory/universe.hpp"
67 #include "oops/access.inline.hpp"
68 #include "oops/instanceClassLoaderKlass.inline.hpp"
69 #include "oops/instanceKlass.inline.hpp"
70 #include "oops/instanceMirrorKlass.inline.hpp"
71 #include "oops/methodData.hpp"
72 #include "oops/objArrayKlass.inline.hpp"
73 #include "oops/oop.inline.hpp"
74 #include "runtime/atomic.hpp"
75 #include "runtime/handles.inline.hpp"
76 #include "runtime/safepoint.hpp"
77 #include "runtime/vmThread.hpp"
78 #include "services/memTracker.hpp"
79 #include "services/memoryService.hpp"
80 #include "utilities/align.hpp"
81 #include "utilities/debug.hpp"
82 #include "utilities/events.hpp"
83 #include "utilities/formatBuffer.hpp"
84 #include "utilities/macros.hpp"
85 #include "utilities/stack.inline.hpp"
86 #if INCLUDE_JVMCI
87 #include "jvmci/jvmci.hpp"
88 #endif
89
90 #include <math.h>
91
92 // All sizes are in HeapWords.
93 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
94 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
95 const size_t ParallelCompactData::RegionSizeBytes =
96 RegionSize << LogHeapWordSize;
97 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
98 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
99 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
100
101 const size_t ParallelCompactData::Log2BlockSize = 7; // 128 words
102 const size_t ParallelCompactData::BlockSize = (size_t)1 << Log2BlockSize;
103 const size_t ParallelCompactData::BlockSizeBytes =
104 BlockSize << LogHeapWordSize;
105 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
106 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
107 const size_t ParallelCompactData::BlockAddrMask = ~BlockAddrOffsetMask;
108
109 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
110 const size_t ParallelCompactData::Log2BlocksPerRegion =
111 Log2RegionSize - Log2BlockSize;
112
113 const ParallelCompactData::RegionData::region_sz_t
114 ParallelCompactData::RegionData::dc_shift = 27;
115
116 const ParallelCompactData::RegionData::region_sz_t
117 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
118
119 const ParallelCompactData::RegionData::region_sz_t
120 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
121
122 const ParallelCompactData::RegionData::region_sz_t
123 ParallelCompactData::RegionData::los_mask = ~dc_mask;
124
125 const ParallelCompactData::RegionData::region_sz_t
126 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
127
128 const ParallelCompactData::RegionData::region_sz_t
129 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
130
131 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
132
133 SpanSubjectToDiscoveryClosure PSParallelCompact::_span_based_discoverer;
134 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
135
136 double PSParallelCompact::_dwl_mean;
137 double PSParallelCompact::_dwl_std_dev;
138 double PSParallelCompact::_dwl_first_term;
139 double PSParallelCompact::_dwl_adjustment;
140 #ifdef ASSERT
141 bool PSParallelCompact::_dwl_initialized = false;
142 #endif // #ifdef ASSERT
143
144 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
145 HeapWord* destination)
146 {
147 assert(src_region_idx != 0, "invalid src_region_idx");
148 assert(partial_obj_size != 0, "invalid partial_obj_size argument");
149 assert(destination != NULL, "invalid destination argument");
150
151 _src_region_idx = src_region_idx;
152 _partial_obj_size = partial_obj_size;
153 _destination = destination;
154
155 // These fields may not be updated below, so make sure they're clear.
156 assert(_dest_region_addr == NULL, "should have been cleared");
157 assert(_first_src_addr == NULL, "should have been cleared");
158
159 // Determine the number of destination regions for the partial object.
160 HeapWord* const last_word = destination + partial_obj_size - 1;
161 const ParallelCompactData& sd = PSParallelCompact::summary_data();
162 HeapWord* const beg_region_addr = sd.region_align_down(destination);
163 HeapWord* const end_region_addr = sd.region_align_down(last_word);
164
165 if (beg_region_addr == end_region_addr) {
166 // One destination region.
167 _destination_count = 1;
168 if (end_region_addr == destination) {
169 // The destination falls on a region boundary, thus the first word of the
170 // partial object will be the first word copied to the destination region.
171 _dest_region_addr = end_region_addr;
172 _first_src_addr = sd.region_to_addr(src_region_idx);
173 }
174 } else {
175 // Two destination regions. When copied, the partial object will cross a
176 // destination region boundary, so a word somewhere within the partial
177 // object will be the first word copied to the second destination region.
178 _destination_count = 2;
179 _dest_region_addr = end_region_addr;
180 const size_t ofs = pointer_delta(end_region_addr, destination);
181 assert(ofs < _partial_obj_size, "sanity");
182 _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
183 }
184 }
185
186 void SplitInfo::clear()
187 {
188 _src_region_idx = 0;
189 _partial_obj_size = 0;
190 _destination = NULL;
191 _destination_count = 0;
192 _dest_region_addr = NULL;
193 _first_src_addr = NULL;
194 assert(!is_valid(), "sanity");
195 }
196
197 #ifdef ASSERT
198 void SplitInfo::verify_clear()
199 {
200 assert(_src_region_idx == 0, "not clear");
201 assert(_partial_obj_size == 0, "not clear");
202 assert(_destination == NULL, "not clear");
203 assert(_destination_count == 0, "not clear");
204 assert(_dest_region_addr == NULL, "not clear");
205 assert(_first_src_addr == NULL, "not clear");
206 }
207 #endif // #ifdef ASSERT
208
209
210 void PSParallelCompact::print_on_error(outputStream* st) {
211 _mark_bitmap.print_on_error(st);
212 }
213
214 #ifndef PRODUCT
215 const char* PSParallelCompact::space_names[] = {
216 "old ", "eden", "from", "to "
217 };
218
219 void PSParallelCompact::print_region_ranges() {
220 if (!log_develop_is_enabled(Trace, gc, compaction)) {
221 return;
222 }
223 Log(gc, compaction) log;
224 ResourceMark rm;
225 LogStream ls(log.trace());
226 Universe::print_on(&ls);
227 log.trace("space bottom top end new_top");
228 log.trace("------ ---------- ---------- ---------- ----------");
229
230 for (unsigned int id = 0; id < last_space_id; ++id) {
231 const MutableSpace* space = _space_info[id].space();
232 log.trace("%u %s "
233 SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
234 SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
235 id, space_names[id],
236 summary_data().addr_to_region_idx(space->bottom()),
237 summary_data().addr_to_region_idx(space->top()),
238 summary_data().addr_to_region_idx(space->end()),
239 summary_data().addr_to_region_idx(_space_info[id].new_top()));
240 }
241 }
242
243 void
244 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
245 {
246 #define REGION_IDX_FORMAT SIZE_FORMAT_W(7)
247 #define REGION_DATA_FORMAT SIZE_FORMAT_W(5)
248
249 ParallelCompactData& sd = PSParallelCompact::summary_data();
250 size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
251 log_develop_trace(gc, compaction)(
252 REGION_IDX_FORMAT " " PTR_FORMAT " "
253 REGION_IDX_FORMAT " " PTR_FORMAT " "
254 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
255 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
256 i, p2i(c->data_location()), dci, p2i(c->destination()),
257 c->partial_obj_size(), c->live_obj_size(),
258 c->data_size(), c->source_region(), c->destination_count());
259
260 #undef REGION_IDX_FORMAT
261 #undef REGION_DATA_FORMAT
262 }
263
264 void
265 print_generic_summary_data(ParallelCompactData& summary_data,
266 HeapWord* const beg_addr,
267 HeapWord* const end_addr)
268 {
269 size_t total_words = 0;
270 size_t i = summary_data.addr_to_region_idx(beg_addr);
271 const size_t last = summary_data.addr_to_region_idx(end_addr);
272 HeapWord* pdest = 0;
273
274 while (i < last) {
275 ParallelCompactData::RegionData* c = summary_data.region(i);
276 if (c->data_size() != 0 || c->destination() != pdest) {
277 print_generic_summary_region(i, c);
278 total_words += c->data_size();
279 pdest = c->destination();
280 }
281 ++i;
282 }
283
284 log_develop_trace(gc, compaction)("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
285 }
286
287 void
288 PSParallelCompact::print_generic_summary_data(ParallelCompactData& summary_data,
289 HeapWord* const beg_addr,
290 HeapWord* const end_addr) {
291 ::print_generic_summary_data(summary_data,beg_addr, end_addr);
292 }
293
294 void
295 print_generic_summary_data(ParallelCompactData& summary_data,
296 SpaceInfo* space_info)
297 {
298 if (!log_develop_is_enabled(Trace, gc, compaction)) {
299 return;
300 }
301
302 for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
303 const MutableSpace* space = space_info[id].space();
304 print_generic_summary_data(summary_data, space->bottom(),
305 MAX2(space->top(), space_info[id].new_top()));
306 }
307 }
308
309 void
310 print_initial_summary_data(ParallelCompactData& summary_data,
311 const MutableSpace* space) {
312 if (space->top() == space->bottom()) {
313 return;
314 }
315
316 const size_t region_size = ParallelCompactData::RegionSize;
317 typedef ParallelCompactData::RegionData RegionData;
318 HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
319 const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
320 const RegionData* c = summary_data.region(end_region - 1);
321 HeapWord* end_addr = c->destination() + c->data_size();
322 const size_t live_in_space = pointer_delta(end_addr, space->bottom());
323
324 // Print (and count) the full regions at the beginning of the space.
325 size_t full_region_count = 0;
326 size_t i = summary_data.addr_to_region_idx(space->bottom());
327 while (i < end_region && summary_data.region(i)->data_size() == region_size) {
328 ParallelCompactData::RegionData* c = summary_data.region(i);
329 log_develop_trace(gc, compaction)(
330 SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
331 i, p2i(c->destination()),
332 c->partial_obj_size(), c->live_obj_size(),
333 c->data_size(), c->source_region(), c->destination_count());
334 ++full_region_count;
335 ++i;
336 }
337
338 size_t live_to_right = live_in_space - full_region_count * region_size;
339
340 double max_reclaimed_ratio = 0.0;
341 size_t max_reclaimed_ratio_region = 0;
342 size_t max_dead_to_right = 0;
343 size_t max_live_to_right = 0;
344
345 // Print the 'reclaimed ratio' for regions while there is something live in
346 // the region or to the right of it. The remaining regions are empty (and
347 // uninteresting), and computing the ratio will result in division by 0.
348 while (i < end_region && live_to_right > 0) {
349 c = summary_data.region(i);
350 HeapWord* const region_addr = summary_data.region_to_addr(i);
351 const size_t used_to_right = pointer_delta(space->top(), region_addr);
352 const size_t dead_to_right = used_to_right - live_to_right;
353 const double reclaimed_ratio = double(dead_to_right) / live_to_right;
354
355 if (reclaimed_ratio > max_reclaimed_ratio) {
356 max_reclaimed_ratio = reclaimed_ratio;
357 max_reclaimed_ratio_region = i;
358 max_dead_to_right = dead_to_right;
359 max_live_to_right = live_to_right;
360 }
361
362 ParallelCompactData::RegionData* c = summary_data.region(i);
363 log_develop_trace(gc, compaction)(
364 SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d"
365 "%12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
366 i, p2i(c->destination()),
367 c->partial_obj_size(), c->live_obj_size(),
368 c->data_size(), c->source_region(), c->destination_count(),
369 reclaimed_ratio, dead_to_right, live_to_right);
370
371
372 live_to_right -= c->data_size();
373 ++i;
374 }
375
376 // Any remaining regions are empty. Print one more if there is one.
377 if (i < end_region) {
378 ParallelCompactData::RegionData* c = summary_data.region(i);
379 log_develop_trace(gc, compaction)(
380 SIZE_FORMAT_W(5) " " PTR_FORMAT " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
381 i, p2i(c->destination()),
382 c->partial_obj_size(), c->live_obj_size(),
383 c->data_size(), c->source_region(), c->destination_count());
384 }
385
386 log_develop_trace(gc, compaction)("max: " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
387 max_reclaimed_ratio_region, max_dead_to_right, max_live_to_right, max_reclaimed_ratio);
388 }
389
390 void
391 print_initial_summary_data(ParallelCompactData& summary_data,
392 SpaceInfo* space_info) {
393 if (!log_develop_is_enabled(Trace, gc, compaction)) {
394 return;
395 }
396
397 unsigned int id = PSParallelCompact::old_space_id;
398 const MutableSpace* space;
399 do {
400 space = space_info[id].space();
401 print_initial_summary_data(summary_data, space);
402 } while (++id < PSParallelCompact::eden_space_id);
403
404 do {
405 space = space_info[id].space();
406 print_generic_summary_data(summary_data, space->bottom(), space->top());
407 } while (++id < PSParallelCompact::last_space_id);
408 }
409 #endif // #ifndef PRODUCT
410
411 #ifdef ASSERT
412 size_t add_obj_count;
413 size_t add_obj_size;
414 size_t mark_bitmap_count;
415 size_t mark_bitmap_size;
416 #endif // #ifdef ASSERT
417
418 ParallelCompactData::ParallelCompactData() :
419 _region_start(NULL),
420 DEBUG_ONLY(_region_end(NULL) COMMA)
421 _region_vspace(NULL),
422 _reserved_byte_size(0),
423 _region_data(NULL),
424 _region_count(0),
425 _block_vspace(NULL),
426 _block_data(NULL),
427 _block_count(0) {}
428
429 bool ParallelCompactData::initialize(MemRegion covered_region)
430 {
431 _region_start = covered_region.start();
432 const size_t region_size = covered_region.word_size();
433 DEBUG_ONLY(_region_end = _region_start + region_size;)
434
435 assert(region_align_down(_region_start) == _region_start,
436 "region start not aligned");
437 assert((region_size & RegionSizeOffsetMask) == 0,
438 "region size not a multiple of RegionSize");
439
440 bool result = initialize_region_data(region_size) && initialize_block_data();
441 return result;
442 }
443
444 PSVirtualSpace*
445 ParallelCompactData::create_vspace(size_t count, size_t element_size)
446 {
447 const size_t raw_bytes = count * element_size;
448 const size_t page_sz = os::page_size_for_region_aligned(raw_bytes, 10);
449 const size_t granularity = os::vm_allocation_granularity();
450 _reserved_byte_size = align_up(raw_bytes, MAX2(page_sz, granularity));
451
452 const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
453 MAX2(page_sz, granularity);
454 ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
455 os::trace_page_sizes("Parallel Compact Data", raw_bytes, raw_bytes, page_sz, rs.base(),
456 rs.size());
457
458 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
459
460 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
461 if (vspace != 0) {
462 if (vspace->expand_by(_reserved_byte_size)) {
463 return vspace;
464 }
465 delete vspace;
466 // Release memory reserved in the space.
467 rs.release();
468 }
469
470 return 0;
471 }
472
473 bool ParallelCompactData::initialize_region_data(size_t region_size)
474 {
475 const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
476 _region_vspace = create_vspace(count, sizeof(RegionData));
477 if (_region_vspace != 0) {
478 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
479 _region_count = count;
480 return true;
481 }
482 return false;
483 }
484
485 bool ParallelCompactData::initialize_block_data()
486 {
487 assert(_region_count != 0, "region data must be initialized first");
488 const size_t count = _region_count << Log2BlocksPerRegion;
489 _block_vspace = create_vspace(count, sizeof(BlockData));
490 if (_block_vspace != 0) {
491 _block_data = (BlockData*)_block_vspace->reserved_low_addr();
492 _block_count = count;
493 return true;
494 }
495 return false;
496 }
497
498 void ParallelCompactData::clear()
499 {
500 memset(_region_data, 0, _region_vspace->committed_size());
501 memset(_block_data, 0, _block_vspace->committed_size());
502 }
503
504 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
505 assert(beg_region <= _region_count, "beg_region out of range");
506 assert(end_region <= _region_count, "end_region out of range");
507 assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
508
509 const size_t region_cnt = end_region - beg_region;
510 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
511
512 const size_t beg_block = beg_region * BlocksPerRegion;
513 const size_t block_cnt = region_cnt * BlocksPerRegion;
514 memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
515 }
516
517 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
518 {
519 const RegionData* cur_cp = region(region_idx);
520 const RegionData* const end_cp = region(region_count() - 1);
521
522 HeapWord* result = region_to_addr(region_idx);
523 if (cur_cp < end_cp) {
524 do {
525 result += cur_cp->partial_obj_size();
526 } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
527 }
528 return result;
529 }
530
531 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
532 {
533 const size_t obj_ofs = pointer_delta(addr, _region_start);
534 const size_t beg_region = obj_ofs >> Log2RegionSize;
535 const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
536
537 DEBUG_ONLY(Atomic::inc(&add_obj_count);)
538 DEBUG_ONLY(Atomic::add(&add_obj_size, len);)
539
540 if (beg_region == end_region) {
541 // All in one region.
542 _region_data[beg_region].add_live_obj(len);
543 return;
544 }
545
546 // First region.
547 const size_t beg_ofs = region_offset(addr);
548 _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
549
550 Klass* klass = ((oop)addr)->klass();
551 // Middle regions--completely spanned by this object.
552 for (size_t region = beg_region + 1; region < end_region; ++region) {
553 _region_data[region].set_partial_obj_size(RegionSize);
554 _region_data[region].set_partial_obj_addr(addr);
555 }
556
557 // Last region.
558 const size_t end_ofs = region_offset(addr + len - 1);
559 _region_data[end_region].set_partial_obj_size(end_ofs + 1);
560 _region_data[end_region].set_partial_obj_addr(addr);
561 }
562
563 void
564 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
565 {
566 assert(region_offset(beg) == 0, "not RegionSize aligned");
567 assert(region_offset(end) == 0, "not RegionSize aligned");
568
569 size_t cur_region = addr_to_region_idx(beg);
570 const size_t end_region = addr_to_region_idx(end);
571 HeapWord* addr = beg;
572 while (cur_region < end_region) {
573 _region_data[cur_region].set_destination(addr);
574 _region_data[cur_region].set_destination_count(0);
575 _region_data[cur_region].set_source_region(cur_region);
576 _region_data[cur_region].set_data_location(addr);
577
578 // Update live_obj_size so the region appears completely full.
579 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
580 _region_data[cur_region].set_live_obj_size(live_size);
581
582 ++cur_region;
583 addr += RegionSize;
584 }
585 }
586
587 // Find the point at which a space can be split and, if necessary, record the
588 // split point.
589 //
590 // If the current src region (which overflowed the destination space) doesn't
591 // have a partial object, the split point is at the beginning of the current src
592 // region (an "easy" split, no extra bookkeeping required).
593 //
594 // If the current src region has a partial object, the split point is in the
595 // region where that partial object starts (call it the split_region). If
596 // split_region has a partial object, then the split point is just after that
597 // partial object (a "hard" split where we have to record the split data and
598 // zero the partial_obj_size field). With a "hard" split, we know that the
599 // partial_obj ends within split_region because the partial object that caused
600 // the overflow starts in split_region. If split_region doesn't have a partial
601 // obj, then the split is at the beginning of split_region (another "easy"
602 // split).
603 HeapWord*
604 ParallelCompactData::summarize_split_space(size_t src_region,
605 SplitInfo& split_info,
606 HeapWord* destination,
607 HeapWord* target_end,
608 HeapWord** target_next)
609 {
610 assert(destination <= target_end, "sanity");
611 assert(destination + _region_data[src_region].data_size() > target_end,
612 "region should not fit into target space");
613 assert(is_region_aligned(target_end), "sanity");
614
615 size_t split_region = src_region;
616 HeapWord* split_destination = destination;
617 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
618
619 if (destination + partial_obj_size > target_end) {
620 // The split point is just after the partial object (if any) in the
621 // src_region that contains the start of the object that overflowed the
622 // destination space.
623 //
624 // Find the start of the "overflow" object and set split_region to the
625 // region containing it.
626 HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
627 split_region = addr_to_region_idx(overflow_obj);
628
629 // Clear the source_region field of all destination regions whose first word
630 // came from data after the split point (a non-null source_region field
631 // implies a region must be filled).
632 //
633 // An alternative to the simple loop below: clear during post_compact(),
634 // which uses memcpy instead of individual stores, and is easy to
635 // parallelize. (The downside is that it clears the entire RegionData
636 // object as opposed to just one field.)
637 //
638 // post_compact() would have to clear the summary data up to the highest
639 // address that was written during the summary phase, which would be
640 //
641 // max(top, max(new_top, clear_top))
642 //
643 // where clear_top is a new field in SpaceInfo. Would have to set clear_top
644 // to target_end.
645 const RegionData* const sr = region(split_region);
646 const size_t beg_idx =
647 addr_to_region_idx(region_align_up(sr->destination() +
648 sr->partial_obj_size()));
649 const size_t end_idx = addr_to_region_idx(target_end);
650
651 log_develop_trace(gc, compaction)("split: clearing source_region field in [" SIZE_FORMAT ", " SIZE_FORMAT ")", beg_idx, end_idx);
652 for (size_t idx = beg_idx; idx < end_idx; ++idx) {
653 _region_data[idx].set_source_region(0);
654 }
655
656 // Set split_destination and partial_obj_size to reflect the split region.
657 split_destination = sr->destination();
658 partial_obj_size = sr->partial_obj_size();
659 }
660
661 // The split is recorded only if a partial object extends onto the region.
662 if (partial_obj_size != 0) {
663 _region_data[split_region].set_partial_obj_size(0);
664 split_info.record(split_region, partial_obj_size, split_destination);
665 }
666
667 // Setup the continuation addresses.
668 *target_next = split_destination + partial_obj_size;
669 HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
670
671 if (log_develop_is_enabled(Trace, gc, compaction)) {
672 const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
673 log_develop_trace(gc, compaction)("%s split: src=" PTR_FORMAT " src_c=" SIZE_FORMAT " pos=" SIZE_FORMAT,
674 split_type, p2i(source_next), split_region, partial_obj_size);
675 log_develop_trace(gc, compaction)("%s split: dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT " tn=" PTR_FORMAT,
676 split_type, p2i(split_destination),
677 addr_to_region_idx(split_destination),
678 p2i(*target_next));
679
680 if (partial_obj_size != 0) {
681 HeapWord* const po_beg = split_info.destination();
682 HeapWord* const po_end = po_beg + split_info.partial_obj_size();
683 log_develop_trace(gc, compaction)("%s split: po_beg=" PTR_FORMAT " " SIZE_FORMAT " po_end=" PTR_FORMAT " " SIZE_FORMAT,
684 split_type,
685 p2i(po_beg), addr_to_region_idx(po_beg),
686 p2i(po_end), addr_to_region_idx(po_end));
687 }
688 }
689
690 return source_next;
691 }
692
693 bool ParallelCompactData::summarize(SplitInfo& split_info,
694 HeapWord* source_beg, HeapWord* source_end,
695 HeapWord** source_next,
696 HeapWord* target_beg, HeapWord* target_end,
697 HeapWord** target_next)
698 {
699 HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
700 log_develop_trace(gc, compaction)(
701 "sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
702 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
703 p2i(source_beg), p2i(source_end), p2i(source_next_val),
704 p2i(target_beg), p2i(target_end), p2i(*target_next));
705
706 size_t cur_region = addr_to_region_idx(source_beg);
707 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
708
709 HeapWord *dest_addr = target_beg;
710 while (cur_region < end_region) {
711 // The destination must be set even if the region has no data.
712 _region_data[cur_region].set_destination(dest_addr);
713
714 size_t words = _region_data[cur_region].data_size();
715 if (words > 0) {
716 // If cur_region does not fit entirely into the target space, find a point
717 // at which the source space can be 'split' so that part is copied to the
718 // target space and the rest is copied elsewhere.
719 if (dest_addr + words > target_end) {
720 assert(source_next != NULL, "source_next is NULL when splitting");
721 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
722 target_end, target_next);
723 return false;
724 }
725
726 // Compute the destination_count for cur_region, and if necessary, update
727 // source_region for a destination region. The source_region field is
728 // updated if cur_region is the first (left-most) region to be copied to a
729 // destination region.
730 //
731 // The destination_count calculation is a bit subtle. A region that has
732 // data that compacts into itself does not count itself as a destination.
733 // This maintains the invariant that a zero count means the region is
734 // available and can be claimed and then filled.
735 uint destination_count = 0;
736 if (split_info.is_split(cur_region)) {
737 // The current region has been split: the partial object will be copied
738 // to one destination space and the remaining data will be copied to
739 // another destination space. Adjust the initial destination_count and,
740 // if necessary, set the source_region field if the partial object will
741 // cross a destination region boundary.
742 destination_count = split_info.destination_count();
743 if (destination_count == 2) {
744 size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
745 _region_data[dest_idx].set_source_region(cur_region);
746 }
747 }
748
749 HeapWord* const last_addr = dest_addr + words - 1;
750 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
751 const size_t dest_region_2 = addr_to_region_idx(last_addr);
752
753 // Initially assume that the destination regions will be the same and
754 // adjust the value below if necessary. Under this assumption, if
755 // cur_region == dest_region_2, then cur_region will be compacted
756 // completely into itself.
757 destination_count += cur_region == dest_region_2 ? 0 : 1;
758 if (dest_region_1 != dest_region_2) {
759 // Destination regions differ; adjust destination_count.
760 destination_count += 1;
761 // Data from cur_region will be copied to the start of dest_region_2.
762 _region_data[dest_region_2].set_source_region(cur_region);
763 } else if (region_offset(dest_addr) == 0) {
764 // Data from cur_region will be copied to the start of the destination
765 // region.
766 _region_data[dest_region_1].set_source_region(cur_region);
767 }
768
769 _region_data[cur_region].set_destination_count(destination_count);
770 _region_data[cur_region].set_data_location(region_to_addr(cur_region));
771 dest_addr += words;
772 }
773
774 ++cur_region;
775 }
776
777 *target_next = dest_addr;
778 return true;
779 }
780
781 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr, ParCompactionManager* cm) {
782 assert(addr != NULL, "Should detect NULL oop earlier");
783 assert(ParallelScavengeHeap::heap()->is_in(addr), "not in heap");
784 assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
785
786 // Region covering the object.
787 RegionData* const region_ptr = addr_to_region_ptr(addr);
788 HeapWord* result = region_ptr->destination();
789
790 // If the entire Region is live, the new location is region->destination + the
791 // offset of the object within in the Region.
792
793 // Run some performance tests to determine if this special case pays off. It
794 // is worth it for pointers into the dense prefix. If the optimization to
795 // avoid pointer updates in regions that only point to the dense prefix is
796 // ever implemented, this should be revisited.
797 if (region_ptr->data_size() == RegionSize) {
798 result += region_offset(addr);
799 return result;
800 }
801
802 // Otherwise, the new location is region->destination + block offset + the
803 // number of live words in the Block that are (a) to the left of addr and (b)
804 // due to objects that start in the Block.
805
806 // Fill in the block table if necessary. This is unsynchronized, so multiple
807 // threads may fill the block table for a region (harmless, since it is
808 // idempotent).
809 if (!region_ptr->blocks_filled()) {
810 PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
811 region_ptr->set_blocks_filled();
812 }
813
814 HeapWord* const search_start = block_align_down(addr);
815 const size_t block_offset = addr_to_block_ptr(addr)->offset();
816
817 const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
818 const size_t live = bitmap->live_words_in_range(cm, search_start, oop(addr));
819 result += block_offset + live;
820 DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
821 return result;
822 }
823
824 #ifdef ASSERT
825 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
826 {
827 const size_t* const beg = (const size_t*)vspace->committed_low_addr();
828 const size_t* const end = (const size_t*)vspace->committed_high_addr();
829 for (const size_t* p = beg; p < end; ++p) {
830 assert(*p == 0, "not zero");
831 }
832 }
833
834 void ParallelCompactData::verify_clear()
835 {
836 verify_clear(_region_vspace);
837 verify_clear(_block_vspace);
838 }
839 #endif // #ifdef ASSERT
840
841 STWGCTimer PSParallelCompact::_gc_timer;
842 ParallelOldTracer PSParallelCompact::_gc_tracer;
843 elapsedTimer PSParallelCompact::_accumulated_time;
844 unsigned int PSParallelCompact::_total_invocations = 0;
845 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
846 CollectorCounters* PSParallelCompact::_counters = NULL;
847 ParMarkBitMap PSParallelCompact::_mark_bitmap;
848 ParallelCompactData PSParallelCompact::_summary_data;
849
850 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
851
852 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
853
854 class PCReferenceProcessor: public ReferenceProcessor {
855 public:
856 PCReferenceProcessor(
857 BoolObjectClosure* is_subject_to_discovery,
858 BoolObjectClosure* is_alive_non_header) :
859 ReferenceProcessor(is_subject_to_discovery,
860 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
861 ParallelGCThreads, // mt processing degree
862 true, // mt discovery
863 ParallelGCThreads, // mt discovery degree
864 true, // atomic_discovery
865 is_alive_non_header) {
866 }
867
868 template<typename T> bool discover(oop obj, ReferenceType type) {
869 T* referent_addr = (T*) java_lang_ref_Reference::referent_addr_raw(obj);
870 T heap_oop = RawAccess<>::oop_load(referent_addr);
871 oop referent = CompressedOops::decode_not_null(heap_oop);
872 return PSParallelCompact::mark_bitmap()->is_unmarked(referent)
873 && ReferenceProcessor::discover_reference(obj, type);
874 }
875 virtual bool discover_reference(oop obj, ReferenceType type) {
876 if (UseCompressedOops) {
877 return discover<narrowOop>(obj, type);
878 } else {
879 return discover<oop>(obj, type);
880 }
881 }
882 };
883
884 void PSParallelCompact::post_initialize() {
885 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
886 _span_based_discoverer.set_span(heap->reserved_region());
887 _ref_processor =
888 new PCReferenceProcessor(&_span_based_discoverer,
889 &_is_alive_closure); // non-header is alive closure
890
891 _counters = new CollectorCounters("Parallel full collection pauses", 1);
892
893 // Initialize static fields in ParCompactionManager.
894 ParCompactionManager::initialize(mark_bitmap());
895 }
896
897 bool PSParallelCompact::initialize() {
898 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
899 MemRegion mr = heap->reserved_region();
900
901 // Was the old gen get allocated successfully?
902 if (!heap->old_gen()->is_allocated()) {
903 return false;
904 }
905
906 initialize_space_info();
907 initialize_dead_wood_limiter();
908
909 if (!_mark_bitmap.initialize(mr)) {
910 vm_shutdown_during_initialization(
911 err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
912 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
913 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
914 return false;
915 }
916
917 if (!_summary_data.initialize(mr)) {
918 vm_shutdown_during_initialization(
919 err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
920 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
921 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
922 return false;
923 }
924
925 return true;
926 }
927
928 void PSParallelCompact::initialize_space_info()
929 {
930 memset(&_space_info, 0, sizeof(_space_info));
931
932 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
933 PSYoungGen* young_gen = heap->young_gen();
934
935 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
936 _space_info[eden_space_id].set_space(young_gen->eden_space());
937 _space_info[from_space_id].set_space(young_gen->from_space());
938 _space_info[to_space_id].set_space(young_gen->to_space());
939
940 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
941 }
942
943 void PSParallelCompact::initialize_dead_wood_limiter()
944 {
945 const size_t max = 100;
946 _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
947 _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
948 _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
949 DEBUG_ONLY(_dwl_initialized = true;)
950 _dwl_adjustment = normal_distribution(1.0);
951 }
952
953 void
954 PSParallelCompact::clear_data_covering_space(SpaceId id)
955 {
956 // At this point, top is the value before GC, new_top() is the value that will
957 // be set at the end of GC. The marking bitmap is cleared to top; nothing
958 // should be marked above top. The summary data is cleared to the larger of
959 // top & new_top.
960 MutableSpace* const space = _space_info[id].space();
961 HeapWord* const bot = space->bottom();
962 HeapWord* const top = space->top();
963 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
964
965 const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
966 const idx_t end_bit = _mark_bitmap.align_range_end(_mark_bitmap.addr_to_bit(top));
967 _mark_bitmap.clear_range(beg_bit, end_bit);
968
969 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
970 const size_t end_region =
971 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
972 _summary_data.clear_range(beg_region, end_region);
973
974 // Clear the data used to 'split' regions.
975 SplitInfo& split_info = _space_info[id].split_info();
976 if (split_info.is_valid()) {
977 split_info.clear();
978 }
979 DEBUG_ONLY(split_info.verify_clear();)
980 }
981
982 void PSParallelCompact::pre_compact()
983 {
984 // Update the from & to space pointers in space_info, since they are swapped
985 // at each young gen gc. Do the update unconditionally (even though a
986 // promotion failure does not swap spaces) because an unknown number of young
987 // collections will have swapped the spaces an unknown number of times.
988 GCTraceTime(Debug, gc, phases) tm("Pre Compact", &_gc_timer);
989 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
990 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
991 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
992
993 DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
994 DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
995
996 // Increment the invocation count
997 heap->increment_total_collections(true);
998
999 // We need to track unique mark sweep invocations as well.
1000 _total_invocations++;
1001
1002 heap->print_heap_before_gc();
1003 heap->trace_heap_before_gc(&_gc_tracer);
1004
1005 // Fill in TLABs
1006 heap->ensure_parsability(true); // retire TLABs
1007
1008 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1009 Universe::verify("Before GC");
1010 }
1011
1012 // Verify object start arrays
1013 if (VerifyObjectStartArray &&
1014 VerifyBeforeGC) {
1015 heap->old_gen()->verify_object_start_array();
1016 }
1017
1018 DEBUG_ONLY(mark_bitmap()->verify_clear();)
1019 DEBUG_ONLY(summary_data().verify_clear();)
1020
1021 ParCompactionManager::reset_all_bitmap_query_caches();
1022 }
1023
1024 void PSParallelCompact::post_compact()
1025 {
1026 GCTraceTime(Info, gc, phases) tm("Post Compact", &_gc_timer);
1027 ParCompactionManager::remove_all_shadow_regions();
1028
1029 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1030 // Clear the marking bitmap, summary data and split info.
1031 clear_data_covering_space(SpaceId(id));
1032 // Update top(). Must be done after clearing the bitmap and summary data.
1033 _space_info[id].publish_new_top();
1034 }
1035
1036 MutableSpace* const eden_space = _space_info[eden_space_id].space();
1037 MutableSpace* const from_space = _space_info[from_space_id].space();
1038 MutableSpace* const to_space = _space_info[to_space_id].space();
1039
1040 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1041 bool eden_empty = eden_space->is_empty();
1042
1043 // Update heap occupancy information which is used as input to the soft ref
1044 // clearing policy at the next gc.
1045 Universe::update_heap_info_at_gc();
1046
1047 Universe::heap()->next_whole_heap_examined();
1048
1049 bool young_gen_empty = eden_empty && from_space->is_empty() &&
1050 to_space->is_empty();
1051
1052 PSCardTable* ct = heap->card_table();
1053 MemRegion old_mr = heap->old_gen()->reserved();
1054 if (young_gen_empty) {
1055 ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1056 } else {
1057 ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1058 }
1059
1060 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1061 ClassLoaderDataGraph::purge();
1062 MetaspaceUtils::verify_metrics();
1063
1064 heap->prune_scavengable_nmethods();
1065
1066 #if COMPILER2_OR_JVMCI
1067 DerivedPointerTable::update_pointers();
1068 #endif
1069
1070 if (ZapUnusedHeapArea) {
1071 heap->gen_mangle_unused_area();
1072 }
1073 }
1074
1075 HeapWord*
1076 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1077 bool maximum_compaction)
1078 {
1079 const size_t region_size = ParallelCompactData::RegionSize;
1080 const ParallelCompactData& sd = summary_data();
1081
1082 const MutableSpace* const space = _space_info[id].space();
1083 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1084 const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1085 const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1086
1087 // Skip full regions at the beginning of the space--they are necessarily part
1088 // of the dense prefix.
1089 size_t full_count = 0;
1090 const RegionData* cp;
1091 for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1092 ++full_count;
1093 }
1094
1095 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1096 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1097 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1098 if (maximum_compaction || cp == end_cp || interval_ended) {
1099 _maximum_compaction_gc_num = total_invocations();
1100 return sd.region_to_addr(cp);
1101 }
1102
1103 HeapWord* const new_top = _space_info[id].new_top();
1104 const size_t space_live = pointer_delta(new_top, space->bottom());
1105 const size_t space_used = space->used_in_words();
1106 const size_t space_capacity = space->capacity_in_words();
1107
1108 const double cur_density = double(space_live) / space_capacity;
1109 const double deadwood_density =
1110 (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1111 const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1112
1113 log_develop_debug(gc, compaction)(
1114 "cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1115 cur_density, deadwood_density, deadwood_goal);
1116 log_develop_debug(gc, compaction)(
1117 "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1118 "space_cap=" SIZE_FORMAT,
1119 space_live, space_used,
1120 space_capacity);
1121
1122 // XXX - Use binary search?
1123 HeapWord* dense_prefix = sd.region_to_addr(cp);
1124 const RegionData* full_cp = cp;
1125 const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1126 while (cp < end_cp) {
1127 HeapWord* region_destination = cp->destination();
1128 const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1129
1130 log_develop_trace(gc, compaction)(
1131 "c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1132 "dp=" PTR_FORMAT " cdw=" SIZE_FORMAT_W(8),
1133 sd.region(cp), p2i(region_destination),
1134 p2i(dense_prefix), cur_deadwood);
1135
1136 if (cur_deadwood >= deadwood_goal) {
1137 // Found the region that has the correct amount of deadwood to the left.
1138 // This typically occurs after crossing a fairly sparse set of regions, so
1139 // iterate backwards over those sparse regions, looking for the region
1140 // that has the lowest density of live objects 'to the right.'
1141 size_t space_to_left = sd.region(cp) * region_size;
1142 size_t live_to_left = space_to_left - cur_deadwood;
1143 size_t space_to_right = space_capacity - space_to_left;
1144 size_t live_to_right = space_live - live_to_left;
1145 double density_to_right = double(live_to_right) / space_to_right;
1146 while (cp > full_cp) {
1147 --cp;
1148 const size_t prev_region_live_to_right = live_to_right -
1149 cp->data_size();
1150 const size_t prev_region_space_to_right = space_to_right + region_size;
1151 double prev_region_density_to_right =
1152 double(prev_region_live_to_right) / prev_region_space_to_right;
1153 if (density_to_right <= prev_region_density_to_right) {
1154 return dense_prefix;
1155 }
1156
1157 log_develop_trace(gc, compaction)(
1158 "backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1159 "pc_d2r=%10.8f",
1160 sd.region(cp), density_to_right,
1161 prev_region_density_to_right);
1162
1163 dense_prefix -= region_size;
1164 live_to_right = prev_region_live_to_right;
1165 space_to_right = prev_region_space_to_right;
1166 density_to_right = prev_region_density_to_right;
1167 }
1168 return dense_prefix;
1169 }
1170
1171 dense_prefix += region_size;
1172 ++cp;
1173 }
1174
1175 return dense_prefix;
1176 }
1177
1178 #ifndef PRODUCT
1179 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1180 const SpaceId id,
1181 const bool maximum_compaction,
1182 HeapWord* const addr)
1183 {
1184 const size_t region_idx = summary_data().addr_to_region_idx(addr);
1185 RegionData* const cp = summary_data().region(region_idx);
1186 const MutableSpace* const space = _space_info[id].space();
1187 HeapWord* const new_top = _space_info[id].new_top();
1188
1189 const size_t space_live = pointer_delta(new_top, space->bottom());
1190 const size_t dead_to_left = pointer_delta(addr, cp->destination());
1191 const size_t space_cap = space->capacity_in_words();
1192 const double dead_to_left_pct = double(dead_to_left) / space_cap;
1193 const size_t live_to_right = new_top - cp->destination();
1194 const size_t dead_to_right = space->top() - addr - live_to_right;
1195
1196 log_develop_debug(gc, compaction)(
1197 "%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1198 "spl=" SIZE_FORMAT " "
1199 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1200 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT " "
1201 "ratio=%10.8f",
1202 algorithm, p2i(addr), region_idx,
1203 space_live,
1204 dead_to_left, dead_to_left_pct,
1205 dead_to_right, live_to_right,
1206 double(dead_to_right) / live_to_right);
1207 }
1208 #endif // #ifndef PRODUCT
1209
1210 // Return a fraction indicating how much of the generation can be treated as
1211 // "dead wood" (i.e., not reclaimed). The function uses a normal distribution
1212 // based on the density of live objects in the generation to determine a limit,
1213 // which is then adjusted so the return value is min_percent when the density is
1214 // 1.
1215 //
1216 // The following table shows some return values for a different values of the
1217 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1218 // min_percent is 1.
1219 //
1220 // fraction allowed as dead wood
1221 // -----------------------------------------------------------------
1222 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1223 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1224 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1225 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1226 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1227 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1228 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1229 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1230 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1231 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1232 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1233 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1234 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1235 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1236 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1237 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1238 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1239 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1240 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1241 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1242 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1243 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1244 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1245
1246 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1247 {
1248 assert(_dwl_initialized, "uninitialized");
1249
1250 // The raw limit is the value of the normal distribution at x = density.
1251 const double raw_limit = normal_distribution(density);
1252
1253 // Adjust the raw limit so it becomes the minimum when the density is 1.
1254 //
1255 // First subtract the adjustment value (which is simply the precomputed value
1256 // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1257 // Then add the minimum value, so the minimum is returned when the density is
1258 // 1. Finally, prevent negative values, which occur when the mean is not 0.5.
1259 const double min = double(min_percent) / 100.0;
1260 const double limit = raw_limit - _dwl_adjustment + min;
1261 return MAX2(limit, 0.0);
1262 }
1263
1264 ParallelCompactData::RegionData*
1265 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1266 const RegionData* end)
1267 {
1268 const size_t region_size = ParallelCompactData::RegionSize;
1269 ParallelCompactData& sd = summary_data();
1270 size_t left = sd.region(beg);
1271 size_t right = end > beg ? sd.region(end) - 1 : left;
1272
1273 // Binary search.
1274 while (left < right) {
1275 // Equivalent to (left + right) / 2, but does not overflow.
1276 const size_t middle = left + (right - left) / 2;
1277 RegionData* const middle_ptr = sd.region(middle);
1278 HeapWord* const dest = middle_ptr->destination();
1279 HeapWord* const addr = sd.region_to_addr(middle);
1280 assert(dest != NULL, "sanity");
1281 assert(dest <= addr, "must move left");
1282
1283 if (middle > left && dest < addr) {
1284 right = middle - 1;
1285 } else if (middle < right && middle_ptr->data_size() == region_size) {
1286 left = middle + 1;
1287 } else {
1288 return middle_ptr;
1289 }
1290 }
1291 return sd.region(left);
1292 }
1293
1294 ParallelCompactData::RegionData*
1295 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1296 const RegionData* end,
1297 size_t dead_words)
1298 {
1299 ParallelCompactData& sd = summary_data();
1300 size_t left = sd.region(beg);
1301 size_t right = end > beg ? sd.region(end) - 1 : left;
1302
1303 // Binary search.
1304 while (left < right) {
1305 // Equivalent to (left + right) / 2, but does not overflow.
1306 const size_t middle = left + (right - left) / 2;
1307 RegionData* const middle_ptr = sd.region(middle);
1308 HeapWord* const dest = middle_ptr->destination();
1309 HeapWord* const addr = sd.region_to_addr(middle);
1310 assert(dest != NULL, "sanity");
1311 assert(dest <= addr, "must move left");
1312
1313 const size_t dead_to_left = pointer_delta(addr, dest);
1314 if (middle > left && dead_to_left > dead_words) {
1315 right = middle - 1;
1316 } else if (middle < right && dead_to_left < dead_words) {
1317 left = middle + 1;
1318 } else {
1319 return middle_ptr;
1320 }
1321 }
1322 return sd.region(left);
1323 }
1324
1325 // The result is valid during the summary phase, after the initial summarization
1326 // of each space into itself, and before final summarization.
1327 inline double
1328 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1329 HeapWord* const bottom,
1330 HeapWord* const top,
1331 HeapWord* const new_top)
1332 {
1333 ParallelCompactData& sd = summary_data();
1334
1335 assert(cp != NULL, "sanity");
1336 assert(bottom != NULL, "sanity");
1337 assert(top != NULL, "sanity");
1338 assert(new_top != NULL, "sanity");
1339 assert(top >= new_top, "summary data problem?");
1340 assert(new_top > bottom, "space is empty; should not be here");
1341 assert(new_top >= cp->destination(), "sanity");
1342 assert(top >= sd.region_to_addr(cp), "sanity");
1343
1344 HeapWord* const destination = cp->destination();
1345 const size_t dense_prefix_live = pointer_delta(destination, bottom);
1346 const size_t compacted_region_live = pointer_delta(new_top, destination);
1347 const size_t compacted_region_used = pointer_delta(top,
1348 sd.region_to_addr(cp));
1349 const size_t reclaimable = compacted_region_used - compacted_region_live;
1350
1351 const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1352 return double(reclaimable) / divisor;
1353 }
1354
1355 // Return the address of the end of the dense prefix, a.k.a. the start of the
1356 // compacted region. The address is always on a region boundary.
1357 //
1358 // Completely full regions at the left are skipped, since no compaction can
1359 // occur in those regions. Then the maximum amount of dead wood to allow is
1360 // computed, based on the density (amount live / capacity) of the generation;
1361 // the region with approximately that amount of dead space to the left is
1362 // identified as the limit region. Regions between the last completely full
1363 // region and the limit region are scanned and the one that has the best
1364 // (maximum) reclaimed_ratio() is selected.
1365 HeapWord*
1366 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1367 bool maximum_compaction)
1368 {
1369 const size_t region_size = ParallelCompactData::RegionSize;
1370 const ParallelCompactData& sd = summary_data();
1371
1372 const MutableSpace* const space = _space_info[id].space();
1373 HeapWord* const top = space->top();
1374 HeapWord* const top_aligned_up = sd.region_align_up(top);
1375 HeapWord* const new_top = _space_info[id].new_top();
1376 HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1377 HeapWord* const bottom = space->bottom();
1378 const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1379 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1380 const RegionData* const new_top_cp =
1381 sd.addr_to_region_ptr(new_top_aligned_up);
1382
1383 // Skip full regions at the beginning of the space--they are necessarily part
1384 // of the dense prefix.
1385 const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1386 assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1387 space->is_empty(), "no dead space allowed to the left");
1388 assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1389 "region must have dead space");
1390
1391 // The gc number is saved whenever a maximum compaction is done, and used to
1392 // determine when the maximum compaction interval has expired. This avoids
1393 // successive max compactions for different reasons.
1394 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1395 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1396 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1397 total_invocations() == HeapFirstMaximumCompactionCount;
1398 if (maximum_compaction || full_cp == top_cp || interval_ended) {
1399 _maximum_compaction_gc_num = total_invocations();
1400 return sd.region_to_addr(full_cp);
1401 }
1402
1403 const size_t space_live = pointer_delta(new_top, bottom);
1404 const size_t space_used = space->used_in_words();
1405 const size_t space_capacity = space->capacity_in_words();
1406
1407 const double density = double(space_live) / double(space_capacity);
1408 const size_t min_percent_free = MarkSweepDeadRatio;
1409 const double limiter = dead_wood_limiter(density, min_percent_free);
1410 const size_t dead_wood_max = space_used - space_live;
1411 const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1412 dead_wood_max);
1413
1414 log_develop_debug(gc, compaction)(
1415 "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1416 "space_cap=" SIZE_FORMAT,
1417 space_live, space_used,
1418 space_capacity);
1419 log_develop_debug(gc, compaction)(
1420 "dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1421 "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1422 density, min_percent_free, limiter,
1423 dead_wood_max, dead_wood_limit);
1424
1425 // Locate the region with the desired amount of dead space to the left.
1426 const RegionData* const limit_cp =
1427 dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1428
1429 // Scan from the first region with dead space to the limit region and find the
1430 // one with the best (largest) reclaimed ratio.
1431 double best_ratio = 0.0;
1432 const RegionData* best_cp = full_cp;
1433 for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1434 double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1435 if (tmp_ratio > best_ratio) {
1436 best_cp = cp;
1437 best_ratio = tmp_ratio;
1438 }
1439 }
1440
1441 return sd.region_to_addr(best_cp);
1442 }
1443
1444 void PSParallelCompact::summarize_spaces_quick()
1445 {
1446 for (unsigned int i = 0; i < last_space_id; ++i) {
1447 const MutableSpace* space = _space_info[i].space();
1448 HeapWord** nta = _space_info[i].new_top_addr();
1449 bool result = _summary_data.summarize(_space_info[i].split_info(),
1450 space->bottom(), space->top(), NULL,
1451 space->bottom(), space->end(), nta);
1452 assert(result, "space must fit into itself");
1453 _space_info[i].set_dense_prefix(space->bottom());
1454 }
1455 }
1456
1457 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1458 {
1459 HeapWord* const dense_prefix_end = dense_prefix(id);
1460 const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1461 const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1462 if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1463 // Only enough dead space is filled so that any remaining dead space to the
1464 // left is larger than the minimum filler object. (The remainder is filled
1465 // during the copy/update phase.)
1466 //
1467 // The size of the dead space to the right of the boundary is not a
1468 // concern, since compaction will be able to use whatever space is
1469 // available.
1470 //
1471 // Here '||' is the boundary, 'x' represents a don't care bit and a box
1472 // surrounds the space to be filled with an object.
1473 //
1474 // In the 32-bit VM, each bit represents two 32-bit words:
1475 // +---+
1476 // a) beg_bits: ... x x x | 0 | || 0 x x ...
1477 // end_bits: ... x x x | 0 | || 0 x x ...
1478 // +---+
1479 //
1480 // In the 64-bit VM, each bit represents one 64-bit word:
1481 // +------------+
1482 // b) beg_bits: ... x x x | 0 || 0 | x x ...
1483 // end_bits: ... x x 1 | 0 || 0 | x x ...
1484 // +------------+
1485 // +-------+
1486 // c) beg_bits: ... x x | 0 0 | || 0 x x ...
1487 // end_bits: ... x 1 | 0 0 | || 0 x x ...
1488 // +-------+
1489 // +-----------+
1490 // d) beg_bits: ... x | 0 0 0 | || 0 x x ...
1491 // end_bits: ... 1 | 0 0 0 | || 0 x x ...
1492 // +-----------+
1493 // +-------+
1494 // e) beg_bits: ... 0 0 | 0 0 | || 0 x x ...
1495 // end_bits: ... 0 0 | 0 0 | || 0 x x ...
1496 // +-------+
1497
1498 // Initially assume case a, c or e will apply.
1499 size_t obj_len = CollectedHeap::min_fill_size();
1500 HeapWord* obj_beg = dense_prefix_end - obj_len;
1501
1502 #ifdef _LP64
1503 if (MinObjAlignment > 1) { // object alignment > heap word size
1504 // Cases a, c or e.
1505 } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1506 // Case b above.
1507 obj_beg = dense_prefix_end - 1;
1508 } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1509 _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1510 // Case d above.
1511 obj_beg = dense_prefix_end - 3;
1512 obj_len = 3;
1513 }
1514 #endif // #ifdef _LP64
1515
1516 CollectedHeap::fill_with_object(obj_beg, obj_len);
1517 _mark_bitmap.mark_obj(obj_beg, obj_len);
1518 _summary_data.add_obj(obj_beg, obj_len);
1519 assert(start_array(id) != NULL, "sanity");
1520 start_array(id)->allocate_block(obj_beg);
1521 }
1522 }
1523
1524 void
1525 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1526 {
1527 assert(id < last_space_id, "id out of range");
1528 assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1529 "should have been reset in summarize_spaces_quick()");
1530
1531 const MutableSpace* space = _space_info[id].space();
1532 if (_space_info[id].new_top() != space->bottom()) {
1533 HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1534 _space_info[id].set_dense_prefix(dense_prefix_end);
1535
1536 #ifndef PRODUCT
1537 if (log_is_enabled(Debug, gc, compaction)) {
1538 print_dense_prefix_stats("ratio", id, maximum_compaction,
1539 dense_prefix_end);
1540 HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1541 print_dense_prefix_stats("density", id, maximum_compaction, addr);
1542 }
1543 #endif // #ifndef PRODUCT
1544
1545 // Recompute the summary data, taking into account the dense prefix. If
1546 // every last byte will be reclaimed, then the existing summary data which
1547 // compacts everything can be left in place.
1548 if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1549 // If dead space crosses the dense prefix boundary, it is (at least
1550 // partially) filled with a dummy object, marked live and added to the
1551 // summary data. This simplifies the copy/update phase and must be done
1552 // before the final locations of objects are determined, to prevent
1553 // leaving a fragment of dead space that is too small to fill.
1554 fill_dense_prefix_end(id);
1555
1556 // Compute the destination of each Region, and thus each object.
1557 _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1558 _summary_data.summarize(_space_info[id].split_info(),
1559 dense_prefix_end, space->top(), NULL,
1560 dense_prefix_end, space->end(),
1561 _space_info[id].new_top_addr());
1562 }
1563 }
1564
1565 if (log_develop_is_enabled(Trace, gc, compaction)) {
1566 const size_t region_size = ParallelCompactData::RegionSize;
1567 HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1568 const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1569 const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1570 HeapWord* const new_top = _space_info[id].new_top();
1571 const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1572 const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1573 log_develop_trace(gc, compaction)(
1574 "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1575 "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1576 "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1577 id, space->capacity_in_words(), p2i(dense_prefix_end),
1578 dp_region, dp_words / region_size,
1579 cr_words / region_size, p2i(new_top));
1580 }
1581 }
1582
1583 #ifndef PRODUCT
1584 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1585 HeapWord* dst_beg, HeapWord* dst_end,
1586 SpaceId src_space_id,
1587 HeapWord* src_beg, HeapWord* src_end)
1588 {
1589 log_develop_trace(gc, compaction)(
1590 "Summarizing %d [%s] into %d [%s]: "
1591 "src=" PTR_FORMAT "-" PTR_FORMAT " "
1592 SIZE_FORMAT "-" SIZE_FORMAT " "
1593 "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1594 SIZE_FORMAT "-" SIZE_FORMAT,
1595 src_space_id, space_names[src_space_id],
1596 dst_space_id, space_names[dst_space_id],
1597 p2i(src_beg), p2i(src_end),
1598 _summary_data.addr_to_region_idx(src_beg),
1599 _summary_data.addr_to_region_idx(src_end),
1600 p2i(dst_beg), p2i(dst_end),
1601 _summary_data.addr_to_region_idx(dst_beg),
1602 _summary_data.addr_to_region_idx(dst_end));
1603 }
1604 #endif // #ifndef PRODUCT
1605
1606 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1607 bool maximum_compaction)
1608 {
1609 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1610
1611 log_develop_debug(gc, marking)(
1612 "add_obj_count=" SIZE_FORMAT " "
1613 "add_obj_bytes=" SIZE_FORMAT,
1614 add_obj_count,
1615 add_obj_size * HeapWordSize);
1616 log_develop_debug(gc, marking)(
1617 "mark_bitmap_count=" SIZE_FORMAT " "
1618 "mark_bitmap_bytes=" SIZE_FORMAT,
1619 mark_bitmap_count,
1620 mark_bitmap_size * HeapWordSize);
1621
1622 // Quick summarization of each space into itself, to see how much is live.
1623 summarize_spaces_quick();
1624
1625 log_develop_trace(gc, compaction)("summary phase: after summarizing each space to self");
1626 NOT_PRODUCT(print_region_ranges());
1627 NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1628
1629 // The amount of live data that will end up in old space (assuming it fits).
1630 size_t old_space_total_live = 0;
1631 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1632 old_space_total_live += pointer_delta(_space_info[id].new_top(),
1633 _space_info[id].space()->bottom());
1634 }
1635
1636 MutableSpace* const old_space = _space_info[old_space_id].space();
1637 const size_t old_capacity = old_space->capacity_in_words();
1638 if (old_space_total_live > old_capacity) {
1639 // XXX - should also try to expand
1640 maximum_compaction = true;
1641 }
1642
1643 // Old generations.
1644 summarize_space(old_space_id, maximum_compaction);
1645
1646 // Summarize the remaining spaces in the young gen. The initial target space
1647 // is the old gen. If a space does not fit entirely into the target, then the
1648 // remainder is compacted into the space itself and that space becomes the new
1649 // target.
1650 SpaceId dst_space_id = old_space_id;
1651 HeapWord* dst_space_end = old_space->end();
1652 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1653 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1654 const MutableSpace* space = _space_info[id].space();
1655 const size_t live = pointer_delta(_space_info[id].new_top(),
1656 space->bottom());
1657 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1658
1659 NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1660 SpaceId(id), space->bottom(), space->top());)
1661 if (live > 0 && live <= available) {
1662 // All the live data will fit.
1663 bool done = _summary_data.summarize(_space_info[id].split_info(),
1664 space->bottom(), space->top(),
1665 NULL,
1666 *new_top_addr, dst_space_end,
1667 new_top_addr);
1668 assert(done, "space must fit into old gen");
1669
1670 // Reset the new_top value for the space.
1671 _space_info[id].set_new_top(space->bottom());
1672 } else if (live > 0) {
1673 // Attempt to fit part of the source space into the target space.
1674 HeapWord* next_src_addr = NULL;
1675 bool done = _summary_data.summarize(_space_info[id].split_info(),
1676 space->bottom(), space->top(),
1677 &next_src_addr,
1678 *new_top_addr, dst_space_end,
1679 new_top_addr);
1680 assert(!done, "space should not fit into old gen");
1681 assert(next_src_addr != NULL, "sanity");
1682
1683 // The source space becomes the new target, so the remainder is compacted
1684 // within the space itself.
1685 dst_space_id = SpaceId(id);
1686 dst_space_end = space->end();
1687 new_top_addr = _space_info[id].new_top_addr();
1688 NOT_PRODUCT(summary_phase_msg(dst_space_id,
1689 space->bottom(), dst_space_end,
1690 SpaceId(id), next_src_addr, space->top());)
1691 done = _summary_data.summarize(_space_info[id].split_info(),
1692 next_src_addr, space->top(),
1693 NULL,
1694 space->bottom(), dst_space_end,
1695 new_top_addr);
1696 assert(done, "space must fit when compacted into itself");
1697 assert(*new_top_addr <= space->top(), "usage should not grow");
1698 }
1699 }
1700
1701 log_develop_trace(gc, compaction)("Summary_phase: after final summarization");
1702 NOT_PRODUCT(print_region_ranges());
1703 NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1704 }
1705
1706 // This method should contain all heap-specific policy for invoking a full
1707 // collection. invoke_no_policy() will only attempt to compact the heap; it
1708 // will do nothing further. If we need to bail out for policy reasons, scavenge
1709 // before full gc, or any other specialized behavior, it needs to be added here.
1710 //
1711 // Note that this method should only be called from the vm_thread while at a
1712 // safepoint.
1713 //
1714 // Note that the all_soft_refs_clear flag in the soft ref policy
1715 // may be true because this method can be called without intervening
1716 // activity. For example when the heap space is tight and full measure
1717 // are being taken to free space.
1718 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1719 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1720 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1721 "should be in vm thread");
1722
1723 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1724 GCCause::Cause gc_cause = heap->gc_cause();
1725 assert(!heap->is_gc_active(), "not reentrant");
1726
1727 PSAdaptiveSizePolicy* policy = heap->size_policy();
1728 IsGCActiveMark mark;
1729
1730 if (ScavengeBeforeFullGC) {
1731 PSScavenge::invoke_no_policy();
1732 }
1733
1734 const bool clear_all_soft_refs =
1735 heap->soft_ref_policy()->should_clear_all_soft_refs();
1736
1737 PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1738 maximum_heap_compaction);
1739 }
1740
1741 // This method contains no policy. You should probably
1742 // be calling invoke() instead.
1743 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1744 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1745 assert(ref_processor() != NULL, "Sanity");
1746
1747 if (GCLocker::check_active_before_gc()) {
1748 return false;
1749 }
1750
1751 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1752
1753 GCIdMark gc_id_mark;
1754 _gc_timer.register_gc_start();
1755 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1756
1757 TimeStamp marking_start;
1758 TimeStamp compaction_start;
1759 TimeStamp collection_exit;
1760
1761 GCCause::Cause gc_cause = heap->gc_cause();
1762 PSYoungGen* young_gen = heap->young_gen();
1763 PSOldGen* old_gen = heap->old_gen();
1764 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1765
1766 // The scope of casr should end after code that can change
1767 // SoftRefPolicy::_should_clear_all_soft_refs.
1768 ClearedAllSoftRefs casr(maximum_heap_compaction,
1769 heap->soft_ref_policy());
1770
1771 if (ZapUnusedHeapArea) {
1772 // Save information needed to minimize mangling
1773 heap->record_gen_tops_before_GC();
1774 }
1775
1776 // Make sure data structures are sane, make the heap parsable, and do other
1777 // miscellaneous bookkeeping.
1778 pre_compact();
1779
1780 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1781
1782 // Get the compaction manager reserved for the VM thread.
1783 ParCompactionManager* const vmthread_cm =
1784 ParCompactionManager::manager_array(ParallelScavengeHeap::heap()->workers().total_workers());
1785
1786 {
1787 ResourceMark rm;
1788
1789 const uint active_workers =
1790 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
1791 ParallelScavengeHeap::heap()->workers().active_workers(),
1792 Threads::number_of_non_daemon_threads());
1793 ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
1794
1795 GCTraceCPUTime tcpu;
1796 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1797
1798 heap->pre_full_gc_dump(&_gc_timer);
1799
1800 TraceCollectorStats tcs(counters());
1801 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1802
1803 if (log_is_enabled(Debug, gc, heap, exit)) {
1804 accumulated_time()->start();
1805 }
1806
1807 // Let the size policy know we're starting
1808 size_policy->major_collection_begin();
1809
1810 #if COMPILER2_OR_JVMCI
1811 DerivedPointerTable::clear();
1812 #endif
1813
1814 ref_processor()->enable_discovery();
1815 ref_processor()->setup_policy(maximum_heap_compaction);
1816
1817 bool marked_for_unloading = false;
1818
1819 marking_start.update();
1820 marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1821
1822 bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1823 && GCCause::is_user_requested_gc(gc_cause);
1824 summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1825
1826 #if COMPILER2_OR_JVMCI
1827 assert(DerivedPointerTable::is_active(), "Sanity");
1828 DerivedPointerTable::set_active(false);
1829 #endif
1830
1831 // adjust_roots() updates Universe::_intArrayKlassObj which is
1832 // needed by the compaction for filling holes in the dense prefix.
1833 adjust_roots(vmthread_cm);
1834
1835 compaction_start.update();
1836 compact();
1837
1838 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1839 // done before resizing.
1840 post_compact();
1841
1842 // Let the size policy know we're done
1843 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1844
1845 if (UseAdaptiveSizePolicy) {
1846 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1847 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1848 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1849
1850 // Don't check if the size_policy is ready here. Let
1851 // the size_policy check that internally.
1852 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1853 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1854 // Swap the survivor spaces if from_space is empty. The
1855 // resize_young_gen() called below is normally used after
1856 // a successful young GC and swapping of survivor spaces;
1857 // otherwise, it will fail to resize the young gen with
1858 // the current implementation.
1859 if (young_gen->from_space()->is_empty()) {
1860 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1861 young_gen->swap_spaces();
1862 }
1863
1864 // Calculate optimal free space amounts
1865 assert(young_gen->max_gen_size() >
1866 young_gen->from_space()->capacity_in_bytes() +
1867 young_gen->to_space()->capacity_in_bytes(),
1868 "Sizes of space in young gen are out-of-bounds");
1869
1870 size_t young_live = young_gen->used_in_bytes();
1871 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1872 size_t old_live = old_gen->used_in_bytes();
1873 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1874 size_t max_old_gen_size = old_gen->max_gen_size();
1875 size_t max_eden_size = young_gen->max_gen_size() -
1876 young_gen->from_space()->capacity_in_bytes() -
1877 young_gen->to_space()->capacity_in_bytes();
1878
1879 // Used for diagnostics
1880 size_policy->clear_generation_free_space_flags();
1881
1882 size_policy->compute_generations_free_space(young_live,
1883 eden_live,
1884 old_live,
1885 cur_eden,
1886 max_old_gen_size,
1887 max_eden_size,
1888 true /* full gc*/);
1889
1890 size_policy->check_gc_overhead_limit(eden_live,
1891 max_old_gen_size,
1892 max_eden_size,
1893 true /* full gc*/,
1894 gc_cause,
1895 heap->soft_ref_policy());
1896
1897 size_policy->decay_supplemental_growth(true /* full gc*/);
1898
1899 heap->resize_old_gen(
1900 size_policy->calculated_old_free_size_in_bytes());
1901
1902 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1903 size_policy->calculated_survivor_size_in_bytes());
1904 }
1905
1906 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1907 }
1908
1909 if (UsePerfData) {
1910 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1911 counters->update_counters();
1912 counters->update_old_capacity(old_gen->capacity_in_bytes());
1913 counters->update_young_capacity(young_gen->capacity_in_bytes());
1914 }
1915
1916 heap->resize_all_tlabs();
1917
1918 // Resize the metaspace capacity after a collection
1919 MetaspaceGC::compute_new_size();
1920
1921 if (log_is_enabled(Debug, gc, heap, exit)) {
1922 accumulated_time()->stop();
1923 }
1924
1925 heap->print_heap_change(pre_gc_values);
1926
1927 // Track memory usage and detect low memory
1928 MemoryService::track_memory_usage();
1929 heap->update_counters();
1930
1931 heap->post_full_gc_dump(&_gc_timer);
1932 }
1933
1934 #ifdef ASSERT
1935 for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1936 ParCompactionManager* const cm =
1937 ParCompactionManager::manager_array(int(i));
1938 assert(cm->marking_stack()->is_empty(), "should be empty");
1939 assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1940 }
1941 #endif // ASSERT
1942
1943 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1944 Universe::verify("After GC");
1945 }
1946
1947 // Re-verify object start arrays
1948 if (VerifyObjectStartArray &&
1949 VerifyAfterGC) {
1950 old_gen->verify_object_start_array();
1951 }
1952
1953 if (ZapUnusedHeapArea) {
1954 old_gen->object_space()->check_mangled_unused_area_complete();
1955 }
1956
1957 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1958
1959 collection_exit.update();
1960
1961 heap->print_heap_after_gc();
1962 heap->trace_heap_after_gc(&_gc_tracer);
1963
1964 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1965 marking_start.ticks(), compaction_start.ticks(),
1966 collection_exit.ticks());
1967
1968 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1969
1970 _gc_timer.register_gc_end();
1971
1972 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1973 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1974
1975 return true;
1976 }
1977
1978 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1979 private:
1980 uint _worker_id;
1981
1982 public:
1983 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1984 void do_thread(Thread* thread) {
1985 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
1986
1987 ResourceMark rm;
1988
1989 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1990
1991 PCMarkAndPushClosure mark_and_push_closure(cm);
1992 MarkingCodeBlobClosure mark_and_push_in_blobs(&mark_and_push_closure, !CodeBlobToOopClosure::FixRelocations);
1993
1994 thread->oops_do(&mark_and_push_closure, &mark_and_push_in_blobs);
1995
1996 // Do the real work
1997 cm->follow_marking_stacks();
1998 }
1999 };
2000
2001 static void mark_from_roots_work(ParallelRootType::Value root_type, uint worker_id) {
2002 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2003
2004 ParCompactionManager* cm =
2005 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2006 PCMarkAndPushClosure mark_and_push_closure(cm);
2007
2008 switch (root_type) {
2009 case ParallelRootType::universe:
2010 Universe::oops_do(&mark_and_push_closure);
2011 break;
2012
2013 case ParallelRootType::object_synchronizer:
2014 ObjectSynchronizer::oops_do(&mark_and_push_closure);
2015 break;
2016
2017 case ParallelRootType::class_loader_data:
2018 {
2019 CLDToOopClosure cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_strong);
2020 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
2021 }
2022 break;
2023
2024 case ParallelRootType::code_cache:
2025 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
2026 //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
2027 AOTLoader::oops_do(&mark_and_push_closure);
2028 break;
2029
2030 case ParallelRootType::sentinel:
2031 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
2032 fatal("Bad enumeration value: %u", root_type);
2033 break;
2034 }
2035
2036 // Do the real work
2037 cm->follow_marking_stacks();
2038 }
2039
2040 static void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
2041 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2042
2043 ParCompactionManager* cm =
2044 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2045
2046 oop obj = NULL;
2047 ObjArrayTask task;
2048 do {
2049 while (ParCompactionManager::steal_objarray(worker_id, task)) {
2050 cm->follow_array((objArrayOop)task.obj(), task.index());
2051 cm->follow_marking_stacks();
2052 }
2053 while (ParCompactionManager::steal(worker_id, obj)) {
2054 cm->follow_contents(obj);
2055 cm->follow_marking_stacks();
2056 }
2057 } while (!terminator.offer_termination());
2058 }
2059
2060 class MarkFromRootsTask : public AbstractGangTask {
2061 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2062 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
2063 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
2064 SequentialSubTasksDone _subtasks;
2065 TaskTerminator _terminator;
2066 uint _active_workers;
2067
2068 public:
2069 MarkFromRootsTask(uint active_workers) :
2070 AbstractGangTask("MarkFromRootsTask"),
2071 _strong_roots_scope(active_workers),
2072 _subtasks(),
2073 _terminator(active_workers, ParCompactionManager::oop_task_queues()),
2074 _active_workers(active_workers) {
2075 _subtasks.set_n_threads(active_workers);
2076 _subtasks.set_n_tasks(ParallelRootType::sentinel);
2077 }
2078
2079 virtual void work(uint worker_id) {
2080 for (uint task = 0; _subtasks.try_claim_task(task); /*empty*/ ) {
2081 mark_from_roots_work(static_cast<ParallelRootType::Value>(task), worker_id);
2082 }
2083 _subtasks.all_tasks_completed();
2084
2085 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
2086 Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
2087
2088 // Mark from OopStorages
2089 {
2090 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2091 PCMarkAndPushClosure closure(cm);
2092 _oop_storage_set_par_state.oops_do(&closure);
2093 // Do the real work
2094 cm->follow_marking_stacks();
2095 }
2096
2097 if (_active_workers > 1) {
2098 steal_marking_work(_terminator, worker_id);
2099 }
2100 }
2101 };
2102
2103 class PCRefProcTask : public AbstractGangTask {
2104 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2105 ProcessTask& _task;
2106 uint _ergo_workers;
2107 TaskTerminator _terminator;
2108
2109 public:
2110 PCRefProcTask(ProcessTask& task, uint ergo_workers) :
2111 AbstractGangTask("PCRefProcTask"),
2112 _task(task),
2113 _ergo_workers(ergo_workers),
2114 _terminator(_ergo_workers, ParCompactionManager::oop_task_queues()) {
2115 }
2116
2117 virtual void work(uint worker_id) {
2118 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2119 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2120
2121 ParCompactionManager* cm =
2122 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2123 PCMarkAndPushClosure mark_and_push_closure(cm);
2124 ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2125 _task.work(worker_id, *PSParallelCompact::is_alive_closure(),
2126 mark_and_push_closure, follow_stack_closure);
2127
2128 steal_marking_work(_terminator, worker_id);
2129 }
2130 };
2131
2132 class RefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2133 void execute(ProcessTask& process_task, uint ergo_workers) {
2134 assert(ParallelScavengeHeap::heap()->workers().active_workers() == ergo_workers,
2135 "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
2136 ergo_workers, ParallelScavengeHeap::heap()->workers().active_workers());
2137
2138 PCRefProcTask task(process_task, ergo_workers);
2139 ParallelScavengeHeap::heap()->workers().run_task(&task);
2140 }
2141 };
2142
2143 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2144 bool maximum_heap_compaction,
2145 ParallelOldTracer *gc_tracer) {
2146 // Recursively traverse all live objects and mark them
2147 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2148
2149 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2150 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2151
2152 PCMarkAndPushClosure mark_and_push_closure(cm);
2153 ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2154
2155 // Need new claim bits before marking starts.
2156 ClassLoaderDataGraph::clear_claimed_marks();
2157
2158 {
2159 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2160
2161 MarkFromRootsTask task(active_gc_threads);
2162 ParallelScavengeHeap::heap()->workers().run_task(&task);
2163 }
2164
2165 // Process reference objects found during marking
2166 {
2167 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2168
2169 ReferenceProcessorStats stats;
2170 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2171
2172 if (ref_processor()->processing_is_mt()) {
2173 ref_processor()->set_active_mt_degree(active_gc_threads);
2174
2175 RefProcTaskExecutor task_executor;
2176 stats = ref_processor()->process_discovered_references(
2177 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2178 &task_executor, &pt);
2179 } else {
2180 stats = ref_processor()->process_discovered_references(
2181 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2182 &pt);
2183 }
2184
2185 gc_tracer->report_gc_reference_stats(stats);
2186 pt.print_all_references();
2187 }
2188
2189 // This is the point where the entire marking should have completed.
2190 assert(cm->marking_stacks_empty(), "Marking should have completed");
2191
2192 {
2193 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2194 WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2195 }
2196
2197 {
2198 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2199
2200 // Follow system dictionary roots and unload classes.
2201 bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2202
2203 // Unload nmethods.
2204 CodeCache::do_unloading(is_alive_closure(), purged_class);
2205
2206 // Prune dead klasses from subklass/sibling/implementor lists.
2207 Klass::clean_weak_klass_links(purged_class);
2208
2209 // Clean JVMCI metadata handles.
2210 JVMCI_ONLY(JVMCI::do_unloading(purged_class));
2211 }
2212
2213 _gc_tracer.report_object_count_after_gc(is_alive_closure());
2214 }
2215
2216 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2217 // Adjust the pointers to reflect the new locations
2218 GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2219
2220 // Need new claim bits when tracing through and adjusting pointers.
2221 ClassLoaderDataGraph::clear_claimed_marks();
2222
2223 PCAdjustPointerClosure oop_closure(cm);
2224
2225 // General strong roots.
2226 Universe::oops_do(&oop_closure);
2227 Threads::oops_do(&oop_closure, NULL);
2228 ObjectSynchronizer::oops_do(&oop_closure);
2229 OopStorageSet::strong_oops_do(&oop_closure);
2230 CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
2231 ClassLoaderDataGraph::cld_do(&cld_closure);
2232
2233 // Now adjust pointers in remaining weak roots. (All of which should
2234 // have been cleared if they pointed to non-surviving objects.)
2235 WeakProcessor::oops_do(&oop_closure);
2236
2237 CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2238 CodeCache::blobs_do(&adjust_from_blobs);
2239 AOT_ONLY(AOTLoader::oops_do(&oop_closure);)
2240
2241 ref_processor()->weak_oops_do(&oop_closure);
2242 // Roots were visited so references into the young gen in roots
2243 // may have been scanned. Process them also.
2244 // Should the reference processor have a span that excludes
2245 // young gen objects?
2246 PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2247 }
2248
2249 // Helper class to print 8 region numbers per line and then print the total at the end.
2250 class FillableRegionLogger : public StackObj {
2251 private:
2252 Log(gc, compaction) log;
2253 static const int LineLength = 8;
2254 size_t _regions[LineLength];
2255 int _next_index;
2256 bool _enabled;
2257 size_t _total_regions;
2258 public:
2259 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
2260 ~FillableRegionLogger() {
2261 log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2262 }
2263
2264 void print_line() {
2265 if (!_enabled || _next_index == 0) {
2266 return;
2267 }
2268 FormatBuffer<> line("Fillable: ");
2269 for (int i = 0; i < _next_index; i++) {
2270 line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2271 }
2272 log.trace("%s", line.buffer());
2273 _next_index = 0;
2274 }
2275
2276 void handle(size_t region) {
2277 if (!_enabled) {
2278 return;
2279 }
2280 _regions[_next_index++] = region;
2281 if (_next_index == LineLength) {
2282 print_line();
2283 }
2284 _total_regions++;
2285 }
2286 };
2287
2288 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
2289 {
2290 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2291
2292 // Find the threads that are active
2293 uint worker_id = 0;
2294
2295 // Find all regions that are available (can be filled immediately) and
2296 // distribute them to the thread stacks. The iteration is done in reverse
2297 // order (high to low) so the regions will be removed in ascending order.
2298
2299 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2300
2301 // id + 1 is used to test termination so unsigned can
2302 // be used with an old_space_id == 0.
2303 FillableRegionLogger region_logger;
2304 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2305 SpaceInfo* const space_info = _space_info + id;
2306 MutableSpace* const space = space_info->space();
2307 HeapWord* const new_top = space_info->new_top();
2308
2309 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2310 const size_t end_region =
2311 sd.addr_to_region_idx(sd.region_align_up(new_top));
2312
2313 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2314 if (sd.region(cur)->claim_unsafe()) {
2315 ParCompactionManager* cm = ParCompactionManager::manager_array(worker_id);
2316 bool result = sd.region(cur)->mark_normal();
2317 assert(result, "Must succeed at this point.");
2318 cm->region_stack()->push(cur);
2319 region_logger.handle(cur);
2320 // Assign regions to tasks in round-robin fashion.
2321 if (++worker_id == parallel_gc_threads) {
2322 worker_id = 0;
2323 }
2324 }
2325 }
2326 region_logger.print_line();
2327 }
2328 }
2329
2330 class TaskQueue : StackObj {
2331 volatile uint _counter;
2332 uint _size;
2333 uint _insert_index;
2334 PSParallelCompact::UpdateDensePrefixTask* _backing_array;
2335 public:
2336 explicit TaskQueue(uint size) : _counter(0), _size(size), _insert_index(0), _backing_array(NULL) {
2337 _backing_array = NEW_C_HEAP_ARRAY(PSParallelCompact::UpdateDensePrefixTask, _size, mtGC);
2338 }
2339 ~TaskQueue() {
2340 assert(_counter >= _insert_index, "not all queue elements were claimed");
2341 FREE_C_HEAP_ARRAY(T, _backing_array);
2342 }
2343
2344 void push(const PSParallelCompact::UpdateDensePrefixTask& value) {
2345 assert(_insert_index < _size, "too small backing array");
2346 _backing_array[_insert_index++] = value;
2347 }
2348
2349 bool try_claim(PSParallelCompact::UpdateDensePrefixTask& reference) {
2350 uint claimed = Atomic::fetch_and_add(&_counter, 1u);
2351 if (claimed < _insert_index) {
2352 reference = _backing_array[claimed];
2353 return true;
2354 } else {
2355 return false;
2356 }
2357 }
2358 };
2359
2360 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2361
2362 void PSParallelCompact::enqueue_dense_prefix_tasks(TaskQueue& task_queue,
2363 uint parallel_gc_threads) {
2364 GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2365
2366 ParallelCompactData& sd = PSParallelCompact::summary_data();
2367
2368 // Iterate over all the spaces adding tasks for updating
2369 // regions in the dense prefix. Assume that 1 gc thread
2370 // will work on opening the gaps and the remaining gc threads
2371 // will work on the dense prefix.
2372 unsigned int space_id;
2373 for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2374 HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2375 const MutableSpace* const space = _space_info[space_id].space();
2376
2377 if (dense_prefix_end == space->bottom()) {
2378 // There is no dense prefix for this space.
2379 continue;
2380 }
2381
2382 // The dense prefix is before this region.
2383 size_t region_index_end_dense_prefix =
2384 sd.addr_to_region_idx(dense_prefix_end);
2385 RegionData* const dense_prefix_cp =
2386 sd.region(region_index_end_dense_prefix);
2387 assert(dense_prefix_end == space->end() ||
2388 dense_prefix_cp->available() ||
2389 dense_prefix_cp->claimed(),
2390 "The region after the dense prefix should always be ready to fill");
2391
2392 size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2393
2394 // Is there dense prefix work?
2395 size_t total_dense_prefix_regions =
2396 region_index_end_dense_prefix - region_index_start;
2397 // How many regions of the dense prefix should be given to
2398 // each thread?
2399 if (total_dense_prefix_regions > 0) {
2400 uint tasks_for_dense_prefix = 1;
2401 if (total_dense_prefix_regions <=
2402 (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2403 // Don't over partition. This assumes that
2404 // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2405 // so there are not many regions to process.
2406 tasks_for_dense_prefix = parallel_gc_threads;
2407 } else {
2408 // Over partition
2409 tasks_for_dense_prefix = parallel_gc_threads *
2410 PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2411 }
2412 size_t regions_per_thread = total_dense_prefix_regions /
2413 tasks_for_dense_prefix;
2414 // Give each thread at least 1 region.
2415 if (regions_per_thread == 0) {
2416 regions_per_thread = 1;
2417 }
2418
2419 for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2420 if (region_index_start >= region_index_end_dense_prefix) {
2421 break;
2422 }
2423 // region_index_end is not processed
2424 size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2425 region_index_end_dense_prefix);
2426 task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2427 region_index_start,
2428 region_index_end));
2429 region_index_start = region_index_end;
2430 }
2431 }
2432 // This gets any part of the dense prefix that did not
2433 // fit evenly.
2434 if (region_index_start < region_index_end_dense_prefix) {
2435 task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2436 region_index_start,
2437 region_index_end_dense_prefix));
2438 }
2439 }
2440 }
2441
2442 #ifdef ASSERT
2443 // Write a histogram of the number of times the block table was filled for a
2444 // region.
2445 void PSParallelCompact::write_block_fill_histogram()
2446 {
2447 if (!log_develop_is_enabled(Trace, gc, compaction)) {
2448 return;
2449 }
2450
2451 Log(gc, compaction) log;
2452 ResourceMark rm;
2453 LogStream ls(log.trace());
2454 outputStream* out = &ls;
2455
2456 typedef ParallelCompactData::RegionData rd_t;
2457 ParallelCompactData& sd = summary_data();
2458
2459 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2460 MutableSpace* const spc = _space_info[id].space();
2461 if (spc->bottom() != spc->top()) {
2462 const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2463 HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2464 const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2465
2466 size_t histo[5] = { 0, 0, 0, 0, 0 };
2467 const size_t histo_len = sizeof(histo) / sizeof(size_t);
2468 const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2469
2470 for (const rd_t* cur = beg; cur < end; ++cur) {
2471 ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2472 }
2473 out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2474 for (size_t i = 0; i < histo_len; ++i) {
2475 out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2476 histo[i], 100.0 * histo[i] / region_cnt);
2477 }
2478 out->cr();
2479 }
2480 }
2481 }
2482 #endif // #ifdef ASSERT
2483
2484 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
2485 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2486
2487 ParCompactionManager* cm =
2488 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2489
2490 // Drain the stacks that have been preloaded with regions
2491 // that are ready to fill.
2492
2493 cm->drain_region_stacks();
2494
2495 guarantee(cm->region_stack()->is_empty(), "Not empty");
2496
2497 size_t region_index = 0;
2498
2499 while (true) {
2500 if (ParCompactionManager::steal(worker_id, region_index)) {
2501 PSParallelCompact::fill_and_update_region(cm, region_index);
2502 cm->drain_region_stacks();
2503 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
2504 // Fill and update an unavailable region with the help of a shadow region
2505 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
2506 cm->drain_region_stacks();
2507 } else {
2508 if (terminator->offer_termination()) {
2509 break;
2510 }
2511 // Go around again.
2512 }
2513 }
2514 return;
2515 }
2516
2517 class UpdateDensePrefixAndCompactionTask: public AbstractGangTask {
2518 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2519 TaskQueue& _tq;
2520 TaskTerminator _terminator;
2521 uint _active_workers;
2522
2523 public:
2524 UpdateDensePrefixAndCompactionTask(TaskQueue& tq, uint active_workers) :
2525 AbstractGangTask("UpdateDensePrefixAndCompactionTask"),
2526 _tq(tq),
2527 _terminator(active_workers, ParCompactionManager::region_task_queues()),
2528 _active_workers(active_workers) {
2529 }
2530 virtual void work(uint worker_id) {
2531 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2532
2533 for (PSParallelCompact::UpdateDensePrefixTask task; _tq.try_claim(task); /* empty */) {
2534 PSParallelCompact::update_and_deadwood_in_dense_prefix(cm,
2535 task._space_id,
2536 task._region_index_start,
2537 task._region_index_end);
2538 }
2539
2540 // Once a thread has drained it's stack, it should try to steal regions from
2541 // other threads.
2542 compaction_with_stealing_work(&_terminator, worker_id);
2543 }
2544 };
2545
2546 void PSParallelCompact::compact() {
2547 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2548
2549 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2550 PSOldGen* old_gen = heap->old_gen();
2551 old_gen->start_array()->reset();
2552 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2553
2554 // for [0..last_space_id)
2555 // for [0..active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)
2556 // push
2557 // push
2558 //
2559 // max push count is thus: last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1)
2560 TaskQueue task_queue(last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1));
2561 initialize_shadow_regions(active_gc_threads);
2562 prepare_region_draining_tasks(active_gc_threads);
2563 enqueue_dense_prefix_tasks(task_queue, active_gc_threads);
2564
2565 {
2566 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2567
2568 UpdateDensePrefixAndCompactionTask task(task_queue, active_gc_threads);
2569 ParallelScavengeHeap::heap()->workers().run_task(&task);
2570
2571 #ifdef ASSERT
2572 // Verify that all regions have been processed before the deferred updates.
2573 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2574 verify_complete(SpaceId(id));
2575 }
2576 #endif
2577 }
2578
2579 {
2580 // Update the deferred objects, if any. Any compaction manager can be used.
2581 GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2582 ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2583 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2584 update_deferred_objects(cm, SpaceId(id));
2585 }
2586 }
2587
2588 DEBUG_ONLY(write_block_fill_histogram());
2589 }
2590
2591 #ifdef ASSERT
2592 void PSParallelCompact::verify_complete(SpaceId space_id) {
2593 // All Regions between space bottom() to new_top() should be marked as filled
2594 // and all Regions between new_top() and top() should be available (i.e.,
2595 // should have been emptied).
2596 ParallelCompactData& sd = summary_data();
2597 SpaceInfo si = _space_info[space_id];
2598 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2599 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2600 const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2601 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2602 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2603
2604 bool issued_a_warning = false;
2605
2606 size_t cur_region;
2607 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2608 const RegionData* const c = sd.region(cur_region);
2609 if (!c->completed()) {
2610 log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2611 cur_region, c->destination_count());
2612 issued_a_warning = true;
2613 }
2614 }
2615
2616 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2617 const RegionData* const c = sd.region(cur_region);
2618 if (!c->available()) {
2619 log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2620 cur_region, c->destination_count());
2621 issued_a_warning = true;
2622 }
2623 }
2624
2625 if (issued_a_warning) {
2626 print_region_ranges();
2627 }
2628 }
2629 #endif // #ifdef ASSERT
2630
2631 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2632 _start_array->allocate_block(addr);
2633 compaction_manager()->update_contents(oop(addr));
2634 }
2635
2636 // Update interior oops in the ranges of regions [beg_region, end_region).
2637 void
2638 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2639 SpaceId space_id,
2640 size_t beg_region,
2641 size_t end_region) {
2642 ParallelCompactData& sd = summary_data();
2643 ParMarkBitMap* const mbm = mark_bitmap();
2644
2645 HeapWord* beg_addr = sd.region_to_addr(beg_region);
2646 HeapWord* const end_addr = sd.region_to_addr(end_region);
2647 assert(beg_region <= end_region, "bad region range");
2648 assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2649
2650 #ifdef ASSERT
2651 // Claim the regions to avoid triggering an assert when they are marked as
2652 // filled.
2653 for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2654 assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2655 }
2656 #endif // #ifdef ASSERT
2657
2658 if (beg_addr != space(space_id)->bottom()) {
2659 // Find the first live object or block of dead space that *starts* in this
2660 // range of regions. If a partial object crosses onto the region, skip it;
2661 // it will be marked for 'deferred update' when the object head is
2662 // processed. If dead space crosses onto the region, it is also skipped; it
2663 // will be filled when the prior region is processed. If neither of those
2664 // apply, the first word in the region is the start of a live object or dead
2665 // space.
2666 assert(beg_addr > space(space_id)->bottom(), "sanity");
2667 const RegionData* const cp = sd.region(beg_region);
2668 if (cp->partial_obj_size() != 0) {
2669 beg_addr = sd.partial_obj_end(beg_region);
2670 } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2671 beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2672 }
2673 }
2674
2675 if (beg_addr < end_addr) {
2676 // A live object or block of dead space starts in this range of Regions.
2677 HeapWord* const dense_prefix_end = dense_prefix(space_id);
2678
2679 // Create closures and iterate.
2680 UpdateOnlyClosure update_closure(mbm, cm, space_id);
2681 FillClosure fill_closure(cm, space_id);
2682 ParMarkBitMap::IterationStatus status;
2683 status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2684 dense_prefix_end);
2685 if (status == ParMarkBitMap::incomplete) {
2686 update_closure.do_addr(update_closure.source());
2687 }
2688 }
2689
2690 // Mark the regions as filled.
2691 RegionData* const beg_cp = sd.region(beg_region);
2692 RegionData* const end_cp = sd.region(end_region);
2693 for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2694 cp->set_completed();
2695 }
2696 }
2697
2698 // Return the SpaceId for the space containing addr. If addr is not in the
2699 // heap, last_space_id is returned. In debug mode it expects the address to be
2700 // in the heap and asserts such.
2701 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2702 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2703
2704 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2705 if (_space_info[id].space()->contains(addr)) {
2706 return SpaceId(id);
2707 }
2708 }
2709
2710 assert(false, "no space contains the addr");
2711 return last_space_id;
2712 }
2713
2714 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2715 SpaceId id) {
2716 assert(id < last_space_id, "bad space id");
2717
2718 ParallelCompactData& sd = summary_data();
2719 const SpaceInfo* const space_info = _space_info + id;
2720 ObjectStartArray* const start_array = space_info->start_array();
2721
2722 const MutableSpace* const space = space_info->space();
2723 assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2724 HeapWord* const beg_addr = space_info->dense_prefix();
2725 HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2726
2727 const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2728 const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2729 const RegionData* cur_region;
2730 for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2731 HeapWord* const addr = cur_region->deferred_obj_addr();
2732 if (addr != NULL) {
2733 if (start_array != NULL) {
2734 start_array->allocate_block(addr);
2735 }
2736 cm->update_contents(oop(addr));
2737 assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2738 }
2739 }
2740 }
2741
2742 // Skip over count live words starting from beg, and return the address of the
2743 // next live word. Unless marked, the word corresponding to beg is assumed to
2744 // be dead. Callers must either ensure beg does not correspond to the middle of
2745 // an object, or account for those live words in some other way. Callers must
2746 // also ensure that there are enough live words in the range [beg, end) to skip.
2747 HeapWord*
2748 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2749 {
2750 assert(count > 0, "sanity");
2751
2752 ParMarkBitMap* m = mark_bitmap();
2753 idx_t bits_to_skip = m->words_to_bits(count);
2754 idx_t cur_beg = m->addr_to_bit(beg);
2755 const idx_t search_end = m->align_range_end(m->addr_to_bit(end));
2756
2757 do {
2758 cur_beg = m->find_obj_beg(cur_beg, search_end);
2759 idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2760 const size_t obj_bits = cur_end - cur_beg + 1;
2761 if (obj_bits > bits_to_skip) {
2762 return m->bit_to_addr(cur_beg + bits_to_skip);
2763 }
2764 bits_to_skip -= obj_bits;
2765 cur_beg = cur_end + 1;
2766 } while (bits_to_skip > 0);
2767
2768 // Skipping the desired number of words landed just past the end of an object.
2769 // Find the start of the next object.
2770 cur_beg = m->find_obj_beg(cur_beg, search_end);
2771 assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2772 return m->bit_to_addr(cur_beg);
2773 }
2774
2775 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2776 SpaceId src_space_id,
2777 size_t src_region_idx)
2778 {
2779 assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2780
2781 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2782 if (split_info.dest_region_addr() == dest_addr) {
2783 // The partial object ending at the split point contains the first word to
2784 // be copied to dest_addr.
2785 return split_info.first_src_addr();
2786 }
2787
2788 const ParallelCompactData& sd = summary_data();
2789 ParMarkBitMap* const bitmap = mark_bitmap();
2790 const size_t RegionSize = ParallelCompactData::RegionSize;
2791
2792 assert(sd.is_region_aligned(dest_addr), "not aligned");
2793 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2794 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2795 HeapWord* const src_region_destination = src_region_ptr->destination();
2796
2797 assert(dest_addr >= src_region_destination, "wrong src region");
2798 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2799
2800 HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2801 HeapWord* const src_region_end = src_region_beg + RegionSize;
2802
2803 HeapWord* addr = src_region_beg;
2804 if (dest_addr == src_region_destination) {
2805 // Return the first live word in the source region.
2806 if (partial_obj_size == 0) {
2807 addr = bitmap->find_obj_beg(addr, src_region_end);
2808 assert(addr < src_region_end, "no objects start in src region");
2809 }
2810 return addr;
2811 }
2812
2813 // Must skip some live data.
2814 size_t words_to_skip = dest_addr - src_region_destination;
2815 assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2816
2817 if (partial_obj_size >= words_to_skip) {
2818 // All the live words to skip are part of the partial object.
2819 addr += words_to_skip;
2820 if (partial_obj_size == words_to_skip) {
2821 // Find the first live word past the partial object.
2822 addr = bitmap->find_obj_beg(addr, src_region_end);
2823 assert(addr < src_region_end, "wrong src region");
2824 }
2825 return addr;
2826 }
2827
2828 // Skip over the partial object (if any).
2829 if (partial_obj_size != 0) {
2830 words_to_skip -= partial_obj_size;
2831 addr += partial_obj_size;
2832 }
2833
2834 // Skip over live words due to objects that start in the region.
2835 addr = skip_live_words(addr, src_region_end, words_to_skip);
2836 assert(addr < src_region_end, "wrong src region");
2837 return addr;
2838 }
2839
2840 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2841 SpaceId src_space_id,
2842 size_t beg_region,
2843 HeapWord* end_addr)
2844 {
2845 ParallelCompactData& sd = summary_data();
2846
2847 #ifdef ASSERT
2848 MutableSpace* const src_space = _space_info[src_space_id].space();
2849 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2850 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2851 "src_space_id does not match beg_addr");
2852 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2853 "src_space_id does not match end_addr");
2854 #endif // #ifdef ASSERT
2855
2856 RegionData* const beg = sd.region(beg_region);
2857 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2858
2859 // Regions up to new_top() are enqueued if they become available.
2860 HeapWord* const new_top = _space_info[src_space_id].new_top();
2861 RegionData* const enqueue_end =
2862 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2863
2864 for (RegionData* cur = beg; cur < end; ++cur) {
2865 assert(cur->data_size() > 0, "region must have live data");
2866 cur->decrement_destination_count();
2867 if (cur < enqueue_end && cur->available() && cur->claim()) {
2868 if (cur->mark_normal()) {
2869 cm->push_region(sd.region(cur));
2870 } else if (cur->mark_copied()) {
2871 // Try to copy the content of the shadow region back to its corresponding
2872 // heap region if the shadow region is filled. Otherwise, the GC thread
2873 // fills the shadow region will copy the data back (see
2874 // MoveAndUpdateShadowClosure::complete_region).
2875 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2876 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2877 cur->set_completed();
2878 }
2879 }
2880 }
2881 }
2882
2883 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2884 SpaceId& src_space_id,
2885 HeapWord*& src_space_top,
2886 HeapWord* end_addr)
2887 {
2888 typedef ParallelCompactData::RegionData RegionData;
2889
2890 ParallelCompactData& sd = PSParallelCompact::summary_data();
2891 const size_t region_size = ParallelCompactData::RegionSize;
2892
2893 size_t src_region_idx = 0;
2894
2895 // Skip empty regions (if any) up to the top of the space.
2896 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2897 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2898 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2899 const RegionData* const top_region_ptr =
2900 sd.addr_to_region_ptr(top_aligned_up);
2901 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2902 ++src_region_ptr;
2903 }
2904
2905 if (src_region_ptr < top_region_ptr) {
2906 // The next source region is in the current space. Update src_region_idx
2907 // and the source address to match src_region_ptr.
2908 src_region_idx = sd.region(src_region_ptr);
2909 HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2910 if (src_region_addr > closure.source()) {
2911 closure.set_source(src_region_addr);
2912 }
2913 return src_region_idx;
2914 }
2915
2916 // Switch to a new source space and find the first non-empty region.
2917 unsigned int space_id = src_space_id + 1;
2918 assert(space_id < last_space_id, "not enough spaces");
2919
2920 HeapWord* const destination = closure.destination();
2921
2922 do {
2923 MutableSpace* space = _space_info[space_id].space();
2924 HeapWord* const bottom = space->bottom();
2925 const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2926
2927 // Iterate over the spaces that do not compact into themselves.
2928 if (bottom_cp->destination() != bottom) {
2929 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2930 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2931
2932 for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2933 if (src_cp->live_obj_size() > 0) {
2934 // Found it.
2935 assert(src_cp->destination() == destination,
2936 "first live obj in the space must match the destination");
2937 assert(src_cp->partial_obj_size() == 0,
2938 "a space cannot begin with a partial obj");
2939
2940 src_space_id = SpaceId(space_id);
2941 src_space_top = space->top();
2942 const size_t src_region_idx = sd.region(src_cp);
2943 closure.set_source(sd.region_to_addr(src_region_idx));
2944 return src_region_idx;
2945 } else {
2946 assert(src_cp->data_size() == 0, "sanity");
2947 }
2948 }
2949 }
2950 } while (++space_id < last_space_id);
2951
2952 assert(false, "no source region was found");
2953 return 0;
2954 }
2955
2956 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2957 {
2958 typedef ParMarkBitMap::IterationStatus IterationStatus;
2959 ParMarkBitMap* const bitmap = mark_bitmap();
2960 ParallelCompactData& sd = summary_data();
2961 RegionData* const region_ptr = sd.region(region_idx);
2962
2963 // Get the source region and related info.
2964 size_t src_region_idx = region_ptr->source_region();
2965 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2966 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2967 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2968
2969 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2970
2971 // Adjust src_region_idx to prepare for decrementing destination counts (the
2972 // destination count is not decremented when a region is copied to itself).
2973 if (src_region_idx == region_idx) {
2974 src_region_idx += 1;
2975 }
2976
2977 if (bitmap->is_unmarked(closure.source())) {
2978 // The first source word is in the middle of an object; copy the remainder
2979 // of the object or as much as will fit. The fact that pointer updates were
2980 // deferred will be noted when the object header is processed.
2981 HeapWord* const old_src_addr = closure.source();
2982 closure.copy_partial_obj();
2983 if (closure.is_full()) {
2984 decrement_destination_counts(cm, src_space_id, src_region_idx,
2985 closure.source());
2986 region_ptr->set_deferred_obj_addr(NULL);
2987 closure.complete_region(cm, dest_addr, region_ptr);
2988 return;
2989 }
2990
2991 HeapWord* const end_addr = sd.region_align_down(closure.source());
2992 if (sd.region_align_down(old_src_addr) != end_addr) {
2993 // The partial object was copied from more than one source region.
2994 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2995
2996 // Move to the next source region, possibly switching spaces as well. All
2997 // args except end_addr may be modified.
2998 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2999 end_addr);
3000 }
3001 }
3002
3003 do {
3004 HeapWord* const cur_addr = closure.source();
3005 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3006 src_space_top);
3007 IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3008
3009 if (status == ParMarkBitMap::incomplete) {
3010 // The last obj that starts in the source region does not end in the
3011 // region.
3012 assert(closure.source() < end_addr, "sanity");
3013 HeapWord* const obj_beg = closure.source();
3014 HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3015 src_space_top);
3016 HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3017 if (obj_end < range_end) {
3018 // The end was found; the entire object will fit.
3019 status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3020 assert(status != ParMarkBitMap::would_overflow, "sanity");
3021 } else {
3022 // The end was not found; the object will not fit.
3023 assert(range_end < src_space_top, "obj cannot cross space boundary");
3024 status = ParMarkBitMap::would_overflow;
3025 }
3026 }
3027
3028 if (status == ParMarkBitMap::would_overflow) {
3029 // The last object did not fit. Note that interior oop updates were
3030 // deferred, then copy enough of the object to fill the region.
3031 region_ptr->set_deferred_obj_addr(closure.destination());
3032 status = closure.copy_until_full(); // copies from closure.source()
3033
3034 decrement_destination_counts(cm, src_space_id, src_region_idx,
3035 closure.source());
3036 closure.complete_region(cm, dest_addr, region_ptr);
3037 return;
3038 }
3039
3040 if (status == ParMarkBitMap::full) {
3041 decrement_destination_counts(cm, src_space_id, src_region_idx,
3042 closure.source());
3043 region_ptr->set_deferred_obj_addr(NULL);
3044 closure.complete_region(cm, dest_addr, region_ptr);
3045 return;
3046 }
3047
3048 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3049
3050 // Move to the next source region, possibly switching spaces as well. All
3051 // args except end_addr may be modified.
3052 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3053 end_addr);
3054 } while (true);
3055 }
3056
3057 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
3058 {
3059 MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3060 fill_region(cm, cl, region_idx);
3061 }
3062
3063 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
3064 {
3065 // Get a shadow region first
3066 ParallelCompactData& sd = summary_data();
3067 RegionData* const region_ptr = sd.region(region_idx);
3068 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
3069 // The InvalidShadow return value indicates the corresponding heap region is available,
3070 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
3071 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
3072 if (shadow_region == ParCompactionManager::InvalidShadow) {
3073 MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3074 region_ptr->shadow_to_normal();
3075 return fill_region(cm, cl, region_idx);
3076 } else {
3077 MoveAndUpdateShadowClosure cl(mark_bitmap(), cm, region_idx, shadow_region);
3078 return fill_region(cm, cl, region_idx);
3079 }
3080 }
3081
3082 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
3083 {
3084 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
3085 }
3086
3087 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
3088 {
3089 size_t next = cm->next_shadow_region();
3090 ParallelCompactData& sd = summary_data();
3091 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
3092 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
3093
3094 while (next < old_new_top) {
3095 if (sd.region(next)->mark_shadow()) {
3096 region_idx = next;
3097 return true;
3098 }
3099 next = cm->move_next_shadow_region_by(active_gc_threads);
3100 }
3101
3102 return false;
3103 }
3104
3105 // The shadow region is an optimization to address region dependencies in full GC. The basic
3106 // idea is making more regions available by temporally storing their live objects in empty
3107 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
3108 // GC threads need not wait destination regions to be available before processing sources.
3109 //
3110 // A typical workflow would be:
3111 // After draining its own stack and failing to steal from others, a GC worker would pick an
3112 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
3113 // the shadow region by copying live objects from source regions of the unavailable one. Once
3114 // the unavailable region becomes available, the data in the shadow region will be copied back.
3115 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
3116 //
3117 // For more details, please refer to ยง4.2 of the VEE'19 paper:
3118 // Haoyu Li, Mingyu Wu, Binyu Zang, and Haibo Chen. 2019. ScissorGC: scalable and efficient
3119 // compaction for Java full garbage collection. In Proceedings of the 15th ACM SIGPLAN/SIGOPS
3120 // International Conference on Virtual Execution Environments (VEE 2019). ACM, New York, NY, USA,
3121 // 108-121. DOI: https://doi.org/10.1145/3313808.3313820
3122 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
3123 {
3124 const ParallelCompactData& sd = PSParallelCompact::summary_data();
3125
3126 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
3127 SpaceInfo* const space_info = _space_info + id;
3128 MutableSpace* const space = space_info->space();
3129
3130 const size_t beg_region =
3131 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
3132 const size_t end_region =
3133 sd.addr_to_region_idx(sd.region_align_down(space->end()));
3134
3135 for (size_t cur = beg_region; cur < end_region; ++cur) {
3136 ParCompactionManager::push_shadow_region(cur);
3137 }
3138 }
3139
3140 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
3141 for (uint i = 0; i < parallel_gc_threads; i++) {
3142 ParCompactionManager *cm = ParCompactionManager::manager_array(i);
3143 cm->set_next_shadow_region(beg_region + i);
3144 }
3145 }
3146
3147 void PSParallelCompact::fill_blocks(size_t region_idx)
3148 {
3149 // Fill in the block table elements for the specified region. Each block
3150 // table element holds the number of live words in the region that are to the
3151 // left of the first object that starts in the block. Thus only blocks in
3152 // which an object starts need to be filled.
3153 //
3154 // The algorithm scans the section of the bitmap that corresponds to the
3155 // region, keeping a running total of the live words. When an object start is
3156 // found, if it's the first to start in the block that contains it, the
3157 // current total is written to the block table element.
3158 const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3159 const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3160 const size_t RegionSize = ParallelCompactData::RegionSize;
3161
3162 ParallelCompactData& sd = summary_data();
3163 const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3164 if (partial_obj_size >= RegionSize) {
3165 return; // No objects start in this region.
3166 }
3167
3168 // Ensure the first loop iteration decides that the block has changed.
3169 size_t cur_block = sd.block_count();
3170
3171 const ParMarkBitMap* const bitmap = mark_bitmap();
3172
3173 const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3174 assert((size_t)1 << Log2BitsPerBlock ==
3175 bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3176
3177 size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3178 const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3179 size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3180 beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3181 while (beg_bit < range_end) {
3182 const size_t new_block = beg_bit >> Log2BitsPerBlock;
3183 if (new_block != cur_block) {
3184 cur_block = new_block;
3185 sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3186 }
3187
3188 const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3189 if (end_bit < range_end - 1) {
3190 live_bits += end_bit - beg_bit + 1;
3191 beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3192 } else {
3193 return;
3194 }
3195 }
3196 }
3197
3198 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3199 {
3200 if (source() != copy_destination()) {
3201 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3202 Copy::aligned_conjoint_words(source(), copy_destination(), words_remaining());
3203 }
3204 update_state(words_remaining());
3205 assert(is_full(), "sanity");
3206 return ParMarkBitMap::full;
3207 }
3208
3209 void MoveAndUpdateClosure::copy_partial_obj()
3210 {
3211 size_t words = words_remaining();
3212
3213 HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3214 HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3215 if (end_addr < range_end) {
3216 words = bitmap()->obj_size(source(), end_addr);
3217 }
3218
3219 // This test is necessary; if omitted, the pointer updates to a partial object
3220 // that crosses the dense prefix boundary could be overwritten.
3221 if (source() != copy_destination()) {
3222 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3223 Copy::aligned_conjoint_words(source(), copy_destination(), words);
3224 }
3225 update_state(words);
3226 }
3227
3228 void MoveAndUpdateClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3229 PSParallelCompact::RegionData *region_ptr) {
3230 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
3231 region_ptr->set_completed();
3232 }
3233
3234 ParMarkBitMapClosure::IterationStatus
3235 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3236 assert(destination() != NULL, "sanity");
3237 assert(bitmap()->obj_size(addr) == words, "bad size");
3238
3239 _source = addr;
3240 assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3241 destination(), "wrong destination");
3242
3243 if (words > words_remaining()) {
3244 return ParMarkBitMap::would_overflow;
3245 }
3246
3247 // The start_array must be updated even if the object is not moving.
3248 if (_start_array != NULL) {
3249 _start_array->allocate_block(destination());
3250 }
3251
3252 if (copy_destination() != source()) {
3253 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3254 Copy::aligned_conjoint_words(source(), copy_destination(), words);
3255 }
3256
3257 oop moved_oop = (oop) copy_destination();
3258 compaction_manager()->update_contents(moved_oop);
3259 assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3260
3261 update_state(words);
3262 assert(copy_destination() == cast_from_oop<HeapWord*>(moved_oop) + moved_oop->size(), "sanity");
3263 return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3264 }
3265
3266 void MoveAndUpdateShadowClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3267 PSParallelCompact::RegionData *region_ptr) {
3268 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
3269 // Record the shadow region index
3270 region_ptr->set_shadow_region(_shadow);
3271 // Mark the shadow region as filled to indicate the data is ready to be
3272 // copied back
3273 region_ptr->mark_filled();
3274 // Try to copy the content of the shadow region back to its corresponding
3275 // heap region if available; the GC thread that decreases the destination
3276 // count to zero will do the copying otherwise (see
3277 // PSParallelCompact::decrement_destination_counts).
3278 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
3279 region_ptr->set_completed();
3280 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
3281 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
3282 }
3283 }
3284
3285 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3286 ParCompactionManager* cm,
3287 PSParallelCompact::SpaceId space_id) :
3288 ParMarkBitMapClosure(mbm, cm),
3289 _space_id(space_id),
3290 _start_array(PSParallelCompact::start_array(space_id))
3291 {
3292 }
3293
3294 // Updates the references in the object to their new values.
3295 ParMarkBitMapClosure::IterationStatus
3296 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3297 do_addr(addr);
3298 return ParMarkBitMap::incomplete;
3299 }
3300
3301 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3302 ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3303 _start_array(PSParallelCompact::start_array(space_id))
3304 {
3305 assert(space_id == PSParallelCompact::old_space_id,
3306 "cannot use FillClosure in the young gen");
3307 }
3308
3309 ParMarkBitMapClosure::IterationStatus
3310 FillClosure::do_addr(HeapWord* addr, size_t size) {
3311 CollectedHeap::fill_with_objects(addr, size);
3312 HeapWord* const end = addr + size;
3313 do {
3314 _start_array->allocate_block(addr);
3315 addr += oop(addr)->size();
3316 } while (addr < end);
3317 return ParMarkBitMap::incomplete;
3318 }