Fri, 01 Nov 2013 17:09:38 +0100
8016309: assert(eden_size > 0 && survivor_size > 0) failed: just checking
7057939: jmap shows MaxNewSize=4GB when Java is using parallel collector
Summary: Major cleanup of the collectorpolicy classes
Reviewed-by: tschatzl, jcoomes
1 /*
2 * Copyright (c) 2005, 2013, 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 */
25 #include "precompiled.hpp"
26 #include "classfile/symbolTable.hpp"
27 #include "classfile/systemDictionary.hpp"
28 #include "code/codeCache.hpp"
29 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
30 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.inline.hpp"
31 #include "gc_implementation/parallelScavenge/pcTasks.hpp"
32 #include "gc_implementation/parallelScavenge/psAdaptiveSizePolicy.hpp"
33 #include "gc_implementation/parallelScavenge/psCompactionManager.inline.hpp"
34 #include "gc_implementation/parallelScavenge/psMarkSweep.hpp"
35 #include "gc_implementation/parallelScavenge/psMarkSweepDecorator.hpp"
36 #include "gc_implementation/parallelScavenge/psOldGen.hpp"
37 #include "gc_implementation/parallelScavenge/psParallelCompact.hpp"
38 #include "gc_implementation/parallelScavenge/psPromotionManager.inline.hpp"
39 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
40 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
41 #include "gc_implementation/shared/gcHeapSummary.hpp"
42 #include "gc_implementation/shared/gcTimer.hpp"
43 #include "gc_implementation/shared/gcTrace.hpp"
44 #include "gc_implementation/shared/gcTraceTime.hpp"
45 #include "gc_implementation/shared/isGCActiveMark.hpp"
46 #include "gc_interface/gcCause.hpp"
47 #include "memory/gcLocker.inline.hpp"
48 #include "memory/referencePolicy.hpp"
49 #include "memory/referenceProcessor.hpp"
50 #include "oops/methodData.hpp"
51 #include "oops/oop.inline.hpp"
52 #include "oops/oop.pcgc.inline.hpp"
53 #include "runtime/fprofiler.hpp"
54 #include "runtime/safepoint.hpp"
55 #include "runtime/vmThread.hpp"
56 #include "services/management.hpp"
57 #include "services/memoryService.hpp"
58 #include "services/memTracker.hpp"
59 #include "utilities/events.hpp"
60 #include "utilities/stack.inline.hpp"
62 #include <math.h>
64 // All sizes are in HeapWords.
65 const size_t ParallelCompactData::Log2RegionSize = 16; // 64K words
66 const size_t ParallelCompactData::RegionSize = (size_t)1 << Log2RegionSize;
67 const size_t ParallelCompactData::RegionSizeBytes =
68 RegionSize << LogHeapWordSize;
69 const size_t ParallelCompactData::RegionSizeOffsetMask = RegionSize - 1;
70 const size_t ParallelCompactData::RegionAddrOffsetMask = RegionSizeBytes - 1;
71 const size_t ParallelCompactData::RegionAddrMask = ~RegionAddrOffsetMask;
73 const size_t ParallelCompactData::Log2BlockSize = 7; // 128 words
74 const size_t ParallelCompactData::BlockSize = (size_t)1 << Log2BlockSize;
75 const size_t ParallelCompactData::BlockSizeBytes =
76 BlockSize << LogHeapWordSize;
77 const size_t ParallelCompactData::BlockSizeOffsetMask = BlockSize - 1;
78 const size_t ParallelCompactData::BlockAddrOffsetMask = BlockSizeBytes - 1;
79 const size_t ParallelCompactData::BlockAddrMask = ~BlockAddrOffsetMask;
81 const size_t ParallelCompactData::BlocksPerRegion = RegionSize / BlockSize;
82 const size_t ParallelCompactData::Log2BlocksPerRegion =
83 Log2RegionSize - Log2BlockSize;
85 const ParallelCompactData::RegionData::region_sz_t
86 ParallelCompactData::RegionData::dc_shift = 27;
88 const ParallelCompactData::RegionData::region_sz_t
89 ParallelCompactData::RegionData::dc_mask = ~0U << dc_shift;
91 const ParallelCompactData::RegionData::region_sz_t
92 ParallelCompactData::RegionData::dc_one = 0x1U << dc_shift;
94 const ParallelCompactData::RegionData::region_sz_t
95 ParallelCompactData::RegionData::los_mask = ~dc_mask;
97 const ParallelCompactData::RegionData::region_sz_t
98 ParallelCompactData::RegionData::dc_claimed = 0x8U << dc_shift;
100 const ParallelCompactData::RegionData::region_sz_t
101 ParallelCompactData::RegionData::dc_completed = 0xcU << dc_shift;
103 SpaceInfo PSParallelCompact::_space_info[PSParallelCompact::last_space_id];
104 bool PSParallelCompact::_print_phases = false;
106 ReferenceProcessor* PSParallelCompact::_ref_processor = NULL;
107 Klass* PSParallelCompact::_updated_int_array_klass_obj = NULL;
109 double PSParallelCompact::_dwl_mean;
110 double PSParallelCompact::_dwl_std_dev;
111 double PSParallelCompact::_dwl_first_term;
112 double PSParallelCompact::_dwl_adjustment;
113 #ifdef ASSERT
114 bool PSParallelCompact::_dwl_initialized = false;
115 #endif // #ifdef ASSERT
117 void SplitInfo::record(size_t src_region_idx, size_t partial_obj_size,
118 HeapWord* destination)
119 {
120 assert(src_region_idx != 0, "invalid src_region_idx");
121 assert(partial_obj_size != 0, "invalid partial_obj_size argument");
122 assert(destination != NULL, "invalid destination argument");
124 _src_region_idx = src_region_idx;
125 _partial_obj_size = partial_obj_size;
126 _destination = destination;
128 // These fields may not be updated below, so make sure they're clear.
129 assert(_dest_region_addr == NULL, "should have been cleared");
130 assert(_first_src_addr == NULL, "should have been cleared");
132 // Determine the number of destination regions for the partial object.
133 HeapWord* const last_word = destination + partial_obj_size - 1;
134 const ParallelCompactData& sd = PSParallelCompact::summary_data();
135 HeapWord* const beg_region_addr = sd.region_align_down(destination);
136 HeapWord* const end_region_addr = sd.region_align_down(last_word);
138 if (beg_region_addr == end_region_addr) {
139 // One destination region.
140 _destination_count = 1;
141 if (end_region_addr == destination) {
142 // The destination falls on a region boundary, thus the first word of the
143 // partial object will be the first word copied to the destination region.
144 _dest_region_addr = end_region_addr;
145 _first_src_addr = sd.region_to_addr(src_region_idx);
146 }
147 } else {
148 // Two destination regions. When copied, the partial object will cross a
149 // destination region boundary, so a word somewhere within the partial
150 // object will be the first word copied to the second destination region.
151 _destination_count = 2;
152 _dest_region_addr = end_region_addr;
153 const size_t ofs = pointer_delta(end_region_addr, destination);
154 assert(ofs < _partial_obj_size, "sanity");
155 _first_src_addr = sd.region_to_addr(src_region_idx) + ofs;
156 }
157 }
159 void SplitInfo::clear()
160 {
161 _src_region_idx = 0;
162 _partial_obj_size = 0;
163 _destination = NULL;
164 _destination_count = 0;
165 _dest_region_addr = NULL;
166 _first_src_addr = NULL;
167 assert(!is_valid(), "sanity");
168 }
170 #ifdef ASSERT
171 void SplitInfo::verify_clear()
172 {
173 assert(_src_region_idx == 0, "not clear");
174 assert(_partial_obj_size == 0, "not clear");
175 assert(_destination == NULL, "not clear");
176 assert(_destination_count == 0, "not clear");
177 assert(_dest_region_addr == NULL, "not clear");
178 assert(_first_src_addr == NULL, "not clear");
179 }
180 #endif // #ifdef ASSERT
183 void PSParallelCompact::print_on_error(outputStream* st) {
184 _mark_bitmap.print_on_error(st);
185 }
187 #ifndef PRODUCT
188 const char* PSParallelCompact::space_names[] = {
189 "old ", "eden", "from", "to "
190 };
192 void PSParallelCompact::print_region_ranges()
193 {
194 tty->print_cr("space bottom top end new_top");
195 tty->print_cr("------ ---------- ---------- ---------- ----------");
197 for (unsigned int id = 0; id < last_space_id; ++id) {
198 const MutableSpace* space = _space_info[id].space();
199 tty->print_cr("%u %s "
200 SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " "
201 SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10) " ",
202 id, space_names[id],
203 summary_data().addr_to_region_idx(space->bottom()),
204 summary_data().addr_to_region_idx(space->top()),
205 summary_data().addr_to_region_idx(space->end()),
206 summary_data().addr_to_region_idx(_space_info[id].new_top()));
207 }
208 }
210 void
211 print_generic_summary_region(size_t i, const ParallelCompactData::RegionData* c)
212 {
213 #define REGION_IDX_FORMAT SIZE_FORMAT_W(7)
214 #define REGION_DATA_FORMAT SIZE_FORMAT_W(5)
216 ParallelCompactData& sd = PSParallelCompact::summary_data();
217 size_t dci = c->destination() ? sd.addr_to_region_idx(c->destination()) : 0;
218 tty->print_cr(REGION_IDX_FORMAT " " PTR_FORMAT " "
219 REGION_IDX_FORMAT " " PTR_FORMAT " "
220 REGION_DATA_FORMAT " " REGION_DATA_FORMAT " "
221 REGION_DATA_FORMAT " " REGION_IDX_FORMAT " %d",
222 i, c->data_location(), dci, c->destination(),
223 c->partial_obj_size(), c->live_obj_size(),
224 c->data_size(), c->source_region(), c->destination_count());
226 #undef REGION_IDX_FORMAT
227 #undef REGION_DATA_FORMAT
228 }
230 void
231 print_generic_summary_data(ParallelCompactData& summary_data,
232 HeapWord* const beg_addr,
233 HeapWord* const end_addr)
234 {
235 size_t total_words = 0;
236 size_t i = summary_data.addr_to_region_idx(beg_addr);
237 const size_t last = summary_data.addr_to_region_idx(end_addr);
238 HeapWord* pdest = 0;
240 while (i <= last) {
241 ParallelCompactData::RegionData* c = summary_data.region(i);
242 if (c->data_size() != 0 || c->destination() != pdest) {
243 print_generic_summary_region(i, c);
244 total_words += c->data_size();
245 pdest = c->destination();
246 }
247 ++i;
248 }
250 tty->print_cr("summary_data_bytes=" SIZE_FORMAT, total_words * HeapWordSize);
251 }
253 void
254 print_generic_summary_data(ParallelCompactData& summary_data,
255 SpaceInfo* space_info)
256 {
257 for (unsigned int id = 0; id < PSParallelCompact::last_space_id; ++id) {
258 const MutableSpace* space = space_info[id].space();
259 print_generic_summary_data(summary_data, space->bottom(),
260 MAX2(space->top(), space_info[id].new_top()));
261 }
262 }
264 void
265 print_initial_summary_region(size_t i,
266 const ParallelCompactData::RegionData* c,
267 bool newline = true)
268 {
269 tty->print(SIZE_FORMAT_W(5) " " PTR_FORMAT " "
270 SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " "
271 SIZE_FORMAT_W(5) " " SIZE_FORMAT_W(5) " %d",
272 i, c->destination(),
273 c->partial_obj_size(), c->live_obj_size(),
274 c->data_size(), c->source_region(), c->destination_count());
275 if (newline) tty->cr();
276 }
278 void
279 print_initial_summary_data(ParallelCompactData& summary_data,
280 const MutableSpace* space) {
281 if (space->top() == space->bottom()) {
282 return;
283 }
285 const size_t region_size = ParallelCompactData::RegionSize;
286 typedef ParallelCompactData::RegionData RegionData;
287 HeapWord* const top_aligned_up = summary_data.region_align_up(space->top());
288 const size_t end_region = summary_data.addr_to_region_idx(top_aligned_up);
289 const RegionData* c = summary_data.region(end_region - 1);
290 HeapWord* end_addr = c->destination() + c->data_size();
291 const size_t live_in_space = pointer_delta(end_addr, space->bottom());
293 // Print (and count) the full regions at the beginning of the space.
294 size_t full_region_count = 0;
295 size_t i = summary_data.addr_to_region_idx(space->bottom());
296 while (i < end_region && summary_data.region(i)->data_size() == region_size) {
297 print_initial_summary_region(i, summary_data.region(i));
298 ++full_region_count;
299 ++i;
300 }
302 size_t live_to_right = live_in_space - full_region_count * region_size;
304 double max_reclaimed_ratio = 0.0;
305 size_t max_reclaimed_ratio_region = 0;
306 size_t max_dead_to_right = 0;
307 size_t max_live_to_right = 0;
309 // Print the 'reclaimed ratio' for regions while there is something live in
310 // the region or to the right of it. The remaining regions are empty (and
311 // uninteresting), and computing the ratio will result in division by 0.
312 while (i < end_region && live_to_right > 0) {
313 c = summary_data.region(i);
314 HeapWord* const region_addr = summary_data.region_to_addr(i);
315 const size_t used_to_right = pointer_delta(space->top(), region_addr);
316 const size_t dead_to_right = used_to_right - live_to_right;
317 const double reclaimed_ratio = double(dead_to_right) / live_to_right;
319 if (reclaimed_ratio > max_reclaimed_ratio) {
320 max_reclaimed_ratio = reclaimed_ratio;
321 max_reclaimed_ratio_region = i;
322 max_dead_to_right = dead_to_right;
323 max_live_to_right = live_to_right;
324 }
326 print_initial_summary_region(i, c, false);
327 tty->print_cr(" %12.10f " SIZE_FORMAT_W(10) " " SIZE_FORMAT_W(10),
328 reclaimed_ratio, dead_to_right, live_to_right);
330 live_to_right -= c->data_size();
331 ++i;
332 }
334 // Any remaining regions are empty. Print one more if there is one.
335 if (i < end_region) {
336 print_initial_summary_region(i, summary_data.region(i));
337 }
339 tty->print_cr("max: " SIZE_FORMAT_W(4) " d2r=" SIZE_FORMAT_W(10) " "
340 "l2r=" SIZE_FORMAT_W(10) " max_ratio=%14.12f",
341 max_reclaimed_ratio_region, max_dead_to_right,
342 max_live_to_right, max_reclaimed_ratio);
343 }
345 void
346 print_initial_summary_data(ParallelCompactData& summary_data,
347 SpaceInfo* space_info) {
348 unsigned int id = PSParallelCompact::old_space_id;
349 const MutableSpace* space;
350 do {
351 space = space_info[id].space();
352 print_initial_summary_data(summary_data, space);
353 } while (++id < PSParallelCompact::eden_space_id);
355 do {
356 space = space_info[id].space();
357 print_generic_summary_data(summary_data, space->bottom(), space->top());
358 } while (++id < PSParallelCompact::last_space_id);
359 }
360 #endif // #ifndef PRODUCT
362 #ifdef ASSERT
363 size_t add_obj_count;
364 size_t add_obj_size;
365 size_t mark_bitmap_count;
366 size_t mark_bitmap_size;
367 #endif // #ifdef ASSERT
369 ParallelCompactData::ParallelCompactData()
370 {
371 _region_start = 0;
373 _region_vspace = 0;
374 _reserved_byte_size = 0;
375 _region_data = 0;
376 _region_count = 0;
378 _block_vspace = 0;
379 _block_data = 0;
380 _block_count = 0;
381 }
383 bool ParallelCompactData::initialize(MemRegion covered_region)
384 {
385 _region_start = covered_region.start();
386 const size_t region_size = covered_region.word_size();
387 DEBUG_ONLY(_region_end = _region_start + region_size;)
389 assert(region_align_down(_region_start) == _region_start,
390 "region start not aligned");
391 assert((region_size & RegionSizeOffsetMask) == 0,
392 "region size not a multiple of RegionSize");
394 bool result = initialize_region_data(region_size) && initialize_block_data();
395 return result;
396 }
398 PSVirtualSpace*
399 ParallelCompactData::create_vspace(size_t count, size_t element_size)
400 {
401 const size_t raw_bytes = count * element_size;
402 const size_t page_sz = os::page_size_for_region(raw_bytes, raw_bytes, 10);
403 const size_t granularity = os::vm_allocation_granularity();
404 _reserved_byte_size = align_size_up(raw_bytes, MAX2(page_sz, granularity));
406 const size_t rs_align = page_sz == (size_t) os::vm_page_size() ? 0 :
407 MAX2(page_sz, granularity);
408 ReservedSpace rs(_reserved_byte_size, rs_align, rs_align > 0);
409 os::trace_page_sizes("par compact", raw_bytes, raw_bytes, page_sz, rs.base(),
410 rs.size());
412 MemTracker::record_virtual_memory_type((address)rs.base(), mtGC);
414 PSVirtualSpace* vspace = new PSVirtualSpace(rs, page_sz);
415 if (vspace != 0) {
416 if (vspace->expand_by(_reserved_byte_size)) {
417 return vspace;
418 }
419 delete vspace;
420 // Release memory reserved in the space.
421 rs.release();
422 }
424 return 0;
425 }
427 bool ParallelCompactData::initialize_region_data(size_t region_size)
428 {
429 const size_t count = (region_size + RegionSizeOffsetMask) >> Log2RegionSize;
430 _region_vspace = create_vspace(count, sizeof(RegionData));
431 if (_region_vspace != 0) {
432 _region_data = (RegionData*)_region_vspace->reserved_low_addr();
433 _region_count = count;
434 return true;
435 }
436 return false;
437 }
439 bool ParallelCompactData::initialize_block_data()
440 {
441 assert(_region_count != 0, "region data must be initialized first");
442 const size_t count = _region_count << Log2BlocksPerRegion;
443 _block_vspace = create_vspace(count, sizeof(BlockData));
444 if (_block_vspace != 0) {
445 _block_data = (BlockData*)_block_vspace->reserved_low_addr();
446 _block_count = count;
447 return true;
448 }
449 return false;
450 }
452 void ParallelCompactData::clear()
453 {
454 memset(_region_data, 0, _region_vspace->committed_size());
455 memset(_block_data, 0, _block_vspace->committed_size());
456 }
458 void ParallelCompactData::clear_range(size_t beg_region, size_t end_region) {
459 assert(beg_region <= _region_count, "beg_region out of range");
460 assert(end_region <= _region_count, "end_region out of range");
461 assert(RegionSize % BlockSize == 0, "RegionSize not a multiple of BlockSize");
463 const size_t region_cnt = end_region - beg_region;
464 memset(_region_data + beg_region, 0, region_cnt * sizeof(RegionData));
466 const size_t beg_block = beg_region * BlocksPerRegion;
467 const size_t block_cnt = region_cnt * BlocksPerRegion;
468 memset(_block_data + beg_block, 0, block_cnt * sizeof(BlockData));
469 }
471 HeapWord* ParallelCompactData::partial_obj_end(size_t region_idx) const
472 {
473 const RegionData* cur_cp = region(region_idx);
474 const RegionData* const end_cp = region(region_count() - 1);
476 HeapWord* result = region_to_addr(region_idx);
477 if (cur_cp < end_cp) {
478 do {
479 result += cur_cp->partial_obj_size();
480 } while (cur_cp->partial_obj_size() == RegionSize && ++cur_cp < end_cp);
481 }
482 return result;
483 }
485 void ParallelCompactData::add_obj(HeapWord* addr, size_t len)
486 {
487 const size_t obj_ofs = pointer_delta(addr, _region_start);
488 const size_t beg_region = obj_ofs >> Log2RegionSize;
489 const size_t end_region = (obj_ofs + len - 1) >> Log2RegionSize;
491 DEBUG_ONLY(Atomic::inc_ptr(&add_obj_count);)
492 DEBUG_ONLY(Atomic::add_ptr(len, &add_obj_size);)
494 if (beg_region == end_region) {
495 // All in one region.
496 _region_data[beg_region].add_live_obj(len);
497 return;
498 }
500 // First region.
501 const size_t beg_ofs = region_offset(addr);
502 _region_data[beg_region].add_live_obj(RegionSize - beg_ofs);
504 Klass* klass = ((oop)addr)->klass();
505 // Middle regions--completely spanned by this object.
506 for (size_t region = beg_region + 1; region < end_region; ++region) {
507 _region_data[region].set_partial_obj_size(RegionSize);
508 _region_data[region].set_partial_obj_addr(addr);
509 }
511 // Last region.
512 const size_t end_ofs = region_offset(addr + len - 1);
513 _region_data[end_region].set_partial_obj_size(end_ofs + 1);
514 _region_data[end_region].set_partial_obj_addr(addr);
515 }
517 void
518 ParallelCompactData::summarize_dense_prefix(HeapWord* beg, HeapWord* end)
519 {
520 assert(region_offset(beg) == 0, "not RegionSize aligned");
521 assert(region_offset(end) == 0, "not RegionSize aligned");
523 size_t cur_region = addr_to_region_idx(beg);
524 const size_t end_region = addr_to_region_idx(end);
525 HeapWord* addr = beg;
526 while (cur_region < end_region) {
527 _region_data[cur_region].set_destination(addr);
528 _region_data[cur_region].set_destination_count(0);
529 _region_data[cur_region].set_source_region(cur_region);
530 _region_data[cur_region].set_data_location(addr);
532 // Update live_obj_size so the region appears completely full.
533 size_t live_size = RegionSize - _region_data[cur_region].partial_obj_size();
534 _region_data[cur_region].set_live_obj_size(live_size);
536 ++cur_region;
537 addr += RegionSize;
538 }
539 }
541 // Find the point at which a space can be split and, if necessary, record the
542 // split point.
543 //
544 // If the current src region (which overflowed the destination space) doesn't
545 // have a partial object, the split point is at the beginning of the current src
546 // region (an "easy" split, no extra bookkeeping required).
547 //
548 // If the current src region has a partial object, the split point is in the
549 // region where that partial object starts (call it the split_region). If
550 // split_region has a partial object, then the split point is just after that
551 // partial object (a "hard" split where we have to record the split data and
552 // zero the partial_obj_size field). With a "hard" split, we know that the
553 // partial_obj ends within split_region because the partial object that caused
554 // the overflow starts in split_region. If split_region doesn't have a partial
555 // obj, then the split is at the beginning of split_region (another "easy"
556 // split).
557 HeapWord*
558 ParallelCompactData::summarize_split_space(size_t src_region,
559 SplitInfo& split_info,
560 HeapWord* destination,
561 HeapWord* target_end,
562 HeapWord** target_next)
563 {
564 assert(destination <= target_end, "sanity");
565 assert(destination + _region_data[src_region].data_size() > target_end,
566 "region should not fit into target space");
567 assert(is_region_aligned(target_end), "sanity");
569 size_t split_region = src_region;
570 HeapWord* split_destination = destination;
571 size_t partial_obj_size = _region_data[src_region].partial_obj_size();
573 if (destination + partial_obj_size > target_end) {
574 // The split point is just after the partial object (if any) in the
575 // src_region that contains the start of the object that overflowed the
576 // destination space.
577 //
578 // Find the start of the "overflow" object and set split_region to the
579 // region containing it.
580 HeapWord* const overflow_obj = _region_data[src_region].partial_obj_addr();
581 split_region = addr_to_region_idx(overflow_obj);
583 // Clear the source_region field of all destination regions whose first word
584 // came from data after the split point (a non-null source_region field
585 // implies a region must be filled).
586 //
587 // An alternative to the simple loop below: clear during post_compact(),
588 // which uses memcpy instead of individual stores, and is easy to
589 // parallelize. (The downside is that it clears the entire RegionData
590 // object as opposed to just one field.)
591 //
592 // post_compact() would have to clear the summary data up to the highest
593 // address that was written during the summary phase, which would be
594 //
595 // max(top, max(new_top, clear_top))
596 //
597 // where clear_top is a new field in SpaceInfo. Would have to set clear_top
598 // to target_end.
599 const RegionData* const sr = region(split_region);
600 const size_t beg_idx =
601 addr_to_region_idx(region_align_up(sr->destination() +
602 sr->partial_obj_size()));
603 const size_t end_idx = addr_to_region_idx(target_end);
605 if (TraceParallelOldGCSummaryPhase) {
606 gclog_or_tty->print_cr("split: clearing source_region field in ["
607 SIZE_FORMAT ", " SIZE_FORMAT ")",
608 beg_idx, end_idx);
609 }
610 for (size_t idx = beg_idx; idx < end_idx; ++idx) {
611 _region_data[idx].set_source_region(0);
612 }
614 // Set split_destination and partial_obj_size to reflect the split region.
615 split_destination = sr->destination();
616 partial_obj_size = sr->partial_obj_size();
617 }
619 // The split is recorded only if a partial object extends onto the region.
620 if (partial_obj_size != 0) {
621 _region_data[split_region].set_partial_obj_size(0);
622 split_info.record(split_region, partial_obj_size, split_destination);
623 }
625 // Setup the continuation addresses.
626 *target_next = split_destination + partial_obj_size;
627 HeapWord* const source_next = region_to_addr(split_region) + partial_obj_size;
629 if (TraceParallelOldGCSummaryPhase) {
630 const char * split_type = partial_obj_size == 0 ? "easy" : "hard";
631 gclog_or_tty->print_cr("%s split: src=" PTR_FORMAT " src_c=" SIZE_FORMAT
632 " pos=" SIZE_FORMAT,
633 split_type, source_next, split_region,
634 partial_obj_size);
635 gclog_or_tty->print_cr("%s split: dst=" PTR_FORMAT " dst_c=" SIZE_FORMAT
636 " tn=" PTR_FORMAT,
637 split_type, split_destination,
638 addr_to_region_idx(split_destination),
639 *target_next);
641 if (partial_obj_size != 0) {
642 HeapWord* const po_beg = split_info.destination();
643 HeapWord* const po_end = po_beg + split_info.partial_obj_size();
644 gclog_or_tty->print_cr("%s split: "
645 "po_beg=" PTR_FORMAT " " SIZE_FORMAT " "
646 "po_end=" PTR_FORMAT " " SIZE_FORMAT,
647 split_type,
648 po_beg, addr_to_region_idx(po_beg),
649 po_end, addr_to_region_idx(po_end));
650 }
651 }
653 return source_next;
654 }
656 bool ParallelCompactData::summarize(SplitInfo& split_info,
657 HeapWord* source_beg, HeapWord* source_end,
658 HeapWord** source_next,
659 HeapWord* target_beg, HeapWord* target_end,
660 HeapWord** target_next)
661 {
662 if (TraceParallelOldGCSummaryPhase) {
663 HeapWord* const source_next_val = source_next == NULL ? NULL : *source_next;
664 tty->print_cr("sb=" PTR_FORMAT " se=" PTR_FORMAT " sn=" PTR_FORMAT
665 "tb=" PTR_FORMAT " te=" PTR_FORMAT " tn=" PTR_FORMAT,
666 source_beg, source_end, source_next_val,
667 target_beg, target_end, *target_next);
668 }
670 size_t cur_region = addr_to_region_idx(source_beg);
671 const size_t end_region = addr_to_region_idx(region_align_up(source_end));
673 HeapWord *dest_addr = target_beg;
674 while (cur_region < end_region) {
675 // The destination must be set even if the region has no data.
676 _region_data[cur_region].set_destination(dest_addr);
678 size_t words = _region_data[cur_region].data_size();
679 if (words > 0) {
680 // If cur_region does not fit entirely into the target space, find a point
681 // at which the source space can be 'split' so that part is copied to the
682 // target space and the rest is copied elsewhere.
683 if (dest_addr + words > target_end) {
684 assert(source_next != NULL, "source_next is NULL when splitting");
685 *source_next = summarize_split_space(cur_region, split_info, dest_addr,
686 target_end, target_next);
687 return false;
688 }
690 // Compute the destination_count for cur_region, and if necessary, update
691 // source_region for a destination region. The source_region field is
692 // updated if cur_region is the first (left-most) region to be copied to a
693 // destination region.
694 //
695 // The destination_count calculation is a bit subtle. A region that has
696 // data that compacts into itself does not count itself as a destination.
697 // This maintains the invariant that a zero count means the region is
698 // available and can be claimed and then filled.
699 uint destination_count = 0;
700 if (split_info.is_split(cur_region)) {
701 // The current region has been split: the partial object will be copied
702 // to one destination space and the remaining data will be copied to
703 // another destination space. Adjust the initial destination_count and,
704 // if necessary, set the source_region field if the partial object will
705 // cross a destination region boundary.
706 destination_count = split_info.destination_count();
707 if (destination_count == 2) {
708 size_t dest_idx = addr_to_region_idx(split_info.dest_region_addr());
709 _region_data[dest_idx].set_source_region(cur_region);
710 }
711 }
713 HeapWord* const last_addr = dest_addr + words - 1;
714 const size_t dest_region_1 = addr_to_region_idx(dest_addr);
715 const size_t dest_region_2 = addr_to_region_idx(last_addr);
717 // Initially assume that the destination regions will be the same and
718 // adjust the value below if necessary. Under this assumption, if
719 // cur_region == dest_region_2, then cur_region will be compacted
720 // completely into itself.
721 destination_count += cur_region == dest_region_2 ? 0 : 1;
722 if (dest_region_1 != dest_region_2) {
723 // Destination regions differ; adjust destination_count.
724 destination_count += 1;
725 // Data from cur_region will be copied to the start of dest_region_2.
726 _region_data[dest_region_2].set_source_region(cur_region);
727 } else if (region_offset(dest_addr) == 0) {
728 // Data from cur_region will be copied to the start of the destination
729 // region.
730 _region_data[dest_region_1].set_source_region(cur_region);
731 }
733 _region_data[cur_region].set_destination_count(destination_count);
734 _region_data[cur_region].set_data_location(region_to_addr(cur_region));
735 dest_addr += words;
736 }
738 ++cur_region;
739 }
741 *target_next = dest_addr;
742 return true;
743 }
745 HeapWord* ParallelCompactData::calc_new_pointer(HeapWord* addr) {
746 assert(addr != NULL, "Should detect NULL oop earlier");
747 assert(PSParallelCompact::gc_heap()->is_in(addr), "not in heap");
748 assert(PSParallelCompact::mark_bitmap()->is_marked(addr), "not marked");
750 // Region covering the object.
751 RegionData* const region_ptr = addr_to_region_ptr(addr);
752 HeapWord* result = region_ptr->destination();
754 // If the entire Region is live, the new location is region->destination + the
755 // offset of the object within in the Region.
757 // Run some performance tests to determine if this special case pays off. It
758 // is worth it for pointers into the dense prefix. If the optimization to
759 // avoid pointer updates in regions that only point to the dense prefix is
760 // ever implemented, this should be revisited.
761 if (region_ptr->data_size() == RegionSize) {
762 result += region_offset(addr);
763 return result;
764 }
766 // Otherwise, the new location is region->destination + block offset + the
767 // number of live words in the Block that are (a) to the left of addr and (b)
768 // due to objects that start in the Block.
770 // Fill in the block table if necessary. This is unsynchronized, so multiple
771 // threads may fill the block table for a region (harmless, since it is
772 // idempotent).
773 if (!region_ptr->blocks_filled()) {
774 PSParallelCompact::fill_blocks(addr_to_region_idx(addr));
775 region_ptr->set_blocks_filled();
776 }
778 HeapWord* const search_start = block_align_down(addr);
779 const size_t block_offset = addr_to_block_ptr(addr)->offset();
781 const ParMarkBitMap* bitmap = PSParallelCompact::mark_bitmap();
782 const size_t live = bitmap->live_words_in_range(search_start, oop(addr));
783 result += block_offset + live;
784 DEBUG_ONLY(PSParallelCompact::check_new_location(addr, result));
785 return result;
786 }
788 #ifdef ASSERT
789 void ParallelCompactData::verify_clear(const PSVirtualSpace* vspace)
790 {
791 const size_t* const beg = (const size_t*)vspace->committed_low_addr();
792 const size_t* const end = (const size_t*)vspace->committed_high_addr();
793 for (const size_t* p = beg; p < end; ++p) {
794 assert(*p == 0, "not zero");
795 }
796 }
798 void ParallelCompactData::verify_clear()
799 {
800 verify_clear(_region_vspace);
801 verify_clear(_block_vspace);
802 }
803 #endif // #ifdef ASSERT
805 STWGCTimer PSParallelCompact::_gc_timer;
806 ParallelOldTracer PSParallelCompact::_gc_tracer;
807 elapsedTimer PSParallelCompact::_accumulated_time;
808 unsigned int PSParallelCompact::_total_invocations = 0;
809 unsigned int PSParallelCompact::_maximum_compaction_gc_num = 0;
810 jlong PSParallelCompact::_time_of_last_gc = 0;
811 CollectorCounters* PSParallelCompact::_counters = NULL;
812 ParMarkBitMap PSParallelCompact::_mark_bitmap;
813 ParallelCompactData PSParallelCompact::_summary_data;
815 PSParallelCompact::IsAliveClosure PSParallelCompact::_is_alive_closure;
817 bool PSParallelCompact::IsAliveClosure::do_object_b(oop p) { return mark_bitmap()->is_marked(p); }
819 void PSParallelCompact::KeepAliveClosure::do_oop(oop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
820 void PSParallelCompact::KeepAliveClosure::do_oop(narrowOop* p) { PSParallelCompact::KeepAliveClosure::do_oop_work(p); }
822 PSParallelCompact::AdjustPointerClosure PSParallelCompact::_adjust_pointer_closure;
823 PSParallelCompact::AdjustKlassClosure PSParallelCompact::_adjust_klass_closure;
825 void PSParallelCompact::AdjustPointerClosure::do_oop(oop* p) { adjust_pointer(p); }
826 void PSParallelCompact::AdjustPointerClosure::do_oop(narrowOop* p) { adjust_pointer(p); }
828 void PSParallelCompact::FollowStackClosure::do_void() { _compaction_manager->follow_marking_stacks(); }
830 void PSParallelCompact::MarkAndPushClosure::do_oop(oop* p) {
831 mark_and_push(_compaction_manager, p);
832 }
833 void PSParallelCompact::MarkAndPushClosure::do_oop(narrowOop* p) { mark_and_push(_compaction_manager, p); }
835 void PSParallelCompact::FollowKlassClosure::do_klass(Klass* klass) {
836 klass->oops_do(_mark_and_push_closure);
837 }
838 void PSParallelCompact::AdjustKlassClosure::do_klass(Klass* klass) {
839 klass->oops_do(&PSParallelCompact::_adjust_pointer_closure);
840 }
842 void PSParallelCompact::post_initialize() {
843 ParallelScavengeHeap* heap = gc_heap();
844 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
846 MemRegion mr = heap->reserved_region();
847 _ref_processor =
848 new ReferenceProcessor(mr, // span
849 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
850 (int) ParallelGCThreads, // mt processing degree
851 true, // mt discovery
852 (int) ParallelGCThreads, // mt discovery degree
853 true, // atomic_discovery
854 &_is_alive_closure, // non-header is alive closure
855 false); // write barrier for next field updates
856 _counters = new CollectorCounters("PSParallelCompact", 1);
858 // Initialize static fields in ParCompactionManager.
859 ParCompactionManager::initialize(mark_bitmap());
860 }
862 bool PSParallelCompact::initialize() {
863 ParallelScavengeHeap* heap = gc_heap();
864 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
865 MemRegion mr = heap->reserved_region();
867 // Was the old gen get allocated successfully?
868 if (!heap->old_gen()->is_allocated()) {
869 return false;
870 }
872 initialize_space_info();
873 initialize_dead_wood_limiter();
875 if (!_mark_bitmap.initialize(mr)) {
876 vm_shutdown_during_initialization(
877 err_msg("Unable to allocate " SIZE_FORMAT "KB bitmaps for parallel "
878 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
879 _mark_bitmap.reserved_byte_size()/K, mr.byte_size()/K));
880 return false;
881 }
883 if (!_summary_data.initialize(mr)) {
884 vm_shutdown_during_initialization(
885 err_msg("Unable to allocate " SIZE_FORMAT "KB card tables for parallel "
886 "garbage collection for the requested " SIZE_FORMAT "KB heap.",
887 _summary_data.reserved_byte_size()/K, mr.byte_size()/K));
888 return false;
889 }
891 return true;
892 }
894 void PSParallelCompact::initialize_space_info()
895 {
896 memset(&_space_info, 0, sizeof(_space_info));
898 ParallelScavengeHeap* heap = gc_heap();
899 PSYoungGen* young_gen = heap->young_gen();
901 _space_info[old_space_id].set_space(heap->old_gen()->object_space());
902 _space_info[eden_space_id].set_space(young_gen->eden_space());
903 _space_info[from_space_id].set_space(young_gen->from_space());
904 _space_info[to_space_id].set_space(young_gen->to_space());
906 _space_info[old_space_id].set_start_array(heap->old_gen()->start_array());
907 }
909 void PSParallelCompact::initialize_dead_wood_limiter()
910 {
911 const size_t max = 100;
912 _dwl_mean = double(MIN2(ParallelOldDeadWoodLimiterMean, max)) / 100.0;
913 _dwl_std_dev = double(MIN2(ParallelOldDeadWoodLimiterStdDev, max)) / 100.0;
914 _dwl_first_term = 1.0 / (sqrt(2.0 * M_PI) * _dwl_std_dev);
915 DEBUG_ONLY(_dwl_initialized = true;)
916 _dwl_adjustment = normal_distribution(1.0);
917 }
919 // Simple class for storing info about the heap at the start of GC, to be used
920 // after GC for comparison/printing.
921 class PreGCValues {
922 public:
923 PreGCValues() { }
924 PreGCValues(ParallelScavengeHeap* heap) { fill(heap); }
926 void fill(ParallelScavengeHeap* heap) {
927 _heap_used = heap->used();
928 _young_gen_used = heap->young_gen()->used_in_bytes();
929 _old_gen_used = heap->old_gen()->used_in_bytes();
930 _metadata_used = MetaspaceAux::allocated_used_bytes();
931 };
933 size_t heap_used() const { return _heap_used; }
934 size_t young_gen_used() const { return _young_gen_used; }
935 size_t old_gen_used() const { return _old_gen_used; }
936 size_t metadata_used() const { return _metadata_used; }
938 private:
939 size_t _heap_used;
940 size_t _young_gen_used;
941 size_t _old_gen_used;
942 size_t _metadata_used;
943 };
945 void
946 PSParallelCompact::clear_data_covering_space(SpaceId id)
947 {
948 // At this point, top is the value before GC, new_top() is the value that will
949 // be set at the end of GC. The marking bitmap is cleared to top; nothing
950 // should be marked above top. The summary data is cleared to the larger of
951 // top & new_top.
952 MutableSpace* const space = _space_info[id].space();
953 HeapWord* const bot = space->bottom();
954 HeapWord* const top = space->top();
955 HeapWord* const max_top = MAX2(top, _space_info[id].new_top());
957 const idx_t beg_bit = _mark_bitmap.addr_to_bit(bot);
958 const idx_t end_bit = BitMap::word_align_up(_mark_bitmap.addr_to_bit(top));
959 _mark_bitmap.clear_range(beg_bit, end_bit);
961 const size_t beg_region = _summary_data.addr_to_region_idx(bot);
962 const size_t end_region =
963 _summary_data.addr_to_region_idx(_summary_data.region_align_up(max_top));
964 _summary_data.clear_range(beg_region, end_region);
966 // Clear the data used to 'split' regions.
967 SplitInfo& split_info = _space_info[id].split_info();
968 if (split_info.is_valid()) {
969 split_info.clear();
970 }
971 DEBUG_ONLY(split_info.verify_clear();)
972 }
974 void PSParallelCompact::pre_compact(PreGCValues* pre_gc_values)
975 {
976 // Update the from & to space pointers in space_info, since they are swapped
977 // at each young gen gc. Do the update unconditionally (even though a
978 // promotion failure does not swap spaces) because an unknown number of minor
979 // collections will have swapped the spaces an unknown number of times.
980 GCTraceTime tm("pre compact", print_phases(), true, &_gc_timer);
981 ParallelScavengeHeap* heap = gc_heap();
982 _space_info[from_space_id].set_space(heap->young_gen()->from_space());
983 _space_info[to_space_id].set_space(heap->young_gen()->to_space());
985 pre_gc_values->fill(heap);
987 DEBUG_ONLY(add_obj_count = add_obj_size = 0;)
988 DEBUG_ONLY(mark_bitmap_count = mark_bitmap_size = 0;)
990 // Increment the invocation count
991 heap->increment_total_collections(true);
993 // We need to track unique mark sweep invocations as well.
994 _total_invocations++;
996 heap->print_heap_before_gc();
997 heap->trace_heap_before_gc(&_gc_tracer);
999 // Fill in TLABs
1000 heap->accumulate_statistics_all_tlabs();
1001 heap->ensure_parsability(true); // retire TLABs
1003 if (VerifyBeforeGC && heap->total_collections() >= VerifyGCStartAt) {
1004 HandleMark hm; // Discard invalid handles created during verification
1005 Universe::verify(" VerifyBeforeGC:");
1006 }
1008 // Verify object start arrays
1009 if (VerifyObjectStartArray &&
1010 VerifyBeforeGC) {
1011 heap->old_gen()->verify_object_start_array();
1012 }
1014 DEBUG_ONLY(mark_bitmap()->verify_clear();)
1015 DEBUG_ONLY(summary_data().verify_clear();)
1017 // Have worker threads release resources the next time they run a task.
1018 gc_task_manager()->release_all_resources();
1019 }
1021 void PSParallelCompact::post_compact()
1022 {
1023 GCTraceTime tm("post compact", print_phases(), true, &_gc_timer);
1025 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1026 // Clear the marking bitmap, summary data and split info.
1027 clear_data_covering_space(SpaceId(id));
1028 // Update top(). Must be done after clearing the bitmap and summary data.
1029 _space_info[id].publish_new_top();
1030 }
1032 MutableSpace* const eden_space = _space_info[eden_space_id].space();
1033 MutableSpace* const from_space = _space_info[from_space_id].space();
1034 MutableSpace* const to_space = _space_info[to_space_id].space();
1036 ParallelScavengeHeap* heap = gc_heap();
1037 bool eden_empty = eden_space->is_empty();
1038 if (!eden_empty) {
1039 eden_empty = absorb_live_data_from_eden(heap->size_policy(),
1040 heap->young_gen(), heap->old_gen());
1041 }
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();
1047 bool young_gen_empty = eden_empty && from_space->is_empty() &&
1048 to_space->is_empty();
1050 BarrierSet* bs = heap->barrier_set();
1051 if (bs->is_a(BarrierSet::ModRef)) {
1052 ModRefBarrierSet* modBS = (ModRefBarrierSet*)bs;
1053 MemRegion old_mr = heap->old_gen()->reserved();
1055 if (young_gen_empty) {
1056 modBS->clear(MemRegion(old_mr.start(), old_mr.end()));
1057 } else {
1058 modBS->invalidate(MemRegion(old_mr.start(), old_mr.end()));
1059 }
1060 }
1062 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1063 ClassLoaderDataGraph::purge();
1064 MetaspaceAux::verify_metrics();
1066 Threads::gc_epilogue();
1067 CodeCache::gc_epilogue();
1068 JvmtiExport::gc_epilogue();
1070 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1072 ref_processor()->enqueue_discovered_references(NULL);
1074 if (ZapUnusedHeapArea) {
1075 heap->gen_mangle_unused_area();
1076 }
1078 // Update time of last GC
1079 reset_millis_since_last_gc();
1080 }
1082 HeapWord*
1083 PSParallelCompact::compute_dense_prefix_via_density(const SpaceId id,
1084 bool maximum_compaction)
1085 {
1086 const size_t region_size = ParallelCompactData::RegionSize;
1087 const ParallelCompactData& sd = summary_data();
1089 const MutableSpace* const space = _space_info[id].space();
1090 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
1091 const RegionData* const beg_cp = sd.addr_to_region_ptr(space->bottom());
1092 const RegionData* const end_cp = sd.addr_to_region_ptr(top_aligned_up);
1094 // Skip full regions at the beginning of the space--they are necessarily part
1095 // of the dense prefix.
1096 size_t full_count = 0;
1097 const RegionData* cp;
1098 for (cp = beg_cp; cp < end_cp && cp->data_size() == region_size; ++cp) {
1099 ++full_count;
1100 }
1102 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1103 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1104 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval;
1105 if (maximum_compaction || cp == end_cp || interval_ended) {
1106 _maximum_compaction_gc_num = total_invocations();
1107 return sd.region_to_addr(cp);
1108 }
1110 HeapWord* const new_top = _space_info[id].new_top();
1111 const size_t space_live = pointer_delta(new_top, space->bottom());
1112 const size_t space_used = space->used_in_words();
1113 const size_t space_capacity = space->capacity_in_words();
1115 const double cur_density = double(space_live) / space_capacity;
1116 const double deadwood_density =
1117 (1.0 - cur_density) * (1.0 - cur_density) * cur_density * cur_density;
1118 const size_t deadwood_goal = size_t(space_capacity * deadwood_density);
1120 if (TraceParallelOldGCDensePrefix) {
1121 tty->print_cr("cur_dens=%5.3f dw_dens=%5.3f dw_goal=" SIZE_FORMAT,
1122 cur_density, deadwood_density, deadwood_goal);
1123 tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1124 "space_cap=" SIZE_FORMAT,
1125 space_live, space_used,
1126 space_capacity);
1127 }
1129 // XXX - Use binary search?
1130 HeapWord* dense_prefix = sd.region_to_addr(cp);
1131 const RegionData* full_cp = cp;
1132 const RegionData* const top_cp = sd.addr_to_region_ptr(space->top() - 1);
1133 while (cp < end_cp) {
1134 HeapWord* region_destination = cp->destination();
1135 const size_t cur_deadwood = pointer_delta(dense_prefix, region_destination);
1136 if (TraceParallelOldGCDensePrefix && Verbose) {
1137 tty->print_cr("c#=" SIZE_FORMAT_W(4) " dst=" PTR_FORMAT " "
1138 "dp=" SIZE_FORMAT_W(8) " " "cdw=" SIZE_FORMAT_W(8),
1139 sd.region(cp), region_destination,
1140 dense_prefix, cur_deadwood);
1141 }
1143 if (cur_deadwood >= deadwood_goal) {
1144 // Found the region that has the correct amount of deadwood to the left.
1145 // This typically occurs after crossing a fairly sparse set of regions, so
1146 // iterate backwards over those sparse regions, looking for the region
1147 // that has the lowest density of live objects 'to the right.'
1148 size_t space_to_left = sd.region(cp) * region_size;
1149 size_t live_to_left = space_to_left - cur_deadwood;
1150 size_t space_to_right = space_capacity - space_to_left;
1151 size_t live_to_right = space_live - live_to_left;
1152 double density_to_right = double(live_to_right) / space_to_right;
1153 while (cp > full_cp) {
1154 --cp;
1155 const size_t prev_region_live_to_right = live_to_right -
1156 cp->data_size();
1157 const size_t prev_region_space_to_right = space_to_right + region_size;
1158 double prev_region_density_to_right =
1159 double(prev_region_live_to_right) / prev_region_space_to_right;
1160 if (density_to_right <= prev_region_density_to_right) {
1161 return dense_prefix;
1162 }
1163 if (TraceParallelOldGCDensePrefix && Verbose) {
1164 tty->print_cr("backing up from c=" SIZE_FORMAT_W(4) " d2r=%10.8f "
1165 "pc_d2r=%10.8f", sd.region(cp), density_to_right,
1166 prev_region_density_to_right);
1167 }
1168 dense_prefix -= region_size;
1169 live_to_right = prev_region_live_to_right;
1170 space_to_right = prev_region_space_to_right;
1171 density_to_right = prev_region_density_to_right;
1172 }
1173 return dense_prefix;
1174 }
1176 dense_prefix += region_size;
1177 ++cp;
1178 }
1180 return dense_prefix;
1181 }
1183 #ifndef PRODUCT
1184 void PSParallelCompact::print_dense_prefix_stats(const char* const algorithm,
1185 const SpaceId id,
1186 const bool maximum_compaction,
1187 HeapWord* const addr)
1188 {
1189 const size_t region_idx = summary_data().addr_to_region_idx(addr);
1190 RegionData* const cp = summary_data().region(region_idx);
1191 const MutableSpace* const space = _space_info[id].space();
1192 HeapWord* const new_top = _space_info[id].new_top();
1194 const size_t space_live = pointer_delta(new_top, space->bottom());
1195 const size_t dead_to_left = pointer_delta(addr, cp->destination());
1196 const size_t space_cap = space->capacity_in_words();
1197 const double dead_to_left_pct = double(dead_to_left) / space_cap;
1198 const size_t live_to_right = new_top - cp->destination();
1199 const size_t dead_to_right = space->top() - addr - live_to_right;
1201 tty->print_cr("%s=" PTR_FORMAT " dpc=" SIZE_FORMAT_W(5) " "
1202 "spl=" SIZE_FORMAT " "
1203 "d2l=" SIZE_FORMAT " d2l%%=%6.4f "
1204 "d2r=" SIZE_FORMAT " l2r=" SIZE_FORMAT
1205 " ratio=%10.8f",
1206 algorithm, addr, region_idx,
1207 space_live,
1208 dead_to_left, dead_to_left_pct,
1209 dead_to_right, live_to_right,
1210 double(dead_to_right) / live_to_right);
1211 }
1212 #endif // #ifndef PRODUCT
1214 // Return a fraction indicating how much of the generation can be treated as
1215 // "dead wood" (i.e., not reclaimed). The function uses a normal distribution
1216 // based on the density of live objects in the generation to determine a limit,
1217 // which is then adjusted so the return value is min_percent when the density is
1218 // 1.
1219 //
1220 // The following table shows some return values for a different values of the
1221 // standard deviation (ParallelOldDeadWoodLimiterStdDev); the mean is 0.5 and
1222 // min_percent is 1.
1223 //
1224 // fraction allowed as dead wood
1225 // -----------------------------------------------------------------
1226 // density std_dev=70 std_dev=75 std_dev=80 std_dev=85 std_dev=90 std_dev=95
1227 // ------- ---------- ---------- ---------- ---------- ---------- ----------
1228 // 0.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1229 // 0.05000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1230 // 0.10000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1231 // 0.15000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1232 // 0.20000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1233 // 0.25000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1234 // 0.30000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1235 // 0.35000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1236 // 0.40000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1237 // 0.45000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1238 // 0.50000 0.13832410 0.11599237 0.09847664 0.08456518 0.07338887 0.06431510
1239 // 0.55000 0.13687208 0.11481163 0.09750361 0.08375387 0.07270534 0.06373386
1240 // 0.60000 0.13253818 0.11128511 0.09459590 0.08132834 0.07066107 0.06199500
1241 // 0.65000 0.12538832 0.10545958 0.08978741 0.07731366 0.06727491 0.05911289
1242 // 0.70000 0.11553050 0.09741183 0.08313394 0.07175114 0.06257797 0.05511132
1243 // 0.75000 0.10311208 0.08724696 0.07471205 0.06469760 0.05661313 0.05002313
1244 // 0.80000 0.08831616 0.07509618 0.06461766 0.05622444 0.04943437 0.04388975
1245 // 0.85000 0.07135702 0.06111390 0.05296419 0.04641639 0.04110601 0.03676066
1246 // 0.90000 0.05247504 0.04547452 0.03988045 0.03537016 0.03170171 0.02869272
1247 // 0.95000 0.03193096 0.02836880 0.02550828 0.02319280 0.02130337 0.01974941
1248 // 1.00000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000 0.01000000
1250 double PSParallelCompact::dead_wood_limiter(double density, size_t min_percent)
1251 {
1252 assert(_dwl_initialized, "uninitialized");
1254 // The raw limit is the value of the normal distribution at x = density.
1255 const double raw_limit = normal_distribution(density);
1257 // Adjust the raw limit so it becomes the minimum when the density is 1.
1258 //
1259 // First subtract the adjustment value (which is simply the precomputed value
1260 // normal_distribution(1.0)); this yields a value of 0 when the density is 1.
1261 // Then add the minimum value, so the minimum is returned when the density is
1262 // 1. Finally, prevent negative values, which occur when the mean is not 0.5.
1263 const double min = double(min_percent) / 100.0;
1264 const double limit = raw_limit - _dwl_adjustment + min;
1265 return MAX2(limit, 0.0);
1266 }
1268 ParallelCompactData::RegionData*
1269 PSParallelCompact::first_dead_space_region(const RegionData* beg,
1270 const RegionData* end)
1271 {
1272 const size_t region_size = ParallelCompactData::RegionSize;
1273 ParallelCompactData& sd = summary_data();
1274 size_t left = sd.region(beg);
1275 size_t right = end > beg ? sd.region(end) - 1 : left;
1277 // Binary search.
1278 while (left < right) {
1279 // Equivalent to (left + right) / 2, but does not overflow.
1280 const size_t middle = left + (right - left) / 2;
1281 RegionData* const middle_ptr = sd.region(middle);
1282 HeapWord* const dest = middle_ptr->destination();
1283 HeapWord* const addr = sd.region_to_addr(middle);
1284 assert(dest != NULL, "sanity");
1285 assert(dest <= addr, "must move left");
1287 if (middle > left && dest < addr) {
1288 right = middle - 1;
1289 } else if (middle < right && middle_ptr->data_size() == region_size) {
1290 left = middle + 1;
1291 } else {
1292 return middle_ptr;
1293 }
1294 }
1295 return sd.region(left);
1296 }
1298 ParallelCompactData::RegionData*
1299 PSParallelCompact::dead_wood_limit_region(const RegionData* beg,
1300 const RegionData* end,
1301 size_t dead_words)
1302 {
1303 ParallelCompactData& sd = summary_data();
1304 size_t left = sd.region(beg);
1305 size_t right = end > beg ? sd.region(end) - 1 : left;
1307 // Binary search.
1308 while (left < right) {
1309 // Equivalent to (left + right) / 2, but does not overflow.
1310 const size_t middle = left + (right - left) / 2;
1311 RegionData* const middle_ptr = sd.region(middle);
1312 HeapWord* const dest = middle_ptr->destination();
1313 HeapWord* const addr = sd.region_to_addr(middle);
1314 assert(dest != NULL, "sanity");
1315 assert(dest <= addr, "must move left");
1317 const size_t dead_to_left = pointer_delta(addr, dest);
1318 if (middle > left && dead_to_left > dead_words) {
1319 right = middle - 1;
1320 } else if (middle < right && dead_to_left < dead_words) {
1321 left = middle + 1;
1322 } else {
1323 return middle_ptr;
1324 }
1325 }
1326 return sd.region(left);
1327 }
1329 // The result is valid during the summary phase, after the initial summarization
1330 // of each space into itself, and before final summarization.
1331 inline double
1332 PSParallelCompact::reclaimed_ratio(const RegionData* const cp,
1333 HeapWord* const bottom,
1334 HeapWord* const top,
1335 HeapWord* const new_top)
1336 {
1337 ParallelCompactData& sd = summary_data();
1339 assert(cp != NULL, "sanity");
1340 assert(bottom != NULL, "sanity");
1341 assert(top != NULL, "sanity");
1342 assert(new_top != NULL, "sanity");
1343 assert(top >= new_top, "summary data problem?");
1344 assert(new_top > bottom, "space is empty; should not be here");
1345 assert(new_top >= cp->destination(), "sanity");
1346 assert(top >= sd.region_to_addr(cp), "sanity");
1348 HeapWord* const destination = cp->destination();
1349 const size_t dense_prefix_live = pointer_delta(destination, bottom);
1350 const size_t compacted_region_live = pointer_delta(new_top, destination);
1351 const size_t compacted_region_used = pointer_delta(top,
1352 sd.region_to_addr(cp));
1353 const size_t reclaimable = compacted_region_used - compacted_region_live;
1355 const double divisor = dense_prefix_live + 1.25 * compacted_region_live;
1356 return double(reclaimable) / divisor;
1357 }
1359 // Return the address of the end of the dense prefix, a.k.a. the start of the
1360 // compacted region. The address is always on a region boundary.
1361 //
1362 // Completely full regions at the left are skipped, since no compaction can
1363 // occur in those regions. Then the maximum amount of dead wood to allow is
1364 // computed, based on the density (amount live / capacity) of the generation;
1365 // the region with approximately that amount of dead space to the left is
1366 // identified as the limit region. Regions between the last completely full
1367 // region and the limit region are scanned and the one that has the best
1368 // (maximum) reclaimed_ratio() is selected.
1369 HeapWord*
1370 PSParallelCompact::compute_dense_prefix(const SpaceId id,
1371 bool maximum_compaction)
1372 {
1373 if (ParallelOldGCSplitALot) {
1374 if (_space_info[id].dense_prefix() != _space_info[id].space()->bottom()) {
1375 // The value was chosen to provoke splitting a young gen space; use it.
1376 return _space_info[id].dense_prefix();
1377 }
1378 }
1380 const size_t region_size = ParallelCompactData::RegionSize;
1381 const ParallelCompactData& sd = summary_data();
1383 const MutableSpace* const space = _space_info[id].space();
1384 HeapWord* const top = space->top();
1385 HeapWord* const top_aligned_up = sd.region_align_up(top);
1386 HeapWord* const new_top = _space_info[id].new_top();
1387 HeapWord* const new_top_aligned_up = sd.region_align_up(new_top);
1388 HeapWord* const bottom = space->bottom();
1389 const RegionData* const beg_cp = sd.addr_to_region_ptr(bottom);
1390 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
1391 const RegionData* const new_top_cp =
1392 sd.addr_to_region_ptr(new_top_aligned_up);
1394 // Skip full regions at the beginning of the space--they are necessarily part
1395 // of the dense prefix.
1396 const RegionData* const full_cp = first_dead_space_region(beg_cp, new_top_cp);
1397 assert(full_cp->destination() == sd.region_to_addr(full_cp) ||
1398 space->is_empty(), "no dead space allowed to the left");
1399 assert(full_cp->data_size() < region_size || full_cp == new_top_cp - 1,
1400 "region must have dead space");
1402 // The gc number is saved whenever a maximum compaction is done, and used to
1403 // determine when the maximum compaction interval has expired. This avoids
1404 // successive max compactions for different reasons.
1405 assert(total_invocations() >= _maximum_compaction_gc_num, "sanity");
1406 const size_t gcs_since_max = total_invocations() - _maximum_compaction_gc_num;
1407 const bool interval_ended = gcs_since_max > HeapMaximumCompactionInterval ||
1408 total_invocations() == HeapFirstMaximumCompactionCount;
1409 if (maximum_compaction || full_cp == top_cp || interval_ended) {
1410 _maximum_compaction_gc_num = total_invocations();
1411 return sd.region_to_addr(full_cp);
1412 }
1414 const size_t space_live = pointer_delta(new_top, bottom);
1415 const size_t space_used = space->used_in_words();
1416 const size_t space_capacity = space->capacity_in_words();
1418 const double density = double(space_live) / double(space_capacity);
1419 const size_t min_percent_free = MarkSweepDeadRatio;
1420 const double limiter = dead_wood_limiter(density, min_percent_free);
1421 const size_t dead_wood_max = space_used - space_live;
1422 const size_t dead_wood_limit = MIN2(size_t(space_capacity * limiter),
1423 dead_wood_max);
1425 if (TraceParallelOldGCDensePrefix) {
1426 tty->print_cr("space_live=" SIZE_FORMAT " " "space_used=" SIZE_FORMAT " "
1427 "space_cap=" SIZE_FORMAT,
1428 space_live, space_used,
1429 space_capacity);
1430 tty->print_cr("dead_wood_limiter(%6.4f, %d)=%6.4f "
1431 "dead_wood_max=" SIZE_FORMAT " dead_wood_limit=" SIZE_FORMAT,
1432 density, min_percent_free, limiter,
1433 dead_wood_max, dead_wood_limit);
1434 }
1436 // Locate the region with the desired amount of dead space to the left.
1437 const RegionData* const limit_cp =
1438 dead_wood_limit_region(full_cp, top_cp, dead_wood_limit);
1440 // Scan from the first region with dead space to the limit region and find the
1441 // one with the best (largest) reclaimed ratio.
1442 double best_ratio = 0.0;
1443 const RegionData* best_cp = full_cp;
1444 for (const RegionData* cp = full_cp; cp < limit_cp; ++cp) {
1445 double tmp_ratio = reclaimed_ratio(cp, bottom, top, new_top);
1446 if (tmp_ratio > best_ratio) {
1447 best_cp = cp;
1448 best_ratio = tmp_ratio;
1449 }
1450 }
1452 #if 0
1453 // Something to consider: if the region with the best ratio is 'close to' the
1454 // first region w/free space, choose the first region with free space
1455 // ("first-free"). The first-free region is usually near the start of the
1456 // heap, which means we are copying most of the heap already, so copy a bit
1457 // more to get complete compaction.
1458 if (pointer_delta(best_cp, full_cp, sizeof(RegionData)) < 4) {
1459 _maximum_compaction_gc_num = total_invocations();
1460 best_cp = full_cp;
1461 }
1462 #endif // #if 0
1464 return sd.region_to_addr(best_cp);
1465 }
1467 #ifndef PRODUCT
1468 void
1469 PSParallelCompact::fill_with_live_objects(SpaceId id, HeapWord* const start,
1470 size_t words)
1471 {
1472 if (TraceParallelOldGCSummaryPhase) {
1473 tty->print_cr("fill_with_live_objects [" PTR_FORMAT " " PTR_FORMAT ") "
1474 SIZE_FORMAT, start, start + words, words);
1475 }
1477 ObjectStartArray* const start_array = _space_info[id].start_array();
1478 CollectedHeap::fill_with_objects(start, words);
1479 for (HeapWord* p = start; p < start + words; p += oop(p)->size()) {
1480 _mark_bitmap.mark_obj(p, words);
1481 _summary_data.add_obj(p, words);
1482 start_array->allocate_block(p);
1483 }
1484 }
1486 void
1487 PSParallelCompact::summarize_new_objects(SpaceId id, HeapWord* start)
1488 {
1489 ParallelCompactData& sd = summary_data();
1490 MutableSpace* space = _space_info[id].space();
1492 // Find the source and destination start addresses.
1493 HeapWord* const src_addr = sd.region_align_down(start);
1494 HeapWord* dst_addr;
1495 if (src_addr < start) {
1496 dst_addr = sd.addr_to_region_ptr(src_addr)->destination();
1497 } else if (src_addr > space->bottom()) {
1498 // The start (the original top() value) is aligned to a region boundary so
1499 // the associated region does not have a destination. Compute the
1500 // destination from the previous region.
1501 RegionData* const cp = sd.addr_to_region_ptr(src_addr) - 1;
1502 dst_addr = cp->destination() + cp->data_size();
1503 } else {
1504 // Filling the entire space.
1505 dst_addr = space->bottom();
1506 }
1507 assert(dst_addr != NULL, "sanity");
1509 // Update the summary data.
1510 bool result = _summary_data.summarize(_space_info[id].split_info(),
1511 src_addr, space->top(), NULL,
1512 dst_addr, space->end(),
1513 _space_info[id].new_top_addr());
1514 assert(result, "should not fail: bad filler object size");
1515 }
1517 void
1518 PSParallelCompact::provoke_split_fill_survivor(SpaceId id)
1519 {
1520 if (total_invocations() % (ParallelOldGCSplitInterval * 3) != 0) {
1521 return;
1522 }
1524 MutableSpace* const space = _space_info[id].space();
1525 if (space->is_empty()) {
1526 HeapWord* b = space->bottom();
1527 HeapWord* t = b + space->capacity_in_words() / 2;
1528 space->set_top(t);
1529 if (ZapUnusedHeapArea) {
1530 space->set_top_for_allocations();
1531 }
1533 size_t min_size = CollectedHeap::min_fill_size();
1534 size_t obj_len = min_size;
1535 while (b + obj_len <= t) {
1536 CollectedHeap::fill_with_object(b, obj_len);
1537 mark_bitmap()->mark_obj(b, obj_len);
1538 summary_data().add_obj(b, obj_len);
1539 b += obj_len;
1540 obj_len = (obj_len & (min_size*3)) + min_size; // 8 16 24 32 8 16 24 32 ...
1541 }
1542 if (b < t) {
1543 // The loop didn't completely fill to t (top); adjust top downward.
1544 space->set_top(b);
1545 if (ZapUnusedHeapArea) {
1546 space->set_top_for_allocations();
1547 }
1548 }
1550 HeapWord** nta = _space_info[id].new_top_addr();
1551 bool result = summary_data().summarize(_space_info[id].split_info(),
1552 space->bottom(), space->top(), NULL,
1553 space->bottom(), space->end(), nta);
1554 assert(result, "space must fit into itself");
1555 }
1556 }
1558 void
1559 PSParallelCompact::provoke_split(bool & max_compaction)
1560 {
1561 if (total_invocations() % ParallelOldGCSplitInterval != 0) {
1562 return;
1563 }
1565 const size_t region_size = ParallelCompactData::RegionSize;
1566 ParallelCompactData& sd = summary_data();
1568 MutableSpace* const eden_space = _space_info[eden_space_id].space();
1569 MutableSpace* const from_space = _space_info[from_space_id].space();
1570 const size_t eden_live = pointer_delta(eden_space->top(),
1571 _space_info[eden_space_id].new_top());
1572 const size_t from_live = pointer_delta(from_space->top(),
1573 _space_info[from_space_id].new_top());
1575 const size_t min_fill_size = CollectedHeap::min_fill_size();
1576 const size_t eden_free = pointer_delta(eden_space->end(), eden_space->top());
1577 const size_t eden_fillable = eden_free >= min_fill_size ? eden_free : 0;
1578 const size_t from_free = pointer_delta(from_space->end(), from_space->top());
1579 const size_t from_fillable = from_free >= min_fill_size ? from_free : 0;
1581 // Choose the space to split; need at least 2 regions live (or fillable).
1582 SpaceId id;
1583 MutableSpace* space;
1584 size_t live_words;
1585 size_t fill_words;
1586 if (eden_live + eden_fillable >= region_size * 2) {
1587 id = eden_space_id;
1588 space = eden_space;
1589 live_words = eden_live;
1590 fill_words = eden_fillable;
1591 } else if (from_live + from_fillable >= region_size * 2) {
1592 id = from_space_id;
1593 space = from_space;
1594 live_words = from_live;
1595 fill_words = from_fillable;
1596 } else {
1597 return; // Give up.
1598 }
1599 assert(fill_words == 0 || fill_words >= min_fill_size, "sanity");
1601 if (live_words < region_size * 2) {
1602 // Fill from top() to end() w/live objects of mixed sizes.
1603 HeapWord* const fill_start = space->top();
1604 live_words += fill_words;
1606 space->set_top(fill_start + fill_words);
1607 if (ZapUnusedHeapArea) {
1608 space->set_top_for_allocations();
1609 }
1611 HeapWord* cur_addr = fill_start;
1612 while (fill_words > 0) {
1613 const size_t r = (size_t)os::random() % (region_size / 2) + min_fill_size;
1614 size_t cur_size = MIN2(align_object_size_(r), fill_words);
1615 if (fill_words - cur_size < min_fill_size) {
1616 cur_size = fill_words; // Avoid leaving a fragment too small to fill.
1617 }
1619 CollectedHeap::fill_with_object(cur_addr, cur_size);
1620 mark_bitmap()->mark_obj(cur_addr, cur_size);
1621 sd.add_obj(cur_addr, cur_size);
1623 cur_addr += cur_size;
1624 fill_words -= cur_size;
1625 }
1627 summarize_new_objects(id, fill_start);
1628 }
1630 max_compaction = false;
1632 // Manipulate the old gen so that it has room for about half of the live data
1633 // in the target young gen space (live_words / 2).
1634 id = old_space_id;
1635 space = _space_info[id].space();
1636 const size_t free_at_end = space->free_in_words();
1637 const size_t free_target = align_object_size(live_words / 2);
1638 const size_t dead = pointer_delta(space->top(), _space_info[id].new_top());
1640 if (free_at_end >= free_target + min_fill_size) {
1641 // Fill space above top() and set the dense prefix so everything survives.
1642 HeapWord* const fill_start = space->top();
1643 const size_t fill_size = free_at_end - free_target;
1644 space->set_top(space->top() + fill_size);
1645 if (ZapUnusedHeapArea) {
1646 space->set_top_for_allocations();
1647 }
1648 fill_with_live_objects(id, fill_start, fill_size);
1649 summarize_new_objects(id, fill_start);
1650 _space_info[id].set_dense_prefix(sd.region_align_down(space->top()));
1651 } else if (dead + free_at_end > free_target) {
1652 // Find a dense prefix that makes the right amount of space available.
1653 HeapWord* cur = sd.region_align_down(space->top());
1654 HeapWord* cur_destination = sd.addr_to_region_ptr(cur)->destination();
1655 size_t dead_to_right = pointer_delta(space->end(), cur_destination);
1656 while (dead_to_right < free_target) {
1657 cur -= region_size;
1658 cur_destination = sd.addr_to_region_ptr(cur)->destination();
1659 dead_to_right = pointer_delta(space->end(), cur_destination);
1660 }
1661 _space_info[id].set_dense_prefix(cur);
1662 }
1663 }
1664 #endif // #ifndef PRODUCT
1666 void PSParallelCompact::summarize_spaces_quick()
1667 {
1668 for (unsigned int i = 0; i < last_space_id; ++i) {
1669 const MutableSpace* space = _space_info[i].space();
1670 HeapWord** nta = _space_info[i].new_top_addr();
1671 bool result = _summary_data.summarize(_space_info[i].split_info(),
1672 space->bottom(), space->top(), NULL,
1673 space->bottom(), space->end(), nta);
1674 assert(result, "space must fit into itself");
1675 _space_info[i].set_dense_prefix(space->bottom());
1676 }
1678 #ifndef PRODUCT
1679 if (ParallelOldGCSplitALot) {
1680 provoke_split_fill_survivor(to_space_id);
1681 }
1682 #endif // #ifndef PRODUCT
1683 }
1685 void PSParallelCompact::fill_dense_prefix_end(SpaceId id)
1686 {
1687 HeapWord* const dense_prefix_end = dense_prefix(id);
1688 const RegionData* region = _summary_data.addr_to_region_ptr(dense_prefix_end);
1689 const idx_t dense_prefix_bit = _mark_bitmap.addr_to_bit(dense_prefix_end);
1690 if (dead_space_crosses_boundary(region, dense_prefix_bit)) {
1691 // Only enough dead space is filled so that any remaining dead space to the
1692 // left is larger than the minimum filler object. (The remainder is filled
1693 // during the copy/update phase.)
1694 //
1695 // The size of the dead space to the right of the boundary is not a
1696 // concern, since compaction will be able to use whatever space is
1697 // available.
1698 //
1699 // Here '||' is the boundary, 'x' represents a don't care bit and a box
1700 // surrounds the space to be filled with an object.
1701 //
1702 // In the 32-bit VM, each bit represents two 32-bit words:
1703 // +---+
1704 // a) beg_bits: ... x x x | 0 | || 0 x x ...
1705 // end_bits: ... x x x | 0 | || 0 x x ...
1706 // +---+
1707 //
1708 // In the 64-bit VM, each bit represents one 64-bit word:
1709 // +------------+
1710 // b) beg_bits: ... x x x | 0 || 0 | x x ...
1711 // end_bits: ... x x 1 | 0 || 0 | x x ...
1712 // +------------+
1713 // +-------+
1714 // c) beg_bits: ... x x | 0 0 | || 0 x x ...
1715 // end_bits: ... x 1 | 0 0 | || 0 x x ...
1716 // +-------+
1717 // +-----------+
1718 // d) beg_bits: ... x | 0 0 0 | || 0 x x ...
1719 // end_bits: ... 1 | 0 0 0 | || 0 x x ...
1720 // +-----------+
1721 // +-------+
1722 // e) beg_bits: ... 0 0 | 0 0 | || 0 x x ...
1723 // end_bits: ... 0 0 | 0 0 | || 0 x x ...
1724 // +-------+
1726 // Initially assume case a, c or e will apply.
1727 size_t obj_len = CollectedHeap::min_fill_size();
1728 HeapWord* obj_beg = dense_prefix_end - obj_len;
1730 #ifdef _LP64
1731 if (MinObjAlignment > 1) { // object alignment > heap word size
1732 // Cases a, c or e.
1733 } else if (_mark_bitmap.is_obj_end(dense_prefix_bit - 2)) {
1734 // Case b above.
1735 obj_beg = dense_prefix_end - 1;
1736 } else if (!_mark_bitmap.is_obj_end(dense_prefix_bit - 3) &&
1737 _mark_bitmap.is_obj_end(dense_prefix_bit - 4)) {
1738 // Case d above.
1739 obj_beg = dense_prefix_end - 3;
1740 obj_len = 3;
1741 }
1742 #endif // #ifdef _LP64
1744 CollectedHeap::fill_with_object(obj_beg, obj_len);
1745 _mark_bitmap.mark_obj(obj_beg, obj_len);
1746 _summary_data.add_obj(obj_beg, obj_len);
1747 assert(start_array(id) != NULL, "sanity");
1748 start_array(id)->allocate_block(obj_beg);
1749 }
1750 }
1752 void
1753 PSParallelCompact::clear_source_region(HeapWord* beg_addr, HeapWord* end_addr)
1754 {
1755 RegionData* const beg_ptr = _summary_data.addr_to_region_ptr(beg_addr);
1756 HeapWord* const end_aligned_up = _summary_data.region_align_up(end_addr);
1757 RegionData* const end_ptr = _summary_data.addr_to_region_ptr(end_aligned_up);
1758 for (RegionData* cur = beg_ptr; cur < end_ptr; ++cur) {
1759 cur->set_source_region(0);
1760 }
1761 }
1763 void
1764 PSParallelCompact::summarize_space(SpaceId id, bool maximum_compaction)
1765 {
1766 assert(id < last_space_id, "id out of range");
1767 assert(_space_info[id].dense_prefix() == _space_info[id].space()->bottom() ||
1768 ParallelOldGCSplitALot && id == old_space_id,
1769 "should have been reset in summarize_spaces_quick()");
1771 const MutableSpace* space = _space_info[id].space();
1772 if (_space_info[id].new_top() != space->bottom()) {
1773 HeapWord* dense_prefix_end = compute_dense_prefix(id, maximum_compaction);
1774 _space_info[id].set_dense_prefix(dense_prefix_end);
1776 #ifndef PRODUCT
1777 if (TraceParallelOldGCDensePrefix) {
1778 print_dense_prefix_stats("ratio", id, maximum_compaction,
1779 dense_prefix_end);
1780 HeapWord* addr = compute_dense_prefix_via_density(id, maximum_compaction);
1781 print_dense_prefix_stats("density", id, maximum_compaction, addr);
1782 }
1783 #endif // #ifndef PRODUCT
1785 // Recompute the summary data, taking into account the dense prefix. If
1786 // every last byte will be reclaimed, then the existing summary data which
1787 // compacts everything can be left in place.
1788 if (!maximum_compaction && dense_prefix_end != space->bottom()) {
1789 // If dead space crosses the dense prefix boundary, it is (at least
1790 // partially) filled with a dummy object, marked live and added to the
1791 // summary data. This simplifies the copy/update phase and must be done
1792 // before the final locations of objects are determined, to prevent
1793 // leaving a fragment of dead space that is too small to fill.
1794 fill_dense_prefix_end(id);
1796 // Compute the destination of each Region, and thus each object.
1797 _summary_data.summarize_dense_prefix(space->bottom(), dense_prefix_end);
1798 _summary_data.summarize(_space_info[id].split_info(),
1799 dense_prefix_end, space->top(), NULL,
1800 dense_prefix_end, space->end(),
1801 _space_info[id].new_top_addr());
1802 }
1803 }
1805 if (TraceParallelOldGCSummaryPhase) {
1806 const size_t region_size = ParallelCompactData::RegionSize;
1807 HeapWord* const dense_prefix_end = _space_info[id].dense_prefix();
1808 const size_t dp_region = _summary_data.addr_to_region_idx(dense_prefix_end);
1809 const size_t dp_words = pointer_delta(dense_prefix_end, space->bottom());
1810 HeapWord* const new_top = _space_info[id].new_top();
1811 const HeapWord* nt_aligned_up = _summary_data.region_align_up(new_top);
1812 const size_t cr_words = pointer_delta(nt_aligned_up, dense_prefix_end);
1813 tty->print_cr("id=%d cap=" SIZE_FORMAT " dp=" PTR_FORMAT " "
1814 "dp_region=" SIZE_FORMAT " " "dp_count=" SIZE_FORMAT " "
1815 "cr_count=" SIZE_FORMAT " " "nt=" PTR_FORMAT,
1816 id, space->capacity_in_words(), dense_prefix_end,
1817 dp_region, dp_words / region_size,
1818 cr_words / region_size, new_top);
1819 }
1820 }
1822 #ifndef PRODUCT
1823 void PSParallelCompact::summary_phase_msg(SpaceId dst_space_id,
1824 HeapWord* dst_beg, HeapWord* dst_end,
1825 SpaceId src_space_id,
1826 HeapWord* src_beg, HeapWord* src_end)
1827 {
1828 if (TraceParallelOldGCSummaryPhase) {
1829 tty->print_cr("summarizing %d [%s] into %d [%s]: "
1830 "src=" PTR_FORMAT "-" PTR_FORMAT " "
1831 SIZE_FORMAT "-" SIZE_FORMAT " "
1832 "dst=" PTR_FORMAT "-" PTR_FORMAT " "
1833 SIZE_FORMAT "-" SIZE_FORMAT,
1834 src_space_id, space_names[src_space_id],
1835 dst_space_id, space_names[dst_space_id],
1836 src_beg, src_end,
1837 _summary_data.addr_to_region_idx(src_beg),
1838 _summary_data.addr_to_region_idx(src_end),
1839 dst_beg, dst_end,
1840 _summary_data.addr_to_region_idx(dst_beg),
1841 _summary_data.addr_to_region_idx(dst_end));
1842 }
1843 }
1844 #endif // #ifndef PRODUCT
1846 void PSParallelCompact::summary_phase(ParCompactionManager* cm,
1847 bool maximum_compaction)
1848 {
1849 GCTraceTime tm("summary phase", print_phases(), true, &_gc_timer);
1850 // trace("2");
1852 #ifdef ASSERT
1853 if (TraceParallelOldGCMarkingPhase) {
1854 tty->print_cr("add_obj_count=" SIZE_FORMAT " "
1855 "add_obj_bytes=" SIZE_FORMAT,
1856 add_obj_count, add_obj_size * HeapWordSize);
1857 tty->print_cr("mark_bitmap_count=" SIZE_FORMAT " "
1858 "mark_bitmap_bytes=" SIZE_FORMAT,
1859 mark_bitmap_count, mark_bitmap_size * HeapWordSize);
1860 }
1861 #endif // #ifdef ASSERT
1863 // Quick summarization of each space into itself, to see how much is live.
1864 summarize_spaces_quick();
1866 if (TraceParallelOldGCSummaryPhase) {
1867 tty->print_cr("summary_phase: after summarizing each space to self");
1868 Universe::print();
1869 NOT_PRODUCT(print_region_ranges());
1870 if (Verbose) {
1871 NOT_PRODUCT(print_initial_summary_data(_summary_data, _space_info));
1872 }
1873 }
1875 // The amount of live data that will end up in old space (assuming it fits).
1876 size_t old_space_total_live = 0;
1877 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
1878 old_space_total_live += pointer_delta(_space_info[id].new_top(),
1879 _space_info[id].space()->bottom());
1880 }
1882 MutableSpace* const old_space = _space_info[old_space_id].space();
1883 const size_t old_capacity = old_space->capacity_in_words();
1884 if (old_space_total_live > old_capacity) {
1885 // XXX - should also try to expand
1886 maximum_compaction = true;
1887 }
1888 #ifndef PRODUCT
1889 if (ParallelOldGCSplitALot && old_space_total_live < old_capacity) {
1890 provoke_split(maximum_compaction);
1891 }
1892 #endif // #ifndef PRODUCT
1894 // Old generations.
1895 summarize_space(old_space_id, maximum_compaction);
1897 // Summarize the remaining spaces in the young gen. The initial target space
1898 // is the old gen. If a space does not fit entirely into the target, then the
1899 // remainder is compacted into the space itself and that space becomes the new
1900 // target.
1901 SpaceId dst_space_id = old_space_id;
1902 HeapWord* dst_space_end = old_space->end();
1903 HeapWord** new_top_addr = _space_info[dst_space_id].new_top_addr();
1904 for (unsigned int id = eden_space_id; id < last_space_id; ++id) {
1905 const MutableSpace* space = _space_info[id].space();
1906 const size_t live = pointer_delta(_space_info[id].new_top(),
1907 space->bottom());
1908 const size_t available = pointer_delta(dst_space_end, *new_top_addr);
1910 NOT_PRODUCT(summary_phase_msg(dst_space_id, *new_top_addr, dst_space_end,
1911 SpaceId(id), space->bottom(), space->top());)
1912 if (live > 0 && live <= available) {
1913 // All the live data will fit.
1914 bool done = _summary_data.summarize(_space_info[id].split_info(),
1915 space->bottom(), space->top(),
1916 NULL,
1917 *new_top_addr, dst_space_end,
1918 new_top_addr);
1919 assert(done, "space must fit into old gen");
1921 // Reset the new_top value for the space.
1922 _space_info[id].set_new_top(space->bottom());
1923 } else if (live > 0) {
1924 // Attempt to fit part of the source space into the target space.
1925 HeapWord* next_src_addr = NULL;
1926 bool done = _summary_data.summarize(_space_info[id].split_info(),
1927 space->bottom(), space->top(),
1928 &next_src_addr,
1929 *new_top_addr, dst_space_end,
1930 new_top_addr);
1931 assert(!done, "space should not fit into old gen");
1932 assert(next_src_addr != NULL, "sanity");
1934 // The source space becomes the new target, so the remainder is compacted
1935 // within the space itself.
1936 dst_space_id = SpaceId(id);
1937 dst_space_end = space->end();
1938 new_top_addr = _space_info[id].new_top_addr();
1939 NOT_PRODUCT(summary_phase_msg(dst_space_id,
1940 space->bottom(), dst_space_end,
1941 SpaceId(id), next_src_addr, space->top());)
1942 done = _summary_data.summarize(_space_info[id].split_info(),
1943 next_src_addr, space->top(),
1944 NULL,
1945 space->bottom(), dst_space_end,
1946 new_top_addr);
1947 assert(done, "space must fit when compacted into itself");
1948 assert(*new_top_addr <= space->top(), "usage should not grow");
1949 }
1950 }
1952 if (TraceParallelOldGCSummaryPhase) {
1953 tty->print_cr("summary_phase: after final summarization");
1954 Universe::print();
1955 NOT_PRODUCT(print_region_ranges());
1956 if (Verbose) {
1957 NOT_PRODUCT(print_generic_summary_data(_summary_data, _space_info));
1958 }
1959 }
1960 }
1962 // This method should contain all heap-specific policy for invoking a full
1963 // collection. invoke_no_policy() will only attempt to compact the heap; it
1964 // will do nothing further. If we need to bail out for policy reasons, scavenge
1965 // before full gc, or any other specialized behavior, it needs to be added here.
1966 //
1967 // Note that this method should only be called from the vm_thread while at a
1968 // safepoint.
1969 //
1970 // Note that the all_soft_refs_clear flag in the collector policy
1971 // may be true because this method can be called without intervening
1972 // activity. For example when the heap space is tight and full measure
1973 // are being taken to free space.
1974 void PSParallelCompact::invoke(bool maximum_heap_compaction) {
1975 assert(SafepointSynchronize::is_at_safepoint(), "should be at safepoint");
1976 assert(Thread::current() == (Thread*)VMThread::vm_thread(),
1977 "should be in vm thread");
1979 ParallelScavengeHeap* heap = gc_heap();
1980 GCCause::Cause gc_cause = heap->gc_cause();
1981 assert(!heap->is_gc_active(), "not reentrant");
1983 PSAdaptiveSizePolicy* policy = heap->size_policy();
1984 IsGCActiveMark mark;
1986 if (ScavengeBeforeFullGC) {
1987 PSScavenge::invoke_no_policy();
1988 }
1990 const bool clear_all_soft_refs =
1991 heap->collector_policy()->should_clear_all_soft_refs();
1993 PSParallelCompact::invoke_no_policy(clear_all_soft_refs ||
1994 maximum_heap_compaction);
1995 }
1997 // This method contains no policy. You should probably
1998 // be calling invoke() instead.
1999 bool PSParallelCompact::invoke_no_policy(bool maximum_heap_compaction) {
2000 assert(SafepointSynchronize::is_at_safepoint(), "must be at a safepoint");
2001 assert(ref_processor() != NULL, "Sanity");
2003 if (GC_locker::check_active_before_gc()) {
2004 return false;
2005 }
2007 ParallelScavengeHeap* heap = gc_heap();
2009 _gc_timer.register_gc_start(os::elapsed_counter());
2010 _gc_tracer.report_gc_start(heap->gc_cause(), _gc_timer.gc_start());
2012 TimeStamp marking_start;
2013 TimeStamp compaction_start;
2014 TimeStamp collection_exit;
2016 GCCause::Cause gc_cause = heap->gc_cause();
2017 PSYoungGen* young_gen = heap->young_gen();
2018 PSOldGen* old_gen = heap->old_gen();
2019 PSAdaptiveSizePolicy* size_policy = heap->size_policy();
2021 // The scope of casr should end after code that can change
2022 // CollectorPolicy::_should_clear_all_soft_refs.
2023 ClearedAllSoftRefs casr(maximum_heap_compaction,
2024 heap->collector_policy());
2026 if (ZapUnusedHeapArea) {
2027 // Save information needed to minimize mangling
2028 heap->record_gen_tops_before_GC();
2029 }
2031 heap->pre_full_gc_dump(&_gc_timer);
2033 _print_phases = PrintGCDetails && PrintParallelOldGCPhaseTimes;
2035 // Make sure data structures are sane, make the heap parsable, and do other
2036 // miscellaneous bookkeeping.
2037 PreGCValues pre_gc_values;
2038 pre_compact(&pre_gc_values);
2040 // Get the compaction manager reserved for the VM thread.
2041 ParCompactionManager* const vmthread_cm =
2042 ParCompactionManager::manager_array(gc_task_manager()->workers());
2044 // Place after pre_compact() where the number of invocations is incremented.
2045 AdaptiveSizePolicyOutput(size_policy, heap->total_collections());
2047 {
2048 ResourceMark rm;
2049 HandleMark hm;
2051 // Set the number of GC threads to be used in this collection
2052 gc_task_manager()->set_active_gang();
2053 gc_task_manager()->task_idle_workers();
2054 heap->set_par_threads(gc_task_manager()->active_workers());
2056 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
2057 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
2058 GCTraceTime t1(GCCauseString("Full GC", gc_cause), PrintGC, !PrintGCDetails, NULL);
2059 TraceCollectorStats tcs(counters());
2060 TraceMemoryManagerStats tms(true /* Full GC */,gc_cause);
2062 if (TraceGen1Time) accumulated_time()->start();
2064 // Let the size policy know we're starting
2065 size_policy->major_collection_begin();
2067 CodeCache::gc_prologue();
2068 Threads::gc_prologue();
2070 COMPILER2_PRESENT(DerivedPointerTable::clear());
2072 ref_processor()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
2073 ref_processor()->setup_policy(maximum_heap_compaction);
2075 bool marked_for_unloading = false;
2077 marking_start.update();
2078 marking_phase(vmthread_cm, maximum_heap_compaction, &_gc_tracer);
2080 bool max_on_system_gc = UseMaximumCompactionOnSystemGC
2081 && gc_cause == GCCause::_java_lang_system_gc;
2082 summary_phase(vmthread_cm, maximum_heap_compaction || max_on_system_gc);
2084 COMPILER2_PRESENT(assert(DerivedPointerTable::is_active(), "Sanity"));
2085 COMPILER2_PRESENT(DerivedPointerTable::set_active(false));
2087 // adjust_roots() updates Universe::_intArrayKlassObj which is
2088 // needed by the compaction for filling holes in the dense prefix.
2089 adjust_roots();
2091 compaction_start.update();
2092 compact();
2094 // Reset the mark bitmap, summary data, and do other bookkeeping. Must be
2095 // done before resizing.
2096 post_compact();
2098 // Let the size policy know we're done
2099 size_policy->major_collection_end(old_gen->used_in_bytes(), gc_cause);
2101 if (UseAdaptiveSizePolicy) {
2102 if (PrintAdaptiveSizePolicy) {
2103 gclog_or_tty->print("AdaptiveSizeStart: ");
2104 gclog_or_tty->stamp();
2105 gclog_or_tty->print_cr(" collection: %d ",
2106 heap->total_collections());
2107 if (Verbose) {
2108 gclog_or_tty->print("old_gen_capacity: %d young_gen_capacity: %d",
2109 old_gen->capacity_in_bytes(), young_gen->capacity_in_bytes());
2110 }
2111 }
2113 // Don't check if the size_policy is ready here. Let
2114 // the size_policy check that internally.
2115 if (UseAdaptiveGenerationSizePolicyAtMajorCollection &&
2116 ((gc_cause != GCCause::_java_lang_system_gc) ||
2117 UseAdaptiveSizePolicyWithSystemGC)) {
2118 // Calculate optimal free space amounts
2119 assert(young_gen->max_size() >
2120 young_gen->from_space()->capacity_in_bytes() +
2121 young_gen->to_space()->capacity_in_bytes(),
2122 "Sizes of space in young gen are out-of-bounds");
2124 size_t young_live = young_gen->used_in_bytes();
2125 size_t eden_live = young_gen->eden_space()->used_in_bytes();
2126 size_t old_live = old_gen->used_in_bytes();
2127 size_t cur_eden = young_gen->eden_space()->capacity_in_bytes();
2128 size_t max_old_gen_size = old_gen->max_gen_size();
2129 size_t max_eden_size = young_gen->max_size() -
2130 young_gen->from_space()->capacity_in_bytes() -
2131 young_gen->to_space()->capacity_in_bytes();
2133 // Used for diagnostics
2134 size_policy->clear_generation_free_space_flags();
2136 size_policy->compute_generations_free_space(young_live,
2137 eden_live,
2138 old_live,
2139 cur_eden,
2140 max_old_gen_size,
2141 max_eden_size,
2142 true /* full gc*/);
2144 size_policy->check_gc_overhead_limit(young_live,
2145 eden_live,
2146 max_old_gen_size,
2147 max_eden_size,
2148 true /* full gc*/,
2149 gc_cause,
2150 heap->collector_policy());
2152 size_policy->decay_supplemental_growth(true /* full gc*/);
2154 heap->resize_old_gen(
2155 size_policy->calculated_old_free_size_in_bytes());
2157 // Don't resize the young generation at an major collection. A
2158 // desired young generation size may have been calculated but
2159 // resizing the young generation complicates the code because the
2160 // resizing of the old generation may have moved the boundary
2161 // between the young generation and the old generation. Let the
2162 // young generation resizing happen at the minor collections.
2163 }
2164 if (PrintAdaptiveSizePolicy) {
2165 gclog_or_tty->print_cr("AdaptiveSizeStop: collection: %d ",
2166 heap->total_collections());
2167 }
2168 }
2170 if (UsePerfData) {
2171 PSGCAdaptivePolicyCounters* const counters = heap->gc_policy_counters();
2172 counters->update_counters();
2173 counters->update_old_capacity(old_gen->capacity_in_bytes());
2174 counters->update_young_capacity(young_gen->capacity_in_bytes());
2175 }
2177 heap->resize_all_tlabs();
2179 // Resize the metaspace capactiy after a collection
2180 MetaspaceGC::compute_new_size();
2182 if (TraceGen1Time) accumulated_time()->stop();
2184 if (PrintGC) {
2185 if (PrintGCDetails) {
2186 // No GC timestamp here. This is after GC so it would be confusing.
2187 young_gen->print_used_change(pre_gc_values.young_gen_used());
2188 old_gen->print_used_change(pre_gc_values.old_gen_used());
2189 heap->print_heap_change(pre_gc_values.heap_used());
2190 MetaspaceAux::print_metaspace_change(pre_gc_values.metadata_used());
2191 } else {
2192 heap->print_heap_change(pre_gc_values.heap_used());
2193 }
2194 }
2196 // Track memory usage and detect low memory
2197 MemoryService::track_memory_usage();
2198 heap->update_counters();
2199 gc_task_manager()->release_idle_workers();
2200 }
2202 #ifdef ASSERT
2203 for (size_t i = 0; i < ParallelGCThreads + 1; ++i) {
2204 ParCompactionManager* const cm =
2205 ParCompactionManager::manager_array(int(i));
2206 assert(cm->marking_stack()->is_empty(), "should be empty");
2207 assert(ParCompactionManager::region_list(int(i))->is_empty(), "should be empty");
2208 }
2209 #endif // ASSERT
2211 if (VerifyAfterGC && heap->total_collections() >= VerifyGCStartAt) {
2212 HandleMark hm; // Discard invalid handles created during verification
2213 Universe::verify(" VerifyAfterGC:");
2214 }
2216 // Re-verify object start arrays
2217 if (VerifyObjectStartArray &&
2218 VerifyAfterGC) {
2219 old_gen->verify_object_start_array();
2220 }
2222 if (ZapUnusedHeapArea) {
2223 old_gen->object_space()->check_mangled_unused_area_complete();
2224 }
2226 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
2228 collection_exit.update();
2230 heap->print_heap_after_gc();
2231 heap->trace_heap_after_gc(&_gc_tracer);
2233 if (PrintGCTaskTimeStamps) {
2234 gclog_or_tty->print_cr("VM-Thread " INT64_FORMAT " " INT64_FORMAT " "
2235 INT64_FORMAT,
2236 marking_start.ticks(), compaction_start.ticks(),
2237 collection_exit.ticks());
2238 gc_task_manager()->print_task_time_stamps();
2239 }
2241 heap->post_full_gc_dump(&_gc_timer);
2243 #ifdef TRACESPINNING
2244 ParallelTaskTerminator::print_termination_counts();
2245 #endif
2247 _gc_timer.register_gc_end(os::elapsed_counter());
2249 _gc_tracer.report_dense_prefix(dense_prefix(old_space_id));
2250 _gc_tracer.report_gc_end(_gc_timer.gc_end(), _gc_timer.time_partitions());
2252 return true;
2253 }
2255 bool PSParallelCompact::absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
2256 PSYoungGen* young_gen,
2257 PSOldGen* old_gen) {
2258 MutableSpace* const eden_space = young_gen->eden_space();
2259 assert(!eden_space->is_empty(), "eden must be non-empty");
2260 assert(young_gen->virtual_space()->alignment() ==
2261 old_gen->virtual_space()->alignment(), "alignments do not match");
2263 if (!(UseAdaptiveSizePolicy && UseAdaptiveGCBoundary)) {
2264 return false;
2265 }
2267 // Both generations must be completely committed.
2268 if (young_gen->virtual_space()->uncommitted_size() != 0) {
2269 return false;
2270 }
2271 if (old_gen->virtual_space()->uncommitted_size() != 0) {
2272 return false;
2273 }
2275 // Figure out how much to take from eden. Include the average amount promoted
2276 // in the total; otherwise the next young gen GC will simply bail out to a
2277 // full GC.
2278 const size_t alignment = old_gen->virtual_space()->alignment();
2279 const size_t eden_used = eden_space->used_in_bytes();
2280 const size_t promoted = (size_t)size_policy->avg_promoted()->padded_average();
2281 const size_t absorb_size = align_size_up(eden_used + promoted, alignment);
2282 const size_t eden_capacity = eden_space->capacity_in_bytes();
2284 if (absorb_size >= eden_capacity) {
2285 return false; // Must leave some space in eden.
2286 }
2288 const size_t new_young_size = young_gen->capacity_in_bytes() - absorb_size;
2289 if (new_young_size < young_gen->min_gen_size()) {
2290 return false; // Respect young gen minimum size.
2291 }
2293 if (TraceAdaptiveGCBoundary && Verbose) {
2294 gclog_or_tty->print(" absorbing " SIZE_FORMAT "K: "
2295 "eden " SIZE_FORMAT "K->" SIZE_FORMAT "K "
2296 "from " SIZE_FORMAT "K, to " SIZE_FORMAT "K "
2297 "young_gen " SIZE_FORMAT "K->" SIZE_FORMAT "K ",
2298 absorb_size / K,
2299 eden_capacity / K, (eden_capacity - absorb_size) / K,
2300 young_gen->from_space()->used_in_bytes() / K,
2301 young_gen->to_space()->used_in_bytes() / K,
2302 young_gen->capacity_in_bytes() / K, new_young_size / K);
2303 }
2305 // Fill the unused part of the old gen.
2306 MutableSpace* const old_space = old_gen->object_space();
2307 HeapWord* const unused_start = old_space->top();
2308 size_t const unused_words = pointer_delta(old_space->end(), unused_start);
2310 if (unused_words > 0) {
2311 if (unused_words < CollectedHeap::min_fill_size()) {
2312 return false; // If the old gen cannot be filled, must give up.
2313 }
2314 CollectedHeap::fill_with_objects(unused_start, unused_words);
2315 }
2317 // Take the live data from eden and set both top and end in the old gen to
2318 // eden top. (Need to set end because reset_after_change() mangles the region
2319 // from end to virtual_space->high() in debug builds).
2320 HeapWord* const new_top = eden_space->top();
2321 old_gen->virtual_space()->expand_into(young_gen->virtual_space(),
2322 absorb_size);
2323 young_gen->reset_after_change();
2324 old_space->set_top(new_top);
2325 old_space->set_end(new_top);
2326 old_gen->reset_after_change();
2328 // Update the object start array for the filler object and the data from eden.
2329 ObjectStartArray* const start_array = old_gen->start_array();
2330 for (HeapWord* p = unused_start; p < new_top; p += oop(p)->size()) {
2331 start_array->allocate_block(p);
2332 }
2334 // Could update the promoted average here, but it is not typically updated at
2335 // full GCs and the value to use is unclear. Something like
2336 //
2337 // cur_promoted_avg + absorb_size / number_of_scavenges_since_last_full_gc.
2339 size_policy->set_bytes_absorbed_from_eden(absorb_size);
2340 return true;
2341 }
2343 GCTaskManager* const PSParallelCompact::gc_task_manager() {
2344 assert(ParallelScavengeHeap::gc_task_manager() != NULL,
2345 "shouldn't return NULL");
2346 return ParallelScavengeHeap::gc_task_manager();
2347 }
2349 void PSParallelCompact::marking_phase(ParCompactionManager* cm,
2350 bool maximum_heap_compaction,
2351 ParallelOldTracer *gc_tracer) {
2352 // Recursively traverse all live objects and mark them
2353 GCTraceTime tm("marking phase", print_phases(), true, &_gc_timer);
2355 ParallelScavengeHeap* heap = gc_heap();
2356 uint parallel_gc_threads = heap->gc_task_manager()->workers();
2357 uint active_gc_threads = heap->gc_task_manager()->active_workers();
2358 TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2359 ParallelTaskTerminator terminator(active_gc_threads, qset);
2361 PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2362 PSParallelCompact::FollowStackClosure follow_stack_closure(cm);
2364 // Need new claim bits before marking starts.
2365 ClassLoaderDataGraph::clear_claimed_marks();
2367 {
2368 GCTraceTime tm_m("par mark", print_phases(), true, &_gc_timer);
2370 ParallelScavengeHeap::ParStrongRootsScope psrs;
2372 GCTaskQueue* q = GCTaskQueue::create();
2374 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::universe));
2375 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jni_handles));
2376 // We scan the thread roots in parallel
2377 Threads::create_thread_roots_marking_tasks(q);
2378 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::object_synchronizer));
2379 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::flat_profiler));
2380 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::management));
2381 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::system_dictionary));
2382 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::class_loader_data));
2383 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::jvmti));
2384 q->enqueue(new MarkFromRootsTask(MarkFromRootsTask::code_cache));
2386 if (active_gc_threads > 1) {
2387 for (uint j = 0; j < active_gc_threads; j++) {
2388 q->enqueue(new StealMarkingTask(&terminator));
2389 }
2390 }
2392 gc_task_manager()->execute_and_wait(q);
2393 }
2395 // Process reference objects found during marking
2396 {
2397 GCTraceTime tm_r("reference processing", print_phases(), true, &_gc_timer);
2399 ReferenceProcessorStats stats;
2400 if (ref_processor()->processing_is_mt()) {
2401 RefProcTaskExecutor task_executor;
2402 stats = ref_processor()->process_discovered_references(
2403 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure,
2404 &task_executor, &_gc_timer);
2405 } else {
2406 stats = ref_processor()->process_discovered_references(
2407 is_alive_closure(), &mark_and_push_closure, &follow_stack_closure, NULL,
2408 &_gc_timer);
2409 }
2411 gc_tracer->report_gc_reference_stats(stats);
2412 }
2414 GCTraceTime tm_c("class unloading", print_phases(), true, &_gc_timer);
2416 // This is the point where the entire marking should have completed.
2417 assert(cm->marking_stacks_empty(), "Marking should have completed");
2419 // Follow system dictionary roots and unload classes.
2420 bool purged_class = SystemDictionary::do_unloading(is_alive_closure());
2422 // Unload nmethods.
2423 CodeCache::do_unloading(is_alive_closure(), purged_class);
2425 // Prune dead klasses from subklass/sibling/implementor lists.
2426 Klass::clean_weak_klass_links(is_alive_closure());
2428 // Delete entries for dead interned strings.
2429 StringTable::unlink(is_alive_closure());
2431 // Clean up unreferenced symbols in symbol table.
2432 SymbolTable::unlink();
2433 _gc_tracer.report_object_count_after_gc(is_alive_closure());
2434 }
2436 void PSParallelCompact::follow_klass(ParCompactionManager* cm, Klass* klass) {
2437 ClassLoaderData* cld = klass->class_loader_data();
2438 // The actual processing of the klass is done when we
2439 // traverse the list of Klasses in the class loader data.
2440 PSParallelCompact::follow_class_loader(cm, cld);
2441 }
2443 void PSParallelCompact::adjust_klass(ParCompactionManager* cm, Klass* klass) {
2444 ClassLoaderData* cld = klass->class_loader_data();
2445 // The actual processing of the klass is done when we
2446 // traverse the list of Klasses in the class loader data.
2447 PSParallelCompact::adjust_class_loader(cm, cld);
2448 }
2450 void PSParallelCompact::follow_class_loader(ParCompactionManager* cm,
2451 ClassLoaderData* cld) {
2452 PSParallelCompact::MarkAndPushClosure mark_and_push_closure(cm);
2453 PSParallelCompact::FollowKlassClosure follow_klass_closure(&mark_and_push_closure);
2455 cld->oops_do(&mark_and_push_closure, &follow_klass_closure, true);
2456 }
2458 void PSParallelCompact::adjust_class_loader(ParCompactionManager* cm,
2459 ClassLoaderData* cld) {
2460 cld->oops_do(PSParallelCompact::adjust_pointer_closure(),
2461 PSParallelCompact::adjust_klass_closure(),
2462 true);
2463 }
2465 // This should be moved to the shared markSweep code!
2466 class PSAlwaysTrueClosure: public BoolObjectClosure {
2467 public:
2468 bool do_object_b(oop p) { return true; }
2469 };
2470 static PSAlwaysTrueClosure always_true;
2472 void PSParallelCompact::adjust_roots() {
2473 // Adjust the pointers to reflect the new locations
2474 GCTraceTime tm("adjust roots", print_phases(), true, &_gc_timer);
2476 // Need new claim bits when tracing through and adjusting pointers.
2477 ClassLoaderDataGraph::clear_claimed_marks();
2479 // General strong roots.
2480 Universe::oops_do(adjust_pointer_closure());
2481 JNIHandles::oops_do(adjust_pointer_closure()); // Global (strong) JNI handles
2482 CLDToOopClosure adjust_from_cld(adjust_pointer_closure());
2483 Threads::oops_do(adjust_pointer_closure(), &adjust_from_cld, NULL);
2484 ObjectSynchronizer::oops_do(adjust_pointer_closure());
2485 FlatProfiler::oops_do(adjust_pointer_closure());
2486 Management::oops_do(adjust_pointer_closure());
2487 JvmtiExport::oops_do(adjust_pointer_closure());
2488 // SO_AllClasses
2489 SystemDictionary::oops_do(adjust_pointer_closure());
2490 ClassLoaderDataGraph::oops_do(adjust_pointer_closure(), adjust_klass_closure(), true);
2492 // Now adjust pointers in remaining weak roots. (All of which should
2493 // have been cleared if they pointed to non-surviving objects.)
2494 // Global (weak) JNI handles
2495 JNIHandles::weak_oops_do(&always_true, adjust_pointer_closure());
2497 CodeCache::oops_do(adjust_pointer_closure());
2498 StringTable::oops_do(adjust_pointer_closure());
2499 ref_processor()->weak_oops_do(adjust_pointer_closure());
2500 // Roots were visited so references into the young gen in roots
2501 // may have been scanned. Process them also.
2502 // Should the reference processor have a span that excludes
2503 // young gen objects?
2504 PSScavenge::reference_processor()->weak_oops_do(adjust_pointer_closure());
2505 }
2507 void PSParallelCompact::enqueue_region_draining_tasks(GCTaskQueue* q,
2508 uint parallel_gc_threads)
2509 {
2510 GCTraceTime tm("drain task setup", print_phases(), true, &_gc_timer);
2512 // Find the threads that are active
2513 unsigned int which = 0;
2515 const uint task_count = MAX2(parallel_gc_threads, 1U);
2516 for (uint j = 0; j < task_count; j++) {
2517 q->enqueue(new DrainStacksCompactionTask(j));
2518 ParCompactionManager::verify_region_list_empty(j);
2519 // Set the region stacks variables to "no" region stack values
2520 // so that they will be recognized and needing a region stack
2521 // in the stealing tasks if they do not get one by executing
2522 // a draining stack.
2523 ParCompactionManager* cm = ParCompactionManager::manager_array(j);
2524 cm->set_region_stack(NULL);
2525 cm->set_region_stack_index((uint)max_uintx);
2526 }
2527 ParCompactionManager::reset_recycled_stack_index();
2529 // Find all regions that are available (can be filled immediately) and
2530 // distribute them to the thread stacks. The iteration is done in reverse
2531 // order (high to low) so the regions will be removed in ascending order.
2533 const ParallelCompactData& sd = PSParallelCompact::summary_data();
2535 size_t fillable_regions = 0; // A count for diagnostic purposes.
2536 // A region index which corresponds to the tasks created above.
2537 // "which" must be 0 <= which < task_count
2539 which = 0;
2540 // id + 1 is used to test termination so unsigned can
2541 // be used with an old_space_id == 0.
2542 for (unsigned int id = to_space_id; id + 1 > old_space_id; --id) {
2543 SpaceInfo* const space_info = _space_info + id;
2544 MutableSpace* const space = space_info->space();
2545 HeapWord* const new_top = space_info->new_top();
2547 const size_t beg_region = sd.addr_to_region_idx(space_info->dense_prefix());
2548 const size_t end_region =
2549 sd.addr_to_region_idx(sd.region_align_up(new_top));
2551 for (size_t cur = end_region - 1; cur + 1 > beg_region; --cur) {
2552 if (sd.region(cur)->claim_unsafe()) {
2553 ParCompactionManager::region_list_push(which, cur);
2555 if (TraceParallelOldGCCompactionPhase && Verbose) {
2556 const size_t count_mod_8 = fillable_regions & 7;
2557 if (count_mod_8 == 0) gclog_or_tty->print("fillable: ");
2558 gclog_or_tty->print(" " SIZE_FORMAT_W(7), cur);
2559 if (count_mod_8 == 7) gclog_or_tty->cr();
2560 }
2562 NOT_PRODUCT(++fillable_regions;)
2564 // Assign regions to tasks in round-robin fashion.
2565 if (++which == task_count) {
2566 assert(which <= parallel_gc_threads,
2567 "Inconsistent number of workers");
2568 which = 0;
2569 }
2570 }
2571 }
2572 }
2574 if (TraceParallelOldGCCompactionPhase) {
2575 if (Verbose && (fillable_regions & 7) != 0) gclog_or_tty->cr();
2576 gclog_or_tty->print_cr("%u initially fillable regions", fillable_regions);
2577 }
2578 }
2580 #define PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING 4
2582 void PSParallelCompact::enqueue_dense_prefix_tasks(GCTaskQueue* q,
2583 uint parallel_gc_threads) {
2584 GCTraceTime tm("dense prefix task setup", print_phases(), true, &_gc_timer);
2586 ParallelCompactData& sd = PSParallelCompact::summary_data();
2588 // Iterate over all the spaces adding tasks for updating
2589 // regions in the dense prefix. Assume that 1 gc thread
2590 // will work on opening the gaps and the remaining gc threads
2591 // will work on the dense prefix.
2592 unsigned int space_id;
2593 for (space_id = old_space_id; space_id < last_space_id; ++ space_id) {
2594 HeapWord* const dense_prefix_end = _space_info[space_id].dense_prefix();
2595 const MutableSpace* const space = _space_info[space_id].space();
2597 if (dense_prefix_end == space->bottom()) {
2598 // There is no dense prefix for this space.
2599 continue;
2600 }
2602 // The dense prefix is before this region.
2603 size_t region_index_end_dense_prefix =
2604 sd.addr_to_region_idx(dense_prefix_end);
2605 RegionData* const dense_prefix_cp =
2606 sd.region(region_index_end_dense_prefix);
2607 assert(dense_prefix_end == space->end() ||
2608 dense_prefix_cp->available() ||
2609 dense_prefix_cp->claimed(),
2610 "The region after the dense prefix should always be ready to fill");
2612 size_t region_index_start = sd.addr_to_region_idx(space->bottom());
2614 // Is there dense prefix work?
2615 size_t total_dense_prefix_regions =
2616 region_index_end_dense_prefix - region_index_start;
2617 // How many regions of the dense prefix should be given to
2618 // each thread?
2619 if (total_dense_prefix_regions > 0) {
2620 uint tasks_for_dense_prefix = 1;
2621 if (total_dense_prefix_regions <=
2622 (parallel_gc_threads * PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING)) {
2623 // Don't over partition. This assumes that
2624 // PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING is a small integer value
2625 // so there are not many regions to process.
2626 tasks_for_dense_prefix = parallel_gc_threads;
2627 } else {
2628 // Over partition
2629 tasks_for_dense_prefix = parallel_gc_threads *
2630 PAR_OLD_DENSE_PREFIX_OVER_PARTITIONING;
2631 }
2632 size_t regions_per_thread = total_dense_prefix_regions /
2633 tasks_for_dense_prefix;
2634 // Give each thread at least 1 region.
2635 if (regions_per_thread == 0) {
2636 regions_per_thread = 1;
2637 }
2639 for (uint k = 0; k < tasks_for_dense_prefix; k++) {
2640 if (region_index_start >= region_index_end_dense_prefix) {
2641 break;
2642 }
2643 // region_index_end is not processed
2644 size_t region_index_end = MIN2(region_index_start + regions_per_thread,
2645 region_index_end_dense_prefix);
2646 q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2647 region_index_start,
2648 region_index_end));
2649 region_index_start = region_index_end;
2650 }
2651 }
2652 // This gets any part of the dense prefix that did not
2653 // fit evenly.
2654 if (region_index_start < region_index_end_dense_prefix) {
2655 q->enqueue(new UpdateDensePrefixTask(SpaceId(space_id),
2656 region_index_start,
2657 region_index_end_dense_prefix));
2658 }
2659 }
2660 }
2662 void PSParallelCompact::enqueue_region_stealing_tasks(
2663 GCTaskQueue* q,
2664 ParallelTaskTerminator* terminator_ptr,
2665 uint parallel_gc_threads) {
2666 GCTraceTime tm("steal task setup", print_phases(), true, &_gc_timer);
2668 // Once a thread has drained it's stack, it should try to steal regions from
2669 // other threads.
2670 if (parallel_gc_threads > 1) {
2671 for (uint j = 0; j < parallel_gc_threads; j++) {
2672 q->enqueue(new StealRegionCompactionTask(terminator_ptr));
2673 }
2674 }
2675 }
2677 #ifdef ASSERT
2678 // Write a histogram of the number of times the block table was filled for a
2679 // region.
2680 void PSParallelCompact::write_block_fill_histogram(outputStream* const out)
2681 {
2682 if (!TraceParallelOldGCCompactionPhase) return;
2684 typedef ParallelCompactData::RegionData rd_t;
2685 ParallelCompactData& sd = summary_data();
2687 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2688 MutableSpace* const spc = _space_info[id].space();
2689 if (spc->bottom() != spc->top()) {
2690 const rd_t* const beg = sd.addr_to_region_ptr(spc->bottom());
2691 HeapWord* const top_aligned_up = sd.region_align_up(spc->top());
2692 const rd_t* const end = sd.addr_to_region_ptr(top_aligned_up);
2694 size_t histo[5] = { 0, 0, 0, 0, 0 };
2695 const size_t histo_len = sizeof(histo) / sizeof(size_t);
2696 const size_t region_cnt = pointer_delta(end, beg, sizeof(rd_t));
2698 for (const rd_t* cur = beg; cur < end; ++cur) {
2699 ++histo[MIN2(cur->blocks_filled_count(), histo_len - 1)];
2700 }
2701 out->print("%u %-4s" SIZE_FORMAT_W(5), id, space_names[id], region_cnt);
2702 for (size_t i = 0; i < histo_len; ++i) {
2703 out->print(" " SIZE_FORMAT_W(5) " %5.1f%%",
2704 histo[i], 100.0 * histo[i] / region_cnt);
2705 }
2706 out->cr();
2707 }
2708 }
2709 }
2710 #endif // #ifdef ASSERT
2712 void PSParallelCompact::compact() {
2713 // trace("5");
2714 GCTraceTime tm("compaction phase", print_phases(), true, &_gc_timer);
2716 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
2717 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
2718 PSOldGen* old_gen = heap->old_gen();
2719 old_gen->start_array()->reset();
2720 uint parallel_gc_threads = heap->gc_task_manager()->workers();
2721 uint active_gc_threads = heap->gc_task_manager()->active_workers();
2722 TaskQueueSetSuper* qset = ParCompactionManager::region_array();
2723 ParallelTaskTerminator terminator(active_gc_threads, qset);
2725 GCTaskQueue* q = GCTaskQueue::create();
2726 enqueue_region_draining_tasks(q, active_gc_threads);
2727 enqueue_dense_prefix_tasks(q, active_gc_threads);
2728 enqueue_region_stealing_tasks(q, &terminator, active_gc_threads);
2730 {
2731 GCTraceTime tm_pc("par compact", print_phases(), true, &_gc_timer);
2733 gc_task_manager()->execute_and_wait(q);
2735 #ifdef ASSERT
2736 // Verify that all regions have been processed before the deferred updates.
2737 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2738 verify_complete(SpaceId(id));
2739 }
2740 #endif
2741 }
2743 {
2744 // Update the deferred objects, if any. Any compaction manager can be used.
2745 GCTraceTime tm_du("deferred updates", print_phases(), true, &_gc_timer);
2746 ParCompactionManager* cm = ParCompactionManager::manager_array(0);
2747 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2748 update_deferred_objects(cm, SpaceId(id));
2749 }
2750 }
2752 DEBUG_ONLY(write_block_fill_histogram(gclog_or_tty));
2753 }
2755 #ifdef ASSERT
2756 void PSParallelCompact::verify_complete(SpaceId space_id) {
2757 // All Regions between space bottom() to new_top() should be marked as filled
2758 // and all Regions between new_top() and top() should be available (i.e.,
2759 // should have been emptied).
2760 ParallelCompactData& sd = summary_data();
2761 SpaceInfo si = _space_info[space_id];
2762 HeapWord* new_top_addr = sd.region_align_up(si.new_top());
2763 HeapWord* old_top_addr = sd.region_align_up(si.space()->top());
2764 const size_t beg_region = sd.addr_to_region_idx(si.space()->bottom());
2765 const size_t new_top_region = sd.addr_to_region_idx(new_top_addr);
2766 const size_t old_top_region = sd.addr_to_region_idx(old_top_addr);
2768 bool issued_a_warning = false;
2770 size_t cur_region;
2771 for (cur_region = beg_region; cur_region < new_top_region; ++cur_region) {
2772 const RegionData* const c = sd.region(cur_region);
2773 if (!c->completed()) {
2774 warning("region " SIZE_FORMAT " not filled: "
2775 "destination_count=" SIZE_FORMAT,
2776 cur_region, c->destination_count());
2777 issued_a_warning = true;
2778 }
2779 }
2781 for (cur_region = new_top_region; cur_region < old_top_region; ++cur_region) {
2782 const RegionData* const c = sd.region(cur_region);
2783 if (!c->available()) {
2784 warning("region " SIZE_FORMAT " not empty: "
2785 "destination_count=" SIZE_FORMAT,
2786 cur_region, c->destination_count());
2787 issued_a_warning = true;
2788 }
2789 }
2791 if (issued_a_warning) {
2792 print_region_ranges();
2793 }
2794 }
2795 #endif // #ifdef ASSERT
2797 // Update interior oops in the ranges of regions [beg_region, end_region).
2798 void
2799 PSParallelCompact::update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
2800 SpaceId space_id,
2801 size_t beg_region,
2802 size_t end_region) {
2803 ParallelCompactData& sd = summary_data();
2804 ParMarkBitMap* const mbm = mark_bitmap();
2806 HeapWord* beg_addr = sd.region_to_addr(beg_region);
2807 HeapWord* const end_addr = sd.region_to_addr(end_region);
2808 assert(beg_region <= end_region, "bad region range");
2809 assert(end_addr <= dense_prefix(space_id), "not in the dense prefix");
2811 #ifdef ASSERT
2812 // Claim the regions to avoid triggering an assert when they are marked as
2813 // filled.
2814 for (size_t claim_region = beg_region; claim_region < end_region; ++claim_region) {
2815 assert(sd.region(claim_region)->claim_unsafe(), "claim() failed");
2816 }
2817 #endif // #ifdef ASSERT
2819 if (beg_addr != space(space_id)->bottom()) {
2820 // Find the first live object or block of dead space that *starts* in this
2821 // range of regions. If a partial object crosses onto the region, skip it;
2822 // it will be marked for 'deferred update' when the object head is
2823 // processed. If dead space crosses onto the region, it is also skipped; it
2824 // will be filled when the prior region is processed. If neither of those
2825 // apply, the first word in the region is the start of a live object or dead
2826 // space.
2827 assert(beg_addr > space(space_id)->bottom(), "sanity");
2828 const RegionData* const cp = sd.region(beg_region);
2829 if (cp->partial_obj_size() != 0) {
2830 beg_addr = sd.partial_obj_end(beg_region);
2831 } else if (dead_space_crosses_boundary(cp, mbm->addr_to_bit(beg_addr))) {
2832 beg_addr = mbm->find_obj_beg(beg_addr, end_addr);
2833 }
2834 }
2836 if (beg_addr < end_addr) {
2837 // A live object or block of dead space starts in this range of Regions.
2838 HeapWord* const dense_prefix_end = dense_prefix(space_id);
2840 // Create closures and iterate.
2841 UpdateOnlyClosure update_closure(mbm, cm, space_id);
2842 FillClosure fill_closure(cm, space_id);
2843 ParMarkBitMap::IterationStatus status;
2844 status = mbm->iterate(&update_closure, &fill_closure, beg_addr, end_addr,
2845 dense_prefix_end);
2846 if (status == ParMarkBitMap::incomplete) {
2847 update_closure.do_addr(update_closure.source());
2848 }
2849 }
2851 // Mark the regions as filled.
2852 RegionData* const beg_cp = sd.region(beg_region);
2853 RegionData* const end_cp = sd.region(end_region);
2854 for (RegionData* cp = beg_cp; cp < end_cp; ++cp) {
2855 cp->set_completed();
2856 }
2857 }
2859 // Return the SpaceId for the space containing addr. If addr is not in the
2860 // heap, last_space_id is returned. In debug mode it expects the address to be
2861 // in the heap and asserts such.
2862 PSParallelCompact::SpaceId PSParallelCompact::space_id(HeapWord* addr) {
2863 assert(Universe::heap()->is_in_reserved(addr), "addr not in the heap");
2865 for (unsigned int id = old_space_id; id < last_space_id; ++id) {
2866 if (_space_info[id].space()->contains(addr)) {
2867 return SpaceId(id);
2868 }
2869 }
2871 assert(false, "no space contains the addr");
2872 return last_space_id;
2873 }
2875 void PSParallelCompact::update_deferred_objects(ParCompactionManager* cm,
2876 SpaceId id) {
2877 assert(id < last_space_id, "bad space id");
2879 ParallelCompactData& sd = summary_data();
2880 const SpaceInfo* const space_info = _space_info + id;
2881 ObjectStartArray* const start_array = space_info->start_array();
2883 const MutableSpace* const space = space_info->space();
2884 assert(space_info->dense_prefix() >= space->bottom(), "dense_prefix not set");
2885 HeapWord* const beg_addr = space_info->dense_prefix();
2886 HeapWord* const end_addr = sd.region_align_up(space_info->new_top());
2888 const RegionData* const beg_region = sd.addr_to_region_ptr(beg_addr);
2889 const RegionData* const end_region = sd.addr_to_region_ptr(end_addr);
2890 const RegionData* cur_region;
2891 for (cur_region = beg_region; cur_region < end_region; ++cur_region) {
2892 HeapWord* const addr = cur_region->deferred_obj_addr();
2893 if (addr != NULL) {
2894 if (start_array != NULL) {
2895 start_array->allocate_block(addr);
2896 }
2897 oop(addr)->update_contents(cm);
2898 assert(oop(addr)->is_oop_or_null(), "should be an oop now");
2899 }
2900 }
2901 }
2903 // Skip over count live words starting from beg, and return the address of the
2904 // next live word. Unless marked, the word corresponding to beg is assumed to
2905 // be dead. Callers must either ensure beg does not correspond to the middle of
2906 // an object, or account for those live words in some other way. Callers must
2907 // also ensure that there are enough live words in the range [beg, end) to skip.
2908 HeapWord*
2909 PSParallelCompact::skip_live_words(HeapWord* beg, HeapWord* end, size_t count)
2910 {
2911 assert(count > 0, "sanity");
2913 ParMarkBitMap* m = mark_bitmap();
2914 idx_t bits_to_skip = m->words_to_bits(count);
2915 idx_t cur_beg = m->addr_to_bit(beg);
2916 const idx_t search_end = BitMap::word_align_up(m->addr_to_bit(end));
2918 do {
2919 cur_beg = m->find_obj_beg(cur_beg, search_end);
2920 idx_t cur_end = m->find_obj_end(cur_beg, search_end);
2921 const size_t obj_bits = cur_end - cur_beg + 1;
2922 if (obj_bits > bits_to_skip) {
2923 return m->bit_to_addr(cur_beg + bits_to_skip);
2924 }
2925 bits_to_skip -= obj_bits;
2926 cur_beg = cur_end + 1;
2927 } while (bits_to_skip > 0);
2929 // Skipping the desired number of words landed just past the end of an object.
2930 // Find the start of the next object.
2931 cur_beg = m->find_obj_beg(cur_beg, search_end);
2932 assert(cur_beg < m->addr_to_bit(end), "not enough live words to skip");
2933 return m->bit_to_addr(cur_beg);
2934 }
2936 HeapWord* PSParallelCompact::first_src_addr(HeapWord* const dest_addr,
2937 SpaceId src_space_id,
2938 size_t src_region_idx)
2939 {
2940 assert(summary_data().is_region_aligned(dest_addr), "not aligned");
2942 const SplitInfo& split_info = _space_info[src_space_id].split_info();
2943 if (split_info.dest_region_addr() == dest_addr) {
2944 // The partial object ending at the split point contains the first word to
2945 // be copied to dest_addr.
2946 return split_info.first_src_addr();
2947 }
2949 const ParallelCompactData& sd = summary_data();
2950 ParMarkBitMap* const bitmap = mark_bitmap();
2951 const size_t RegionSize = ParallelCompactData::RegionSize;
2953 assert(sd.is_region_aligned(dest_addr), "not aligned");
2954 const RegionData* const src_region_ptr = sd.region(src_region_idx);
2955 const size_t partial_obj_size = src_region_ptr->partial_obj_size();
2956 HeapWord* const src_region_destination = src_region_ptr->destination();
2958 assert(dest_addr >= src_region_destination, "wrong src region");
2959 assert(src_region_ptr->data_size() > 0, "src region cannot be empty");
2961 HeapWord* const src_region_beg = sd.region_to_addr(src_region_idx);
2962 HeapWord* const src_region_end = src_region_beg + RegionSize;
2964 HeapWord* addr = src_region_beg;
2965 if (dest_addr == src_region_destination) {
2966 // Return the first live word in the source region.
2967 if (partial_obj_size == 0) {
2968 addr = bitmap->find_obj_beg(addr, src_region_end);
2969 assert(addr < src_region_end, "no objects start in src region");
2970 }
2971 return addr;
2972 }
2974 // Must skip some live data.
2975 size_t words_to_skip = dest_addr - src_region_destination;
2976 assert(src_region_ptr->data_size() > words_to_skip, "wrong src region");
2978 if (partial_obj_size >= words_to_skip) {
2979 // All the live words to skip are part of the partial object.
2980 addr += words_to_skip;
2981 if (partial_obj_size == words_to_skip) {
2982 // Find the first live word past the partial object.
2983 addr = bitmap->find_obj_beg(addr, src_region_end);
2984 assert(addr < src_region_end, "wrong src region");
2985 }
2986 return addr;
2987 }
2989 // Skip over the partial object (if any).
2990 if (partial_obj_size != 0) {
2991 words_to_skip -= partial_obj_size;
2992 addr += partial_obj_size;
2993 }
2995 // Skip over live words due to objects that start in the region.
2996 addr = skip_live_words(addr, src_region_end, words_to_skip);
2997 assert(addr < src_region_end, "wrong src region");
2998 return addr;
2999 }
3001 void PSParallelCompact::decrement_destination_counts(ParCompactionManager* cm,
3002 SpaceId src_space_id,
3003 size_t beg_region,
3004 HeapWord* end_addr)
3005 {
3006 ParallelCompactData& sd = summary_data();
3008 #ifdef ASSERT
3009 MutableSpace* const src_space = _space_info[src_space_id].space();
3010 HeapWord* const beg_addr = sd.region_to_addr(beg_region);
3011 assert(src_space->contains(beg_addr) || beg_addr == src_space->end(),
3012 "src_space_id does not match beg_addr");
3013 assert(src_space->contains(end_addr) || end_addr == src_space->end(),
3014 "src_space_id does not match end_addr");
3015 #endif // #ifdef ASSERT
3017 RegionData* const beg = sd.region(beg_region);
3018 RegionData* const end = sd.addr_to_region_ptr(sd.region_align_up(end_addr));
3020 // Regions up to new_top() are enqueued if they become available.
3021 HeapWord* const new_top = _space_info[src_space_id].new_top();
3022 RegionData* const enqueue_end =
3023 sd.addr_to_region_ptr(sd.region_align_up(new_top));
3025 for (RegionData* cur = beg; cur < end; ++cur) {
3026 assert(cur->data_size() > 0, "region must have live data");
3027 cur->decrement_destination_count();
3028 if (cur < enqueue_end && cur->available() && cur->claim()) {
3029 cm->push_region(sd.region(cur));
3030 }
3031 }
3032 }
3034 size_t PSParallelCompact::next_src_region(MoveAndUpdateClosure& closure,
3035 SpaceId& src_space_id,
3036 HeapWord*& src_space_top,
3037 HeapWord* end_addr)
3038 {
3039 typedef ParallelCompactData::RegionData RegionData;
3041 ParallelCompactData& sd = PSParallelCompact::summary_data();
3042 const size_t region_size = ParallelCompactData::RegionSize;
3044 size_t src_region_idx = 0;
3046 // Skip empty regions (if any) up to the top of the space.
3047 HeapWord* const src_aligned_up = sd.region_align_up(end_addr);
3048 RegionData* src_region_ptr = sd.addr_to_region_ptr(src_aligned_up);
3049 HeapWord* const top_aligned_up = sd.region_align_up(src_space_top);
3050 const RegionData* const top_region_ptr =
3051 sd.addr_to_region_ptr(top_aligned_up);
3052 while (src_region_ptr < top_region_ptr && src_region_ptr->data_size() == 0) {
3053 ++src_region_ptr;
3054 }
3056 if (src_region_ptr < top_region_ptr) {
3057 // The next source region is in the current space. Update src_region_idx
3058 // and the source address to match src_region_ptr.
3059 src_region_idx = sd.region(src_region_ptr);
3060 HeapWord* const src_region_addr = sd.region_to_addr(src_region_idx);
3061 if (src_region_addr > closure.source()) {
3062 closure.set_source(src_region_addr);
3063 }
3064 return src_region_idx;
3065 }
3067 // Switch to a new source space and find the first non-empty region.
3068 unsigned int space_id = src_space_id + 1;
3069 assert(space_id < last_space_id, "not enough spaces");
3071 HeapWord* const destination = closure.destination();
3073 do {
3074 MutableSpace* space = _space_info[space_id].space();
3075 HeapWord* const bottom = space->bottom();
3076 const RegionData* const bottom_cp = sd.addr_to_region_ptr(bottom);
3078 // Iterate over the spaces that do not compact into themselves.
3079 if (bottom_cp->destination() != bottom) {
3080 HeapWord* const top_aligned_up = sd.region_align_up(space->top());
3081 const RegionData* const top_cp = sd.addr_to_region_ptr(top_aligned_up);
3083 for (const RegionData* src_cp = bottom_cp; src_cp < top_cp; ++src_cp) {
3084 if (src_cp->live_obj_size() > 0) {
3085 // Found it.
3086 assert(src_cp->destination() == destination,
3087 "first live obj in the space must match the destination");
3088 assert(src_cp->partial_obj_size() == 0,
3089 "a space cannot begin with a partial obj");
3091 src_space_id = SpaceId(space_id);
3092 src_space_top = space->top();
3093 const size_t src_region_idx = sd.region(src_cp);
3094 closure.set_source(sd.region_to_addr(src_region_idx));
3095 return src_region_idx;
3096 } else {
3097 assert(src_cp->data_size() == 0, "sanity");
3098 }
3099 }
3100 }
3101 } while (++space_id < last_space_id);
3103 assert(false, "no source region was found");
3104 return 0;
3105 }
3107 void PSParallelCompact::fill_region(ParCompactionManager* cm, size_t region_idx)
3108 {
3109 typedef ParMarkBitMap::IterationStatus IterationStatus;
3110 const size_t RegionSize = ParallelCompactData::RegionSize;
3111 ParMarkBitMap* const bitmap = mark_bitmap();
3112 ParallelCompactData& sd = summary_data();
3113 RegionData* const region_ptr = sd.region(region_idx);
3115 // Get the items needed to construct the closure.
3116 HeapWord* dest_addr = sd.region_to_addr(region_idx);
3117 SpaceId dest_space_id = space_id(dest_addr);
3118 ObjectStartArray* start_array = _space_info[dest_space_id].start_array();
3119 HeapWord* new_top = _space_info[dest_space_id].new_top();
3120 assert(dest_addr < new_top, "sanity");
3121 const size_t words = MIN2(pointer_delta(new_top, dest_addr), RegionSize);
3123 // Get the source region and related info.
3124 size_t src_region_idx = region_ptr->source_region();
3125 SpaceId src_space_id = space_id(sd.region_to_addr(src_region_idx));
3126 HeapWord* src_space_top = _space_info[src_space_id].space()->top();
3128 MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3129 closure.set_source(first_src_addr(dest_addr, src_space_id, src_region_idx));
3131 // Adjust src_region_idx to prepare for decrementing destination counts (the
3132 // destination count is not decremented when a region is copied to itself).
3133 if (src_region_idx == region_idx) {
3134 src_region_idx += 1;
3135 }
3137 if (bitmap->is_unmarked(closure.source())) {
3138 // The first source word is in the middle of an object; copy the remainder
3139 // of the object or as much as will fit. The fact that pointer updates were
3140 // deferred will be noted when the object header is processed.
3141 HeapWord* const old_src_addr = closure.source();
3142 closure.copy_partial_obj();
3143 if (closure.is_full()) {
3144 decrement_destination_counts(cm, src_space_id, src_region_idx,
3145 closure.source());
3146 region_ptr->set_deferred_obj_addr(NULL);
3147 region_ptr->set_completed();
3148 return;
3149 }
3151 HeapWord* const end_addr = sd.region_align_down(closure.source());
3152 if (sd.region_align_down(old_src_addr) != end_addr) {
3153 // The partial object was copied from more than one source region.
3154 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3156 // Move to the next source region, possibly switching spaces as well. All
3157 // args except end_addr may be modified.
3158 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3159 end_addr);
3160 }
3161 }
3163 do {
3164 HeapWord* const cur_addr = closure.source();
3165 HeapWord* const end_addr = MIN2(sd.region_align_up(cur_addr + 1),
3166 src_space_top);
3167 IterationStatus status = bitmap->iterate(&closure, cur_addr, end_addr);
3169 if (status == ParMarkBitMap::incomplete) {
3170 // The last obj that starts in the source region does not end in the
3171 // region.
3172 assert(closure.source() < end_addr, "sanity");
3173 HeapWord* const obj_beg = closure.source();
3174 HeapWord* const range_end = MIN2(obj_beg + closure.words_remaining(),
3175 src_space_top);
3176 HeapWord* const obj_end = bitmap->find_obj_end(obj_beg, range_end);
3177 if (obj_end < range_end) {
3178 // The end was found; the entire object will fit.
3179 status = closure.do_addr(obj_beg, bitmap->obj_size(obj_beg, obj_end));
3180 assert(status != ParMarkBitMap::would_overflow, "sanity");
3181 } else {
3182 // The end was not found; the object will not fit.
3183 assert(range_end < src_space_top, "obj cannot cross space boundary");
3184 status = ParMarkBitMap::would_overflow;
3185 }
3186 }
3188 if (status == ParMarkBitMap::would_overflow) {
3189 // The last object did not fit. Note that interior oop updates were
3190 // deferred, then copy enough of the object to fill the region.
3191 region_ptr->set_deferred_obj_addr(closure.destination());
3192 status = closure.copy_until_full(); // copies from closure.source()
3194 decrement_destination_counts(cm, src_space_id, src_region_idx,
3195 closure.source());
3196 region_ptr->set_completed();
3197 return;
3198 }
3200 if (status == ParMarkBitMap::full) {
3201 decrement_destination_counts(cm, src_space_id, src_region_idx,
3202 closure.source());
3203 region_ptr->set_deferred_obj_addr(NULL);
3204 region_ptr->set_completed();
3205 return;
3206 }
3208 decrement_destination_counts(cm, src_space_id, src_region_idx, end_addr);
3210 // Move to the next source region, possibly switching spaces as well. All
3211 // args except end_addr may be modified.
3212 src_region_idx = next_src_region(closure, src_space_id, src_space_top,
3213 end_addr);
3214 } while (true);
3215 }
3217 void PSParallelCompact::fill_blocks(size_t region_idx)
3218 {
3219 // Fill in the block table elements for the specified region. Each block
3220 // table element holds the number of live words in the region that are to the
3221 // left of the first object that starts in the block. Thus only blocks in
3222 // which an object starts need to be filled.
3223 //
3224 // The algorithm scans the section of the bitmap that corresponds to the
3225 // region, keeping a running total of the live words. When an object start is
3226 // found, if it's the first to start in the block that contains it, the
3227 // current total is written to the block table element.
3228 const size_t Log2BlockSize = ParallelCompactData::Log2BlockSize;
3229 const size_t Log2RegionSize = ParallelCompactData::Log2RegionSize;
3230 const size_t RegionSize = ParallelCompactData::RegionSize;
3232 ParallelCompactData& sd = summary_data();
3233 const size_t partial_obj_size = sd.region(region_idx)->partial_obj_size();
3234 if (partial_obj_size >= RegionSize) {
3235 return; // No objects start in this region.
3236 }
3238 // Ensure the first loop iteration decides that the block has changed.
3239 size_t cur_block = sd.block_count();
3241 const ParMarkBitMap* const bitmap = mark_bitmap();
3243 const size_t Log2BitsPerBlock = Log2BlockSize - LogMinObjAlignment;
3244 assert((size_t)1 << Log2BitsPerBlock ==
3245 bitmap->words_to_bits(ParallelCompactData::BlockSize), "sanity");
3247 size_t beg_bit = bitmap->words_to_bits(region_idx << Log2RegionSize);
3248 const size_t range_end = beg_bit + bitmap->words_to_bits(RegionSize);
3249 size_t live_bits = bitmap->words_to_bits(partial_obj_size);
3250 beg_bit = bitmap->find_obj_beg(beg_bit + live_bits, range_end);
3251 while (beg_bit < range_end) {
3252 const size_t new_block = beg_bit >> Log2BitsPerBlock;
3253 if (new_block != cur_block) {
3254 cur_block = new_block;
3255 sd.block(cur_block)->set_offset(bitmap->bits_to_words(live_bits));
3256 }
3258 const size_t end_bit = bitmap->find_obj_end(beg_bit, range_end);
3259 if (end_bit < range_end - 1) {
3260 live_bits += end_bit - beg_bit + 1;
3261 beg_bit = bitmap->find_obj_beg(end_bit + 1, range_end);
3262 } else {
3263 return;
3264 }
3265 }
3266 }
3268 void
3269 PSParallelCompact::move_and_update(ParCompactionManager* cm, SpaceId space_id) {
3270 const MutableSpace* sp = space(space_id);
3271 if (sp->is_empty()) {
3272 return;
3273 }
3275 ParallelCompactData& sd = PSParallelCompact::summary_data();
3276 ParMarkBitMap* const bitmap = mark_bitmap();
3277 HeapWord* const dp_addr = dense_prefix(space_id);
3278 HeapWord* beg_addr = sp->bottom();
3279 HeapWord* end_addr = sp->top();
3281 assert(beg_addr <= dp_addr && dp_addr <= end_addr, "bad dense prefix");
3283 const size_t beg_region = sd.addr_to_region_idx(beg_addr);
3284 const size_t dp_region = sd.addr_to_region_idx(dp_addr);
3285 if (beg_region < dp_region) {
3286 update_and_deadwood_in_dense_prefix(cm, space_id, beg_region, dp_region);
3287 }
3289 // The destination of the first live object that starts in the region is one
3290 // past the end of the partial object entering the region (if any).
3291 HeapWord* const dest_addr = sd.partial_obj_end(dp_region);
3292 HeapWord* const new_top = _space_info[space_id].new_top();
3293 assert(new_top >= dest_addr, "bad new_top value");
3294 const size_t words = pointer_delta(new_top, dest_addr);
3296 if (words > 0) {
3297 ObjectStartArray* start_array = _space_info[space_id].start_array();
3298 MoveAndUpdateClosure closure(bitmap, cm, start_array, dest_addr, words);
3300 ParMarkBitMap::IterationStatus status;
3301 status = bitmap->iterate(&closure, dest_addr, end_addr);
3302 assert(status == ParMarkBitMap::full, "iteration not complete");
3303 assert(bitmap->find_obj_beg(closure.source(), end_addr) == end_addr,
3304 "live objects skipped because closure is full");
3305 }
3306 }
3308 jlong PSParallelCompact::millis_since_last_gc() {
3309 // We need a monotonically non-deccreasing time in ms but
3310 // os::javaTimeMillis() does not guarantee monotonicity.
3311 jlong now = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3312 jlong ret_val = now - _time_of_last_gc;
3313 // XXX See note in genCollectedHeap::millis_since_last_gc().
3314 if (ret_val < 0) {
3315 NOT_PRODUCT(warning("time warp: "INT64_FORMAT, ret_val);)
3316 return 0;
3317 }
3318 return ret_val;
3319 }
3321 void PSParallelCompact::reset_millis_since_last_gc() {
3322 // We need a monotonically non-deccreasing time in ms but
3323 // os::javaTimeMillis() does not guarantee monotonicity.
3324 _time_of_last_gc = os::javaTimeNanos() / NANOSECS_PER_MILLISEC;
3325 }
3327 ParMarkBitMap::IterationStatus MoveAndUpdateClosure::copy_until_full()
3328 {
3329 if (source() != destination()) {
3330 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3331 Copy::aligned_conjoint_words(source(), destination(), words_remaining());
3332 }
3333 update_state(words_remaining());
3334 assert(is_full(), "sanity");
3335 return ParMarkBitMap::full;
3336 }
3338 void MoveAndUpdateClosure::copy_partial_obj()
3339 {
3340 size_t words = words_remaining();
3342 HeapWord* const range_end = MIN2(source() + words, bitmap()->region_end());
3343 HeapWord* const end_addr = bitmap()->find_obj_end(source(), range_end);
3344 if (end_addr < range_end) {
3345 words = bitmap()->obj_size(source(), end_addr);
3346 }
3348 // This test is necessary; if omitted, the pointer updates to a partial object
3349 // that crosses the dense prefix boundary could be overwritten.
3350 if (source() != destination()) {
3351 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3352 Copy::aligned_conjoint_words(source(), destination(), words);
3353 }
3354 update_state(words);
3355 }
3357 ParMarkBitMapClosure::IterationStatus
3358 MoveAndUpdateClosure::do_addr(HeapWord* addr, size_t words) {
3359 assert(destination() != NULL, "sanity");
3360 assert(bitmap()->obj_size(addr) == words, "bad size");
3362 _source = addr;
3363 assert(PSParallelCompact::summary_data().calc_new_pointer(source()) ==
3364 destination(), "wrong destination");
3366 if (words > words_remaining()) {
3367 return ParMarkBitMap::would_overflow;
3368 }
3370 // The start_array must be updated even if the object is not moving.
3371 if (_start_array != NULL) {
3372 _start_array->allocate_block(destination());
3373 }
3375 if (destination() != source()) {
3376 DEBUG_ONLY(PSParallelCompact::check_new_location(source(), destination());)
3377 Copy::aligned_conjoint_words(source(), destination(), words);
3378 }
3380 oop moved_oop = (oop) destination();
3381 moved_oop->update_contents(compaction_manager());
3382 assert(moved_oop->is_oop_or_null(), "Object should be whole at this point");
3384 update_state(words);
3385 assert(destination() == (HeapWord*)moved_oop + moved_oop->size(), "sanity");
3386 return is_full() ? ParMarkBitMap::full : ParMarkBitMap::incomplete;
3387 }
3389 UpdateOnlyClosure::UpdateOnlyClosure(ParMarkBitMap* mbm,
3390 ParCompactionManager* cm,
3391 PSParallelCompact::SpaceId space_id) :
3392 ParMarkBitMapClosure(mbm, cm),
3393 _space_id(space_id),
3394 _start_array(PSParallelCompact::start_array(space_id))
3395 {
3396 }
3398 // Updates the references in the object to their new values.
3399 ParMarkBitMapClosure::IterationStatus
3400 UpdateOnlyClosure::do_addr(HeapWord* addr, size_t words) {
3401 do_addr(addr);
3402 return ParMarkBitMap::incomplete;
3403 }