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