1/*
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3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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5 * This code is free software; you can redistribute it and/or modify it
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11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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13 * accompanied this code).
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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
41class 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
59bool CLDRemSet::mod_union_is_clear() {
60 HasAccumulatedModifiedOopsClosure closure;
61 ClassLoaderDataGraph::cld_do(&closure);
62
63 return !closure.found();
64}
65
66
67class 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
76void CLDRemSet::clear_mod_union() {
77 ClearCLDModUnionClosure closure;
78 ClassLoaderDataGraph::cld_do(&closure);
79}
80
81CardTable::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
100void 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
115void 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
124inline 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
132inline 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(CardTableRS::clean_card_val(), entry, entry_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
169inline 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
180ClearNoncleanCardWrapper::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
185bool 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.
193void 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// clean (by dirty->clean before) ==> cur_younger_gen
248// dirty ==> cur_youngergen_and_prev_nonclean_card
249// precleaned ==> cur_youngergen_and_prev_nonclean_card
250// prev-younger-gen ==> cur_youngergen_and_prev_nonclean_card
251// cur-younger-gen ==> cur_younger_gen
252// cur_youngergen_and_prev_nonclean_card ==> no change.
253void CardTableRS::write_ref_field_gc_par(void* field, oop new_val) {
254 volatile CardValue* entry = byte_for(field);
255 do {
256 CardValue entry_val = *entry;
257 // We put this first because it's probably the most common case.
258 if (entry_val == clean_card_val()) {
259 // No threat of contention with cleaning threads.
260 *entry = cur_youngergen_card_val();
261 return;
262 } else if (card_is_dirty_wrt_gen_iter(entry_val)
263 || is_prev_youngergen_card_val(entry_val)) {
264 // Mark it as both cur and prev youngergen; card cleaning thread will
265 // eventually remove the previous stuff.
266 CardValue new_val = cur_youngergen_and_prev_nonclean_card;
267 CardValue res = Atomic::cmpxchg(new_val, entry, entry_val);
268 // Did the CAS succeed?
269 if (res == entry_val) return;
270 // Otherwise, retry, to see the new value.
271 continue;
272 } else {
273 assert(entry_val == cur_youngergen_and_prev_nonclean_card
274 || entry_val == cur_youngergen_card_val(),
275 "should be only possibilities.");
276 return;
277 }
278 } while (true);
279}
280
281void CardTableRS::younger_refs_in_space_iterate(Space* sp,
282 OopsInGenClosure* cl,
283 uint n_threads) {
284 verify_used_region_at_save_marks(sp);
285
286 const MemRegion urasm = sp->used_region_at_save_marks();
287 non_clean_card_iterate_possibly_parallel(sp, urasm, cl, this, n_threads);
288}
289
290#ifdef ASSERT
291void CardTableRS::verify_used_region_at_save_marks(Space* sp) const {
292 MemRegion ur = sp->used_region();
293 MemRegion urasm = sp->used_region_at_save_marks();
294
295 assert(ur.contains(urasm),
296 "Did you forget to call save_marks()? "
297 "[" PTR_FORMAT ", " PTR_FORMAT ") is not contained in "
298 "[" PTR_FORMAT ", " PTR_FORMAT ")",
299 p2i(urasm.start()), p2i(urasm.end()), p2i(ur.start()), p2i(ur.end()));
300}
301#endif
302
303void CardTableRS::clear_into_younger(Generation* old_gen) {
304 assert(GenCollectedHeap::heap()->is_old_gen(old_gen),
305 "Should only be called for the old generation");
306 // The card tables for the youngest gen need never be cleared.
307 // There's a bit of subtlety in the clear() and invalidate()
308 // methods that we exploit here and in invalidate_or_clear()
309 // below to avoid missing cards at the fringes. If clear() or
310 // invalidate() are changed in the future, this code should
311 // be revisited. 20040107.ysr
312 clear(old_gen->prev_used_region());
313}
314
315void CardTableRS::invalidate_or_clear(Generation* old_gen) {
316 assert(GenCollectedHeap::heap()->is_old_gen(old_gen),
317 "Should only be called for the old generation");
318 // Invalidate the cards for the currently occupied part of
319 // the old generation and clear the cards for the
320 // unoccupied part of the generation (if any, making use
321 // of that generation's prev_used_region to determine that
322 // region). No need to do anything for the youngest
323 // generation. Also see note#20040107.ysr above.
324 MemRegion used_mr = old_gen->used_region();
325 MemRegion to_be_cleared_mr = old_gen->prev_used_region().minus(used_mr);
326 if (!to_be_cleared_mr.is_empty()) {
327 clear(to_be_cleared_mr);
328 }
329 invalidate(used_mr);
330}
331
332
333class VerifyCleanCardClosure: public BasicOopIterateClosure {
334private:
335 HeapWord* _boundary;
336 HeapWord* _begin;
337 HeapWord* _end;
338protected:
339 template <class T> void do_oop_work(T* p) {
340 HeapWord* jp = (HeapWord*)p;
341 assert(jp >= _begin && jp < _end,
342 "Error: jp " PTR_FORMAT " should be within "
343 "[_begin, _end) = [" PTR_FORMAT "," PTR_FORMAT ")",
344 p2i(jp), p2i(_begin), p2i(_end));
345 oop obj = RawAccess<>::oop_load(p);
346 guarantee(obj == NULL || (HeapWord*)obj >= _boundary,
347 "pointer " PTR_FORMAT " at " PTR_FORMAT " on "
348 "clean card crosses boundary" PTR_FORMAT,
349 p2i(obj), p2i(jp), p2i(_boundary));
350 }
351
352public:
353 VerifyCleanCardClosure(HeapWord* b, HeapWord* begin, HeapWord* end) :
354 _boundary(b), _begin(begin), _end(end) {
355 assert(b <= begin,
356 "Error: boundary " PTR_FORMAT " should be at or below begin " PTR_FORMAT,
357 p2i(b), p2i(begin));
358 assert(begin <= end,
359 "Error: begin " PTR_FORMAT " should be strictly below end " PTR_FORMAT,
360 p2i(begin), p2i(end));
361 }
362
363 virtual void do_oop(oop* p) { VerifyCleanCardClosure::do_oop_work(p); }
364 virtual void do_oop(narrowOop* p) { VerifyCleanCardClosure::do_oop_work(p); }
365};
366
367class VerifyCTSpaceClosure: public SpaceClosure {
368private:
369 CardTableRS* _ct;
370 HeapWord* _boundary;
371public:
372 VerifyCTSpaceClosure(CardTableRS* ct, HeapWord* boundary) :
373 _ct(ct), _boundary(boundary) {}
374 virtual void do_space(Space* s) { _ct->verify_space(s, _boundary); }
375};
376
377class VerifyCTGenClosure: public GenCollectedHeap::GenClosure {
378 CardTableRS* _ct;
379public:
380 VerifyCTGenClosure(CardTableRS* ct) : _ct(ct) {}
381 void do_generation(Generation* gen) {
382 // Skip the youngest generation.
383 if (GenCollectedHeap::heap()->is_young_gen(gen)) {
384 return;
385 }
386 // Normally, we're interested in pointers to younger generations.
387 VerifyCTSpaceClosure blk(_ct, gen->reserved().start());
388 gen->space_iterate(&blk, true);
389 }
390};
391
392void CardTableRS::verify_space(Space* s, HeapWord* gen_boundary) {
393 // We don't need to do young-gen spaces.
394 if (s->end() <= gen_boundary) return;
395 MemRegion used = s->used_region();
396
397 CardValue* cur_entry = byte_for(used.start());
398 CardValue* limit = byte_after(used.last());
399 while (cur_entry < limit) {
400 if (*cur_entry == clean_card_val()) {
401 CardValue* first_dirty = cur_entry+1;
402 while (first_dirty < limit &&
403 *first_dirty == clean_card_val()) {
404 first_dirty++;
405 }
406 // If the first object is a regular object, and it has a
407 // young-to-old field, that would mark the previous card.
408 HeapWord* boundary = addr_for(cur_entry);
409 HeapWord* end = (first_dirty >= limit) ? used.end() : addr_for(first_dirty);
410 HeapWord* boundary_block = s->block_start(boundary);
411 HeapWord* begin = boundary; // Until proven otherwise.
412 HeapWord* start_block = boundary_block; // Until proven otherwise.
413 if (boundary_block < boundary) {
414 if (s->block_is_obj(boundary_block) && s->obj_is_alive(boundary_block)) {
415 oop boundary_obj = oop(boundary_block);
416 if (!boundary_obj->is_objArray() &&
417 !boundary_obj->is_typeArray()) {
418 guarantee(cur_entry > byte_for(used.start()),
419 "else boundary would be boundary_block");
420 if (*byte_for(boundary_block) != clean_card_val()) {
421 begin = boundary_block + s->block_size(boundary_block);
422 start_block = begin;
423 }
424 }
425 }
426 }
427 // Now traverse objects until end.
428 if (begin < end) {
429 MemRegion mr(begin, end);
430 VerifyCleanCardClosure verify_blk(gen_boundary, begin, end);
431 for (HeapWord* cur = start_block; cur < end; cur += s->block_size(cur)) {
432 if (s->block_is_obj(cur) && s->obj_is_alive(cur)) {
433 oop(cur)->oop_iterate(&verify_blk, mr);
434 }
435 }
436 }
437 cur_entry = first_dirty;
438 } else {
439 // We'd normally expect that cur_youngergen_and_prev_nonclean_card
440 // is a transient value, that cannot be in the card table
441 // except during GC, and thus assert that:
442 // guarantee(*cur_entry != cur_youngergen_and_prev_nonclean_card,
443 // "Illegal CT value");
444 // That however, need not hold, as will become clear in the
445 // following...
446
447 // We'd normally expect that if we are in the parallel case,
448 // we can't have left a prev value (which would be different
449 // from the current value) in the card table, and so we'd like to
450 // assert that:
451 // guarantee(cur_youngergen_card_val() == youngergen_card
452 // || !is_prev_youngergen_card_val(*cur_entry),
453 // "Illegal CT value");
454 // That, however, may not hold occasionally, because of
455 // CMS or MSC in the old gen. To wit, consider the
456 // following two simple illustrative scenarios:
457 // (a) CMS: Consider the case where a large object L
458 // spanning several cards is allocated in the old
459 // gen, and has a young gen reference stored in it, dirtying
460 // some interior cards. A young collection scans the card,
461 // finds a young ref and installs a youngergenP_n value.
462 // L then goes dead. Now a CMS collection starts,
463 // finds L dead and sweeps it up. Assume that L is
464 // abutting _unallocated_blk, so _unallocated_blk is
465 // adjusted down to (below) L. Assume further that
466 // no young collection intervenes during this CMS cycle.
467 // The next young gen cycle will not get to look at this
468 // youngergenP_n card since it lies in the unoccupied
469 // part of the space.
470 // Some young collections later the blocks on this
471 // card can be re-allocated either due to direct allocation
472 // or due to absorbing promotions. At this time, the
473 // before-gc verification will fail the above assert.
474 // (b) MSC: In this case, an object L with a young reference
475 // is on a card that (therefore) holds a youngergen_n value.
476 // Suppose also that L lies towards the end of the used
477 // the used space before GC. An MSC collection
478 // occurs that compacts to such an extent that this
479 // card is no longer in the occupied part of the space.
480 // Since current code in MSC does not always clear cards
481 // in the unused part of old gen, this stale youngergen_n
482 // value is left behind and can later be covered by
483 // an object when promotion or direct allocation
484 // re-allocates that part of the heap.
485 //
486 // Fortunately, the presence of such stale card values is
487 // "only" a minor annoyance in that subsequent young collections
488 // might needlessly scan such cards, but would still never corrupt
489 // the heap as a result. However, it's likely not to be a significant
490 // performance inhibitor in practice. For instance,
491 // some recent measurements with unoccupied cards eagerly cleared
492 // out to maintain this invariant, showed next to no
493 // change in young collection times; of course one can construct
494 // degenerate examples where the cost can be significant.)
495 // Note, in particular, that if the "stale" card is modified
496 // after re-allocation, it would be dirty, not "stale". Thus,
497 // we can never have a younger ref in such a card and it is
498 // safe not to scan that card in any collection. [As we see
499 // below, we do some unnecessary scanning
500 // in some cases in the current parallel scanning algorithm.]
501 //
502 // The main point below is that the parallel card scanning code
503 // deals correctly with these stale card values. There are two main
504 // cases to consider where we have a stale "young gen" value and a
505 // "derivative" case to consider, where we have a stale
506 // "cur_younger_gen_and_prev_non_clean" value, as will become
507 // apparent in the case analysis below.
508 // o Case 1. If the stale value corresponds to a younger_gen_n
509 // value other than the cur_younger_gen value then the code
510 // treats this as being tantamount to a prev_younger_gen
511 // card. This means that the card may be unnecessarily scanned.
512 // There are two sub-cases to consider:
513 // o Case 1a. Let us say that the card is in the occupied part
514 // of the generation at the time the collection begins. In
515 // that case the card will be either cleared when it is scanned
516 // for young pointers, or will be set to cur_younger_gen as a
517 // result of promotion. (We have elided the normal case where
518 // the scanning thread and the promoting thread interleave
519 // possibly resulting in a transient
520 // cur_younger_gen_and_prev_non_clean value before settling
521 // to cur_younger_gen. [End Case 1a.]
522 // o Case 1b. Consider now the case when the card is in the unoccupied
523 // part of the space which becomes occupied because of promotions
524 // into it during the current young GC. In this case the card
525 // will never be scanned for young references. The current
526 // code will set the card value to either
527 // cur_younger_gen_and_prev_non_clean or leave
528 // it with its stale value -- because the promotions didn't
529 // result in any younger refs on that card. Of these two
530 // cases, the latter will be covered in Case 1a during
531 // a subsequent scan. To deal with the former case, we need
532 // to further consider how we deal with a stale value of
533 // cur_younger_gen_and_prev_non_clean in our case analysis
534 // below. This we do in Case 3 below. [End Case 1b]
535 // [End Case 1]
536 // o Case 2. If the stale value corresponds to cur_younger_gen being
537 // a value not necessarily written by a current promotion, the
538 // card will not be scanned by the younger refs scanning code.
539 // (This is OK since as we argued above such cards cannot contain
540 // any younger refs.) The result is that this value will be
541 // treated as a prev_younger_gen value in a subsequent collection,
542 // which is addressed in Case 1 above. [End Case 2]
543 // o Case 3. We here consider the "derivative" case from Case 1b. above
544 // because of which we may find a stale
545 // cur_younger_gen_and_prev_non_clean card value in the table.
546 // Once again, as in Case 1, we consider two subcases, depending
547 // on whether the card lies in the occupied or unoccupied part
548 // of the space at the start of the young collection.
549 // o Case 3a. Let us say the card is in the occupied part of
550 // the old gen at the start of the young collection. In that
551 // case, the card will be scanned by the younger refs scanning
552 // code which will set it to cur_younger_gen. In a subsequent
553 // scan, the card will be considered again and get its final
554 // correct value. [End Case 3a]
555 // o Case 3b. Now consider the case where the card is in the
556 // unoccupied part of the old gen, and is occupied as a result
557 // of promotions during thus young gc. In that case,
558 // the card will not be scanned for younger refs. The presence
559 // of newly promoted objects on the card will then result in
560 // its keeping the value cur_younger_gen_and_prev_non_clean
561 // value, which we have dealt with in Case 3 here. [End Case 3b]
562 // [End Case 3]
563 //
564 // (Please refer to the code in the helper class
565 // ClearNonCleanCardWrapper and in CardTable for details.)
566 //
567 // The informal arguments above can be tightened into a formal
568 // correctness proof and it behooves us to write up such a proof,
569 // or to use model checking to prove that there are no lingering
570 // concerns.
571 //
572 // Clearly because of Case 3b one cannot bound the time for
573 // which a card will retain what we have called a "stale" value.
574 // However, one can obtain a Loose upper bound on the redundant
575 // work as a result of such stale values. Note first that any
576 // time a stale card lies in the occupied part of the space at
577 // the start of the collection, it is scanned by younger refs
578 // code and we can define a rank function on card values that
579 // declines when this is so. Note also that when a card does not
580 // lie in the occupied part of the space at the beginning of a
581 // young collection, its rank can either decline or stay unchanged.
582 // In this case, no extra work is done in terms of redundant
583 // younger refs scanning of that card.
584 // Then, the case analysis above reveals that, in the worst case,
585 // any such stale card will be scanned unnecessarily at most twice.
586 //
587 // It is nonetheless advisable to try and get rid of some of this
588 // redundant work in a subsequent (low priority) re-design of
589 // the card-scanning code, if only to simplify the underlying
590 // state machine analysis/proof. ysr 1/28/2002. XXX
591 cur_entry++;
592 }
593 }
594}
595
596void CardTableRS::verify() {
597 // At present, we only know how to verify the card table RS for
598 // generational heaps.
599 VerifyCTGenClosure blk(this);
600 GenCollectedHeap::heap()->generation_iterate(&blk, false);
601 CardTable::verify();
602}
603
604CardTableRS::CardTableRS(MemRegion whole_heap, bool scanned_concurrently) :
605 CardTable(whole_heap, scanned_concurrently),
606 _cur_youngergen_card_val(youngergenP1_card),
607 // LNC functionality
608 _lowest_non_clean(NULL),
609 _lowest_non_clean_chunk_size(NULL),
610 _lowest_non_clean_base_chunk_index(NULL),
611 _last_LNC_resizing_collection(NULL)
612{
613 // max_gens is really GenCollectedHeap::heap()->gen_policy()->number_of_generations()
614 // (which is always 2, young & old), but GenCollectedHeap has not been initialized yet.
615 uint max_gens = 2;
616 _last_cur_val_in_gen = NEW_C_HEAP_ARRAY3(CardValue, max_gens + 1,
617 mtGC, CURRENT_PC, AllocFailStrategy::RETURN_NULL);
618 if (_last_cur_val_in_gen == NULL) {
619 vm_exit_during_initialization("Could not create last_cur_val_in_gen array.");
620 }
621 for (uint i = 0; i < max_gens + 1; i++) {
622 _last_cur_val_in_gen[i] = clean_card_val();
623 }
624}
625
626CardTableRS::~CardTableRS() {
627 if (_last_cur_val_in_gen) {
628 FREE_C_HEAP_ARRAY(CardValue, _last_cur_val_in_gen);
629 _last_cur_val_in_gen = NULL;
630 }
631 if (_lowest_non_clean) {
632 FREE_C_HEAP_ARRAY(CardArr, _lowest_non_clean);
633 _lowest_non_clean = NULL;
634 }
635 if (_lowest_non_clean_chunk_size) {
636 FREE_C_HEAP_ARRAY(size_t, _lowest_non_clean_chunk_size);
637 _lowest_non_clean_chunk_size = NULL;
638 }
639 if (_lowest_non_clean_base_chunk_index) {
640 FREE_C_HEAP_ARRAY(uintptr_t, _lowest_non_clean_base_chunk_index);
641 _lowest_non_clean_base_chunk_index = NULL;
642 }
643 if (_last_LNC_resizing_collection) {
644 FREE_C_HEAP_ARRAY(int, _last_LNC_resizing_collection);
645 _last_LNC_resizing_collection = NULL;
646 }
647}
648
649void CardTableRS::initialize() {
650 CardTable::initialize();
651 _lowest_non_clean =
652 NEW_C_HEAP_ARRAY(CardArr, _max_covered_regions, mtGC);
653 _lowest_non_clean_chunk_size =
654 NEW_C_HEAP_ARRAY(size_t, _max_covered_regions, mtGC);
655 _lowest_non_clean_base_chunk_index =
656 NEW_C_HEAP_ARRAY(uintptr_t, _max_covered_regions, mtGC);
657 _last_LNC_resizing_collection =
658 NEW_C_HEAP_ARRAY(int, _max_covered_regions, mtGC);
659 if (_lowest_non_clean == NULL
660 || _lowest_non_clean_chunk_size == NULL
661 || _lowest_non_clean_base_chunk_index == NULL
662 || _last_LNC_resizing_collection == NULL)
663 vm_exit_during_initialization("couldn't allocate an LNC array.");
664 for (int i = 0; i < _max_covered_regions; i++) {
665 _lowest_non_clean[i] = NULL;
666 _lowest_non_clean_chunk_size[i] = 0;
667 _last_LNC_resizing_collection[i] = -1;
668 }
669}
670
671bool CardTableRS::card_will_be_scanned(CardValue cv) {
672 return card_is_dirty_wrt_gen_iter(cv) || is_prev_nonclean_card_val(cv);
673}
674
675bool CardTableRS::card_may_have_been_dirty(CardValue cv) {
676 return
677 cv != clean_card &&
678 (card_is_dirty_wrt_gen_iter(cv) ||
679 CardTableRS::youngergen_may_have_been_dirty(cv));
680}
681
682void CardTableRS::non_clean_card_iterate_possibly_parallel(
683 Space* sp,
684 MemRegion mr,
685 OopsInGenClosure* cl,
686 CardTableRS* ct,
687 uint n_threads)
688{
689 if (!mr.is_empty()) {
690 if (n_threads > 0) {
691 non_clean_card_iterate_parallel_work(sp, mr, cl, ct, n_threads);
692 } else {
693 // clear_cl finds contiguous dirty ranges of cards to process and clear.
694
695 // This is the single-threaded version used by DefNew.
696 const bool parallel = false;
697
698 DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, precision(), cl->gen_boundary(), parallel);
699 ClearNoncleanCardWrapper clear_cl(dcto_cl, ct, parallel);
700
701 clear_cl.do_MemRegion(mr);
702 }
703 }
704}
705
706void CardTableRS::non_clean_card_iterate_parallel_work(Space* sp, MemRegion mr,
707 OopsInGenClosure* cl, CardTableRS* ct,
708 uint n_threads) {
709 fatal("Parallel gc not supported here.");
710}
711
712bool CardTableRS::is_in_young(oop obj) const {
713 return GenCollectedHeap::heap()->is_in_young(obj);
714}
715