1 /*
2 * Copyright (c) 2001, 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 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
24
25 #include "precompiled.hpp"
26 #include "classfile/classLoaderDataGraph.hpp"
27 #include "gc/shared/cardTableRS.hpp"
28 #include "gc/shared/genCollectedHeap.hpp"
29 #include "gc/shared/genOopClosures.hpp"
30 #include "gc/shared/generation.hpp"
31 #include "gc/shared/space.inline.hpp"
32 #include "memory/allocation.inline.hpp"
33 #include "memory/iterator.inline.hpp"
34 #include "oops/access.inline.hpp"
35 #include "oops/oop.inline.hpp"
36 #include "runtime/atomic.hpp"
37 #include "runtime/java.hpp"
38 #include "runtime/os.hpp"
39 #include "utilities/macros.hpp"
40
41 class HasAccumulatedModifiedOopsClosure : public CLDClosure {
42 bool _found;
43 public:
44 HasAccumulatedModifiedOopsClosure() : _found(false) {}
45 void do_cld(ClassLoaderData* cld) {
46 if (_found) {
47 return;
48 }
49
50 if (cld->has_accumulated_modified_oops()) {
51 _found = true;
52 }
53 }
54 bool found() {
55 return _found;
56 }
57 };
58
59 bool CLDRemSet::mod_union_is_clear() {
60 HasAccumulatedModifiedOopsClosure closure;
61 ClassLoaderDataGraph::cld_do(&closure);
62
63 return !closure.found();
64 }
65
66
67 class ClearCLDModUnionClosure : public CLDClosure {
68 public:
69 void do_cld(ClassLoaderData* cld) {
70 if (cld->has_accumulated_modified_oops()) {
71 cld->clear_accumulated_modified_oops();
72 }
73 }
74 };
75
76 void CLDRemSet::clear_mod_union() {
77 ClearCLDModUnionClosure closure;
78 ClassLoaderDataGraph::cld_do(&closure);
79 }
80
81 CardTable::CardValue CardTableRS::find_unused_youngergenP_card_value() {
82 for (CardValue v = youngergenP1_card;
83 v < cur_youngergen_and_prev_nonclean_card;
84 v++) {
85 bool seen = false;
86 for (int g = 0; g < _regions_to_iterate; g++) {
87 if (_last_cur_val_in_gen[g] == v) {
88 seen = true;
89 break;
90 }
91 }
92 if (!seen) {
93 return v;
94 }
95 }
96 ShouldNotReachHere();
97 return 0;
98 }
99
100 void CardTableRS::prepare_for_younger_refs_iterate(bool parallel) {
101 // Parallel or sequential, we must always set the prev to equal the
102 // last one written.
103 if (parallel) {
104 // Find a parallel value to be used next.
105 jbyte next_val = find_unused_youngergenP_card_value();
106 set_cur_youngergen_card_val(next_val);
107
108 } else {
109 // In an sequential traversal we will always write youngergen, so that
110 // the inline barrier is correct.
111 set_cur_youngergen_card_val(youngergen_card);
112 }
113 }
114
115 void CardTableRS::younger_refs_iterate(Generation* g,
116 OopsInGenClosure* blk,
117 uint n_threads) {
118 // The indexing in this array is slightly odd. We want to access
119 // the old generation record here, which is at index 2.
120 _last_cur_val_in_gen[2] = cur_youngergen_card_val();
121 g->younger_refs_iterate(blk, n_threads);
122 }
123
124 inline bool ClearNoncleanCardWrapper::clear_card(CardValue* entry) {
125 if (_is_par) {
126 return clear_card_parallel(entry);
127 } else {
128 return clear_card_serial(entry);
129 }
130 }
131
132 inline bool ClearNoncleanCardWrapper::clear_card_parallel(CardValue* entry) {
133 while (true) {
134 // In the parallel case, we may have to do this several times.
135 CardValue entry_val = *entry;
136 assert(entry_val != CardTableRS::clean_card_val(),
137 "We shouldn't be looking at clean cards, and this should "
138 "be the only place they get cleaned.");
139 if (CardTableRS::card_is_dirty_wrt_gen_iter(entry_val)
140 || _ct->is_prev_youngergen_card_val(entry_val)) {
141 CardValue res =
142 Atomic::cmpxchg(entry, entry_val, CardTableRS::clean_card_val());
143 if (res == entry_val) {
144 break;
145 } else {
146 assert(res == CardTableRS::cur_youngergen_and_prev_nonclean_card,
147 "The CAS above should only fail if another thread did "
148 "a GC write barrier.");
149 }
150 } else if (entry_val ==
151 CardTableRS::cur_youngergen_and_prev_nonclean_card) {
152 // Parallelism shouldn't matter in this case. Only the thread
153 // assigned to scan the card should change this value.
154 *entry = _ct->cur_youngergen_card_val();
155 break;
156 } else {
157 assert(entry_val == _ct->cur_youngergen_card_val(),
158 "Should be the only possibility.");
159 // In this case, the card was clean before, and become
160 // cur_youngergen only because of processing of a promoted object.
161 // We don't have to look at the card.
162 return false;
163 }
164 }
165 return true;
166 }
167
168
169 inline bool ClearNoncleanCardWrapper::clear_card_serial(CardValue* entry) {
170 CardValue entry_val = *entry;
171 assert(entry_val != CardTableRS::clean_card_val(),
172 "We shouldn't be looking at clean cards, and this should "
173 "be the only place they get cleaned.");
174 assert(entry_val != CardTableRS::cur_youngergen_and_prev_nonclean_card,
175 "This should be possible in the sequential case.");
176 *entry = CardTableRS::clean_card_val();
177 return true;
178 }
179
180 ClearNoncleanCardWrapper::ClearNoncleanCardWrapper(
181 DirtyCardToOopClosure* dirty_card_closure, CardTableRS* ct, bool is_par) :
182 _dirty_card_closure(dirty_card_closure), _ct(ct), _is_par(is_par) {
183 }
184
185 bool ClearNoncleanCardWrapper::is_word_aligned(CardTable::CardValue* entry) {
186 return (((intptr_t)entry) & (BytesPerWord-1)) == 0;
187 }
188
189 // The regions are visited in *decreasing* address order.
190 // This order aids with imprecise card marking, where a dirty
191 // card may cause scanning, and summarization marking, of objects
192 // that extend onto subsequent cards.
193 void ClearNoncleanCardWrapper::do_MemRegion(MemRegion mr) {
194 assert(mr.word_size() > 0, "Error");
195 assert(_ct->is_aligned(mr.start()), "mr.start() should be card aligned");
196 // mr.end() may not necessarily be card aligned.
197 CardValue* cur_entry = _ct->byte_for(mr.last());
198 const CardValue* limit = _ct->byte_for(mr.start());
199 HeapWord* end_of_non_clean = mr.end();
200 HeapWord* start_of_non_clean = end_of_non_clean;
201 while (cur_entry >= limit) {
202 HeapWord* cur_hw = _ct->addr_for(cur_entry);
203 if ((*cur_entry != CardTableRS::clean_card_val()) && clear_card(cur_entry)) {
204 // Continue the dirty range by opening the
205 // dirty window one card to the left.
206 start_of_non_clean = cur_hw;
207 } else {
208 // We hit a "clean" card; process any non-empty
209 // "dirty" range accumulated so far.
210 if (start_of_non_clean < end_of_non_clean) {
211 const MemRegion mrd(start_of_non_clean, end_of_non_clean);
212 _dirty_card_closure->do_MemRegion(mrd);
213 }
214
215 // fast forward through potential continuous whole-word range of clean cards beginning at a word-boundary
216 if (is_word_aligned(cur_entry)) {
217 CardValue* cur_row = cur_entry - BytesPerWord;
218 while (cur_row >= limit && *((intptr_t*)cur_row) == CardTableRS::clean_card_row_val()) {
219 cur_row -= BytesPerWord;
220 }
221 cur_entry = cur_row + BytesPerWord;
222 cur_hw = _ct->addr_for(cur_entry);
223 }
224
225 // Reset the dirty window, while continuing to look
226 // for the next dirty card that will start a
227 // new dirty window.
228 end_of_non_clean = cur_hw;
229 start_of_non_clean = cur_hw;
230 }
231 // Note that "cur_entry" leads "start_of_non_clean" in
232 // its leftward excursion after this point
233 // in the loop and, when we hit the left end of "mr",
234 // will point off of the left end of the card-table
235 // for "mr".
236 cur_entry--;
237 }
238 // If the first card of "mr" was dirty, we will have
239 // been left with a dirty window, co-initial with "mr",
240 // which we now process.
241 if (start_of_non_clean < end_of_non_clean) {
242 const MemRegion mrd(start_of_non_clean, end_of_non_clean);
243 _dirty_card_closure->do_MemRegion(mrd);
244 }
245 }
246
247 void CardTableRS::younger_refs_in_space_iterate(Space* sp,
248 OopsInGenClosure* cl,
249 uint n_threads) {
250 verify_used_region_at_save_marks(sp);
251
252 const MemRegion urasm = sp->used_region_at_save_marks();
253 non_clean_card_iterate_possibly_parallel(sp, urasm, cl, this, n_threads);
254 }
255
256 #ifdef ASSERT
257 void CardTableRS::verify_used_region_at_save_marks(Space* sp) const {
258 MemRegion ur = sp->used_region();
259 MemRegion urasm = sp->used_region_at_save_marks();
260
261 assert(ur.contains(urasm),
262 "Did you forget to call save_marks()? "
263 "[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
264 "[" PTR_FORMAT ", " PTR_FORMAT ")",
265 p2i(urasm.start()), p2i(urasm.end()), p2i(ur.start()), p2i(ur.end()));
266 }
267 #endif
268
269 void CardTableRS::clear_into_younger(Generation* old_gen) {
270 assert(GenCollectedHeap::heap()->is_old_gen(old_gen),
271 "Should only be called for the old generation");
272 // The card tables for the youngest gen need never be cleared.
273 // There's a bit of subtlety in the clear() and invalidate()
274 // methods that we exploit here and in invalidate_or_clear()
275 // below to avoid missing cards at the fringes. If clear() or
276 // invalidate() are changed in the future, this code should
277 // be revisited. 20040107.ysr
278 clear(old_gen->prev_used_region());
279 }
280
281 void CardTableRS::invalidate_or_clear(Generation* old_gen) {
282 assert(GenCollectedHeap::heap()->is_old_gen(old_gen),
283 "Should only be called for the old generation");
284 // Invalidate the cards for the currently occupied part of
285 // the old generation and clear the cards for the
286 // unoccupied part of the generation (if any, making use
287 // of that generation's prev_used_region to determine that
288 // region). No need to do anything for the youngest
289 // generation. Also see note#20040107.ysr above.
290 MemRegion used_mr = old_gen->used_region();
291 MemRegion to_be_cleared_mr = old_gen->prev_used_region().minus(used_mr);
292 if (!to_be_cleared_mr.is_empty()) {
293 clear(to_be_cleared_mr);
294 }
295 invalidate(used_mr);
296 }
297
298
299 class VerifyCleanCardClosure: public BasicOopIterateClosure {
300 private:
301 HeapWord* _boundary;
302 HeapWord* _begin;
303 HeapWord* _end;
304 protected:
305 template <class T> void do_oop_work(T* p) {
306 HeapWord* jp = (HeapWord*)p;
307 assert(jp >= _begin && jp < _end,
308 "Error: jp " PTR_FORMAT " should be within "
309 "[_begin, _end) = [" PTR_FORMAT "," PTR_FORMAT ")",
310 p2i(jp), p2i(_begin), p2i(_end));
311 oop obj = RawAccess<>::oop_load(p);
312 guarantee(obj == NULL || cast_from_oop<HeapWord*>(obj) >= _boundary,
313 "pointer " PTR_FORMAT " at " PTR_FORMAT " on "
314 "clean card crosses boundary" PTR_FORMAT,
315 p2i(obj), p2i(jp), p2i(_boundary));
316 }
317
318 public:
319 VerifyCleanCardClosure(HeapWord* b, HeapWord* begin, HeapWord* end) :
320 _boundary(b), _begin(begin), _end(end) {
321 assert(b <= begin,
322 "Error: boundary " PTR_FORMAT " should be at or below begin " PTR_FORMAT,
323 p2i(b), p2i(begin));
324 assert(begin <= end,
325 "Error: begin " PTR_FORMAT " should be strictly below end " PTR_FORMAT,
326 p2i(begin), p2i(end));
327 }
328
329 virtual void do_oop(oop* p) { VerifyCleanCardClosure::do_oop_work(p); }
330 virtual void do_oop(narrowOop* p) { VerifyCleanCardClosure::do_oop_work(p); }
331 };
332
333 class VerifyCTSpaceClosure: public SpaceClosure {
334 private:
335 CardTableRS* _ct;
336 HeapWord* _boundary;
337 public:
338 VerifyCTSpaceClosure(CardTableRS* ct, HeapWord* boundary) :
339 _ct(ct), _boundary(boundary) {}
340 virtual void do_space(Space* s) { _ct->verify_space(s, _boundary); }
341 };
342
343 class VerifyCTGenClosure: public GenCollectedHeap::GenClosure {
344 CardTableRS* _ct;
345 public:
346 VerifyCTGenClosure(CardTableRS* ct) : _ct(ct) {}
347 void do_generation(Generation* gen) {
348 // Skip the youngest generation.
349 if (GenCollectedHeap::heap()->is_young_gen(gen)) {
350 return;
351 }
352 // Normally, we're interested in pointers to younger generations.
353 VerifyCTSpaceClosure blk(_ct, gen->reserved().start());
354 gen->space_iterate(&blk, true);
355 }
356 };
357
358 void CardTableRS::verify_space(Space* s, HeapWord* gen_boundary) {
359 // We don't need to do young-gen spaces.
360 if (s->end() <= gen_boundary) return;
361 MemRegion used = s->used_region();
362
363 CardValue* cur_entry = byte_for(used.start());
364 CardValue* limit = byte_after(used.last());
365 while (cur_entry < limit) {
366 if (*cur_entry == clean_card_val()) {
367 CardValue* first_dirty = cur_entry+1;
368 while (first_dirty < limit &&
369 *first_dirty == clean_card_val()) {
370 first_dirty++;
371 }
372 // If the first object is a regular object, and it has a
373 // young-to-old field, that would mark the previous card.
374 HeapWord* boundary = addr_for(cur_entry);
375 HeapWord* end = (first_dirty >= limit) ? used.end() : addr_for(first_dirty);
376 HeapWord* boundary_block = s->block_start(boundary);
377 HeapWord* begin = boundary; // Until proven otherwise.
378 HeapWord* start_block = boundary_block; // Until proven otherwise.
379 if (boundary_block < boundary) {
380 if (s->block_is_obj(boundary_block) && s->obj_is_alive(boundary_block)) {
381 oop boundary_obj = oop(boundary_block);
382 if (!boundary_obj->is_objArray() &&
383 !boundary_obj->is_typeArray()) {
384 guarantee(cur_entry > byte_for(used.start()),
385 "else boundary would be boundary_block");
386 if (*byte_for(boundary_block) != clean_card_val()) {
387 begin = boundary_block + s->block_size(boundary_block);
388 start_block = begin;
389 }
390 }
391 }
392 }
393 // Now traverse objects until end.
394 if (begin < end) {
395 MemRegion mr(begin, end);
396 VerifyCleanCardClosure verify_blk(gen_boundary, begin, end);
397 for (HeapWord* cur = start_block; cur < end; cur += s->block_size(cur)) {
398 if (s->block_is_obj(cur) && s->obj_is_alive(cur)) {
399 oop(cur)->oop_iterate(&verify_blk, mr);
400 }
401 }
402 }
403 cur_entry = first_dirty;
404 } else {
405 // We'd normally expect that cur_youngergen_and_prev_nonclean_card
406 // is a transient value, that cannot be in the card table
407 // except during GC, and thus assert that:
408 // guarantee(*cur_entry != cur_youngergen_and_prev_nonclean_card,
409 // "Illegal CT value");
410 // That however, need not hold, as will become clear in the
411 // following...
412
413 // We'd normally expect that if we are in the parallel case,
414 // we can't have left a prev value (which would be different
415 // from the current value) in the card table, and so we'd like to
416 // assert that:
417 // guarantee(cur_youngergen_card_val() == youngergen_card
418 // || !is_prev_youngergen_card_val(*cur_entry),
419 // "Illegal CT value");
420 // That, however, may not hold occasionally, because of
421 // CMS or MSC in the old gen. To wit, consider the
422 // following two simple illustrative scenarios:
423 // (a) CMS: Consider the case where a large object L
424 // spanning several cards is allocated in the old
425 // gen, and has a young gen reference stored in it, dirtying
426 // some interior cards. A young collection scans the card,
427 // finds a young ref and installs a youngergenP_n value.
428 // L then goes dead. Now a CMS collection starts,
429 // finds L dead and sweeps it up. Assume that L is
430 // abutting _unallocated_blk, so _unallocated_blk is
431 // adjusted down to (below) L. Assume further that
432 // no young collection intervenes during this CMS cycle.
433 // The next young gen cycle will not get to look at this
434 // youngergenP_n card since it lies in the unoccupied
435 // part of the space.
436 // Some young collections later the blocks on this
437 // card can be re-allocated either due to direct allocation
438 // or due to absorbing promotions. At this time, the
439 // before-gc verification will fail the above assert.
440 // (b) MSC: In this case, an object L with a young reference
441 // is on a card that (therefore) holds a youngergen_n value.
442 // Suppose also that L lies towards the end of the used
443 // the used space before GC. An MSC collection
444 // occurs that compacts to such an extent that this
445 // card is no longer in the occupied part of the space.
446 // Since current code in MSC does not always clear cards
447 // in the unused part of old gen, this stale youngergen_n
448 // value is left behind and can later be covered by
449 // an object when promotion or direct allocation
450 // re-allocates that part of the heap.
451 //
452 // Fortunately, the presence of such stale card values is
453 // "only" a minor annoyance in that subsequent young collections
454 // might needlessly scan such cards, but would still never corrupt
455 // the heap as a result. However, it's likely not to be a significant
456 // performance inhibitor in practice. For instance,
457 // some recent measurements with unoccupied cards eagerly cleared
458 // out to maintain this invariant, showed next to no
459 // change in young collection times; of course one can construct
460 // degenerate examples where the cost can be significant.)
461 // Note, in particular, that if the "stale" card is modified
462 // after re-allocation, it would be dirty, not "stale". Thus,
463 // we can never have a younger ref in such a card and it is
464 // safe not to scan that card in any collection. [As we see
465 // below, we do some unnecessary scanning
466 // in some cases in the current parallel scanning algorithm.]
467 //
468 // The main point below is that the parallel card scanning code
469 // deals correctly with these stale card values. There are two main
470 // cases to consider where we have a stale "young gen" value and a
471 // "derivative" case to consider, where we have a stale
472 // "cur_younger_gen_and_prev_non_clean" value, as will become
473 // apparent in the case analysis below.
474 // o Case 1. If the stale value corresponds to a younger_gen_n
475 // value other than the cur_younger_gen value then the code
476 // treats this as being tantamount to a prev_younger_gen
477 // card. This means that the card may be unnecessarily scanned.
478 // There are two sub-cases to consider:
479 // o Case 1a. Let us say that the card is in the occupied part
480 // of the generation at the time the collection begins. In
481 // that case the card will be either cleared when it is scanned
482 // for young pointers, or will be set to cur_younger_gen as a
483 // result of promotion. (We have elided the normal case where
484 // the scanning thread and the promoting thread interleave
485 // possibly resulting in a transient
486 // cur_younger_gen_and_prev_non_clean value before settling
487 // to cur_younger_gen. [End Case 1a.]
488 // o Case 1b. Consider now the case when the card is in the unoccupied
489 // part of the space which becomes occupied because of promotions
490 // into it during the current young GC. In this case the card
491 // will never be scanned for young references. The current
492 // code will set the card value to either
493 // cur_younger_gen_and_prev_non_clean or leave
494 // it with its stale value -- because the promotions didn't
495 // result in any younger refs on that card. Of these two
496 // cases, the latter will be covered in Case 1a during
497 // a subsequent scan. To deal with the former case, we need
498 // to further consider how we deal with a stale value of
499 // cur_younger_gen_and_prev_non_clean in our case analysis
500 // below. This we do in Case 3 below. [End Case 1b]
501 // [End Case 1]
502 // o Case 2. If the stale value corresponds to cur_younger_gen being
503 // a value not necessarily written by a current promotion, the
504 // card will not be scanned by the younger refs scanning code.
505 // (This is OK since as we argued above such cards cannot contain
506 // any younger refs.) The result is that this value will be
507 // treated as a prev_younger_gen value in a subsequent collection,
508 // which is addressed in Case 1 above. [End Case 2]
509 // o Case 3. We here consider the "derivative" case from Case 1b. above
510 // because of which we may find a stale
511 // cur_younger_gen_and_prev_non_clean card value in the table.
512 // Once again, as in Case 1, we consider two subcases, depending
513 // on whether the card lies in the occupied or unoccupied part
514 // of the space at the start of the young collection.
515 // o Case 3a. Let us say the card is in the occupied part of
516 // the old gen at the start of the young collection. In that
517 // case, the card will be scanned by the younger refs scanning
518 // code which will set it to cur_younger_gen. In a subsequent
519 // scan, the card will be considered again and get its final
520 // correct value. [End Case 3a]
521 // o Case 3b. Now consider the case where the card is in the
522 // unoccupied part of the old gen, and is occupied as a result
523 // of promotions during thus young gc. In that case,
524 // the card will not be scanned for younger refs. The presence
525 // of newly promoted objects on the card will then result in
526 // its keeping the value cur_younger_gen_and_prev_non_clean
527 // value, which we have dealt with in Case 3 here. [End Case 3b]
528 // [End Case 3]
529 //
530 // (Please refer to the code in the helper class
531 // ClearNonCleanCardWrapper and in CardTable for details.)
532 //
533 // The informal arguments above can be tightened into a formal
534 // correctness proof and it behooves us to write up such a proof,
535 // or to use model checking to prove that there are no lingering
536 // concerns.
537 //
538 // Clearly because of Case 3b one cannot bound the time for
539 // which a card will retain what we have called a "stale" value.
540 // However, one can obtain a Loose upper bound on the redundant
541 // work as a result of such stale values. Note first that any
542 // time a stale card lies in the occupied part of the space at
543 // the start of the collection, it is scanned by younger refs
544 // code and we can define a rank function on card values that
545 // declines when this is so. Note also that when a card does not
546 // lie in the occupied part of the space at the beginning of a
547 // young collection, its rank can either decline or stay unchanged.
548 // In this case, no extra work is done in terms of redundant
549 // younger refs scanning of that card.
550 // Then, the case analysis above reveals that, in the worst case,
551 // any such stale card will be scanned unnecessarily at most twice.
552 //
553 // It is nonetheless advisable to try and get rid of some of this
554 // redundant work in a subsequent (low priority) re-design of
555 // the card-scanning code, if only to simplify the underlying
556 // state machine analysis/proof. ysr 1/28/2002. XXX
557 cur_entry++;
558 }
559 }
560 }
561
562 void CardTableRS::verify() {
563 // At present, we only know how to verify the card table RS for
564 // generational heaps.
565 VerifyCTGenClosure blk(this);
566 GenCollectedHeap::heap()->generation_iterate(&blk, false);
567 CardTable::verify();
568 }
569
570 CardTableRS::CardTableRS(MemRegion whole_heap, bool scanned_concurrently) :
571 CardTable(whole_heap, scanned_concurrently),
572 _cur_youngergen_card_val(youngergenP1_card),
573 // LNC functionality
574 _lowest_non_clean(NULL),
575 _lowest_non_clean_chunk_size(NULL),
576 _lowest_non_clean_base_chunk_index(NULL),
577 _last_LNC_resizing_collection(NULL)
578 {
579 // max_gens is really GenCollectedHeap::heap()->gen_policy()->number_of_generations()
580 // (which is always 2, young & old), but GenCollectedHeap has not been initialized yet.
581 uint max_gens = 2;
582 _last_cur_val_in_gen = NEW_C_HEAP_ARRAY3(CardValue, max_gens + 1,
583 mtGC, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
584 if (_last_cur_val_in_gen == NULL) {
585 vm_exit_during_initialization("Could not create last_cur_val_in_gen array.");
586 }
587 for (uint i = 0; i < max_gens + 1; i++) {
588 _last_cur_val_in_gen[i] = clean_card_val();
589 }
590 }
591
592 CardTableRS::~CardTableRS() {
593 FREE_C_HEAP_ARRAY(CardValue, _last_cur_val_in_gen);
594 FREE_C_HEAP_ARRAY(CardArr, _lowest_non_clean);
595 FREE_C_HEAP_ARRAY(size_t, _lowest_non_clean_chunk_size);
596 FREE_C_HEAP_ARRAY(uintptr_t, _lowest_non_clean_base_chunk_index);
597 FREE_C_HEAP_ARRAY(int, _last_LNC_resizing_collection);
598 }
599
600 void CardTableRS::initialize() {
601 CardTable::initialize();
602 _lowest_non_clean =
603 NEW_C_HEAP_ARRAY(CardArr, _max_covered_regions, mtGC);
604 _lowest_non_clean_chunk_size =
605 NEW_C_HEAP_ARRAY(size_t, _max_covered_regions, mtGC);
606 _lowest_non_clean_base_chunk_index =
607 NEW_C_HEAP_ARRAY(uintptr_t, _max_covered_regions, mtGC);
608 _last_LNC_resizing_collection =
609 NEW_C_HEAP_ARRAY(int, _max_covered_regions, mtGC);
610
611 for (int i = 0; i < _max_covered_regions; i++) {
612 _lowest_non_clean[i] = NULL;
613 _lowest_non_clean_chunk_size[i] = 0;
614 _last_LNC_resizing_collection[i] = -1;
615 }
616 }
617
618 bool CardTableRS::card_will_be_scanned(CardValue cv) {
619 return card_is_dirty_wrt_gen_iter(cv) || is_prev_nonclean_card_val(cv);
620 }
621
622 bool CardTableRS::card_may_have_been_dirty(CardValue cv) {
623 return
624 cv != clean_card &&
625 (card_is_dirty_wrt_gen_iter(cv) ||
626 CardTableRS::youngergen_may_have_been_dirty(cv));
627 }
628
629 void CardTableRS::non_clean_card_iterate_possibly_parallel(
630 Space* sp,
631 MemRegion mr,
632 OopsInGenClosure* cl,
633 CardTableRS* ct,
634 uint n_threads)
635 {
636 if (!mr.is_empty()) {
637 if (n_threads > 0) {
638 non_clean_card_iterate_parallel_work(sp, mr, cl, ct, n_threads);
639 } else {
640 // clear_cl finds contiguous dirty ranges of cards to process and clear.
641
642 // This is the single-threaded version used by DefNew.
643 const bool parallel = false;
644
645 DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(), cl->gen_boundary(), parallel);
646 ClearNoncleanCardWrapper clear_cl(dcto_cl, ct, parallel);
647
648 clear_cl.do_MemRegion(mr);
649 }
650 }
651 }
652
653 void CardTableRS::non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
654 OopsInGenClosure* cl, CardTableRS* ct,
655 uint n_threads) {
656 fatal("Parallel gc not supported here.");
657 }
658
659 bool CardTableRS::is_in_young(oop obj) const {
660 return GenCollectedHeap::heap()->is_in_young(obj);
661 }