1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)cardTableRS.cpp 1.45 07/05/25 12:54:50 JVM"
3 #endif
4 /*
5 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 # include "incls/_precompiled.incl"
29 # include "incls/_cardTableRS.cpp.incl"
30
31 CardTableRS::CardTableRS(MemRegion whole_heap,
32 int max_covered_regions) :
33 GenRemSet(),
34 _cur_youngergen_card_val(youngergenP1_card),
35 _regions_to_iterate(max_covered_regions - 1)
36 {
37 #ifndef SERIALGC
38 if (UseG1GC) {
39 if (G1RSBarrierUseQueue) {
40 _ct_bs = new G1SATBCardTableLoggingModRefBS(whole_heap,
41 max_covered_regions);
42 } else {
43 _ct_bs = new G1SATBCardTableModRefBS(whole_heap, max_covered_regions);
44 }
45 } else {
46 _ct_bs = new CardTableModRefBSForCTRS(whole_heap, max_covered_regions);
47 }
48 #else
49 _ct_bs = new CardTableModRefBSForCTRS(whole_heap, max_covered_regions);
50 #endif
51 set_bs(_ct_bs);
52 _last_cur_val_in_gen = new jbyte[GenCollectedHeap::max_gens + 1];
53 if (_last_cur_val_in_gen == NULL) {
54 vm_exit_during_initialization("Could not last_cur_val_in_gen array.");
55 }
56 for (int i = 0; i < GenCollectedHeap::max_gens + 1; i++) {
57 _last_cur_val_in_gen[i] = clean_card_val();
58 }
59 _ct_bs->set_CTRS(this);
60 }
61
62 void CardTableRS::resize_covered_region(MemRegion new_region) {
63 _ct_bs->resize_covered_region(new_region);
64 }
65
66 jbyte CardTableRS::find_unused_youngergenP_card_value() {
67 for (jbyte v = youngergenP1_card;
68 v < cur_youngergen_and_prev_nonclean_card;
69 v++) {
70 bool seen = false;
71 for (int g = 0; g < _regions_to_iterate; g++) {
72 if (_last_cur_val_in_gen[g] == v) {
73 seen = true;
74 break;
75 }
76 }
77 if (!seen) return v;
78 }
79 ShouldNotReachHere();
80 return 0;
81 }
82
83 void CardTableRS::prepare_for_younger_refs_iterate(bool parallel) {
84 // Parallel or sequential, we must always set the prev to equal the
85 // last one written.
86 if (parallel) {
87 // Find a parallel value to be used next.
88 jbyte next_val = find_unused_youngergenP_card_value();
89 set_cur_youngergen_card_val(next_val);
90
91 } else {
92 // In an sequential traversal we will always write youngergen, so that
93 // the inline barrier is correct.
94 set_cur_youngergen_card_val(youngergen_card);
95 }
96 }
97
98 void CardTableRS::younger_refs_iterate(Generation* g,
99 OopsInGenClosure* blk) {
100 _last_cur_val_in_gen[g->level()+1] = cur_youngergen_card_val();
101 g->younger_refs_iterate(blk);
102 }
103
104 class ClearNoncleanCardWrapper: public MemRegionClosure {
105 MemRegionClosure* _dirty_card_closure;
106 CardTableRS* _ct;
107 bool _is_par;
108 private:
109 // Clears the given card, return true if the corresponding card should be
110 // processed.
111 bool clear_card(jbyte* entry) {
112 if (_is_par) {
113 while (true) {
114 // In the parallel case, we may have to do this several times.
115 jbyte entry_val = *entry;
116 assert(entry_val != CardTableRS::clean_card_val(),
117 "We shouldn't be looking at clean cards, and this should "
118 "be the only place they get cleaned.");
119 if (CardTableRS::card_is_dirty_wrt_gen_iter(entry_val)
120 || _ct->is_prev_youngergen_card_val(entry_val)) {
121 jbyte res =
122 Atomic::cmpxchg(CardTableRS::clean_card_val(), entry, entry_val);
123 if (res == entry_val) {
124 break;
125 } else {
126 assert(res == CardTableRS::cur_youngergen_and_prev_nonclean_card,
127 "The CAS above should only fail if another thread did "
128 "a GC write barrier.");
129 }
130 } else if (entry_val ==
131 CardTableRS::cur_youngergen_and_prev_nonclean_card) {
132 // Parallelism shouldn't matter in this case. Only the thread
133 // assigned to scan the card should change this value.
134 *entry = _ct->cur_youngergen_card_val();
135 break;
136 } else {
137 assert(entry_val == _ct->cur_youngergen_card_val(),
138 "Should be the only possibility.");
139 // In this case, the card was clean before, and become
140 // cur_youngergen only because of processing of a promoted object.
141 // We don't have to look at the card.
142 return false;
143 }
144 }
145 return true;
146 } else {
147 jbyte entry_val = *entry;
148 assert(entry_val != CardTableRS::clean_card_val(),
149 "We shouldn't be looking at clean cards, and this should "
150 "be the only place they get cleaned.");
151 assert(entry_val != CardTableRS::cur_youngergen_and_prev_nonclean_card,
152 "This should be possible in the sequential case.");
153 *entry = CardTableRS::clean_card_val();
154 return true;
155 }
156 }
157
158 public:
159 ClearNoncleanCardWrapper(MemRegionClosure* dirty_card_closure,
160 CardTableRS* ct) :
161 _dirty_card_closure(dirty_card_closure), _ct(ct) {
162 _is_par = (SharedHeap::heap()->n_par_threads() > 0);
163 }
164 void do_MemRegion(MemRegion mr) {
165 // We start at the high end of "mr", walking backwards
166 // while accumulating a contiguous dirty range of cards in
167 // [start_of_non_clean, end_of_non_clean) which we then
168 // process en masse.
169 HeapWord* end_of_non_clean = mr.end();
170 HeapWord* start_of_non_clean = end_of_non_clean;
171 jbyte* entry = _ct->byte_for(mr.last());
172 const jbyte* first_entry = _ct->byte_for(mr.start());
173 while (entry >= first_entry) {
174 HeapWord* cur = _ct->addr_for(entry);
175 if (!clear_card(entry)) {
176 // We hit a clean card; process any non-empty
177 // dirty range accumulated so far.
178 if (start_of_non_clean < end_of_non_clean) {
179 MemRegion mr2(start_of_non_clean, end_of_non_clean);
180 _dirty_card_closure->do_MemRegion(mr2);
181 }
182 // Reset the dirty window while continuing to
183 // look for the next dirty window to process.
184 end_of_non_clean = cur;
185 start_of_non_clean = end_of_non_clean;
186 }
187 // Open the left end of the window one card to the left.
188 start_of_non_clean = cur;
189 // Note that "entry" leads "start_of_non_clean" in
190 // its leftward excursion after this point
191 // in the loop and, when we hit the left end of "mr",
192 // will point off of the left end of the card-table
193 // for "mr".
194 entry--;
195 }
196 // If the first card of "mr" was dirty, we will have
197 // been left with a dirty window, co-initial with "mr",
198 // which we now process.
199 if (start_of_non_clean < end_of_non_clean) {
200 MemRegion mr2(start_of_non_clean, end_of_non_clean);
201 _dirty_card_closure->do_MemRegion(mr2);
202 }
203 }
204 };
205 // clean (by dirty->clean before) ==> cur_younger_gen
206 // dirty ==> cur_youngergen_and_prev_nonclean_card
207 // precleaned ==> cur_youngergen_and_prev_nonclean_card
208 // prev-younger-gen ==> cur_youngergen_and_prev_nonclean_card
209 // cur-younger-gen ==> cur_younger_gen
210 // cur_youngergen_and_prev_nonclean_card ==> no change.
211 void CardTableRS::write_ref_field_gc_par(void* field, oop new_val) {
212 jbyte* entry = ct_bs()->byte_for(field);
213 do {
214 jbyte entry_val = *entry;
215 // We put this first because it's probably the most common case.
216 if (entry_val == clean_card_val()) {
217 // No threat of contention with cleaning threads.
218 *entry = cur_youngergen_card_val();
219 return;
220 } else if (card_is_dirty_wrt_gen_iter(entry_val)
221 || is_prev_youngergen_card_val(entry_val)) {
222 // Mark it as both cur and prev youngergen; card cleaning thread will
223 // eventually remove the previous stuff.
224 jbyte new_val = cur_youngergen_and_prev_nonclean_card;
225 jbyte res = Atomic::cmpxchg(new_val, entry, entry_val);
226 // Did the CAS succeed?
227 if (res == entry_val) return;
228 // Otherwise, retry, to see the new value.
229 continue;
230 } else {
231 assert(entry_val == cur_youngergen_and_prev_nonclean_card
232 || entry_val == cur_youngergen_card_val(),
233 "should be only possibilities.");
234 return;
235 }
236 } while (true);
237 }
238
239 void CardTableRS::younger_refs_in_space_iterate(Space* sp,
240 OopsInGenClosure* cl) {
241 DirtyCardToOopClosure* dcto_cl = sp->new_dcto_cl(cl, _ct_bs->precision(),
242 cl->gen_boundary());
243 ClearNoncleanCardWrapper clear_cl(dcto_cl, this);
244
245 _ct_bs->non_clean_card_iterate(sp, sp->used_region_at_save_marks(),
246 dcto_cl, &clear_cl, false);
247 }
248
249 void CardTableRS::clear_into_younger(Generation* gen, bool clear_perm) {
250 GenCollectedHeap* gch = GenCollectedHeap::heap();
251 // Generations younger than gen have been evacuated. We can clear
252 // card table entries for gen (we know that it has no pointers
253 // to younger gens) and for those below. The card tables for
254 // the youngest gen need never be cleared, and those for perm gen
255 // will be cleared based on the parameter clear_perm.
256 // There's a bit of subtlety in the clear() and invalidate()
257 // methods that we exploit here and in invalidate_or_clear()
258 // below to avoid missing cards at the fringes. If clear() or
259 // invalidate() are changed in the future, this code should
260 // be revisited. 20040107.ysr
261 Generation* g = gen;
262 for(Generation* prev_gen = gch->prev_gen(g);
263 prev_gen != NULL;
264 g = prev_gen, prev_gen = gch->prev_gen(g)) {
265 MemRegion to_be_cleared_mr = g->prev_used_region();
266 clear(to_be_cleared_mr);
267 }
268 // Clear perm gen cards if asked to do so.
269 if (clear_perm) {
270 MemRegion to_be_cleared_mr = gch->perm_gen()->prev_used_region();
271 clear(to_be_cleared_mr);
272 }
273 }
274
275 void CardTableRS::invalidate_or_clear(Generation* gen, bool younger,
276 bool perm) {
277 GenCollectedHeap* gch = GenCollectedHeap::heap();
278 // For each generation gen (and younger and/or perm)
279 // invalidate the cards for the currently occupied part
280 // of that generation and clear the cards for the
281 // unoccupied part of the generation (if any, making use
282 // of that generation's prev_used_region to determine that
283 // region). No need to do anything for the youngest
284 // generation. Also see note#20040107.ysr above.
285 Generation* g = gen;
286 for(Generation* prev_gen = gch->prev_gen(g); prev_gen != NULL;
287 g = prev_gen, prev_gen = gch->prev_gen(g)) {
288 MemRegion used_mr = g->used_region();
289 MemRegion to_be_cleared_mr = g->prev_used_region().minus(used_mr);
290 if (!to_be_cleared_mr.is_empty()) {
291 clear(to_be_cleared_mr);
292 }
293 invalidate(used_mr);
294 if (!younger) break;
295 }
296 // Clear perm gen cards if asked to do so.
297 if (perm) {
298 g = gch->perm_gen();
299 MemRegion used_mr = g->used_region();
300 MemRegion to_be_cleared_mr = g->prev_used_region().minus(used_mr);
301 if (!to_be_cleared_mr.is_empty()) {
302 clear(to_be_cleared_mr);
303 }
304 invalidate(used_mr);
305 }
306 }
307
308
309 class VerifyCleanCardClosure: public OopClosure {
310 private:
311 HeapWord* _boundary;
312 HeapWord* _begin;
313 HeapWord* _end;
314 protected:
315 template <class T> void do_oop_work(T* p) {
316 HeapWord* jp = (HeapWord*)p;
317 if (jp >= _begin && jp < _end) {
318 oop obj = oopDesc::load_decode_heap_oop(p);
319 guarantee(obj == NULL ||
320 (HeapWord*)p < _boundary ||
321 (HeapWord*)obj >= _boundary,
322 "pointer on clean card crosses boundary");
323 }
324 }
325 public:
326 VerifyCleanCardClosure(HeapWord* b, HeapWord* begin, HeapWord* end) :
327 _boundary(b), _begin(begin), _end(end) {}
328 virtual void do_oop(oop* p) { VerifyCleanCardClosure::do_oop_work(p); }
329 virtual void do_oop(narrowOop* p) { VerifyCleanCardClosure::do_oop_work(p); }
330 };
331
332 class VerifyCTSpaceClosure: public SpaceClosure {
333 private:
334 CardTableRS* _ct;
335 HeapWord* _boundary;
336 public:
337 VerifyCTSpaceClosure(CardTableRS* ct, HeapWord* boundary) :
338 _ct(ct), _boundary(boundary) {}
339 virtual void do_space(Space* s) { _ct->verify_space(s, _boundary); }
340 };
341
342 class VerifyCTGenClosure: public GenCollectedHeap::GenClosure {
343 CardTableRS* _ct;
344 public:
345 VerifyCTGenClosure(CardTableRS* ct) : _ct(ct) {}
346 void do_generation(Generation* gen) {
347 // Skip the youngest generation.
348 if (gen->level() == 0) return;
349 // Normally, we're interested in pointers to younger generations.
350 VerifyCTSpaceClosure blk(_ct, gen->reserved().start());
351 gen->space_iterate(&blk, true);
352 }
353 };
354
355 void CardTableRS::verify_space(Space* s, HeapWord* gen_boundary) {
356 // We don't need to do young-gen spaces.
357 if (s->end() <= gen_boundary) return;
358 MemRegion used = s->used_region();
359
360 jbyte* cur_entry = byte_for(used.start());
361 jbyte* limit = byte_after(used.last());
362 while (cur_entry < limit) {
363 if (*cur_entry == CardTableModRefBS::clean_card) {
364 jbyte* first_dirty = cur_entry+1;
365 while (first_dirty < limit &&
366 *first_dirty == CardTableModRefBS::clean_card) {
367 first_dirty++;
368 }
369 // If the first object is a regular object, and it has a
370 // young-to-old field, that would mark the previous card.
371 HeapWord* boundary = addr_for(cur_entry);
372 HeapWord* end = (first_dirty >= limit) ? used.end() : addr_for(first_dirty);
373 HeapWord* boundary_block = s->block_start(boundary);
374 HeapWord* begin = boundary; // Until proven otherwise.
375 HeapWord* start_block = boundary_block; // Until proven otherwise.
376 if (boundary_block < boundary) {
377 if (s->block_is_obj(boundary_block) && s->obj_is_alive(boundary_block)) {
378 oop boundary_obj = oop(boundary_block);
379 if (!boundary_obj->is_objArray() &&
380 !boundary_obj->is_typeArray()) {
381 guarantee(cur_entry > byte_for(used.start()),
382 "else boundary would be boundary_block");
383 if (*byte_for(boundary_block) != CardTableModRefBS::clean_card) {
384 begin = boundary_block + s->block_size(boundary_block);
385 start_block = begin;
386 }
387 }
388 }
389 }
390 // Now traverse objects until end.
391 HeapWord* cur = start_block;
392 VerifyCleanCardClosure verify_blk(gen_boundary, begin, end);
393 while (cur < end) {
394 if (s->block_is_obj(cur) && s->obj_is_alive(cur)) {
395 oop(cur)->oop_iterate(&verify_blk);
396 }
397 cur += s->block_size(cur);
398 }
399 cur_entry = first_dirty;
400 } else {
401 // We'd normally expect that cur_youngergen_and_prev_nonclean_card
402 // is a transient value, that cannot be in the card table
403 // except during GC, and thus assert that:
404 // guarantee(*cur_entry != cur_youngergen_and_prev_nonclean_card,
405 // "Illegal CT value");
406 // That however, need not hold, as will become clear in the
407 // following...
408
409 // We'd normally expect that if we are in the parallel case,
410 // we can't have left a prev value (which would be different
411 // from the current value) in the card table, and so we'd like to
412 // assert that:
413 // guarantee(cur_youngergen_card_val() == youngergen_card
414 // || !is_prev_youngergen_card_val(*cur_entry),
415 // "Illegal CT value");
416 // That, however, may not hold occasionally, because of
417 // CMS or MSC in the old gen. To wit, consider the
418 // following two simple illustrative scenarios:
419 // (a) CMS: Consider the case where a large object L
420 // spanning several cards is allocated in the old
421 // gen, and has a young gen reference stored in it, dirtying
422 // some interior cards. A young collection scans the card,
423 // finds a young ref and installs a youngergenP_n value.
424 // L then goes dead. Now a CMS collection starts,
425 // finds L dead and sweeps it up. Assume that L is
426 // abutting _unallocated_blk, so _unallocated_blk is
427 // adjusted down to (below) L. Assume further that
428 // no young collection intervenes during this CMS cycle.
429 // The next young gen cycle will not get to look at this
430 // youngergenP_n card since it lies in the unoccupied
431 // part of the space.
432 // Some young collections later the blocks on this
433 // card can be re-allocated either due to direct allocation
434 // or due to absorbing promotions. At this time, the
435 // before-gc verification will fail the above assert.
436 // (b) MSC: In this case, an object L with a young reference
437 // is on a card that (therefore) holds a youngergen_n value.
438 // Suppose also that L lies towards the end of the used
439 // the used space before GC. An MSC collection
440 // occurs that compacts to such an extent that this
441 // card is no longer in the occupied part of the space.
442 // Since current code in MSC does not always clear cards
443 // in the unused part of old gen, this stale youngergen_n
444 // value is left behind and can later be covered by
445 // an object when promotion or direct allocation
446 // re-allocates that part of the heap.
447 //
448 // Fortunately, the presence of such stale card values is
449 // "only" a minor annoyance in that subsequent young collections
450 // might needlessly scan such cards, but would still never corrupt
451 // the heap as a result. However, it's likely not to be a significant
452 // performance inhibitor in practice. For instance,
453 // some recent measurements with unoccupied cards eagerly cleared
454 // out to maintain this invariant, showed next to no
455 // change in young collection times; of course one can construct
456 // degenerate examples where the cost can be significant.)
457 // Note, in particular, that if the "stale" card is modified
458 // after re-allocation, it would be dirty, not "stale". Thus,
459 // we can never have a younger ref in such a card and it is
460 // safe not to scan that card in any collection. [As we see
461 // below, we do some unnecessary scanning
462 // in some cases in the current parallel scanning algorithm.]
463 //
464 // The main point below is that the parallel card scanning code
465 // deals correctly with these stale card values. There are two main
466 // cases to consider where we have a stale "younger gen" value and a
467 // "derivative" case to consider, where we have a stale
468 // "cur_younger_gen_and_prev_non_clean" value, as will become
469 // apparent in the case analysis below.
470 // o Case 1. If the stale value corresponds to a younger_gen_n
471 // value other than the cur_younger_gen value then the code
472 // treats this as being tantamount to a prev_younger_gen
473 // card. This means that the card may be unnecessarily scanned.
474 // There are two sub-cases to consider:
475 // o Case 1a. Let us say that the card is in the occupied part
476 // of the generation at the time the collection begins. In
477 // that case the card will be either cleared when it is scanned
478 // for young pointers, or will be set to cur_younger_gen as a
479 // result of promotion. (We have elided the normal case where
480 // the scanning thread and the promoting thread interleave
481 // possibly resulting in a transient
482 // cur_younger_gen_and_prev_non_clean value before settling
483 // to cur_younger_gen. [End Case 1a.]
484 // o Case 1b. Consider now the case when the card is in the unoccupied
485 // part of the space which becomes occupied because of promotions
486 // into it during the current young GC. In this case the card
487 // will never be scanned for young references. The current
488 // code will set the card value to either
489 // cur_younger_gen_and_prev_non_clean or leave
490 // it with its stale value -- because the promotions didn't
491 // result in any younger refs on that card. Of these two
492 // cases, the latter will be covered in Case 1a during
493 // a subsequent scan. To deal with the former case, we need
494 // to further consider how we deal with a stale value of
495 // cur_younger_gen_and_prev_non_clean in our case analysis
496 // below. This we do in Case 3 below. [End Case 1b]
497 // [End Case 1]
498 // o Case 2. If the stale value corresponds to cur_younger_gen being
499 // a value not necessarily written by a current promotion, the
500 // card will not be scanned by the younger refs scanning code.
501 // (This is OK since as we argued above such cards cannot contain
502 // any younger refs.) The result is that this value will be
503 // treated as a prev_younger_gen value in a subsequent collection,
504 // which is addressed in Case 1 above. [End Case 2]
505 // o Case 3. We here consider the "derivative" case from Case 1b. above
506 // because of which we may find a stale
507 // cur_younger_gen_and_prev_non_clean card value in the table.
508 // Once again, as in Case 1, we consider two subcases, depending
509 // on whether the card lies in the occupied or unoccupied part
510 // of the space at the start of the young collection.
511 // o Case 3a. Let us say the card is in the occupied part of
512 // the old gen at the start of the young collection. In that
513 // case, the card will be scanned by the younger refs scanning
514 // code which will set it to cur_younger_gen. In a subsequent
515 // scan, the card will be considered again and get its final
516 // correct value. [End Case 3a]
517 // o Case 3b. Now consider the case where the card is in the
518 // unoccupied part of the old gen, and is occupied as a result
519 // of promotions during thus young gc. In that case,
520 // the card will not be scanned for younger refs. The presence
521 // of newly promoted objects on the card will then result in
522 // its keeping the value cur_younger_gen_and_prev_non_clean
523 // value, which we have dealt with in Case 3 here. [End Case 3b]
524 // [End Case 3]
525 //
526 // (Please refer to the code in the helper class
527 // ClearNonCleanCardWrapper and in CardTableModRefBS for details.)
528 //
529 // The informal arguments above can be tightened into a formal
530 // correctness proof and it behooves us to write up such a proof,
531 // or to use model checking to prove that there are no lingering
532 // concerns.
533 //
534 // Clearly because of Case 3b one cannot bound the time for
535 // which a card will retain what we have called a "stale" value.
536 // However, one can obtain a Loose upper bound on the redundant
537 // work as a result of such stale values. Note first that any
538 // time a stale card lies in the occupied part of the space at
539 // the start of the collection, it is scanned by younger refs
540 // code and we can define a rank function on card values that
541 // declines when this is so. Note also that when a card does not
542 // lie in the occupied part of the space at the beginning of a
543 // young collection, its rank can either decline or stay unchanged.
544 // In this case, no extra work is done in terms of redundant
545 // younger refs scanning of that card.
546 // Then, the case analysis above reveals that, in the worst case,
547 // any such stale card will be scanned unnecessarily at most twice.
548 //
549 // It is nonethelss advisable to try and get rid of some of this
550 // redundant work in a subsequent (low priority) re-design of
551 // the card-scanning code, if only to simplify the underlying
552 // state machine analysis/proof. ysr 1/28/2002. XXX
553 cur_entry++;
554 }
555 }
556 }
557
558 void CardTableRS::verify() {
559 // At present, we only know how to verify the card table RS for
560 // generational heaps.
561 VerifyCTGenClosure blk(this);
562 CollectedHeap* ch = Universe::heap();
563 // We will do the perm-gen portion of the card table, too.
564 Generation* pg = SharedHeap::heap()->perm_gen();
565 HeapWord* pg_boundary = pg->reserved().start();
566
567 if (ch->kind() == CollectedHeap::GenCollectedHeap) {
568 GenCollectedHeap::heap()->generation_iterate(&blk, false);
569 _ct_bs->verify();
570
571 // If the old gen collections also collect perm, then we are only
572 // interested in perm-to-young pointers, not perm-to-old pointers.
573 GenCollectedHeap* gch = GenCollectedHeap::heap();
574 CollectorPolicy* cp = gch->collector_policy();
575 if (cp->is_mark_sweep_policy() || cp->is_concurrent_mark_sweep_policy()) {
576 pg_boundary = gch->get_gen(1)->reserved().start();
577 }
578 }
579 VerifyCTSpaceClosure perm_space_blk(this, pg_boundary);
580 SharedHeap::heap()->perm_gen()->space_iterate(&perm_space_blk, true);
581 }
582
583
584 void CardTableRS::verify_aligned_region_empty(MemRegion mr) {
585 if (!mr.is_empty()) {
586 jbyte* cur_entry = byte_for(mr.start());
587 jbyte* limit = byte_after(mr.last());
588 // The region mr may not start on a card boundary so
589 // the first card may reflect a write to the space
590 // just prior to mr.
591 if (!is_aligned(mr.start())) {
592 cur_entry++;
593 }
594 for (;cur_entry < limit; cur_entry++) {
595 guarantee(*cur_entry == CardTableModRefBS::clean_card,
596 "Unexpected dirty card found");
597 }
598 }
599 }