1 /*
2 * Copyright (c) 2005, 2019, 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 *
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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 *
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16 * 2 along with this work; if not, write to the Free Software Foundation,
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23 */
24
25 #ifndef SHARE_GC_PARALLEL_PSPARALLELCOMPACT_HPP
26 #define SHARE_GC_PARALLEL_PSPARALLELCOMPACT_HPP
27
28 #include "gc/parallel/mutableSpace.hpp"
29 #include "gc/parallel/objectStartArray.hpp"
30 #include "gc/parallel/parMarkBitMap.hpp"
31 #include "gc/parallel/parallelScavengeHeap.hpp"
32 #include "gc/shared/collectedHeap.hpp"
33 #include "gc/shared/collectorCounters.hpp"
34 #include "gc/shared/taskqueue.hpp"
35 #include "oops/oop.hpp"
36
37 class ParallelScavengeHeap;
38 class PSAdaptiveSizePolicy;
39 class PSYoungGen;
40 class PSOldGen;
41 class ParCompactionManager;
42 class ParallelTaskTerminator;
43 class PSParallelCompact;
44 class GCTaskManager;
45 class GCTaskQueue;
46 class PreGCValues;
47 class MoveAndUpdateClosure;
48 class RefProcTaskExecutor;
49 class ParallelOldTracer;
50 class STWGCTimer;
51
52 // The SplitInfo class holds the information needed to 'split' a source region
53 // so that the live data can be copied to two destination *spaces*. Normally,
54 // all the live data in a region is copied to a single destination space (e.g.,
55 // everything live in a region in eden is copied entirely into the old gen).
56 // However, when the heap is nearly full, all the live data in eden may not fit
57 // into the old gen. Copying only some of the regions from eden to old gen
58 // requires finding a region that does not contain a partial object (i.e., no
59 // live object crosses the region boundary) somewhere near the last object that
60 // does fit into the old gen. Since it's not always possible to find such a
61 // region, splitting is necessary for predictable behavior.
62 //
63 // A region is always split at the end of the partial object. This avoids
64 // additional tests when calculating the new location of a pointer, which is a
65 // very hot code path. The partial object and everything to its left will be
66 // copied to another space (call it dest_space_1). The live data to the right
67 // of the partial object will be copied either within the space itself, or to a
68 // different destination space (distinct from dest_space_1).
69 //
70 // Split points are identified during the summary phase, when region
71 // destinations are computed: data about the split, including the
72 // partial_object_size, is recorded in a SplitInfo record and the
73 // partial_object_size field in the summary data is set to zero. The zeroing is
74 // possible (and necessary) since the partial object will move to a different
75 // destination space than anything to its right, thus the partial object should
76 // not affect the locations of any objects to its right.
77 //
78 // The recorded data is used during the compaction phase, but only rarely: when
79 // the partial object on the split region will be copied across a destination
80 // region boundary. This test is made once each time a region is filled, and is
81 // a simple address comparison, so the overhead is negligible (see
82 // PSParallelCompact::first_src_addr()).
83 //
84 // Notes:
85 //
86 // Only regions with partial objects are split; a region without a partial
87 // object does not need any extra bookkeeping.
88 //
89 // At most one region is split per space, so the amount of data required is
90 // constant.
91 //
92 // A region is split only when the destination space would overflow. Once that
93 // happens, the destination space is abandoned and no other data (even from
94 // other source spaces) is targeted to that destination space. Abandoning the
95 // destination space may leave a somewhat large unused area at the end, if a
96 // large object caused the overflow.
97 //
98 // Future work:
99 //
100 // More bookkeeping would be required to continue to use the destination space.
101 // The most general solution would allow data from regions in two different
102 // source spaces to be "joined" in a single destination region. At the very
103 // least, additional code would be required in next_src_region() to detect the
104 // join and skip to an out-of-order source region. If the join region was also
105 // the last destination region to which a split region was copied (the most
106 // likely case), then additional work would be needed to get fill_region() to
107 // stop iteration and switch to a new source region at the right point. Basic
108 // idea would be to use a fake value for the top of the source space. It is
109 // doable, if a bit tricky.
110 //
111 // A simpler (but less general) solution would fill the remainder of the
112 // destination region with a dummy object and continue filling the next
113 // destination region.
114
115 class SplitInfo
116 {
117 public:
118 // Return true if this split info is valid (i.e., if a split has been
119 // recorded). The very first region cannot have a partial object and thus is
120 // never split, so 0 is the 'invalid' value.
121 bool is_valid() const { return _src_region_idx > 0; }
122
123 // Return true if this split holds data for the specified source region.
124 inline bool is_split(size_t source_region) const;
125
126 // The index of the split region, the size of the partial object on that
127 // region and the destination of the partial object.
128 size_t src_region_idx() const { return _src_region_idx; }
129 size_t partial_obj_size() const { return _partial_obj_size; }
130 HeapWord* destination() const { return _destination; }
131
132 // The destination count of the partial object referenced by this split
133 // (either 1 or 2). This must be added to the destination count of the
134 // remainder of the source region.
135 unsigned int destination_count() const { return _destination_count; }
136
137 // If a word within the partial object will be written to the first word of a
138 // destination region, this is the address of the destination region;
139 // otherwise this is NULL.
140 HeapWord* dest_region_addr() const { return _dest_region_addr; }
141
142 // If a word within the partial object will be written to the first word of a
143 // destination region, this is the address of that word within the partial
144 // object; otherwise this is NULL.
145 HeapWord* first_src_addr() const { return _first_src_addr; }
146
147 // Record the data necessary to split the region src_region_idx.
148 void record(size_t src_region_idx, size_t partial_obj_size,
149 HeapWord* destination);
150
151 void clear();
152
153 DEBUG_ONLY(void verify_clear();)
154
155 private:
156 size_t _src_region_idx;
157 size_t _partial_obj_size;
158 HeapWord* _destination;
159 unsigned int _destination_count;
160 HeapWord* _dest_region_addr;
161 HeapWord* _first_src_addr;
162 };
163
164 inline bool SplitInfo::is_split(size_t region_idx) const
165 {
166 return _src_region_idx == region_idx && is_valid();
167 }
168
169 class SpaceInfo
170 {
171 public:
172 MutableSpace* space() const { return _space; }
173
174 // Where the free space will start after the collection. Valid only after the
175 // summary phase completes.
176 HeapWord* new_top() const { return _new_top; }
177
178 // Allows new_top to be set.
179 HeapWord** new_top_addr() { return &_new_top; }
180
181 // Where the smallest allowable dense prefix ends (used only for perm gen).
182 HeapWord* min_dense_prefix() const { return _min_dense_prefix; }
183
184 // Where the dense prefix ends, or the compacted region begins.
185 HeapWord* dense_prefix() const { return _dense_prefix; }
186
187 // The start array for the (generation containing the) space, or NULL if there
188 // is no start array.
189 ObjectStartArray* start_array() const { return _start_array; }
190
191 SplitInfo& split_info() { return _split_info; }
192
193 void set_space(MutableSpace* s) { _space = s; }
194 void set_new_top(HeapWord* addr) { _new_top = addr; }
195 void set_min_dense_prefix(HeapWord* addr) { _min_dense_prefix = addr; }
196 void set_dense_prefix(HeapWord* addr) { _dense_prefix = addr; }
197 void set_start_array(ObjectStartArray* s) { _start_array = s; }
198
199 void publish_new_top() const { _space->set_top(_new_top); }
200
201 private:
202 MutableSpace* _space;
203 HeapWord* _new_top;
204 HeapWord* _min_dense_prefix;
205 HeapWord* _dense_prefix;
206 ObjectStartArray* _start_array;
207 SplitInfo _split_info;
208 };
209
210 class ParallelCompactData
211 {
212 public:
213 // Sizes are in HeapWords, unless indicated otherwise.
214 static const size_t Log2RegionSize;
215 static const size_t RegionSize;
216 static const size_t RegionSizeBytes;
217
218 // Mask for the bits in a size_t to get an offset within a region.
219 static const size_t RegionSizeOffsetMask;
220 // Mask for the bits in a pointer to get an offset within a region.
221 static const size_t RegionAddrOffsetMask;
222 // Mask for the bits in a pointer to get the address of the start of a region.
223 static const size_t RegionAddrMask;
224
225 static const size_t Log2BlockSize;
226 static const size_t BlockSize;
227 static const size_t BlockSizeBytes;
228
229 static const size_t BlockSizeOffsetMask;
230 static const size_t BlockAddrOffsetMask;
231 static const size_t BlockAddrMask;
232
233 static const size_t BlocksPerRegion;
234 static const size_t Log2BlocksPerRegion;
235
236 class RegionData
237 {
238 public:
239 // Destination address of the region.
240 HeapWord* destination() const { return _destination; }
241
242 // The first region containing data destined for this region.
243 size_t source_region() const { return _source_region; }
244
245 // The object (if any) starting in this region and ending in a different
246 // region that could not be updated during the main (parallel) compaction
247 // phase. This is different from _partial_obj_addr, which is an object that
248 // extends onto a source region. However, the two uses do not overlap in
249 // time, so the same field is used to save space.
250 HeapWord* deferred_obj_addr() const { return _partial_obj_addr; }
251
252 // The starting address of the partial object extending onto the region.
253 HeapWord* partial_obj_addr() const { return _partial_obj_addr; }
254
255 // Size of the partial object extending onto the region (words).
256 size_t partial_obj_size() const { return _partial_obj_size; }
257
258 // Size of live data that lies within this region due to objects that start
259 // in this region (words). This does not include the partial object
260 // extending onto the region (if any), or the part of an object that extends
261 // onto the next region (if any).
262 size_t live_obj_size() const { return _dc_and_los & los_mask; }
263
264 // Total live data that lies within the region (words).
265 size_t data_size() const { return partial_obj_size() + live_obj_size(); }
266
267 // The destination_count is the number of other regions to which data from
268 // this region will be copied. At the end of the summary phase, the valid
269 // values of destination_count are
270 //
271 // 0 - data from the region will be compacted completely into itself, or the
272 // region is empty. The region can be claimed and then filled.
273 // 1 - data from the region will be compacted into 1 other region; some
274 // data from the region may also be compacted into the region itself.
275 // 2 - data from the region will be copied to 2 other regions.
276 //
277 // During compaction as regions are emptied, the destination_count is
278 // decremented (atomically) and when it reaches 0, it can be claimed and
279 // then filled.
280 //
281 // A region is claimed for processing by atomically changing the
282 // destination_count to the claimed value (dc_claimed). After a region has
283 // been filled, the destination_count should be set to the completed value
284 // (dc_completed).
285 inline uint destination_count() const;
286 inline uint destination_count_raw() const;
287
288 // Whether the block table for this region has been filled.
289 inline bool blocks_filled() const;
290
291 // Number of times the block table was filled.
292 DEBUG_ONLY(inline size_t blocks_filled_count() const;)
293
294 // The location of the java heap data that corresponds to this region.
295 inline HeapWord* data_location() const;
296
297 // The highest address referenced by objects in this region.
298 inline HeapWord* highest_ref() const;
299
300 // Whether this region is available to be claimed, has been claimed, or has
301 // been completed.
302 //
303 // Minor subtlety: claimed() returns true if the region is marked
304 // completed(), which is desirable since a region must be claimed before it
305 // can be completed.
306 bool available() const { return _dc_and_los < dc_one; }
307 bool claimed() const { return _dc_and_los >= dc_claimed; }
308 bool completed() const { return _dc_and_los >= dc_completed; }
309
310 // These are not atomic.
311 void set_destination(HeapWord* addr) { _destination = addr; }
312 void set_source_region(size_t region) { _source_region = region; }
313 void set_deferred_obj_addr(HeapWord* addr) { _partial_obj_addr = addr; }
314 void set_partial_obj_addr(HeapWord* addr) { _partial_obj_addr = addr; }
315 void set_partial_obj_size(size_t words) {
316 _partial_obj_size = (region_sz_t) words;
317 }
318 inline void set_blocks_filled();
319
320 inline void set_destination_count(uint count);
321 inline void set_live_obj_size(size_t words);
322 inline void set_data_location(HeapWord* addr);
323 inline void set_completed();
324 inline bool claim_unsafe();
325
326 // These are atomic.
327 inline void add_live_obj(size_t words);
328 inline void set_highest_ref(HeapWord* addr);
329 inline void decrement_destination_count();
330 inline bool claim();
331
332 private:
333 // The type used to represent object sizes within a region.
334 typedef uint region_sz_t;
335
336 // Constants for manipulating the _dc_and_los field, which holds both the
337 // destination count and live obj size. The live obj size lives at the
338 // least significant end so no masking is necessary when adding.
339 static const region_sz_t dc_shift; // Shift amount.
340 static const region_sz_t dc_mask; // Mask for destination count.
341 static const region_sz_t dc_one; // 1, shifted appropriately.
342 static const region_sz_t dc_claimed; // Region has been claimed.
343 static const region_sz_t dc_completed; // Region has been completed.
344 static const region_sz_t los_mask; // Mask for live obj size.
345
346 HeapWord* _destination;
347 size_t _source_region;
348 HeapWord* _partial_obj_addr;
349 region_sz_t _partial_obj_size;
350 region_sz_t volatile _dc_and_los;
351 bool volatile _blocks_filled;
352
353 #ifdef ASSERT
354 size_t _blocks_filled_count; // Number of block table fills.
355
356 // These enable optimizations that are only partially implemented. Use
357 // debug builds to prevent the code fragments from breaking.
358 HeapWord* _data_location;
359 HeapWord* _highest_ref;
360 #endif // #ifdef ASSERT
361
362 #ifdef ASSERT
363 public:
364 uint _pushed; // 0 until region is pushed onto a stack
365 private:
366 #endif
367 };
368
369 // "Blocks" allow shorter sections of the bitmap to be searched. Each Block
370 // holds an offset, which is the amount of live data in the Region to the left
371 // of the first live object that starts in the Block.
372 class BlockData
373 {
374 public:
375 typedef unsigned short int blk_ofs_t;
376
377 blk_ofs_t offset() const { return _offset; }
378 void set_offset(size_t val) { _offset = (blk_ofs_t)val; }
379
380 private:
381 blk_ofs_t _offset;
382 };
383
384 public:
385 ParallelCompactData();
386 bool initialize(MemRegion covered_region);
387
388 size_t region_count() const { return _region_count; }
389 size_t reserved_byte_size() const { return _reserved_byte_size; }
390
391 // Convert region indices to/from RegionData pointers.
392 inline RegionData* region(size_t region_idx) const;
393 inline size_t region(const RegionData* const region_ptr) const;
394
395 size_t block_count() const { return _block_count; }
396 inline BlockData* block(size_t block_idx) const;
397 inline size_t block(const BlockData* block_ptr) const;
398
399 void add_obj(HeapWord* addr, size_t len);
400 void add_obj(oop p, size_t len) { add_obj((HeapWord*)p, len); }
401
402 // Fill in the regions covering [beg, end) so that no data moves; i.e., the
403 // destination of region n is simply the start of region n. The argument beg
404 // must be region-aligned; end need not be.
405 void summarize_dense_prefix(HeapWord* beg, HeapWord* end);
406
407 HeapWord* summarize_split_space(size_t src_region, SplitInfo& split_info,
408 HeapWord* destination, HeapWord* target_end,
409 HeapWord** target_next);
410 bool summarize(SplitInfo& split_info,
411 HeapWord* source_beg, HeapWord* source_end,
412 HeapWord** source_next,
413 HeapWord* target_beg, HeapWord* target_end,
414 HeapWord** target_next);
415
416 void clear();
417 void clear_range(size_t beg_region, size_t end_region);
418 void clear_range(HeapWord* beg, HeapWord* end) {
419 clear_range(addr_to_region_idx(beg), addr_to_region_idx(end));
420 }
421
422 // Return the number of words between addr and the start of the region
423 // containing addr.
424 inline size_t region_offset(const HeapWord* addr) const;
425
426 // Convert addresses to/from a region index or region pointer.
427 inline size_t addr_to_region_idx(const HeapWord* addr) const;
428 inline RegionData* addr_to_region_ptr(const HeapWord* addr) const;
429 inline HeapWord* region_to_addr(size_t region) const;
430 inline HeapWord* region_to_addr(size_t region, size_t offset) const;
431 inline HeapWord* region_to_addr(const RegionData* region) const;
432
433 inline HeapWord* region_align_down(HeapWord* addr) const;
434 inline HeapWord* region_align_up(HeapWord* addr) const;
435 inline bool is_region_aligned(HeapWord* addr) const;
436
437 // Analogous to region_offset() for blocks.
438 size_t block_offset(const HeapWord* addr) const;
439 size_t addr_to_block_idx(const HeapWord* addr) const;
440 size_t addr_to_block_idx(const oop obj) const {
441 return addr_to_block_idx((HeapWord*) obj);
442 }
443 inline BlockData* addr_to_block_ptr(const HeapWord* addr) const;
444 inline HeapWord* block_to_addr(size_t block) const;
445 inline size_t region_to_block_idx(size_t region) const;
446
447 inline HeapWord* block_align_down(HeapWord* addr) const;
448 inline HeapWord* block_align_up(HeapWord* addr) const;
449 inline bool is_block_aligned(HeapWord* addr) const;
450
451 // Return the address one past the end of the partial object.
452 HeapWord* partial_obj_end(size_t region_idx) const;
453
454 // Return the location of the object after compaction.
455 HeapWord* calc_new_pointer(HeapWord* addr, ParCompactionManager* cm);
456
457 HeapWord* calc_new_pointer(oop p, ParCompactionManager* cm) {
458 return calc_new_pointer((HeapWord*) p, cm);
459 }
460
461 #ifdef ASSERT
462 void verify_clear(const PSVirtualSpace* vspace);
463 void verify_clear();
464 #endif // #ifdef ASSERT
465
466 private:
467 bool initialize_block_data();
468 bool initialize_region_data(size_t region_size);
469 PSVirtualSpace* create_vspace(size_t count, size_t element_size);
470
471 private:
472 HeapWord* _region_start;
473 #ifdef ASSERT
474 HeapWord* _region_end;
475 #endif // #ifdef ASSERT
476
477 PSVirtualSpace* _region_vspace;
478 size_t _reserved_byte_size;
479 RegionData* _region_data;
480 size_t _region_count;
481
482 PSVirtualSpace* _block_vspace;
483 BlockData* _block_data;
484 size_t _block_count;
485 };
486
487 inline uint
488 ParallelCompactData::RegionData::destination_count_raw() const
489 {
490 return _dc_and_los & dc_mask;
491 }
492
493 inline uint
494 ParallelCompactData::RegionData::destination_count() const
495 {
496 return destination_count_raw() >> dc_shift;
497 }
498
499 inline bool
500 ParallelCompactData::RegionData::blocks_filled() const
501 {
502 bool result = _blocks_filled;
503 OrderAccess::acquire();
504 return result;
505 }
506
507 #ifdef ASSERT
508 inline size_t
509 ParallelCompactData::RegionData::blocks_filled_count() const
510 {
511 return _blocks_filled_count;
512 }
513 #endif // #ifdef ASSERT
514
515 inline void
516 ParallelCompactData::RegionData::set_blocks_filled()
517 {
518 OrderAccess::release();
519 _blocks_filled = true;
520 // Debug builds count the number of times the table was filled.
521 DEBUG_ONLY(Atomic::inc(&_blocks_filled_count));
522 }
523
524 inline void
525 ParallelCompactData::RegionData::set_destination_count(uint count)
526 {
527 assert(count <= (dc_completed >> dc_shift), "count too large");
528 const region_sz_t live_sz = (region_sz_t) live_obj_size();
529 _dc_and_los = (count << dc_shift) | live_sz;
530 }
531
532 inline void ParallelCompactData::RegionData::set_live_obj_size(size_t words)
533 {
534 assert(words <= los_mask, "would overflow");
535 _dc_and_los = destination_count_raw() | (region_sz_t)words;
536 }
537
538 inline void ParallelCompactData::RegionData::decrement_destination_count()
539 {
540 assert(_dc_and_los < dc_claimed, "already claimed");
541 assert(_dc_and_los >= dc_one, "count would go negative");
542 Atomic::add(dc_mask, &_dc_and_los);
543 }
544
545 inline HeapWord* ParallelCompactData::RegionData::data_location() const
546 {
547 DEBUG_ONLY(return _data_location;)
548 NOT_DEBUG(return NULL;)
549 }
550
551 inline HeapWord* ParallelCompactData::RegionData::highest_ref() const
552 {
553 DEBUG_ONLY(return _highest_ref;)
554 NOT_DEBUG(return NULL;)
555 }
556
557 inline void ParallelCompactData::RegionData::set_data_location(HeapWord* addr)
558 {
559 DEBUG_ONLY(_data_location = addr;)
560 }
561
562 inline void ParallelCompactData::RegionData::set_completed()
563 {
564 assert(claimed(), "must be claimed first");
565 _dc_and_los = dc_completed | (region_sz_t) live_obj_size();
566 }
567
568 // MT-unsafe claiming of a region. Should only be used during single threaded
569 // execution.
570 inline bool ParallelCompactData::RegionData::claim_unsafe()
571 {
572 if (available()) {
573 _dc_and_los |= dc_claimed;
574 return true;
575 }
576 return false;
577 }
578
579 inline void ParallelCompactData::RegionData::add_live_obj(size_t words)
580 {
581 assert(words <= (size_t)los_mask - live_obj_size(), "overflow");
582 Atomic::add(static_cast<region_sz_t>(words), &_dc_and_los);
583 }
584
585 inline void ParallelCompactData::RegionData::set_highest_ref(HeapWord* addr)
586 {
587 #ifdef ASSERT
588 HeapWord* tmp = _highest_ref;
589 while (addr > tmp) {
590 tmp = Atomic::cmpxchg(addr, &_highest_ref, tmp);
591 }
592 #endif // #ifdef ASSERT
593 }
594
595 inline bool ParallelCompactData::RegionData::claim()
596 {
597 const region_sz_t los = static_cast<region_sz_t>(live_obj_size());
598 const region_sz_t old = Atomic::cmpxchg(dc_claimed | los, &_dc_and_los, los);
599 return old == los;
600 }
601
602 inline ParallelCompactData::RegionData*
603 ParallelCompactData::region(size_t region_idx) const
604 {
605 assert(region_idx <= region_count(), "bad arg");
606 return _region_data + region_idx;
607 }
608
609 inline size_t
610 ParallelCompactData::region(const RegionData* const region_ptr) const
611 {
612 assert(region_ptr >= _region_data, "bad arg");
613 assert(region_ptr <= _region_data + region_count(), "bad arg");
614 return pointer_delta(region_ptr, _region_data, sizeof(RegionData));
615 }
616
617 inline ParallelCompactData::BlockData*
618 ParallelCompactData::block(size_t n) const {
619 assert(n < block_count(), "bad arg");
620 return _block_data + n;
621 }
622
623 inline size_t
624 ParallelCompactData::region_offset(const HeapWord* addr) const
625 {
626 assert(addr >= _region_start, "bad addr");
627 assert(addr <= _region_end, "bad addr");
628 return (size_t(addr) & RegionAddrOffsetMask) >> LogHeapWordSize;
629 }
630
631 inline size_t
632 ParallelCompactData::addr_to_region_idx(const HeapWord* addr) const
633 {
634 assert(addr >= _region_start, "bad addr " PTR_FORMAT " _region_start " PTR_FORMAT, p2i(addr), p2i(_region_start));
635 assert(addr <= _region_end, "bad addr " PTR_FORMAT " _region_end " PTR_FORMAT, p2i(addr), p2i(_region_end));
636 return pointer_delta(addr, _region_start) >> Log2RegionSize;
637 }
638
639 inline ParallelCompactData::RegionData*
640 ParallelCompactData::addr_to_region_ptr(const HeapWord* addr) const
641 {
642 return region(addr_to_region_idx(addr));
643 }
644
645 inline HeapWord*
646 ParallelCompactData::region_to_addr(size_t region) const
647 {
648 assert(region <= _region_count, "region out of range");
649 return _region_start + (region << Log2RegionSize);
650 }
651
652 inline HeapWord*
653 ParallelCompactData::region_to_addr(const RegionData* region) const
654 {
655 return region_to_addr(pointer_delta(region, _region_data,
656 sizeof(RegionData)));
657 }
658
659 inline HeapWord*
660 ParallelCompactData::region_to_addr(size_t region, size_t offset) const
661 {
662 assert(region <= _region_count, "region out of range");
663 assert(offset < RegionSize, "offset too big"); // This may be too strict.
664 return region_to_addr(region) + offset;
665 }
666
667 inline HeapWord*
668 ParallelCompactData::region_align_down(HeapWord* addr) const
669 {
670 assert(addr >= _region_start, "bad addr");
671 assert(addr < _region_end + RegionSize, "bad addr");
672 return (HeapWord*)(size_t(addr) & RegionAddrMask);
673 }
674
675 inline HeapWord*
676 ParallelCompactData::region_align_up(HeapWord* addr) const
677 {
678 assert(addr >= _region_start, "bad addr");
679 assert(addr <= _region_end, "bad addr");
680 return region_align_down(addr + RegionSizeOffsetMask);
681 }
682
683 inline bool
684 ParallelCompactData::is_region_aligned(HeapWord* addr) const
685 {
686 return region_offset(addr) == 0;
687 }
688
689 inline size_t
690 ParallelCompactData::block_offset(const HeapWord* addr) const
691 {
692 assert(addr >= _region_start, "bad addr");
693 assert(addr <= _region_end, "bad addr");
694 return (size_t(addr) & BlockAddrOffsetMask) >> LogHeapWordSize;
695 }
696
697 inline size_t
698 ParallelCompactData::addr_to_block_idx(const HeapWord* addr) const
699 {
700 assert(addr >= _region_start, "bad addr");
701 assert(addr <= _region_end, "bad addr");
702 return pointer_delta(addr, _region_start) >> Log2BlockSize;
703 }
704
705 inline ParallelCompactData::BlockData*
706 ParallelCompactData::addr_to_block_ptr(const HeapWord* addr) const
707 {
708 return block(addr_to_block_idx(addr));
709 }
710
711 inline HeapWord*
712 ParallelCompactData::block_to_addr(size_t block) const
713 {
714 assert(block < _block_count, "block out of range");
715 return _region_start + (block << Log2BlockSize);
716 }
717
718 inline size_t
719 ParallelCompactData::region_to_block_idx(size_t region) const
720 {
721 return region << Log2BlocksPerRegion;
722 }
723
724 inline HeapWord*
725 ParallelCompactData::block_align_down(HeapWord* addr) const
726 {
727 assert(addr >= _region_start, "bad addr");
728 assert(addr < _region_end + RegionSize, "bad addr");
729 return (HeapWord*)(size_t(addr) & BlockAddrMask);
730 }
731
732 inline HeapWord*
733 ParallelCompactData::block_align_up(HeapWord* addr) const
734 {
735 assert(addr >= _region_start, "bad addr");
736 assert(addr <= _region_end, "bad addr");
737 return block_align_down(addr + BlockSizeOffsetMask);
738 }
739
740 inline bool
741 ParallelCompactData::is_block_aligned(HeapWord* addr) const
742 {
743 return block_offset(addr) == 0;
744 }
745
746 // Abstract closure for use with ParMarkBitMap::iterate(), which will invoke the
747 // do_addr() method.
748 //
749 // The closure is initialized with the number of heap words to process
750 // (words_remaining()), and becomes 'full' when it reaches 0. The do_addr()
751 // methods in subclasses should update the total as words are processed. Since
752 // only one subclass actually uses this mechanism to terminate iteration, the
753 // default initial value is > 0. The implementation is here and not in the
754 // single subclass that uses it to avoid making is_full() virtual, and thus
755 // adding a virtual call per live object.
756
757 class ParMarkBitMapClosure: public StackObj {
758 public:
759 typedef ParMarkBitMap::idx_t idx_t;
760 typedef ParMarkBitMap::IterationStatus IterationStatus;
761
762 public:
763 inline ParMarkBitMapClosure(ParMarkBitMap* mbm, ParCompactionManager* cm,
764 size_t words = max_uintx);
765
766 inline ParCompactionManager* compaction_manager() const;
767 inline ParMarkBitMap* bitmap() const;
768 inline size_t words_remaining() const;
769 inline bool is_full() const;
770 inline HeapWord* source() const;
771
772 inline void set_source(HeapWord* addr);
773
774 virtual IterationStatus do_addr(HeapWord* addr, size_t words) = 0;
775
776 protected:
777 inline void decrement_words_remaining(size_t words);
778
779 private:
780 ParMarkBitMap* const _bitmap;
781 ParCompactionManager* const _compaction_manager;
782 DEBUG_ONLY(const size_t _initial_words_remaining;) // Useful in debugger.
783 size_t _words_remaining; // Words left to copy.
784
785 protected:
786 HeapWord* _source; // Next addr that would be read.
787 };
788
789 inline
790 ParMarkBitMapClosure::ParMarkBitMapClosure(ParMarkBitMap* bitmap,
791 ParCompactionManager* cm,
792 size_t words):
793 _bitmap(bitmap), _compaction_manager(cm)
794 #ifdef ASSERT
795 , _initial_words_remaining(words)
796 #endif
797 {
798 _words_remaining = words;
799 _source = NULL;
800 }
801
802 inline ParCompactionManager* ParMarkBitMapClosure::compaction_manager() const {
803 return _compaction_manager;
804 }
805
806 inline ParMarkBitMap* ParMarkBitMapClosure::bitmap() const {
807 return _bitmap;
808 }
809
810 inline size_t ParMarkBitMapClosure::words_remaining() const {
811 return _words_remaining;
812 }
813
814 inline bool ParMarkBitMapClosure::is_full() const {
815 return words_remaining() == 0;
816 }
817
818 inline HeapWord* ParMarkBitMapClosure::source() const {
819 return _source;
820 }
821
822 inline void ParMarkBitMapClosure::set_source(HeapWord* addr) {
823 _source = addr;
824 }
825
826 inline void ParMarkBitMapClosure::decrement_words_remaining(size_t words) {
827 assert(_words_remaining >= words, "processed too many words");
828 _words_remaining -= words;
829 }
830
831 // The UseParallelOldGC collector is a stop-the-world garbage collector that
832 // does parts of the collection using parallel threads. The collection includes
833 // the tenured generation and the young generation. The permanent generation is
834 // collected at the same time as the other two generations but the permanent
835 // generation is collect by a single GC thread. The permanent generation is
836 // collected serially because of the requirement that during the processing of a
837 // klass AAA, any objects reference by AAA must already have been processed.
838 // This requirement is enforced by a left (lower address) to right (higher
839 // address) sliding compaction.
840 //
841 // There are four phases of the collection.
842 //
843 // - marking phase
844 // - summary phase
845 // - compacting phase
846 // - clean up phase
847 //
848 // Roughly speaking these phases correspond, respectively, to
849 // - mark all the live objects
850 // - calculate the destination of each object at the end of the collection
851 // - move the objects to their destination
852 // - update some references and reinitialize some variables
853 //
854 // These three phases are invoked in PSParallelCompact::invoke_no_policy(). The
855 // marking phase is implemented in PSParallelCompact::marking_phase() and does a
856 // complete marking of the heap. The summary phase is implemented in
857 // PSParallelCompact::summary_phase(). The move and update phase is implemented
858 // in PSParallelCompact::compact().
859 //
860 // A space that is being collected is divided into regions and with each region
861 // is associated an object of type ParallelCompactData. Each region is of a
862 // fixed size and typically will contain more than 1 object and may have parts
863 // of objects at the front and back of the region.
864 //
865 // region -----+---------------------+----------
866 // objects covered [ AAA )[ BBB )[ CCC )[ DDD )
867 //
868 // The marking phase does a complete marking of all live objects in the heap.
869 // The marking also compiles the size of the data for all live objects covered
870 // by the region. This size includes the part of any live object spanning onto
871 // the region (part of AAA if it is live) from the front, all live objects
872 // contained in the region (BBB and/or CCC if they are live), and the part of
873 // any live objects covered by the region that extends off the region (part of
874 // DDD if it is live). The marking phase uses multiple GC threads and marking
875 // is done in a bit array of type ParMarkBitMap. The marking of the bit map is
876 // done atomically as is the accumulation of the size of the live objects
877 // covered by a region.
878 //
879 // The summary phase calculates the total live data to the left of each region
880 // XXX. Based on that total and the bottom of the space, it can calculate the
881 // starting location of the live data in XXX. The summary phase calculates for
882 // each region XXX quantities such as
883 //
884 // - the amount of live data at the beginning of a region from an object
885 // entering the region.
886 // - the location of the first live data on the region
887 // - a count of the number of regions receiving live data from XXX.
888 //
889 // See ParallelCompactData for precise details. The summary phase also
890 // calculates the dense prefix for the compaction. The dense prefix is a
891 // portion at the beginning of the space that is not moved. The objects in the
892 // dense prefix do need to have their object references updated. See method
893 // summarize_dense_prefix().
894 //
895 // The summary phase is done using 1 GC thread.
896 //
897 // The compaction phase moves objects to their new location and updates all
898 // references in the object.
899 //
900 // A current exception is that objects that cross a region boundary are moved
901 // but do not have their references updated. References are not updated because
902 // it cannot easily be determined if the klass pointer KKK for the object AAA
903 // has been updated. KKK likely resides in a region to the left of the region
904 // containing AAA. These AAA's have there references updated at the end in a
905 // clean up phase. See the method PSParallelCompact::update_deferred_objects().
906 // An alternate strategy is being investigated for this deferral of updating.
907 //
908 // Compaction is done on a region basis. A region that is ready to be filled is
909 // put on a ready list and GC threads take region off the list and fill them. A
910 // region is ready to be filled if it empty of live objects. Such a region may
911 // have been initially empty (only contained dead objects) or may have had all
912 // its live objects copied out already. A region that compacts into itself is
913 // also ready for filling. The ready list is initially filled with empty
914 // regions and regions compacting into themselves. There is always at least 1
915 // region that can be put on the ready list. The regions are atomically added
916 // and removed from the ready list.
917
918 class TaskQueue;
919
920 class PSParallelCompact : AllStatic {
921 public:
922 // Convenient access to type names.
923 typedef ParMarkBitMap::idx_t idx_t;
924 typedef ParallelCompactData::RegionData RegionData;
925 typedef ParallelCompactData::BlockData BlockData;
926
927 typedef enum {
928 old_space_id, eden_space_id,
929 from_space_id, to_space_id, last_space_id
930 } SpaceId;
931
932 struct UpdateDensePrefixTask : public CHeapObj<mtGC> {
933 SpaceId _space_id;
934 size_t _region_index_start;
935 size_t _region_index_end;
936
937 UpdateDensePrefixTask()
938 : _space_id(SpaceId(0)),
939 _region_index_start(0),
940 _region_index_end(0) {
941 }
942
943 UpdateDensePrefixTask(SpaceId space_id,
944 size_t region_index_start,
945 size_t region_index_end)
946 : _space_id(space_id),
947 _region_index_start(region_index_start),
948 _region_index_end(region_index_end) {
949 }
950 };
951
952 public:
953 // Inline closure decls
954 //
955 class IsAliveClosure: public BoolObjectClosure {
956 public:
957 virtual bool do_object_b(oop p);
958 };
959
960 friend class RefProcTaskProxy;
961 friend class PSParallelCompactTest;
962
963 private:
964 static STWGCTimer _gc_timer;
965 static ParallelOldTracer _gc_tracer;
966 static elapsedTimer _accumulated_time;
967 static unsigned int _total_invocations;
968 static unsigned int _maximum_compaction_gc_num;
969 static jlong _time_of_last_gc; // ms
970 static CollectorCounters* _counters;
971 static ParMarkBitMap _mark_bitmap;
972 static ParallelCompactData _summary_data;
973 static IsAliveClosure _is_alive_closure;
974 static SpaceInfo _space_info[last_space_id];
975
976 // Reference processing (used in ...follow_contents)
977 static SpanSubjectToDiscoveryClosure _span_based_discoverer;
978 static ReferenceProcessor* _ref_processor;
979
980 // Values computed at initialization and used by dead_wood_limiter().
981 static double _dwl_mean;
982 static double _dwl_std_dev;
983 static double _dwl_first_term;
984 static double _dwl_adjustment;
985 #ifdef ASSERT
986 static bool _dwl_initialized;
987 #endif // #ifdef ASSERT
988
989 public:
990 static ParallelOldTracer* gc_tracer() { return &_gc_tracer; }
991
992 private:
993
994 static void initialize_space_info();
995
996 // Clear the marking bitmap and summary data that cover the specified space.
997 static void clear_data_covering_space(SpaceId id);
998
999 static void pre_compact();
1000 static void post_compact();
1001
1002 // Mark live objects
1003 static void marking_phase(ParCompactionManager* cm,
1004 bool maximum_heap_compaction,
1005 ParallelOldTracer *gc_tracer);
1006
1007 // Compute the dense prefix for the designated space. This is an experimental
1008 // implementation currently not used in production.
1009 static HeapWord* compute_dense_prefix_via_density(const SpaceId id,
1010 bool maximum_compaction);
1011
1012 // Methods used to compute the dense prefix.
1013
1014 // Compute the value of the normal distribution at x = density. The mean and
1015 // standard deviation are values saved by initialize_dead_wood_limiter().
1016 static inline double normal_distribution(double density);
1017
1018 // Initialize the static vars used by dead_wood_limiter().
1019 static void initialize_dead_wood_limiter();
1020
1021 // Return the percentage of space that can be treated as "dead wood" (i.e.,
1022 // not reclaimed).
1023 static double dead_wood_limiter(double density, size_t min_percent);
1024
1025 // Find the first (left-most) region in the range [beg, end) that has at least
1026 // dead_words of dead space to the left. The argument beg must be the first
1027 // region in the space that is not completely live.
1028 static RegionData* dead_wood_limit_region(const RegionData* beg,
1029 const RegionData* end,
1030 size_t dead_words);
1031
1032 // Return a pointer to the first region in the range [beg, end) that is not
1033 // completely full.
1034 static RegionData* first_dead_space_region(const RegionData* beg,
1035 const RegionData* end);
1036
1037 // Return a value indicating the benefit or 'yield' if the compacted region
1038 // were to start (or equivalently if the dense prefix were to end) at the
1039 // candidate region. Higher values are better.
1040 //
1041 // The value is based on the amount of space reclaimed vs. the costs of (a)
1042 // updating references in the dense prefix plus (b) copying objects and
1043 // updating references in the compacted region.
1044 static inline double reclaimed_ratio(const RegionData* const candidate,
1045 HeapWord* const bottom,
1046 HeapWord* const top,
1047 HeapWord* const new_top);
1048
1049 // Compute the dense prefix for the designated space.
1050 static HeapWord* compute_dense_prefix(const SpaceId id,
1051 bool maximum_compaction);
1052
1053 // Return true if dead space crosses onto the specified Region; bit must be
1054 // the bit index corresponding to the first word of the Region.
1055 static inline bool dead_space_crosses_boundary(const RegionData* region,
1056 idx_t bit);
1057
1058 // Summary phase utility routine to fill dead space (if any) at the dense
1059 // prefix boundary. Should only be called if the the dense prefix is
1060 // non-empty.
1061 static void fill_dense_prefix_end(SpaceId id);
1062
1063 static void summarize_spaces_quick();
1064 static void summarize_space(SpaceId id, bool maximum_compaction);
1065 static void summary_phase(ParCompactionManager* cm, bool maximum_compaction);
1066
1067 // Adjust addresses in roots. Does not adjust addresses in heap.
1068 static void adjust_roots(ParCompactionManager* cm);
1069
1070 DEBUG_ONLY(static void write_block_fill_histogram();)
1071
1072 // Move objects to new locations.
1073 static void compact_perm(ParCompactionManager* cm);
1074 static void compact();
1075
1076 // Add available regions to the stack and draining tasks to the task queue.
1077 static void prepare_region_draining_tasks(uint parallel_gc_threads);
1078
1079 // Add dense prefix update tasks to the task queue.
1080 static void enqueue_dense_prefix_tasks(TaskQueue& task_queue,
1081 uint parallel_gc_threads);
1082
1083 // If objects are left in eden after a collection, try to move the boundary
1084 // and absorb them into the old gen. Returns true if eden was emptied.
1085 static bool absorb_live_data_from_eden(PSAdaptiveSizePolicy* size_policy,
1086 PSYoungGen* young_gen,
1087 PSOldGen* old_gen);
1088
1089 // Reset time since last full gc
1090 static void reset_millis_since_last_gc();
1091
1092 #ifndef PRODUCT
1093 // Print generic summary data
1094 static void print_generic_summary_data(ParallelCompactData& summary_data,
1095 HeapWord* const beg_addr,
1096 HeapWord* const end_addr);
1097 #endif // #ifndef PRODUCT
1098
1099 public:
1100
1101 PSParallelCompact();
1102
1103 static void invoke(bool maximum_heap_compaction);
1104 static bool invoke_no_policy(bool maximum_heap_compaction);
1105
1106 static void post_initialize();
1107 // Perform initialization for PSParallelCompact that requires
1108 // allocations. This should be called during the VM initialization
1109 // at a pointer where it would be appropriate to return a JNI_ENOMEM
1110 // in the event of a failure.
1111 static bool initialize();
1112
1113 // Closure accessors
1114 static BoolObjectClosure* is_alive_closure() { return (BoolObjectClosure*)&_is_alive_closure; }
1115
1116 // Public accessors
1117 static elapsedTimer* accumulated_time() { return &_accumulated_time; }
1118 static unsigned int total_invocations() { return _total_invocations; }
1119 static CollectorCounters* counters() { return _counters; }
1120
1121 // Used to add tasks
1122 static GCTaskManager* const gc_task_manager();
1123
1124 // Marking support
1125 static inline bool mark_obj(oop obj);
1126 static inline bool is_marked(oop obj);
1127
1128 template <class T> static inline void adjust_pointer(T* p, ParCompactionManager* cm);
1129
1130 // Compaction support.
1131 // Return true if p is in the range [beg_addr, end_addr).
1132 static inline bool is_in(HeapWord* p, HeapWord* beg_addr, HeapWord* end_addr);
1133 static inline bool is_in(oop* p, HeapWord* beg_addr, HeapWord* end_addr);
1134
1135 // Convenience wrappers for per-space data kept in _space_info.
1136 static inline MutableSpace* space(SpaceId space_id);
1137 static inline HeapWord* new_top(SpaceId space_id);
1138 static inline HeapWord* dense_prefix(SpaceId space_id);
1139 static inline ObjectStartArray* start_array(SpaceId space_id);
1140
1141 // Move and update the live objects in the specified space.
1142 static void move_and_update(ParCompactionManager* cm, SpaceId space_id);
1143
1144 // Process the end of the given region range in the dense prefix.
1145 // This includes saving any object not updated.
1146 static void dense_prefix_regions_epilogue(ParCompactionManager* cm,
1147 size_t region_start_index,
1148 size_t region_end_index,
1149 idx_t exiting_object_offset,
1150 idx_t region_offset_start,
1151 idx_t region_offset_end);
1152
1153 // Update a region in the dense prefix. For each live object
1154 // in the region, update it's interior references. For each
1155 // dead object, fill it with deadwood. Dead space at the end
1156 // of a region range will be filled to the start of the next
1157 // live object regardless of the region_index_end. None of the
1158 // objects in the dense prefix move and dead space is dead
1159 // (holds only dead objects that don't need any processing), so
1160 // dead space can be filled in any order.
1161 static void update_and_deadwood_in_dense_prefix(ParCompactionManager* cm,
1162 SpaceId space_id,
1163 size_t region_index_start,
1164 size_t region_index_end);
1165
1166 // Return the address of the count + 1st live word in the range [beg, end).
1167 static HeapWord* skip_live_words(HeapWord* beg, HeapWord* end, size_t count);
1168
1169 // Return the address of the word to be copied to dest_addr, which must be
1170 // aligned to a region boundary.
1171 static HeapWord* first_src_addr(HeapWord* const dest_addr,
1172 SpaceId src_space_id,
1173 size_t src_region_idx);
1174
1175 // Determine the next source region, set closure.source() to the start of the
1176 // new region return the region index. Parameter end_addr is the address one
1177 // beyond the end of source range just processed. If necessary, switch to a
1178 // new source space and set src_space_id (in-out parameter) and src_space_top
1179 // (out parameter) accordingly.
1180 static size_t next_src_region(MoveAndUpdateClosure& closure,
1181 SpaceId& src_space_id,
1182 HeapWord*& src_space_top,
1183 HeapWord* end_addr);
1184
1185 // Decrement the destination count for each non-empty source region in the
1186 // range [beg_region, region(region_align_up(end_addr))). If the destination
1187 // count for a region goes to 0 and it needs to be filled, enqueue it.
1188 static void decrement_destination_counts(ParCompactionManager* cm,
1189 SpaceId src_space_id,
1190 size_t beg_region,
1191 HeapWord* end_addr);
1192
1193 // Fill a region, copying objects from one or more source regions.
1194 static void fill_region(ParCompactionManager* cm, size_t region_idx);
1195 static void fill_and_update_region(ParCompactionManager* cm, size_t region) {
1196 fill_region(cm, region);
1197 }
1198
1199 // Fill in the block table for the specified region.
1200 static void fill_blocks(size_t region_idx);
1201
1202 // Update the deferred objects in the space.
1203 static void update_deferred_objects(ParCompactionManager* cm, SpaceId id);
1204
1205 static ParMarkBitMap* mark_bitmap() { return &_mark_bitmap; }
1206 static ParallelCompactData& summary_data() { return _summary_data; }
1207
1208 // Reference Processing
1209 static ReferenceProcessor* const ref_processor() { return _ref_processor; }
1210
1211 static STWGCTimer* gc_timer() { return &_gc_timer; }
1212
1213 // Return the SpaceId for the given address.
1214 static SpaceId space_id(HeapWord* addr);
1215
1216 // Time since last full gc (in milliseconds).
1217 static jlong millis_since_last_gc();
1218
1219 static void print_on_error(outputStream* st);
1220
1221 #ifndef PRODUCT
1222 // Debugging support.
1223 static const char* space_names[last_space_id];
1224 static void print_region_ranges();
1225 static void print_dense_prefix_stats(const char* const algorithm,
1226 const SpaceId id,
1227 const bool maximum_compaction,
1228 HeapWord* const addr);
1229 static void summary_phase_msg(SpaceId dst_space_id,
1230 HeapWord* dst_beg, HeapWord* dst_end,
1231 SpaceId src_space_id,
1232 HeapWord* src_beg, HeapWord* src_end);
1233 #endif // #ifndef PRODUCT
1234
1235 #ifdef ASSERT
1236 // Sanity check the new location of a word in the heap.
1237 static inline void check_new_location(HeapWord* old_addr, HeapWord* new_addr);
1238 // Verify that all the regions have been emptied.
1239 static void verify_complete(SpaceId space_id);
1240 #endif // #ifdef ASSERT
1241 };
1242
1243 class MoveAndUpdateClosure: public ParMarkBitMapClosure {
1244 public:
1245 inline MoveAndUpdateClosure(ParMarkBitMap* bitmap, ParCompactionManager* cm,
1246 ObjectStartArray* start_array,
1247 HeapWord* destination, size_t words);
1248
1249 // Accessors.
1250 HeapWord* destination() const { return _destination; }
1251
1252 // If the object will fit (size <= words_remaining()), copy it to the current
1253 // destination, update the interior oops and the start array and return either
1254 // full (if the closure is full) or incomplete. If the object will not fit,
1255 // return would_overflow.
1256 virtual IterationStatus do_addr(HeapWord* addr, size_t size);
1257
1258 // Copy enough words to fill this closure, starting at source(). Interior
1259 // oops and the start array are not updated. Return full.
1260 IterationStatus copy_until_full();
1261
1262 // Copy enough words to fill this closure or to the end of an object,
1263 // whichever is smaller, starting at source(). Interior oops and the start
1264 // array are not updated.
1265 void copy_partial_obj();
1266
1267 protected:
1268 // Update variables to indicate that word_count words were processed.
1269 inline void update_state(size_t word_count);
1270
1271 protected:
1272 ObjectStartArray* const _start_array;
1273 HeapWord* _destination; // Next addr to be written.
1274 };
1275
1276 inline
1277 MoveAndUpdateClosure::MoveAndUpdateClosure(ParMarkBitMap* bitmap,
1278 ParCompactionManager* cm,
1279 ObjectStartArray* start_array,
1280 HeapWord* destination,
1281 size_t words) :
1282 ParMarkBitMapClosure(bitmap, cm, words), _start_array(start_array)
1283 {
1284 _destination = destination;
1285 }
1286
1287 inline void MoveAndUpdateClosure::update_state(size_t words)
1288 {
1289 decrement_words_remaining(words);
1290 _source += words;
1291 _destination += words;
1292 }
1293
1294 class UpdateOnlyClosure: public ParMarkBitMapClosure {
1295 private:
1296 const PSParallelCompact::SpaceId _space_id;
1297 ObjectStartArray* const _start_array;
1298
1299 public:
1300 UpdateOnlyClosure(ParMarkBitMap* mbm,
1301 ParCompactionManager* cm,
1302 PSParallelCompact::SpaceId space_id);
1303
1304 // Update the object.
1305 virtual IterationStatus do_addr(HeapWord* addr, size_t words);
1306
1307 inline void do_addr(HeapWord* addr);
1308 };
1309
1310 class FillClosure: public ParMarkBitMapClosure {
1311 public:
1312 FillClosure(ParCompactionManager* cm, PSParallelCompact::SpaceId space_id);
1313
1314 virtual IterationStatus do_addr(HeapWord* addr, size_t size);
1315
1316 private:
1317 ObjectStartArray* const _start_array;
1318 };
1319
1320 #endif // SHARE_GC_PARALLEL_PSPARALLELCOMPACT_HPP