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 bool young_gen_empty = eden_empty && from_space->is_empty() &&
1048 to_space->is_empty();
1049
1050 PSCardTable* ct = heap->card_table();
1051 MemRegion old_mr = heap->old_gen()->reserved();
1052 if (young_gen_empty) {
1053 ct->clear(MemRegion(old_mr.start(), old_mr.end()));
1054 } else {
1055 ct->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1056 }
1057
1058 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1059 ClassLoaderDataGraph::purge();
1060 MetaspaceUtils::verify_metrics();
1061
1062 heap->prune_scavengable_nmethods();
1063
1064 #if COMPILER2_OR_JVMCI
1065 DerivedPointerTable::update_pointers();
1066 #endif
1067
1068 if (ZapUnusedHeapArea) {
1069 heap->gen_mangle_unused_area();
1070 }
1071
1072 // Signal that we have completed a visit to all live objects.
1073 Universe::heap()->record_whole_heap_examined_timestamp();
1074 }
1075
1076 HeapWord*
1077 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1078 bool maximum_compaction)
1079 {
1080 const size_t region_size = ParallelCompactData::RegionSize;
1081 const ParallelCompactData& sd = summary_data();
1082
1083 const MutableSpace* const space = _space_info[id].space();
1084 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1085 const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1086 const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1087
1088 // Skip full regions at the beginning of the space--they are necessarily part
1089 // of the dense prefix.
1090 size_t full_count = 0;
1091 const RegionData* cp;
1092 for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1093 ++full_count;
1094 }
1095
1096 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1097 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1098 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1099 if (maximum_compaction || cp == end_cp || interval_ended) {
1100 _maximum_compaction_gc_num = total_invocations();
1101 return sd.region_to_addr(cp);
1102 }
1103
1104 HeapWord* const new_top = _space_info[id].new_top();
1105 const size_t space_live = pointer_delta(new_top, space->bottom());
1106 const size_t space_used = space->used_in_words();
1107 const size_t space_capacity = space->capacity_in_words();
1108
1109 const double cur_density = double(space_live) / space_capacity;
1110 const double deadwood_density =
1111 (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1112 const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1113
1114 log_develop_debug(gc, compaction)(
1115 "cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1116 cur_density, deadwood_density, deadwood_goal);
1117 log_develop_debug(gc, compaction)(
1118 "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1119 "space_cap=" SIZE_FORMAT,
1120 space_live, space_used,
1121 space_capacity);
1122
1123 // XXX - Use binary search?
1124 HeapWord* dense_prefix = sd.region_to_addr(cp);
1125 const RegionData* full_cp = cp;
1126 const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1127 while (cp < end_cp) {
1128 HeapWord* region_destination = cp->destination();
1129 const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1130
1131 log_develop_trace(gc, compaction)(
1132 "c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1133 "dp=" PTR_FORMAT " cdw=" SIZE_FORMAT_W(8),
1134 sd.region(cp), p2i(region_destination),
1135 p2i(dense_prefix), cur_deadwood);
1136
1137 if (cur_deadwood >= deadwood_goal) {
1138 // Found the region that has the correct amount of deadwood to the left.
1139 // This typically occurs after crossing a fairly sparse set of regions, so
1140 // iterate backwards over those sparse regions, looking for the region
1141 // that has the lowest density of live objects 'to the right.'
1142 size_t space_to_left = sd.region(cp) * region_size;
1143 size_t live_to_left = space_to_left - cur_deadwood;
1144 size_t space_to_right = space_capacity - space_to_left;
1145 size_t live_to_right = space_live - live_to_left;
1146 double density_to_right = double(live_to_right) / space_to_right;
1147 while (cp > full_cp) {
1148 --cp;
1149 const size_t prev_region_live_to_right = live_to_right -
1150 cp->data_size();
1151 const size_t prev_region_space_to_right = space_to_right + region_size;
1152 double prev_region_density_to_right =
1153 double(prev_region_live_to_right) / prev_region_space_to_right;
1154 if (density_to_right <= prev_region_density_to_right) {
1155 return dense_prefix;
1156 }
1157
1158 log_develop_trace(gc, compaction)(
1159 "backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1160 "pc_d2r=%10.8f",
1161 sd.region(cp), density_to_right,
1162 prev_region_density_to_right);
1163
1164 dense_prefix -= region_size;
1165 live_to_right = prev_region_live_to_right;
1166 space_to_right = prev_region_space_to_right;
1167 density_to_right = prev_region_density_to_right;
1168 }
1169 return dense_prefix;
1170 }
1171
1172 dense_prefix += region_size;
1173 ++cp;
1174 }
1175
1176 return dense_prefix;
1177 }
1178
1179 #ifndef PRODUCT
1180 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1181 const SpaceId id,
1182 const bool maximum_compaction,
1183 HeapWord* const addr)
1184 {
1185 const size_t region_idx = summary_data().addr_to_region_idx(addr);
1186 RegionData* const cp = summary_data().region(region_idx);
1187 const MutableSpace* const space = _space_info[id].space();
1188 HeapWord* const new_top = _space_info[id].new_top();
1189
1190 const size_t space_live = pointer_delta(new_top, space->bottom());
1191 const size_t dead_to_left = pointer_delta(addr, cp->destination());
1192 const size_t space_cap = space->capacity_in_words();
1193 const double dead_to_left_pct = double(dead_to_left) / space_cap;
1194 const size_t live_to_right = new_top - cp->destination();
1195 const size_t dead_to_right = space->top() - addr - live_to_right;
1196
1197 log_develop_debug(gc, compaction)(
1198 "%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1199 "spl=" SIZE_FORMAT " "
1200 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1201 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT " "
1202 "ratio=%10.8f",
1203 algorithm, p2i(addr), region_idx,
1204 space_live,
1205 dead_to_left, dead_to_left_pct,
1206 dead_to_right, live_to_right,
1207 double(dead_to_right) / live_to_right);
1208 }
1209 #endif // #ifndef PRODUCT
1210
1211 // Return a fraction indicating how much of the generation can be treated as
1212 // "dead wood" (i.e., not reclaimed). The function uses a normal distribution
1213 // based on the density of live objects in the generation to determine a limit,
1214 // which is then adjusted so the return value is min_percent when the density is
1215 // 1.
1216 //
1217 // The following table shows some return values for a different values of the
1218 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1219 // min_percent is 1.
1220 //
1221 // fraction allowed as dead wood
1222 // -----------------------------------------------------------------
1223 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1224 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1225 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1226 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1227 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1228 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1229 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1230 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1231 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1232 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1233 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1234 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1235 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1236 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1237 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1238 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1239 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1240 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1241 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1242 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1243 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1244 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1245 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1246
1247 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1248 {
1249 assert(_dwl_initialized, "uninitialized");
1250
1251 // The raw limit is the value of the normal distribution at x = density.
1252 const double raw_limit = normal_distribution(density);
1253
1254 // Adjust the raw limit so it becomes the minimum when the density is 1.
1255 //
1256 // First subtract the adjustment value (which is simply the precomputed value
1257 // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1258 // Then add the minimum value, so the minimum is returned when the density is
1259 // 1. Finally, prevent negative values, which occur when the mean is not 0.5.
1260 const double min = double(min_percent) / 100.0;
1261 const double limit = raw_limit - _dwl_adjustment + min;
1262 return MAX2(limit, 0.0);
1263 }
1264
1265 ParallelCompactData::RegionData*
1266 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1267 const RegionData* end)
1268 {
1269 const size_t region_size = ParallelCompactData::RegionSize;
1270 ParallelCompactData& sd = summary_data();
1271 size_t left = sd.region(beg);
1272 size_t right = end > beg ? sd.region(end) - 1 : left;
1273
1274 // Binary search.
1275 while (left < right) {
1276 // Equivalent to (left + right) / 2, but does not overflow.
1277 const size_t middle = left + (right - left) / 2;
1278 RegionData* const middle_ptr = sd.region(middle);
1279 HeapWord* const dest = middle_ptr->destination();
1280 HeapWord* const addr = sd.region_to_addr(middle);
1281 assert(dest != NULL, "sanity");
1282 assert(dest <= addr, "must move left");
1283
1284 if (middle > left && dest < addr) {
1285 right = middle - 1;
1286 } else if (middle < right && middle_ptr->data_size() == region_size) {
1287 left = middle + 1;
1288 } else {
1289 return middle_ptr;
1290 }
1291 }
1292 return sd.region(left);
1293 }
1294
1295 ParallelCompactData::RegionData*
1296 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1297 const RegionData* end,
1298 size_t dead_words)
1299 {
1300 ParallelCompactData& sd = summary_data();
1301 size_t left = sd.region(beg);
1302 size_t right = end > beg ? sd.region(end) - 1 : left;
1303
1304 // Binary search.
1305 while (left < right) {
1306 // Equivalent to (left + right) / 2, but does not overflow.
1307 const size_t middle = left + (right - left) / 2;
1308 RegionData* const middle_ptr = sd.region(middle);
1309 HeapWord* const dest = middle_ptr->destination();
1310 HeapWord* const addr = sd.region_to_addr(middle);
1311 assert(dest != NULL, "sanity");
1312 assert(dest <= addr, "must move left");
1313
1314 const size_t dead_to_left = pointer_delta(addr, dest);
1315 if (middle > left && dead_to_left > dead_words) {
1316 right = middle - 1;
1317 } else if (middle < right && dead_to_left < dead_words) {
1318 left = middle + 1;
1319 } else {
1320 return middle_ptr;
1321 }
1322 }
1323 return sd.region(left);
1324 }
1325
1326 // The result is valid during the summary phase, after the initial summarization
1327 // of each space into itself, and before final summarization.
1328 inline double
1329 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1330 HeapWord* const bottom,
1331 HeapWord* const top,
1332 HeapWord* const new_top)
1333 {
1334 ParallelCompactData& sd = summary_data();
1335
1336 assert(cp != NULL, "sanity");
1337 assert(bottom != NULL, "sanity");
1338 assert(top != NULL, "sanity");
1339 assert(new_top != NULL, "sanity");
1340 assert(top >= new_top, "summary data problem?");
1341 assert(new_top > bottom, "space is empty; should not be here");
1342 assert(new_top >= cp->destination(), "sanity");
1343 assert(top >= sd.region_to_addr(cp), "sanity");
1344
1345 HeapWord* const destination = cp->destination();
1346 const size_t dense_prefix_live = pointer_delta(destination, bottom);
1347 const size_t compacted_region_live = pointer_delta(new_top, destination);
1348 const size_t compacted_region_used = pointer_delta(top,
1349 sd.region_to_addr(cp));
1350 const size_t reclaimable = compacted_region_used - compacted_region_live;
1351
1352 const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1353 return double(reclaimable) / divisor;
1354 }
1355
1356 // Return the address of the end of the dense prefix, a.k.a. the start of the
1357 // compacted region. The address is always on a region boundary.
1358 //
1359 // Completely full regions at the left are skipped, since no compaction can
1360 // occur in those regions. Then the maximum amount of dead wood to allow is
1361 // computed, based on the density (amount live / capacity) of the generation;
1362 // the region with approximately that amount of dead space to the left is
1363 // identified as the limit region. Regions between the last completely full
1364 // region and the limit region are scanned and the one that has the best
1365 // (maximum) reclaimed_ratio() is selected.
1366 HeapWord*
1367 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1368 bool maximum_compaction)
1369 {
1370 const size_t region_size = ParallelCompactData::RegionSize;
1371 const ParallelCompactData& sd = summary_data();
1372
1373 const MutableSpace* const space = _space_info[id].space();
1374 HeapWord* const top = space->top();
1375 HeapWord* const top_aligned_up = sd.region_align_up(top);
1376 HeapWord* const new_top = _space_info[id].new_top();
1377 HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1378 HeapWord* const bottom = space->bottom();
1379 const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1380 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1381 const RegionData* const new_top_cp =
1382 sd.addr_to_region_ptr(new_top_aligned_up);
1383
1384 // Skip full regions at the beginning of the space--they are necessarily part
1385 // of the dense prefix.
1386 const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1387 assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1388 space->is_empty(), "no dead space allowed to the left");
1389 assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1390 "region must have dead space");
1391
1392 // The gc number is saved whenever a maximum compaction is done, and used to
1393 // determine when the maximum compaction interval has expired. This avoids
1394 // successive max compactions for different reasons.
1395 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1396 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1397 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1398 total_invocations() == HeapFirstMaximumCompactionCount;
1399 if (maximum_compaction || full_cp == top_cp || interval_ended) {
1400 _maximum_compaction_gc_num = total_invocations();
1401 return sd.region_to_addr(full_cp);
1402 }
1403
1404 const size_t space_live = pointer_delta(new_top, bottom);
1405 const size_t space_used = space->used_in_words();
1406 const size_t space_capacity = space->capacity_in_words();
1407
1408 const double density = double(space_live) / double(space_capacity);
1409 const size_t min_percent_free = MarkSweepDeadRatio;
1410 const double limiter = dead_wood_limiter(density, min_percent_free);
1411 const size_t dead_wood_max = space_used - space_live;
1412 const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1413 dead_wood_max);
1414
1415 log_develop_debug(gc, compaction)(
1416 "space_live=" SIZE_FORMAT " space_used=" SIZE_FORMAT " "
1417 "space_cap=" SIZE_FORMAT,
1418 space_live, space_used,
1419 space_capacity);
1420 log_develop_debug(gc, compaction)(
1421 "dead_wood_limiter(%6.4f, " SIZE_FORMAT ")=%6.4f "
1422 "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1423 density, min_percent_free, limiter,
1424 dead_wood_max, dead_wood_limit);
1425
1426 // Locate the region with the desired amount of dead space to the left.
1427 const RegionData* const limit_cp =
1428 dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1429
1430 // Scan from the first region with dead space to the limit region and find the
1431 // one with the best (largest) reclaimed ratio.
1432 double best_ratio = 0.0;
1433 const RegionData* best_cp = full_cp;
1434 for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1435 double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1436 if (tmp_ratio > best_ratio) {
1437 best_cp = cp;
1438 best_ratio = tmp_ratio;
1439 }
1440 }
1441
1442 return sd.region_to_addr(best_cp);
1443 }
1444
1445 void PSParallelCompact::summarize_spaces_quick()
1446 {
1447 for (unsigned int i = 0; i < last_space_id; ++i) {
1448 const MutableSpace* space = _space_info[i].space();
1449 HeapWord** nta = _space_info[i].new_top_addr();
1450 bool result = _summary_data.summarize(_space_info[i].split_info(),
1451 space->bottom(), space->top(), NULL,
1452 space->bottom(), space->end(), nta);
1453 assert(result, "space must fit into itself");
1454 _space_info[i].set_dense_prefix(space->bottom());
1455 }
1456 }
1457
1458 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1459 {
1460 HeapWord* const dense_prefix_end = dense_prefix(id);
1461 const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1462 const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1463 if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1464 // Only enough dead space is filled so that any remaining dead space to the
1465 // left is larger than the minimum filler object. (The remainder is filled
1466 // during the copy/update phase.)
1467 //
1468 // The size of the dead space to the right of the boundary is not a
1469 // concern, since compaction will be able to use whatever space is
1470 // available.
1471 //
1472 // Here '||' is the boundary, 'x' represents a don't care bit and a box
1473 // surrounds the space to be filled with an object.
1474 //
1475 // In the 32-bit VM, each bit represents two 32-bit words:
1476 // +---+
1477 // a) beg_bits: ... x x x | 0 | || 0 x x ...
1478 // end_bits: ... x x x | 0 | || 0 x x ...
1479 // +---+
1480 //
1481 // In the 64-bit VM, each bit represents one 64-bit word:
1482 // +------------+
1483 // b) beg_bits: ... x x x | 0 || 0 | x x ...
1484 // end_bits: ... x x 1 | 0 || 0 | x x ...
1485 // +------------+
1486 // +-------+
1487 // c) beg_bits: ... x x | 0 0 | || 0 x x ...
1488 // end_bits: ... x 1 | 0 0 | || 0 x x ...
1489 // +-------+
1490 // +-----------+
1491 // d) beg_bits: ... x | 0 0 0 | || 0 x x ...
1492 // end_bits: ... 1 | 0 0 0 | || 0 x x ...
1493 // +-----------+
1494 // +-------+
1495 // e) beg_bits: ... 0 0 | 0 0 | || 0 x x ...
1496 // end_bits: ... 0 0 | 0 0 | || 0 x x ...
1497 // +-------+
1498
1499 // Initially assume case a, c or e will apply.
1500 size_t obj_len = CollectedHeap::min_fill_size();
1501 HeapWord* obj_beg = dense_prefix_end - obj_len;
1502
1503 #ifdef _LP64
1504 if (MinObjAlignment > 1) { // object alignment > heap word size
1505 // Cases a, c or e.
1506 } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1507 // Case b above.
1508 obj_beg = dense_prefix_end - 1;
1509 } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1510 _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1511 // Case d above.
1512 obj_beg = dense_prefix_end - 3;
1513 obj_len = 3;
1514 }
1515 #endif // #ifdef _LP64
1516
1517 CollectedHeap::fill_with_object(obj_beg, obj_len);
1518 _mark_bitmap.mark_obj(obj_beg, obj_len);
1519 _summary_data.add_obj(obj_beg, obj_len);
1520 assert(start_array(id) != NULL, "sanity");
1521 start_array(id)->allocate_block(obj_beg);
1522 }
1523 }
1524
1525 void
1526 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1527 {
1528 assert(id < last_space_id, "id out of range");
1529 assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom(),
1530 "should have been reset in summarize_spaces_quick()");
1531
1532 const MutableSpace* space = _space_info[id].space();
1533 if (_space_info[id].new_top() != space->bottom()) {
1534 HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1535 _space_info[id].set_dense_prefix(dense_prefix_end);
1536
1537 #ifndef PRODUCT
1538 if (log_is_enabled(Debug, gc, compaction)) {
1539 print_dense_prefix_stats("ratio", id, maximum_compaction,
1540 dense_prefix_end);
1541 HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1542 print_dense_prefix_stats("density", id, maximum_compaction, addr);
1543 }
1544 #endif // #ifndef PRODUCT
1545
1546 // Recompute the summary data, taking into account the dense prefix. If
1547 // every last byte will be reclaimed, then the existing summary data which
1548 // compacts everything can be left in place.
1549 if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1550 // If dead space crosses the dense prefix boundary, it is (at least
1551 // partially) filled with a dummy object, marked live and added to the
1552 // summary data. This simplifies the copy/update phase and must be done
1553 // before the final locations of objects are determined, to prevent
1554 // leaving a fragment of dead space that is too small to fill.
1555 fill_dense_prefix_end(id);
1556
1557 // Compute the destination of each Region, and thus each object.
1558 _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1559 _summary_data.summarize(_space_info[id].split_info(),
1560 dense_prefix_end, space->top(), NULL,
1561 dense_prefix_end, space->end(),
1562 _space_info[id].new_top_addr());
1563 }
1564 }
1565
1566 if (log_develop_is_enabled(Trace, gc, compaction)) {
1567 const size_t region_size = ParallelCompactData::RegionSize;
1568 HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1569 const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1570 const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1571 HeapWord* const new_top = _space_info[id].new_top();
1572 const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1573 const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1574 log_develop_trace(gc, compaction)(
1575 "id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1576 "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1577 "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1578 id, space->capacity_in_words(), p2i(dense_prefix_end),
1579 dp_region, dp_words / region_size,
1580 cr_words / region_size, p2i(new_top));
1581 }
1582 }
1583
1584 #ifndef PRODUCT
1585 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1586 HeapWord* dst_beg, HeapWord* dst_end,
1587 SpaceId src_space_id,
1588 HeapWord* src_beg, HeapWord* src_end)
1589 {
1590 log_develop_trace(gc, compaction)(
1591 "Summarizing %d [%s] into %d [%s]: "
1592 "src=" PTR_FORMAT "-" PTR_FORMAT " "
1593 SIZE_FORMAT "-" SIZE_FORMAT " "
1594 "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1595 SIZE_FORMAT "-" SIZE_FORMAT,
1596 src_space_id, space_names[src_space_id],
1597 dst_space_id, space_names[dst_space_id],
1598 p2i(src_beg), p2i(src_end),
1599 _summary_data.addr_to_region_idx(src_beg),
1600 _summary_data.addr_to_region_idx(src_end),
1601 p2i(dst_beg), p2i(dst_end),
1602 _summary_data.addr_to_region_idx(dst_beg),
1603 _summary_data.addr_to_region_idx(dst_end));
1604 }
1605 #endif // #ifndef PRODUCT
1606
1607 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1608 bool maximum_compaction)
1609 {
1610 GCTraceTime(Info, gc, phases) tm("Summary Phase", &_gc_timer);
1611
1612 log_develop_debug(gc, marking)(
1613 "add_obj_count=" SIZE_FORMAT " "
1614 "add_obj_bytes=" SIZE_FORMAT,
1615 add_obj_count,
1616 add_obj_size * HeapWordSize);
1617 log_develop_debug(gc, marking)(
1618 "mark_bitmap_count=" SIZE_FORMAT " "
1619 "mark_bitmap_bytes=" SIZE_FORMAT,
1620 mark_bitmap_count,
1621 mark_bitmap_size * HeapWordSize);
1622
1623 // Quick summarization of each space into itself, to see how much is live.
1624 summarize_spaces_quick();
1625
1626 log_develop_trace(gc, compaction)("summary phase: after summarizing each space to self");
1627 NOT_PRODUCT(print_region_ranges());
1628 NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1629
1630 // The amount of live data that will end up in old space (assuming it fits).
1631 size_t old_space_total_live = 0;
1632 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1633 old_space_total_live += pointer_delta(_space_info[id].new_top(),
1634 _space_info[id].space()->bottom());
1635 }
1636
1637 MutableSpace* const old_space = _space_info[old_space_id].space();
1638 const size_t old_capacity = old_space->capacity_in_words();
1639 if (old_space_total_live > old_capacity) {
1640 // XXX - should also try to expand
1641 maximum_compaction = true;
1642 }
1643
1644 // Old generations.
1645 summarize_space(old_space_id, maximum_compaction);
1646
1647 // Summarize the remaining spaces in the young gen. The initial target space
1648 // is the old gen. If a space does not fit entirely into the target, then the
1649 // remainder is compacted into the space itself and that space becomes the new
1650 // target.
1651 SpaceId dst_space_id = old_space_id;
1652 HeapWord* dst_space_end = old_space->end();
1653 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1654 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1655 const MutableSpace* space = _space_info[id].space();
1656 const size_t live = pointer_delta(_space_info[id].new_top(),
1657 space->bottom());
1658 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1659
1660 NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1661 SpaceId(id), space->bottom(), space->top());)
1662 if (live > 0 && live <= available) {
1663 // All the live data will fit.
1664 bool done = _summary_data.summarize(_space_info[id].split_info(),
1665 space->bottom(), space->top(),
1666 NULL,
1667 *new_top_addr, dst_space_end,
1668 new_top_addr);
1669 assert(done, "space must fit into old gen");
1670
1671 // Reset the new_top value for the space.
1672 _space_info[id].set_new_top(space->bottom());
1673 } else if (live > 0) {
1674 // Attempt to fit part of the source space into the target space.
1675 HeapWord* next_src_addr = NULL;
1676 bool done = _summary_data.summarize(_space_info[id].split_info(),
1677 space->bottom(), space->top(),
1678 &next_src_addr,
1679 *new_top_addr, dst_space_end,
1680 new_top_addr);
1681 assert(!done, "space should not fit into old gen");
1682 assert(next_src_addr != NULL, "sanity");
1683
1684 // The source space becomes the new target, so the remainder is compacted
1685 // within the space itself.
1686 dst_space_id = SpaceId(id);
1687 dst_space_end = space->end();
1688 new_top_addr = _space_info[id].new_top_addr();
1689 NOT_PRODUCT(summary_phase_msg(dst_space_id,
1690 space->bottom(), dst_space_end,
1691 SpaceId(id), next_src_addr, space->top());)
1692 done = _summary_data.summarize(_space_info[id].split_info(),
1693 next_src_addr, space->top(),
1694 NULL,
1695 space->bottom(), dst_space_end,
1696 new_top_addr);
1697 assert(done, "space must fit when compacted into itself");
1698 assert(*new_top_addr <= space->top(), "usage should not grow");
1699 }
1700 }
1701
1702 log_develop_trace(gc, compaction)("Summary_phase: after final summarization");
1703 NOT_PRODUCT(print_region_ranges());
1704 NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1705 }
1706
1707 // This method should contain all heap-specific policy for invoking a full
1708 // collection. invoke_no_policy() will only attempt to compact the heap; it
1709 // will do nothing further. If we need to bail out for policy reasons, scavenge
1710 // before full gc, or any other specialized behavior, it needs to be added here.
1711 //
1712 // Note that this method should only be called from the vm_thread while at a
1713 // safepoint.
1714 //
1715 // Note that the all_soft_refs_clear flag in the soft ref policy
1716 // may be true because this method can be called without intervening
1717 // activity. For example when the heap space is tight and full measure
1718 // are being taken to free space.
1719 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1720 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1721 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1722 "should be in vm thread");
1723
1724 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1725 GCCause::Cause gc_cause = heap->gc_cause();
1726 assert(!heap->is_gc_active(), "not reentrant");
1727
1728 PSAdaptiveSizePolicy* policy = heap->size_policy();
1729 IsGCActiveMark mark;
1730
1731 if (ScavengeBeforeFullGC) {
1732 PSScavenge::invoke_no_policy();
1733 }
1734
1735 const bool clear_all_soft_refs =
1736 heap->soft_ref_policy()->should_clear_all_soft_refs();
1737
1738 PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1739 maximum_heap_compaction);
1740 }
1741
1742 // This method contains no policy. You should probably
1743 // be calling invoke() instead.
1744 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
1745 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
1746 assert(ref_processor() != NULL, "Sanity");
1747
1748 if (GCLocker::check_active_before_gc()) {
1749 return false;
1750 }
1751
1752 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
1753
1754 GCIdMark gc_id_mark;
1755 _gc_timer.register_gc_start();
1756 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
1757
1758 TimeStamp marking_start;
1759 TimeStamp compaction_start;
1760 TimeStamp collection_exit;
1761
1762 GCCause::Cause gc_cause = heap->gc_cause();
1763 PSYoungGen* young_gen = heap->young_gen();
1764 PSOldGen* old_gen = heap->old_gen();
1765 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
1766
1767 // The scope of casr should end after code that can change
1768 // SoftRefPolicy::_should_clear_all_soft_refs.
1769 ClearedAllSoftRefs casr(maximum_heap_compaction,
1770 heap->soft_ref_policy());
1771
1772 if (ZapUnusedHeapArea) {
1773 // Save information needed to minimize mangling
1774 heap->record_gen_tops_before_GC();
1775 }
1776
1777 // Make sure data structures are sane, make the heap parsable, and do other
1778 // miscellaneous bookkeeping.
1779 pre_compact();
1780
1781 const PreGenGCValues pre_gc_values = heap->get_pre_gc_values();
1782
1783 // Get the compaction manager reserved for the VM thread.
1784 ParCompactionManager* const vmthread_cm =
1785 ParCompactionManager::manager_array(ParallelScavengeHeap::heap()->workers().total_workers());
1786
1787 {
1788 ResourceMark rm;
1789
1790 const uint active_workers =
1791 WorkerPolicy::calc_active_workers(ParallelScavengeHeap::heap()->workers().total_workers(),
1792 ParallelScavengeHeap::heap()->workers().active_workers(),
1793 Threads::number_of_non_daemon_threads());
1794 ParallelScavengeHeap::heap()->workers().update_active_workers(active_workers);
1795
1796 GCTraceCPUTime tcpu;
1797 GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause, true);
1798
1799 heap->pre_full_gc_dump(&_gc_timer);
1800
1801 TraceCollectorStats tcs(counters());
1802 TraceMemoryManagerStats tms(heap->old_gc_manager(), gc_cause);
1803
1804 if (log_is_enabled(Debug, gc, heap, exit)) {
1805 accumulated_time()->start();
1806 }
1807
1808 // Let the size policy know we're starting
1809 size_policy->major_collection_begin();
1810
1811 #if COMPILER2_OR_JVMCI
1812 DerivedPointerTable::clear();
1813 #endif
1814
1815 ref_processor()->enable_discovery();
1816 ref_processor()->setup_policy(maximum_heap_compaction);
1817
1818 bool marked_for_unloading = false;
1819
1820 marking_start.update();
1821 marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
1822
1823 bool max_on_system_gc = UseMaximumCompactionOnSystemGC
1824 && GCCause::is_user_requested_gc(gc_cause);
1825 summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
1826
1827 #if COMPILER2_OR_JVMCI
1828 assert(DerivedPointerTable::is_active(), "Sanity");
1829 DerivedPointerTable::set_active(false);
1830 #endif
1831
1832 // adjust_roots() updates Universe::_intArrayKlassObj which is
1833 // needed by the compaction for filling holes in the dense prefix.
1834 adjust_roots(vmthread_cm);
1835
1836 compaction_start.update();
1837 compact();
1838
1839 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
1840 // done before resizing.
1841 post_compact();
1842
1843 // Let the size policy know we're done
1844 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
1845
1846 if (UseAdaptiveSizePolicy) {
1847 log_debug(gc, ergo)("AdaptiveSizeStart: collection: %d ", heap->total_collections());
1848 log_trace(gc, ergo)("old_gen_capacity: " SIZE_FORMAT " young_gen_capacity: " SIZE_FORMAT,
1849 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
1850
1851 // Don't check if the size_policy is ready here. Let
1852 // the size_policy check that internally.
1853 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
1854 AdaptiveSizePolicy::should_update_promo_stats(gc_cause)) {
1855 // Swap the survivor spaces if from_space is empty. The
1856 // resize_young_gen() called below is normally used after
1857 // a successful young GC and swapping of survivor spaces;
1858 // otherwise, it will fail to resize the young gen with
1859 // the current implementation.
1860 if (young_gen->from_space()->is_empty()) {
1861 young_gen->from_space()->clear(SpaceDecorator::Mangle);
1862 young_gen->swap_spaces();
1863 }
1864
1865 // Calculate optimal free space amounts
1866 assert(young_gen->max_gen_size() >
1867 young_gen->from_space()->capacity_in_bytes() +
1868 young_gen->to_space()->capacity_in_bytes(),
1869 "Sizes of space in young gen are out-of-bounds");
1870
1871 size_t young_live = young_gen->used_in_bytes();
1872 size_t eden_live = young_gen->eden_space()->used_in_bytes();
1873 size_t old_live = old_gen->used_in_bytes();
1874 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
1875 size_t max_old_gen_size = old_gen->max_gen_size();
1876 size_t max_eden_size = young_gen->max_gen_size() -
1877 young_gen->from_space()->capacity_in_bytes() -
1878 young_gen->to_space()->capacity_in_bytes();
1879
1880 // Used for diagnostics
1881 size_policy->clear_generation_free_space_flags();
1882
1883 size_policy->compute_generations_free_space(young_live,
1884 eden_live,
1885 old_live,
1886 cur_eden,
1887 max_old_gen_size,
1888 max_eden_size,
1889 true /* full gc*/);
1890
1891 size_policy->check_gc_overhead_limit(eden_live,
1892 max_old_gen_size,
1893 max_eden_size,
1894 true /* full gc*/,
1895 gc_cause,
1896 heap->soft_ref_policy());
1897
1898 size_policy->decay_supplemental_growth(true /* full gc*/);
1899
1900 heap->resize_old_gen(
1901 size_policy->calculated_old_free_size_in_bytes());
1902
1903 heap->resize_young_gen(size_policy->calculated_eden_size_in_bytes(),
1904 size_policy->calculated_survivor_size_in_bytes());
1905 }
1906
1907 log_debug(gc, ergo)("AdaptiveSizeStop: collection: %d ", heap->total_collections());
1908 }
1909
1910 if (UsePerfData) {
1911 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
1912 counters->update_counters();
1913 counters->update_old_capacity(old_gen->capacity_in_bytes());
1914 counters->update_young_capacity(young_gen->capacity_in_bytes());
1915 }
1916
1917 heap->resize_all_tlabs();
1918
1919 // Resize the metaspace capacity after a collection
1920 MetaspaceGC::compute_new_size();
1921
1922 if (log_is_enabled(Debug, gc, heap, exit)) {
1923 accumulated_time()->stop();
1924 }
1925
1926 heap->print_heap_change(pre_gc_values);
1927
1928 // Track memory usage and detect low memory
1929 MemoryService::track_memory_usage();
1930 heap->update_counters();
1931
1932 heap->post_full_gc_dump(&_gc_timer);
1933 }
1934
1935 #ifdef ASSERT
1936 for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
1937 ParCompactionManager* const cm =
1938 ParCompactionManager::manager_array(int(i));
1939 assert(cm->marking_stack()->is_empty(), "should be empty");
1940 assert(cm->region_stack()->is_empty(), "Region stack " SIZE_FORMAT " is not empty", i);
1941 }
1942 #endif // ASSERT
1943
1944 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
1945 Universe::verify("After GC");
1946 }
1947
1948 // Re-verify object start arrays
1949 if (VerifyObjectStartArray &&
1950 VerifyAfterGC) {
1951 old_gen->verify_object_start_array();
1952 }
1953
1954 if (ZapUnusedHeapArea) {
1955 old_gen->object_space()->check_mangled_unused_area_complete();
1956 }
1957
1958 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1959
1960 collection_exit.update();
1961
1962 heap->print_heap_after_gc();
1963 heap->trace_heap_after_gc(&_gc_tracer);
1964
1965 log_debug(gc, task, time)("VM-Thread " JLONG_FORMAT " " JLONG_FORMAT " " JLONG_FORMAT,
1966 marking_start.ticks(), compaction_start.ticks(),
1967 collection_exit.ticks());
1968
1969 AdaptiveSizePolicyOutput::print(size_policy, heap->total_collections());
1970
1971 _gc_timer.register_gc_end();
1972
1973 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
1974 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
1975
1976 return true;
1977 }
1978
1979 class PCAddThreadRootsMarkingTaskClosure : public ThreadClosure {
1980 private:
1981 uint _worker_id;
1982
1983 public:
1984 PCAddThreadRootsMarkingTaskClosure(uint worker_id) : _worker_id(worker_id) { }
1985 void do_thread(Thread* thread) {
1986 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
1987
1988 ResourceMark rm;
1989
1990 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(_worker_id);
1991
1992 PCMarkAndPushClosure mark_and_push_closure(cm);
1993 MarkingCodeBlobClosure mark_and_push_in_blobs(&mark_and_push_closure, !CodeBlobToOopClosure::FixRelocations);
1994
1995 thread->oops_do(&mark_and_push_closure, &mark_and_push_in_blobs);
1996
1997 // Do the real work
1998 cm->follow_marking_stacks();
1999 }
2000 };
2001
2002 static void mark_from_roots_work(ParallelRootType::Value root_type, uint worker_id) {
2003 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2004
2005 ParCompactionManager* cm =
2006 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2007 PCMarkAndPushClosure mark_and_push_closure(cm);
2008
2009 switch (root_type) {
2010 case ParallelRootType::object_synchronizer:
2011 ObjectSynchronizer::oops_do(&mark_and_push_closure);
2012 break;
2013
2014 case ParallelRootType::class_loader_data:
2015 {
2016 CLDToOopClosure cld_closure(&mark_and_push_closure, ClassLoaderData::_claim_strong);
2017 ClassLoaderDataGraph::always_strong_cld_do(&cld_closure);
2018 }
2019 break;
2020
2021 case ParallelRootType::code_cache:
2022 // Do not treat nmethods as strong roots for mark/sweep, since we can unload them.
2023 //ScavengableNMethods::scavengable_nmethods_do(CodeBlobToOopClosure(&mark_and_push_closure));
2024 AOTLoader::oops_do(&mark_and_push_closure);
2025 break;
2026
2027 case ParallelRootType::sentinel:
2028 DEBUG_ONLY(default:) // DEBUG_ONLY hack will create compile error on release builds (-Wswitch) and runtime check on debug builds
2029 fatal("Bad enumeration value: %u", root_type);
2030 break;
2031 }
2032
2033 // Do the real work
2034 cm->follow_marking_stacks();
2035 }
2036
2037 static void steal_marking_work(TaskTerminator& terminator, uint worker_id) {
2038 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2039
2040 ParCompactionManager* cm =
2041 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2042
2043 oop obj = NULL;
2044 ObjArrayTask task;
2045 do {
2046 while (ParCompactionManager::steal_objarray(worker_id, task)) {
2047 cm->follow_array((objArrayOop)task.obj(), task.index());
2048 cm->follow_marking_stacks();
2049 }
2050 while (ParCompactionManager::steal(worker_id, obj)) {
2051 cm->follow_contents(obj);
2052 cm->follow_marking_stacks();
2053 }
2054 } while (!terminator.offer_termination());
2055 }
2056
2057 class MarkFromRootsTask : public AbstractGangTask {
2058 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2059 StrongRootsScope _strong_roots_scope; // needed for Threads::possibly_parallel_threads_do
2060 OopStorageSetStrongParState<false /* concurrent */, false /* is_const */> _oop_storage_set_par_state;
2061 SequentialSubTasksDone _subtasks;
2062 TaskTerminator _terminator;
2063 uint _active_workers;
2064
2065 public:
2066 MarkFromRootsTask(uint active_workers) :
2067 AbstractGangTask("MarkFromRootsTask"),
2068 _strong_roots_scope(active_workers),
2069 _subtasks(),
2070 _terminator(active_workers, ParCompactionManager::oop_task_queues()),
2071 _active_workers(active_workers) {
2072 _subtasks.set_n_threads(active_workers);
2073 _subtasks.set_n_tasks(ParallelRootType::sentinel);
2074 }
2075
2076 virtual void work(uint worker_id) {
2077 for (uint task = 0; _subtasks.try_claim_task(task); /*empty*/ ) {
2078 mark_from_roots_work(static_cast<ParallelRootType::Value>(task), worker_id);
2079 }
2080 _subtasks.all_tasks_completed();
2081
2082 PCAddThreadRootsMarkingTaskClosure closure(worker_id);
2083 Threads::possibly_parallel_threads_do(true /*parallel */, &closure);
2084
2085 // Mark from OopStorages
2086 {
2087 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2088 PCMarkAndPushClosure closure(cm);
2089 _oop_storage_set_par_state.oops_do(&closure);
2090 // Do the real work
2091 cm->follow_marking_stacks();
2092 }
2093
2094 if (_active_workers > 1) {
2095 steal_marking_work(_terminator, worker_id);
2096 }
2097 }
2098 };
2099
2100 class PCRefProcTask : public AbstractGangTask {
2101 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2102 ProcessTask& _task;
2103 uint _ergo_workers;
2104 TaskTerminator _terminator;
2105
2106 public:
2107 PCRefProcTask(ProcessTask& task, uint ergo_workers) :
2108 AbstractGangTask("PCRefProcTask"),
2109 _task(task),
2110 _ergo_workers(ergo_workers),
2111 _terminator(_ergo_workers, ParCompactionManager::oop_task_queues()) {
2112 }
2113
2114 virtual void work(uint worker_id) {
2115 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2116 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2117
2118 ParCompactionManager* cm =
2119 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2120 PCMarkAndPushClosure mark_and_push_closure(cm);
2121 ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2122 _task.work(worker_id, *PSParallelCompact::is_alive_closure(),
2123 mark_and_push_closure, follow_stack_closure);
2124
2125 steal_marking_work(_terminator, worker_id);
2126 }
2127 };
2128
2129 class RefProcTaskExecutor: public AbstractRefProcTaskExecutor {
2130 void execute(ProcessTask& process_task, uint ergo_workers) {
2131 assert(ParallelScavengeHeap::heap()->workers().active_workers() == ergo_workers,
2132 "Ergonomically chosen workers (%u) must be equal to active workers (%u)",
2133 ergo_workers, ParallelScavengeHeap::heap()->workers().active_workers());
2134
2135 PCRefProcTask task(process_task, ergo_workers);
2136 ParallelScavengeHeap::heap()->workers().run_task(&task);
2137 }
2138 };
2139
2140 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2141 bool maximum_heap_compaction,
2142 ParallelOldTracer *gc_tracer) {
2143 // Recursively traverse all live objects and mark them
2144 GCTraceTime(Info, gc, phases) tm("Marking Phase", &_gc_timer);
2145
2146 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2147 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2148
2149 PCMarkAndPushClosure mark_and_push_closure(cm);
2150 ParCompactionManager::FollowStackClosure follow_stack_closure(cm);
2151
2152 // Need new claim bits before marking starts.
2153 ClassLoaderDataGraph::clear_claimed_marks();
2154
2155 {
2156 GCTraceTime(Debug, gc, phases) tm("Par Mark", &_gc_timer);
2157
2158 MarkFromRootsTask task(active_gc_threads);
2159 ParallelScavengeHeap::heap()->workers().run_task(&task);
2160 }
2161
2162 // Process reference objects found during marking
2163 {
2164 GCTraceTime(Debug, gc, phases) tm("Reference Processing", &_gc_timer);
2165
2166 ReferenceProcessorStats stats;
2167 ReferenceProcessorPhaseTimes pt(&_gc_timer, ref_processor()->max_num_queues());
2168
2169 if (ref_processor()->processing_is_mt()) {
2170 ref_processor()->set_active_mt_degree(active_gc_threads);
2171
2172 RefProcTaskExecutor task_executor;
2173 stats = ref_processor()->process_discovered_references(
2174 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2175 &task_executor, &pt);
2176 } else {
2177 stats = ref_processor()->process_discovered_references(
2178 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2179 &pt);
2180 }
2181
2182 gc_tracer->report_gc_reference_stats(stats);
2183 pt.print_all_references();
2184 }
2185
2186 // This is the point where the entire marking should have completed.
2187 assert(cm->marking_stacks_empty(), "Marking should have completed");
2188
2189 {
2190 GCTraceTime(Debug, gc, phases) tm("Weak Processing", &_gc_timer);
2191 WeakProcessor::weak_oops_do(is_alive_closure(), &do_nothing_cl);
2192 }
2193
2194 {
2195 GCTraceTime(Debug, gc, phases) tm_m("Class Unloading", &_gc_timer);
2196
2197 // Follow system dictionary roots and unload classes.
2198 bool purged_class = SystemDictionary::do_unloading(&_gc_timer);
2199
2200 // Unload nmethods.
2201 CodeCache::do_unloading(is_alive_closure(), purged_class);
2202
2203 // Prune dead klasses from subklass/sibling/implementor lists.
2204 Klass::clean_weak_klass_links(purged_class);
2205
2206 // Clean JVMCI metadata handles.
2207 JVMCI_ONLY(JVMCI::do_unloading(purged_class));
2208 }
2209
2210 _gc_tracer.report_object_count_after_gc(is_alive_closure());
2211 }
2212
2213 void PSParallelCompact::adjust_roots(ParCompactionManager* cm) {
2214 // Adjust the pointers to reflect the new locations
2215 GCTraceTime(Info, gc, phases) tm("Adjust Roots", &_gc_timer);
2216
2217 // Need new claim bits when tracing through and adjusting pointers.
2218 ClassLoaderDataGraph::clear_claimed_marks();
2219
2220 PCAdjustPointerClosure oop_closure(cm);
2221
2222 // General strong roots.
2223 Threads::oops_do(&oop_closure, NULL);
2224 ObjectSynchronizer::oops_do(&oop_closure);
2225 OopStorageSet::strong_oops_do(&oop_closure);
2226 CLDToOopClosure cld_closure(&oop_closure, ClassLoaderData::_claim_strong);
2227 ClassLoaderDataGraph::cld_do(&cld_closure);
2228
2229 // Now adjust pointers in remaining weak roots. (All of which should
2230 // have been cleared if they pointed to non-surviving objects.)
2231 WeakProcessor::oops_do(&oop_closure);
2232
2233 CodeBlobToOopClosure adjust_from_blobs(&oop_closure, CodeBlobToOopClosure::FixRelocations);
2234 CodeCache::blobs_do(&adjust_from_blobs);
2235 AOT_ONLY(AOTLoader::oops_do(&oop_closure);)
2236
2237 ref_processor()->weak_oops_do(&oop_closure);
2238 // Roots were visited so references into the young gen in roots
2239 // may have been scanned. Process them also.
2240 // Should the reference processor have a span that excludes
2241 // young gen objects?
2242 PSScavenge::reference_processor()->weak_oops_do(&oop_closure);
2243 }
2244
2245 // Helper class to print 8 region numbers per line and then print the total at the end.
2246 class FillableRegionLogger : public StackObj {
2247 private:
2248 Log(gc, compaction) log;
2249 static const int LineLength = 8;
2250 size_t _regions[LineLength];
2251 int _next_index;
2252 bool _enabled;
2253 size_t _total_regions;
2254 public:
2255 FillableRegionLogger() : _next_index(0), _enabled(log_develop_is_enabled(Trace, gc, compaction)), _total_regions(0) { }
2256 ~FillableRegionLogger() {
2257 log.trace(SIZE_FORMAT " initially fillable regions", _total_regions);
2258 }
2259
2260 void print_line() {
2261 if (!_enabled || _next_index == 0) {
2262 return;
2263 }
2264 FormatBuffer<> line("Fillable: ");
2265 for (int i = 0; i < _next_index; i++) {
2266 line.append(" " SIZE_FORMAT_W(7), _regions[i]);
2267 }
2268 log.trace("%s", line.buffer());
2269 _next_index = 0;
2270 }
2271
2272 void handle(size_t region) {
2273 if (!_enabled) {
2274 return;
2275 }
2276 _regions[_next_index++] = region;
2277 if (_next_index == LineLength) {
2278 print_line();
2279 }
2280 _total_regions++;
2281 }
2282 };
2283
2284 void PSParallelCompact::prepare_region_draining_tasks(uint parallel_gc_threads)
2285 {
2286 GCTraceTime(Trace, gc, phases) tm("Drain Task Setup", &_gc_timer);
2287
2288 // Find the threads that are active
2289 uint worker_id = 0;
2290
2291 // Find all regions that are available (can be filled immediately) and
2292 // distribute them to the thread stacks. The iteration is done in reverse
2293 // order (high to low) so the regions will be removed in ascending order.
2294
2295 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2296
2297 // id + 1 is used to test termination so unsigned can
2298 // be used with an old_space_id == 0.
2299 FillableRegionLogger region_logger;
2300 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2301 SpaceInfo* const space_info = _space_info + id;
2302 MutableSpace* const space = space_info->space();
2303 HeapWord* const new_top = space_info->new_top();
2304
2305 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2306 const size_t end_region =
2307 sd.addr_to_region_idx(sd.region_align_up(new_top));
2308
2309 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2310 if (sd.region(cur)->claim_unsafe()) {
2311 ParCompactionManager* cm = ParCompactionManager::manager_array(worker_id);
2312 bool result = sd.region(cur)->mark_normal();
2313 assert(result, "Must succeed at this point.");
2314 cm->region_stack()->push(cur);
2315 region_logger.handle(cur);
2316 // Assign regions to tasks in round-robin fashion.
2317 if (++worker_id == parallel_gc_threads) {
2318 worker_id = 0;
2319 }
2320 }
2321 }
2322 region_logger.print_line();
2323 }
2324 }
2325
2326 class TaskQueue : StackObj {
2327 volatile uint _counter;
2328 uint _size;
2329 uint _insert_index;
2330 PSParallelCompact::UpdateDensePrefixTask* _backing_array;
2331 public:
2332 explicit TaskQueue(uint size) : _counter(0), _size(size), _insert_index(0), _backing_array(NULL) {
2333 _backing_array = NEW_C_HEAP_ARRAY(PSParallelCompact::UpdateDensePrefixTask, _size, mtGC);
2334 }
2335 ~TaskQueue() {
2336 assert(_counter >= _insert_index, "not all queue elements were claimed");
2337 FREE_C_HEAP_ARRAY(T, _backing_array);
2338 }
2339
2340 void push(const PSParallelCompact::UpdateDensePrefixTask& value) {
2341 assert(_insert_index < _size, "too small backing array");
2342 _backing_array[_insert_index++] = value;
2343 }
2344
2345 bool try_claim(PSParallelCompact::UpdateDensePrefixTask& reference) {
2346 uint claimed = Atomic::fetch_and_add(&_counter, 1u);
2347 if (claimed < _insert_index) {
2348 reference = _backing_array[claimed];
2349 return true;
2350 } else {
2351 return false;
2352 }
2353 }
2354 };
2355
2356 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2357
2358 void PSParallelCompact::enqueue_dense_prefix_tasks(TaskQueue& task_queue,
2359 uint parallel_gc_threads) {
2360 GCTraceTime(Trace, gc, phases) tm("Dense Prefix Task Setup", &_gc_timer);
2361
2362 ParallelCompactData& sd = PSParallelCompact::summary_data();
2363
2364 // Iterate over all the spaces adding tasks for updating
2365 // regions in the dense prefix. Assume that 1 gc thread
2366 // will work on opening the gaps and the remaining gc threads
2367 // will work on the dense prefix.
2368 unsigned int space_id;
2369 for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2370 HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2371 const MutableSpace* const space = _space_info[space_id].space();
2372
2373 if (dense_prefix_end == space->bottom()) {
2374 // There is no dense prefix for this space.
2375 continue;
2376 }
2377
2378 // The dense prefix is before this region.
2379 size_t region_index_end_dense_prefix =
2380 sd.addr_to_region_idx(dense_prefix_end);
2381 RegionData* const dense_prefix_cp =
2382 sd.region(region_index_end_dense_prefix);
2383 assert(dense_prefix_end == space->end() ||
2384 dense_prefix_cp->available() ||
2385 dense_prefix_cp->claimed(),
2386 "The region after the dense prefix should always be ready to fill");
2387
2388 size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2389
2390 // Is there dense prefix work?
2391 size_t total_dense_prefix_regions =
2392 region_index_end_dense_prefix - region_index_start;
2393 // How many regions of the dense prefix should be given to
2394 // each thread?
2395 if (total_dense_prefix_regions > 0) {
2396 uint tasks_for_dense_prefix = 1;
2397 if (total_dense_prefix_regions <=
2398 (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2399 // Don't over partition. This assumes that
2400 // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2401 // so there are not many regions to process.
2402 tasks_for_dense_prefix = parallel_gc_threads;
2403 } else {
2404 // Over partition
2405 tasks_for_dense_prefix = parallel_gc_threads *
2406 PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2407 }
2408 size_t regions_per_thread = total_dense_prefix_regions /
2409 tasks_for_dense_prefix;
2410 // Give each thread at least 1 region.
2411 if (regions_per_thread == 0) {
2412 regions_per_thread = 1;
2413 }
2414
2415 for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2416 if (region_index_start >= region_index_end_dense_prefix) {
2417 break;
2418 }
2419 // region_index_end is not processed
2420 size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2421 region_index_end_dense_prefix);
2422 task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2423 region_index_start,
2424 region_index_end));
2425 region_index_start = region_index_end;
2426 }
2427 }
2428 // This gets any part of the dense prefix that did not
2429 // fit evenly.
2430 if (region_index_start < region_index_end_dense_prefix) {
2431 task_queue.push(UpdateDensePrefixTask(SpaceId(space_id),
2432 region_index_start,
2433 region_index_end_dense_prefix));
2434 }
2435 }
2436 }
2437
2438 #ifdef ASSERT
2439 // Write a histogram of the number of times the block table was filled for a
2440 // region.
2441 void PSParallelCompact::write_block_fill_histogram()
2442 {
2443 if (!log_develop_is_enabled(Trace, gc, compaction)) {
2444 return;
2445 }
2446
2447 Log(gc, compaction) log;
2448 ResourceMark rm;
2449 LogStream ls(log.trace());
2450 outputStream* out = &ls;
2451
2452 typedef ParallelCompactData::RegionData rd_t;
2453 ParallelCompactData& sd = summary_data();
2454
2455 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2456 MutableSpace* const spc = _space_info[id].space();
2457 if (spc->bottom() != spc->top()) {
2458 const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2459 HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2460 const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2461
2462 size_t histo[5] = { 0, 0, 0, 0, 0 };
2463 const size_t histo_len = sizeof(histo) / sizeof(size_t);
2464 const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2465
2466 for (const rd_t* cur = beg; cur < end; ++cur) {
2467 ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2468 }
2469 out->print("Block fill histogram: %u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2470 for (size_t i = 0; i < histo_len; ++i) {
2471 out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2472 histo[i], 100.0 * histo[i] / region_cnt);
2473 }
2474 out->cr();
2475 }
2476 }
2477 }
2478 #endif // #ifdef ASSERT
2479
2480 static void compaction_with_stealing_work(TaskTerminator* terminator, uint worker_id) {
2481 assert(ParallelScavengeHeap::heap()->is_gc_active(), "called outside gc");
2482
2483 ParCompactionManager* cm =
2484 ParCompactionManager::gc_thread_compaction_manager(worker_id);
2485
2486 // Drain the stacks that have been preloaded with regions
2487 // that are ready to fill.
2488
2489 cm->drain_region_stacks();
2490
2491 guarantee(cm->region_stack()->is_empty(), "Not empty");
2492
2493 size_t region_index = 0;
2494
2495 while (true) {
2496 if (ParCompactionManager::steal(worker_id, region_index)) {
2497 PSParallelCompact::fill_and_update_region(cm, region_index);
2498 cm->drain_region_stacks();
2499 } else if (PSParallelCompact::steal_unavailable_region(cm, region_index)) {
2500 // Fill and update an unavailable region with the help of a shadow region
2501 PSParallelCompact::fill_and_update_shadow_region(cm, region_index);
2502 cm->drain_region_stacks();
2503 } else {
2504 if (terminator->offer_termination()) {
2505 break;
2506 }
2507 // Go around again.
2508 }
2509 }
2510 return;
2511 }
2512
2513 class UpdateDensePrefixAndCompactionTask: public AbstractGangTask {
2514 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
2515 TaskQueue& _tq;
2516 TaskTerminator _terminator;
2517 uint _active_workers;
2518
2519 public:
2520 UpdateDensePrefixAndCompactionTask(TaskQueue& tq, uint active_workers) :
2521 AbstractGangTask("UpdateDensePrefixAndCompactionTask"),
2522 _tq(tq),
2523 _terminator(active_workers, ParCompactionManager::region_task_queues()),
2524 _active_workers(active_workers) {
2525 }
2526 virtual void work(uint worker_id) {
2527 ParCompactionManager* cm = ParCompactionManager::gc_thread_compaction_manager(worker_id);
2528
2529 for (PSParallelCompact::UpdateDensePrefixTask task; _tq.try_claim(task); /* empty */) {
2530 PSParallelCompact::update_and_deadwood_in_dense_prefix(cm,
2531 task._space_id,
2532 task._region_index_start,
2533 task._region_index_end);
2534 }
2535
2536 // Once a thread has drained it's stack, it should try to steal regions from
2537 // other threads.
2538 compaction_with_stealing_work(&_terminator, worker_id);
2539 }
2540 };
2541
2542 void PSParallelCompact::compact() {
2543 GCTraceTime(Info, gc, phases) tm("Compaction Phase", &_gc_timer);
2544
2545 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
2546 PSOldGen* old_gen = heap->old_gen();
2547 old_gen->start_array()->reset();
2548 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
2549
2550 // for [0..last_space_id)
2551 // for [0..active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)
2552 // push
2553 // push
2554 //
2555 // max push count is thus: last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1)
2556 TaskQueue task_queue(last_space_id * (active_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING + 1));
2557 initialize_shadow_regions(active_gc_threads);
2558 prepare_region_draining_tasks(active_gc_threads);
2559 enqueue_dense_prefix_tasks(task_queue, active_gc_threads);
2560
2561 {
2562 GCTraceTime(Trace, gc, phases) tm("Par Compact", &_gc_timer);
2563
2564 UpdateDensePrefixAndCompactionTask task(task_queue, active_gc_threads);
2565 ParallelScavengeHeap::heap()->workers().run_task(&task);
2566
2567 #ifdef ASSERT
2568 // Verify that all regions have been processed before the deferred updates.
2569 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2570 verify_complete(SpaceId(id));
2571 }
2572 #endif
2573 }
2574
2575 {
2576 // Update the deferred objects, if any. Any compaction manager can be used.
2577 GCTraceTime(Trace, gc, phases) tm("Deferred Updates", &_gc_timer);
2578 ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2579 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2580 update_deferred_objects(cm, SpaceId(id));
2581 }
2582 }
2583
2584 DEBUG_ONLY(write_block_fill_histogram());
2585 }
2586
2587 #ifdef ASSERT
2588 void PSParallelCompact::verify_complete(SpaceId space_id) {
2589 // All Regions between space bottom() to new_top() should be marked as filled
2590 // and all Regions between new_top() and top() should be available (i.e.,
2591 // should have been emptied).
2592 ParallelCompactData& sd = summary_data();
2593 SpaceInfo si = _space_info[space_id];
2594 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2595 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2596 const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2597 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2598 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2599
2600 bool issued_a_warning = false;
2601
2602 size_t cur_region;
2603 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2604 const RegionData* const c = sd.region(cur_region);
2605 if (!c->completed()) {
2606 log_warning(gc)("region " SIZE_FORMAT " not filled: destination_count=%u",
2607 cur_region, c->destination_count());
2608 issued_a_warning = true;
2609 }
2610 }
2611
2612 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2613 const RegionData* const c = sd.region(cur_region);
2614 if (!c->available()) {
2615 log_warning(gc)("region " SIZE_FORMAT " not empty: destination_count=%u",
2616 cur_region, c->destination_count());
2617 issued_a_warning = true;
2618 }
2619 }
2620
2621 if (issued_a_warning) {
2622 print_region_ranges();
2623 }
2624 }
2625 #endif // #ifdef ASSERT
2626
2627 inline void UpdateOnlyClosure::do_addr(HeapWord* addr) {
2628 _start_array->allocate_block(addr);
2629 compaction_manager()->update_contents(oop(addr));
2630 }
2631
2632 // Update interior oops in the ranges of regions [beg_region, end_region).
2633 void
2634 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2635 SpaceId space_id,
2636 size_t beg_region,
2637 size_t end_region) {
2638 ParallelCompactData& sd = summary_data();
2639 ParMarkBitMap* const mbm = mark_bitmap();
2640
2641 HeapWord* beg_addr = sd.region_to_addr(beg_region);
2642 HeapWord* const end_addr = sd.region_to_addr(end_region);
2643 assert(beg_region <= end_region, "bad region range");
2644 assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2645
2646 #ifdef ASSERT
2647 // Claim the regions to avoid triggering an assert when they are marked as
2648 // filled.
2649 for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2650 assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2651 }
2652 #endif // #ifdef ASSERT
2653
2654 if (beg_addr != space(space_id)->bottom()) {
2655 // Find the first live object or block of dead space that *starts* in this
2656 // range of regions. If a partial object crosses onto the region, skip it;
2657 // it will be marked for 'deferred update' when the object head is
2658 // processed. If dead space crosses onto the region, it is also skipped; it
2659 // will be filled when the prior region is processed. If neither of those
2660 // apply, the first word in the region is the start of a live object or dead
2661 // space.
2662 assert(beg_addr > space(space_id)->bottom(), "sanity");
2663 const RegionData* const cp = sd.region(beg_region);
2664 if (cp->partial_obj_size() != 0) {
2665 beg_addr = sd.partial_obj_end(beg_region);
2666 } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2667 beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2668 }
2669 }
2670
2671 if (beg_addr < end_addr) {
2672 // A live object or block of dead space starts in this range of Regions.
2673 HeapWord* const dense_prefix_end = dense_prefix(space_id);
2674
2675 // Create closures and iterate.
2676 UpdateOnlyClosure update_closure(mbm, cm, space_id);
2677 FillClosure fill_closure(cm, space_id);
2678 ParMarkBitMap::IterationStatus status;
2679 status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2680 dense_prefix_end);
2681 if (status == ParMarkBitMap::incomplete) {
2682 update_closure.do_addr(update_closure.source());
2683 }
2684 }
2685
2686 // Mark the regions as filled.
2687 RegionData* const beg_cp = sd.region(beg_region);
2688 RegionData* const end_cp = sd.region(end_region);
2689 for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2690 cp->set_completed();
2691 }
2692 }
2693
2694 // Return the SpaceId for the space containing addr. If addr is not in the
2695 // heap, last_space_id is returned. In debug mode it expects the address to be
2696 // in the heap and asserts such.
2697 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2698 assert(ParallelScavengeHeap::heap()->is_in_reserved(addr), "addr not in the heap");
2699
2700 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2701 if (_space_info[id].space()->contains(addr)) {
2702 return SpaceId(id);
2703 }
2704 }
2705
2706 assert(false, "no space contains the addr");
2707 return last_space_id;
2708 }
2709
2710 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2711 SpaceId id) {
2712 assert(id < last_space_id, "bad space id");
2713
2714 ParallelCompactData& sd = summary_data();
2715 const SpaceInfo* const space_info = _space_info + id;
2716 ObjectStartArray* const start_array = space_info->start_array();
2717
2718 const MutableSpace* const space = space_info->space();
2719 assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2720 HeapWord* const beg_addr = space_info->dense_prefix();
2721 HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2722
2723 const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2724 const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2725 const RegionData* cur_region;
2726 for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2727 HeapWord* const addr = cur_region->deferred_obj_addr();
2728 if (addr != NULL) {
2729 if (start_array != NULL) {
2730 start_array->allocate_block(addr);
2731 }
2732 cm->update_contents(oop(addr));
2733 assert(oopDesc::is_oop_or_null(oop(addr)), "Expected an oop or NULL at " PTR_FORMAT, p2i(oop(addr)));
2734 }
2735 }
2736 }
2737
2738 // Skip over count live words starting from beg, and return the address of the
2739 // next live word. Unless marked, the word corresponding to beg is assumed to
2740 // be dead. Callers must either ensure beg does not correspond to the middle of
2741 // an object, or account for those live words in some other way. Callers must
2742 // also ensure that there are enough live words in the range [beg, end) to skip.
2743 HeapWord*
2744 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2745 {
2746 assert(count > 0, "sanity");
2747
2748 ParMarkBitMap* m = mark_bitmap();
2749 idx_t bits_to_skip = m->words_to_bits(count);
2750 idx_t cur_beg = m->addr_to_bit(beg);
2751 const idx_t search_end = m->align_range_end(m->addr_to_bit(end));
2752
2753 do {
2754 cur_beg = m->find_obj_beg(cur_beg, search_end);
2755 idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2756 const size_t obj_bits = cur_end - cur_beg + 1;
2757 if (obj_bits > bits_to_skip) {
2758 return m->bit_to_addr(cur_beg + bits_to_skip);
2759 }
2760 bits_to_skip -= obj_bits;
2761 cur_beg = cur_end + 1;
2762 } while (bits_to_skip > 0);
2763
2764 // Skipping the desired number of words landed just past the end of an object.
2765 // Find the start of the next object.
2766 cur_beg = m->find_obj_beg(cur_beg, search_end);
2767 assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2768 return m->bit_to_addr(cur_beg);
2769 }
2770
2771 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2772 SpaceId src_space_id,
2773 size_t src_region_idx)
2774 {
2775 assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2776
2777 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2778 if (split_info.dest_region_addr() == dest_addr) {
2779 // The partial object ending at the split point contains the first word to
2780 // be copied to dest_addr.
2781 return split_info.first_src_addr();
2782 }
2783
2784 const ParallelCompactData& sd = summary_data();
2785 ParMarkBitMap* const bitmap = mark_bitmap();
2786 const size_t RegionSize = ParallelCompactData::RegionSize;
2787
2788 assert(sd.is_region_aligned(dest_addr), "not aligned");
2789 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2790 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2791 HeapWord* const src_region_destination = src_region_ptr->destination();
2792
2793 assert(dest_addr >= src_region_destination, "wrong src region");
2794 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2795
2796 HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2797 HeapWord* const src_region_end = src_region_beg + RegionSize;
2798
2799 HeapWord* addr = src_region_beg;
2800 if (dest_addr == src_region_destination) {
2801 // Return the first live word in the source region.
2802 if (partial_obj_size == 0) {
2803 addr = bitmap->find_obj_beg(addr, src_region_end);
2804 assert(addr < src_region_end, "no objects start in src region");
2805 }
2806 return addr;
2807 }
2808
2809 // Must skip some live data.
2810 size_t words_to_skip = dest_addr - src_region_destination;
2811 assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2812
2813 if (partial_obj_size >= words_to_skip) {
2814 // All the live words to skip are part of the partial object.
2815 addr += words_to_skip;
2816 if (partial_obj_size == words_to_skip) {
2817 // Find the first live word past the partial object.
2818 addr = bitmap->find_obj_beg(addr, src_region_end);
2819 assert(addr < src_region_end, "wrong src region");
2820 }
2821 return addr;
2822 }
2823
2824 // Skip over the partial object (if any).
2825 if (partial_obj_size != 0) {
2826 words_to_skip -= partial_obj_size;
2827 addr += partial_obj_size;
2828 }
2829
2830 // Skip over live words due to objects that start in the region.
2831 addr = skip_live_words(addr, src_region_end, words_to_skip);
2832 assert(addr < src_region_end, "wrong src region");
2833 return addr;
2834 }
2835
2836 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
2837 SpaceId src_space_id,
2838 size_t beg_region,
2839 HeapWord* end_addr)
2840 {
2841 ParallelCompactData& sd = summary_data();
2842
2843 #ifdef ASSERT
2844 MutableSpace* const src_space = _space_info[src_space_id].space();
2845 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
2846 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
2847 "src_space_id does not match beg_addr");
2848 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
2849 "src_space_id does not match end_addr");
2850 #endif // #ifdef ASSERT
2851
2852 RegionData* const beg = sd.region(beg_region);
2853 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
2854
2855 // Regions up to new_top() are enqueued if they become available.
2856 HeapWord* const new_top = _space_info[src_space_id].new_top();
2857 RegionData* const enqueue_end =
2858 sd.addr_to_region_ptr(sd.region_align_up(new_top));
2859
2860 for (RegionData* cur = beg; cur < end; ++cur) {
2861 assert(cur->data_size() > 0, "region must have live data");
2862 cur->decrement_destination_count();
2863 if (cur < enqueue_end && cur->available() && cur->claim()) {
2864 if (cur->mark_normal()) {
2865 cm->push_region(sd.region(cur));
2866 } else if (cur->mark_copied()) {
2867 // Try to copy the content of the shadow region back to its corresponding
2868 // heap region if the shadow region is filled. Otherwise, the GC thread
2869 // fills the shadow region will copy the data back (see
2870 // MoveAndUpdateShadowClosure::complete_region).
2871 copy_back(sd.region_to_addr(cur->shadow_region()), sd.region_to_addr(cur));
2872 ParCompactionManager::push_shadow_region_mt_safe(cur->shadow_region());
2873 cur->set_completed();
2874 }
2875 }
2876 }
2877 }
2878
2879 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
2880 SpaceId& src_space_id,
2881 HeapWord*& src_space_top,
2882 HeapWord* end_addr)
2883 {
2884 typedef ParallelCompactData::RegionData RegionData;
2885
2886 ParallelCompactData& sd = PSParallelCompact::summary_data();
2887 const size_t region_size = ParallelCompactData::RegionSize;
2888
2889 size_t src_region_idx = 0;
2890
2891 // Skip empty regions (if any) up to the top of the space.
2892 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
2893 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
2894 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
2895 const RegionData* const top_region_ptr =
2896 sd.addr_to_region_ptr(top_aligned_up);
2897 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
2898 ++src_region_ptr;
2899 }
2900
2901 if (src_region_ptr < top_region_ptr) {
2902 // The next source region is in the current space. Update src_region_idx
2903 // and the source address to match src_region_ptr.
2904 src_region_idx = sd.region(src_region_ptr);
2905 HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
2906 if (src_region_addr > closure.source()) {
2907 closure.set_source(src_region_addr);
2908 }
2909 return src_region_idx;
2910 }
2911
2912 // Switch to a new source space and find the first non-empty region.
2913 unsigned int space_id = src_space_id + 1;
2914 assert(space_id < last_space_id, "not enough spaces");
2915
2916 HeapWord* const destination = closure.destination();
2917
2918 do {
2919 MutableSpace* space = _space_info[space_id].space();
2920 HeapWord* const bottom = space->bottom();
2921 const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
2922
2923 // Iterate over the spaces that do not compact into themselves.
2924 if (bottom_cp->destination() != bottom) {
2925 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
2926 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
2927
2928 for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
2929 if (src_cp->live_obj_size() > 0) {
2930 // Found it.
2931 assert(src_cp->destination() == destination,
2932 "first live obj in the space must match the destination");
2933 assert(src_cp->partial_obj_size() == 0,
2934 "a space cannot begin with a partial obj");
2935
2936 src_space_id = SpaceId(space_id);
2937 src_space_top = space->top();
2938 const size_t src_region_idx = sd.region(src_cp);
2939 closure.set_source(sd.region_to_addr(src_region_idx));
2940 return src_region_idx;
2941 } else {
2942 assert(src_cp->data_size() == 0, "sanity");
2943 }
2944 }
2945 }
2946 } while (++space_id < last_space_id);
2947
2948 assert(false, "no source region was found");
2949 return 0;
2950 }
2951
2952 void PSParallelCompact::fill_region(ParCompactionManager* cm, MoveAndUpdateClosure& closure, size_t region_idx)
2953 {
2954 typedef ParMarkBitMap::IterationStatus IterationStatus;
2955 ParMarkBitMap* const bitmap = mark_bitmap();
2956 ParallelCompactData& sd = summary_data();
2957 RegionData* const region_ptr = sd.region(region_idx);
2958
2959 // Get the source region and related info.
2960 size_t src_region_idx = region_ptr->source_region();
2961 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
2962 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
2963 HeapWord* dest_addr = sd.region_to_addr(region_idx);
2964
2965 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
2966
2967 // Adjust src_region_idx to prepare for decrementing destination counts (the
2968 // destination count is not decremented when a region is copied to itself).
2969 if (src_region_idx == region_idx) {
2970 src_region_idx += 1;
2971 }
2972
2973 if (bitmap->is_unmarked(closure.source())) {
2974 // The first source word is in the middle of an object; copy the remainder
2975 // of the object or as much as will fit. The fact that pointer updates were
2976 // deferred will be noted when the object header is processed.
2977 HeapWord* const old_src_addr = closure.source();
2978 closure.copy_partial_obj();
2979 if (closure.is_full()) {
2980 decrement_destination_counts(cm, src_space_id, src_region_idx,
2981 closure.source());
2982 region_ptr->set_deferred_obj_addr(NULL);
2983 closure.complete_region(cm, dest_addr, region_ptr);
2984 return;
2985 }
2986
2987 HeapWord* const end_addr = sd.region_align_down(closure.source());
2988 if (sd.region_align_down(old_src_addr) != end_addr) {
2989 // The partial object was copied from more than one source region.
2990 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
2991
2992 // Move to the next source region, possibly switching spaces as well. All
2993 // args except end_addr may be modified.
2994 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
2995 end_addr);
2996 }
2997 }
2998
2999 do {
3000 HeapWord* const cur_addr = closure.source();
3001 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3002 src_space_top);
3003 IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3004
3005 if (status == ParMarkBitMap::incomplete) {
3006 // The last obj that starts in the source region does not end in the
3007 // region.
3008 assert(closure.source() < end_addr, "sanity");
3009 HeapWord* const obj_beg = closure.source();
3010 HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3011 src_space_top);
3012 HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3013 if (obj_end < range_end) {
3014 // The end was found; the entire object will fit.
3015 status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3016 assert(status != ParMarkBitMap::would_overflow, "sanity");
3017 } else {
3018 // The end was not found; the object will not fit.
3019 assert(range_end < src_space_top, "obj cannot cross space boundary");
3020 status = ParMarkBitMap::would_overflow;
3021 }
3022 }
3023
3024 if (status == ParMarkBitMap::would_overflow) {
3025 // The last object did not fit. Note that interior oop updates were
3026 // deferred, then copy enough of the object to fill the region.
3027 region_ptr->set_deferred_obj_addr(closure.destination());
3028 status = closure.copy_until_full(); // copies from closure.source()
3029
3030 decrement_destination_counts(cm, src_space_id, src_region_idx,
3031 closure.source());
3032 closure.complete_region(cm, dest_addr, region_ptr);
3033 return;
3034 }
3035
3036 if (status == ParMarkBitMap::full) {
3037 decrement_destination_counts(cm, src_space_id, src_region_idx,
3038 closure.source());
3039 region_ptr->set_deferred_obj_addr(NULL);
3040 closure.complete_region(cm, dest_addr, region_ptr);
3041 return;
3042 }
3043
3044 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3045
3046 // Move to the next source region, possibly switching spaces as well. All
3047 // args except end_addr may be modified.
3048 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3049 end_addr);
3050 } while (true);
3051 }
3052
3053 void PSParallelCompact::fill_and_update_region(ParCompactionManager* cm, size_t region_idx)
3054 {
3055 MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3056 fill_region(cm, cl, region_idx);
3057 }
3058
3059 void PSParallelCompact::fill_and_update_shadow_region(ParCompactionManager* cm, size_t region_idx)
3060 {
3061 // Get a shadow region first
3062 ParallelCompactData& sd = summary_data();
3063 RegionData* const region_ptr = sd.region(region_idx);
3064 size_t shadow_region = ParCompactionManager::pop_shadow_region_mt_safe(region_ptr);
3065 // The InvalidShadow return value indicates the corresponding heap region is available,
3066 // so use MoveAndUpdateClosure to fill the normal region. Otherwise, use
3067 // MoveAndUpdateShadowClosure to fill the acquired shadow region.
3068 if (shadow_region == ParCompactionManager::InvalidShadow) {
3069 MoveAndUpdateClosure cl(mark_bitmap(), cm, region_idx);
3070 region_ptr->shadow_to_normal();
3071 return fill_region(cm, cl, region_idx);
3072 } else {
3073 MoveAndUpdateShadowClosure cl(mark_bitmap(), cm, region_idx, shadow_region);
3074 return fill_region(cm, cl, region_idx);
3075 }
3076 }
3077
3078 void PSParallelCompact::copy_back(HeapWord *shadow_addr, HeapWord *region_addr)
3079 {
3080 Copy::aligned_conjoint_words(shadow_addr, region_addr, _summary_data.RegionSize);
3081 }
3082
3083 bool PSParallelCompact::steal_unavailable_region(ParCompactionManager* cm, size_t ®ion_idx)
3084 {
3085 size_t next = cm->next_shadow_region();
3086 ParallelCompactData& sd = summary_data();
3087 size_t old_new_top = sd.addr_to_region_idx(_space_info[old_space_id].new_top());
3088 uint active_gc_threads = ParallelScavengeHeap::heap()->workers().active_workers();
3089
3090 while (next < old_new_top) {
3091 if (sd.region(next)->mark_shadow()) {
3092 region_idx = next;
3093 return true;
3094 }
3095 next = cm->move_next_shadow_region_by(active_gc_threads);
3096 }
3097
3098 return false;
3099 }
3100
3101 // The shadow region is an optimization to address region dependencies in full GC. The basic
3102 // idea is making more regions available by temporally storing their live objects in empty
3103 // shadow regions to resolve dependencies between them and the destination regions. Therefore,
3104 // GC threads need not wait destination regions to be available before processing sources.
3105 //
3106 // A typical workflow would be:
3107 // After draining its own stack and failing to steal from others, a GC worker would pick an
3108 // unavailable region (destination count > 0) and get a shadow region. Then the worker fills
3109 // the shadow region by copying live objects from source regions of the unavailable one. Once
3110 // the unavailable region becomes available, the data in the shadow region will be copied back.
3111 // Shadow regions are empty regions in the to-space and regions between top and end of other spaces.
3112 //
3113 // For more details, please refer to ยง4.2 of the VEE'19 paper:
3114 // Haoyu Li, Mingyu Wu, Binyu Zang, and Haibo Chen. 2019. ScissorGC: scalable and efficient
3115 // compaction for Java full garbage collection. In Proceedings of the 15th ACM SIGPLAN/SIGOPS
3116 // International Conference on Virtual Execution Environments (VEE 2019). ACM, New York, NY, USA,
3117 // 108-121. DOI: https://doi.org/10.1145/3313808.3313820
3118 void PSParallelCompact::initialize_shadow_regions(uint parallel_gc_threads)
3119 {
3120 const ParallelCompactData& sd = PSParallelCompact::summary_data();
3121
3122 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
3123 SpaceInfo* const space_info = _space_info + id;
3124 MutableSpace* const space = space_info->space();
3125
3126 const size_t beg_region =
3127 sd.addr_to_region_idx(sd.region_align_up(MAX2(space_info->new_top(), space->top())));
3128 const size_t end_region =
3129 sd.addr_to_region_idx(sd.region_align_down(space->end()));
3130
3131 for (size_t cur = beg_region; cur < end_region; ++cur) {
3132 ParCompactionManager::push_shadow_region(cur);
3133 }
3134 }
3135
3136 size_t beg_region = sd.addr_to_region_idx(_space_info[old_space_id].dense_prefix());
3137 for (uint i = 0; i < parallel_gc_threads; i++) {
3138 ParCompactionManager *cm = ParCompactionManager::manager_array(i);
3139 cm->set_next_shadow_region(beg_region + i);
3140 }
3141 }
3142
3143 void PSParallelCompact::fill_blocks(size_t region_idx)
3144 {
3145 // Fill in the block table elements for the specified region. Each block
3146 // table element holds the number of live words in the region that are to the
3147 // left of the first object that starts in the block. Thus only blocks in
3148 // which an object starts need to be filled.
3149 //
3150 // The algorithm scans the section of the bitmap that corresponds to the
3151 // region, keeping a running total of the live words. When an object start is
3152 // found, if it's the first to start in the block that contains it, the
3153 // current total is written to the block table element.
3154 const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3155 const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3156 const size_t RegionSize = ParallelCompactData::RegionSize;
3157
3158 ParallelCompactData& sd = summary_data();
3159 const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3160 if (partial_obj_size >= RegionSize) {
3161 return; // No objects start in this region.
3162 }
3163
3164 // Ensure the first loop iteration decides that the block has changed.
3165 size_t cur_block = sd.block_count();
3166
3167 const ParMarkBitMap* const bitmap = mark_bitmap();
3168
3169 const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3170 assert((size_t)1 << Log2BitsPerBlock ==
3171 bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3172
3173 size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3174 const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3175 size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3176 beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3177 while (beg_bit < range_end) {
3178 const size_t new_block = beg_bit >> Log2BitsPerBlock;
3179 if (new_block != cur_block) {
3180 cur_block = new_block;
3181 sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3182 }
3183
3184 const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3185 if (end_bit < range_end - 1) {
3186 live_bits += end_bit - beg_bit + 1;
3187 beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3188 } else {
3189 return;
3190 }
3191 }
3192 }
3193
3194 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3195 {
3196 if (source() != copy_destination()) {
3197 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3198 Copy::aligned_conjoint_words(source(), copy_destination(), words_remaining());
3199 }
3200 update_state(words_remaining());
3201 assert(is_full(), "sanity");
3202 return ParMarkBitMap::full;
3203 }
3204
3205 void MoveAndUpdateClosure::copy_partial_obj()
3206 {
3207 size_t words = words_remaining();
3208
3209 HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3210 HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3211 if (end_addr < range_end) {
3212 words = bitmap()->obj_size(source(), end_addr);
3213 }
3214
3215 // This test is necessary; if omitted, the pointer updates to a partial object
3216 // that crosses the dense prefix boundary could be overwritten.
3217 if (source() != copy_destination()) {
3218 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3219 Copy::aligned_conjoint_words(source(), copy_destination(), words);
3220 }
3221 update_state(words);
3222 }
3223
3224 void MoveAndUpdateClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3225 PSParallelCompact::RegionData *region_ptr) {
3226 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::NormalRegion, "Region should be finished");
3227 region_ptr->set_completed();
3228 }
3229
3230 ParMarkBitMapClosure::IterationStatus
3231 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3232 assert(destination() != NULL, "sanity");
3233 assert(bitmap()->obj_size(addr) == words, "bad size");
3234
3235 _source = addr;
3236 assert(PSParallelCompact::summary_data().calc_new_pointer(source(), compaction_manager()) ==
3237 destination(), "wrong destination");
3238
3239 if (words > words_remaining()) {
3240 return ParMarkBitMap::would_overflow;
3241 }
3242
3243 // The start_array must be updated even if the object is not moving.
3244 if (_start_array != NULL) {
3245 _start_array->allocate_block(destination());
3246 }
3247
3248 if (copy_destination() != source()) {
3249 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3250 Copy::aligned_conjoint_words(source(), copy_destination(), words);
3251 }
3252
3253 oop moved_oop = (oop) copy_destination();
3254 compaction_manager()->update_contents(moved_oop);
3255 assert(oopDesc::is_oop_or_null(moved_oop), "Expected an oop or NULL at " PTR_FORMAT, p2i(moved_oop));
3256
3257 update_state(words);
3258 assert(copy_destination() == cast_from_oop<HeapWord*>(moved_oop) + moved_oop->size(), "sanity");
3259 return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3260 }
3261
3262 void MoveAndUpdateShadowClosure::complete_region(ParCompactionManager *cm, HeapWord *dest_addr,
3263 PSParallelCompact::RegionData *region_ptr) {
3264 assert(region_ptr->shadow_state() == ParallelCompactData::RegionData::ShadowRegion, "Region should be shadow");
3265 // Record the shadow region index
3266 region_ptr->set_shadow_region(_shadow);
3267 // Mark the shadow region as filled to indicate the data is ready to be
3268 // copied back
3269 region_ptr->mark_filled();
3270 // Try to copy the content of the shadow region back to its corresponding
3271 // heap region if available; the GC thread that decreases the destination
3272 // count to zero will do the copying otherwise (see
3273 // PSParallelCompact::decrement_destination_counts).
3274 if (((region_ptr->available() && region_ptr->claim()) || region_ptr->claimed()) && region_ptr->mark_copied()) {
3275 region_ptr->set_completed();
3276 PSParallelCompact::copy_back(PSParallelCompact::summary_data().region_to_addr(_shadow), dest_addr);
3277 ParCompactionManager::push_shadow_region_mt_safe(_shadow);
3278 }
3279 }
3280
3281 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3282 ParCompactionManager* cm,
3283 PSParallelCompact::SpaceId space_id) :
3284 ParMarkBitMapClosure(mbm, cm),
3285 _space_id(space_id),
3286 _start_array(PSParallelCompact::start_array(space_id))
3287 {
3288 }
3289
3290 // Updates the references in the object to their new values.
3291 ParMarkBitMapClosure::IterationStatus
3292 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3293 do_addr(addr);
3294 return ParMarkBitMap::incomplete;
3295 }
3296
3297 FillClosure::FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id) :
3298 ParMarkBitMapClosure(PSParallelCompact::mark_bitmap(), cm),
3299 _start_array(PSParallelCompact::start_array(space_id))
3300 {
3301 assert(space_id == PSParallelCompact::old_space_id,
3302 "cannot use FillClosure in the young gen");
3303 }
3304
3305 ParMarkBitMapClosure::IterationStatus
3306 FillClosure::do_addr(HeapWord* addr, size_t size) {
3307 CollectedHeap::fill_with_objects(addr, size);
3308 HeapWord* const end = addr + size;
3309 do {
3310 _start_array->allocate_block(addr);
3311 addr += oop(addr)->size();
3312 } while (addr < end);
3313 return ParMarkBitMap::incomplete;
3314 }