1 /*
2 * Copyright (c) 2001, 2018, 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.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/parallel/gcTaskManager.hpp"
27 #include "gc/parallel/objectStartArray.inline.hpp"
28 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
29 #include "gc/parallel/psCardTable.hpp"
30 #include "gc/parallel/psPromotionManager.inline.hpp"
31 #include "gc/parallel/psScavenge.hpp"
32 #include "gc/parallel/psTasks.hpp"
33 #include "gc/parallel/psYoungGen.hpp"
34 #include "oops/oop.inline.hpp"
35 #include "runtime/prefetch.inline.hpp"
36 #include "utilities/align.hpp"
37
38 // Checks an individual oop for missing precise marks. Mark
39 // may be either dirty or newgen.
40 class CheckForUnmarkedOops : public OopClosure {
41 private:
42 PSYoungGen* _young_gen;
43 PSCardTable* _card_table;
44 HeapWord* _unmarked_addr;
45
46 protected:
47 template <class T> void do_oop_work(T* p) {
48 oop obj = oopDesc::load_decode_heap_oop(p);
49 if (_young_gen->is_in_reserved(obj) &&
50 !_card_table->addr_is_marked_imprecise(p)) {
51 // Don't overwrite the first missing card mark
52 if (_unmarked_addr == NULL) {
53 _unmarked_addr = (HeapWord*)p;
54 }
55 }
56 }
57
58 public:
59 CheckForUnmarkedOops(PSYoungGen* young_gen, PSCardTable* card_table) :
60 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
61
62 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); }
63 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
64
65 bool has_unmarked_oop() {
66 return _unmarked_addr != NULL;
67 }
68 };
69
70 // Checks all objects for the existence of some type of mark,
71 // precise or imprecise, dirty or newgen.
72 class CheckForUnmarkedObjects : public ObjectClosure {
73 private:
74 PSYoungGen* _young_gen;
75 PSCardTable* _card_table;
76
77 public:
78 CheckForUnmarkedObjects() {
79 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
80 _young_gen = heap->young_gen();
81 _card_table = heap->card_table();
82 }
83
84 // Card marks are not precise. The current system can leave us with
85 // a mismatch of precise marks and beginning of object marks. This means
86 // we test for missing precise marks first. If any are found, we don't
87 // fail unless the object head is also unmarked.
88 virtual void do_object(oop obj) {
89 CheckForUnmarkedOops object_check(_young_gen, _card_table);
90 obj->oop_iterate_no_header(&object_check);
91 if (object_check.has_unmarked_oop()) {
92 guarantee(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
93 }
94 }
95 };
96
97 // Checks for precise marking of oops as newgen.
98 class CheckForPreciseMarks : public OopClosure {
99 private:
100 PSYoungGen* _young_gen;
101 PSCardTable* _card_table;
102
103 protected:
104 template <class T> void do_oop_work(T* p) {
105 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
106 if (_young_gen->is_in_reserved(obj)) {
107 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
108 _card_table->set_card_newgen(p);
109 }
110 }
111
112 public:
113 CheckForPreciseMarks(PSYoungGen* young_gen, PSCardTable* card_table) :
114 _young_gen(young_gen), _card_table(card_table) { }
115
116 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); }
117 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
118 };
119
120 // We get passed the space_top value to prevent us from traversing into
121 // the old_gen promotion labs, which cannot be safely parsed.
122
123 // Do not call this method if the space is empty.
124 // It is a waste to start tasks and get here only to
125 // do no work. If this method needs to be called
126 // when the space is empty, fix the calculation of
127 // end_card to allow sp_top == sp->bottom().
128
129 void PSCardTable::scavenge_contents_parallel(ObjectStartArray* start_array,
130 MutableSpace* sp,
131 HeapWord* space_top,
132 PSPromotionManager* pm,
133 uint stripe_number,
134 uint stripe_total) {
135 int ssize = 128; // Naked constant! Work unit = 64k.
136 int dirty_card_count = 0;
137
138 // It is a waste to get here if empty.
139 assert(sp->bottom() < sp->top(), "Should not be called if empty");
140 oop* sp_top = (oop*)space_top;
141 jbyte* start_card = byte_for(sp->bottom());
142 jbyte* end_card = byte_for(sp_top - 1) + 1;
143 oop* last_scanned = NULL; // Prevent scanning objects more than once
144 // The width of the stripe ssize*stripe_total must be
145 // consistent with the number of stripes so that the complete slice
146 // is covered.
147 size_t slice_width = ssize * stripe_total;
148 for (jbyte* slice = start_card; slice < end_card; slice += slice_width) {
149 jbyte* worker_start_card = slice + stripe_number * ssize;
150 if (worker_start_card >= end_card)
151 return; // We're done.
152
153 jbyte* worker_end_card = worker_start_card + ssize;
154 if (worker_end_card > end_card)
155 worker_end_card = end_card;
156
157 // We do not want to scan objects more than once. In order to accomplish
158 // this, we assert that any object with an object head inside our 'slice'
159 // belongs to us. We may need to extend the range of scanned cards if the
160 // last object continues into the next 'slice'.
161 //
162 // Note! ending cards are exclusive!
163 HeapWord* slice_start = addr_for(worker_start_card);
164 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
165
166 #ifdef ASSERT
167 if (GCWorkerDelayMillis > 0) {
168 // Delay 1 worker so that it proceeds after all the work
169 // has been completed.
170 if (stripe_number < 2) {
171 os::sleep(Thread::current(), GCWorkerDelayMillis, false);
172 }
173 }
174 #endif
175
176 // If there are not objects starting within the chunk, skip it.
177 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
178 continue;
179 }
180 // Update our beginning addr
181 HeapWord* first_object = start_array->object_start(slice_start);
182 debug_only(oop* first_object_within_slice = (oop*) first_object;)
183 if (first_object < slice_start) {
184 last_scanned = (oop*)(first_object + oop(first_object)->size());
185 debug_only(first_object_within_slice = last_scanned;)
186 worker_start_card = byte_for(last_scanned);
187 }
188
189 // Update the ending addr
190 if (slice_end < (HeapWord*)sp_top) {
191 // The subtraction is important! An object may start precisely at slice_end.
192 HeapWord* last_object = start_array->object_start(slice_end - 1);
193 slice_end = last_object + oop(last_object)->size();
194 // worker_end_card is exclusive, so bump it one past the end of last_object's
195 // covered span.
196 worker_end_card = byte_for(slice_end) + 1;
197
198 if (worker_end_card > end_card)
199 worker_end_card = end_card;
200 }
201
202 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
203 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
204 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
205 // Note that worker_start_card >= worker_end_card is legal, and happens when
206 // an object spans an entire slice.
207 assert(worker_start_card <= end_card, "worker start card beyond end card");
208 assert(worker_end_card <= end_card, "worker end card beyond end card");
209
210 jbyte* current_card = worker_start_card;
211 while (current_card < worker_end_card) {
212 // Find an unclean card.
213 while (current_card < worker_end_card && card_is_clean(*current_card)) {
214 current_card++;
215 }
216 jbyte* first_unclean_card = current_card;
217
218 // Find the end of a run of contiguous unclean cards
219 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
220 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
221 current_card++;
222 }
223
224 if (current_card < worker_end_card) {
225 // Some objects may be large enough to span several cards. If such
226 // an object has more than one dirty card, separated by a clean card,
227 // we will attempt to scan it twice. The test against "last_scanned"
228 // prevents the redundant object scan, but it does not prevent newly
229 // marked cards from being cleaned.
230 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
231 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
232 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
233 jbyte* ending_card_of_last_object = byte_for(end_of_last_object);
234 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
235 if (ending_card_of_last_object > current_card) {
236 // This means the object spans the next complete card.
237 // We need to bump the current_card to ending_card_of_last_object
238 current_card = ending_card_of_last_object;
239 }
240 }
241 }
242 jbyte* following_clean_card = current_card;
243
244 if (first_unclean_card < worker_end_card) {
245 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
246 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
247 // "p" should always be >= "last_scanned" because newly GC dirtied
248 // cards are no longer scanned again (see comment at end
249 // of loop on the increment of "current_card"). Test that
250 // hypothesis before removing this code.
251 // If this code is removed, deal with the first time through
252 // the loop when the last_scanned is the object starting in
253 // the previous slice.
254 assert((p >= last_scanned) ||
255 (last_scanned == first_object_within_slice),
256 "Should no longer be possible");
257 if (p < last_scanned) {
258 // Avoid scanning more than once; this can happen because
259 // newgen cards set by GC may a different set than the
260 // originally dirty set
261 p = last_scanned;
262 }
263 oop* to = (oop*)addr_for(following_clean_card);
264
265 // Test slice_end first!
266 if ((HeapWord*)to > slice_end) {
267 to = (oop*)slice_end;
268 } else if (to > sp_top) {
269 to = sp_top;
270 }
271
272 // we know which cards to scan, now clear them
273 if (first_unclean_card <= worker_start_card+1)
274 first_unclean_card = worker_start_card+1;
275 if (following_clean_card >= worker_end_card-1)
276 following_clean_card = worker_end_card-1;
277
278 while (first_unclean_card < following_clean_card) {
279 *first_unclean_card++ = clean_card;
280 }
281
282 const int interval = PrefetchScanIntervalInBytes;
283 // scan all objects in the range
284 if (interval != 0) {
285 while (p < to) {
286 Prefetch::write(p, interval);
287 oop m = oop(p);
288 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
289 pm->push_contents(m);
290 p += m->size();
291 }
292 pm->drain_stacks_cond_depth();
293 } else {
294 while (p < to) {
295 oop m = oop(p);
296 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
297 pm->push_contents(m);
298 p += m->size();
299 }
300 pm->drain_stacks_cond_depth();
301 }
302 last_scanned = p;
303 }
304 // "current_card" is still the "following_clean_card" or
305 // the current_card is >= the worker_end_card so the
306 // loop will not execute again.
307 assert((current_card == following_clean_card) ||
308 (current_card >= worker_end_card),
309 "current_card should only be incremented if it still equals "
310 "following_clean_card");
311 // Increment current_card so that it is not processed again.
312 // It may now be dirty because a old-to-young pointer was
313 // found on it an updated. If it is now dirty, it cannot be
314 // be safely cleaned in the next iteration.
315 current_card++;
316 }
317 }
318 }
319
320 // This should be called before a scavenge.
321 void PSCardTable::verify_all_young_refs_imprecise() {
322 CheckForUnmarkedObjects check;
323
324 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
325 PSOldGen* old_gen = heap->old_gen();
326
327 old_gen->object_iterate(&check);
328 }
329
330 // This should be called immediately after a scavenge, before mutators resume.
331 void PSCardTable::verify_all_young_refs_precise() {
332 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
333 PSOldGen* old_gen = heap->old_gen();
334
335 CheckForPreciseMarks check(heap->young_gen(), this);
336
337 old_gen->oop_iterate_no_header(&check);
338
339 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
340 }
341
342 void PSCardTable::verify_all_young_refs_precise_helper(MemRegion mr) {
343 jbyte* bot = byte_for(mr.start());
344 jbyte* top = byte_for(mr.end());
345 while (bot <= top) {
346 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
347 if (*bot == verify_card)
348 *bot = youngergen_card;
349 bot++;
350 }
351 }
352
353 bool PSCardTable::addr_is_marked_imprecise(void *addr) {
354 jbyte* p = byte_for(addr);
355 jbyte val = *p;
356
357 if (card_is_dirty(val))
358 return true;
359
360 if (card_is_newgen(val))
361 return true;
362
363 if (card_is_clean(val))
364 return false;
365
366 assert(false, "Found unhandled card mark type");
367
368 return false;
369 }
370
371 // Also includes verify_card
372 bool PSCardTable::addr_is_marked_precise(void *addr) {
373 jbyte* p = byte_for(addr);
374 jbyte val = *p;
375
376 if (card_is_newgen(val))
377 return true;
378
379 if (card_is_verify(val))
380 return true;
381
382 if (card_is_clean(val))
383 return false;
384
385 if (card_is_dirty(val))
386 return false;
387
388 assert(false, "Found unhandled card mark type");
389
390 return false;
391 }
392
393 // Assumes that only the base or the end changes. This allows indentification
394 // of the region that is being resized. The
395 // CardTable::resize_covered_region() is used for the normal case
396 // where the covered regions are growing or shrinking at the high end.
397 // The method resize_covered_region_by_end() is analogous to
398 // CardTable::resize_covered_region() but
399 // for regions that grow or shrink at the low end.
400 void PSCardTable::resize_covered_region(MemRegion new_region) {
401 for (int i = 0; i < _cur_covered_regions; i++) {
402 if (_covered[i].start() == new_region.start()) {
403 // Found a covered region with the same start as the
404 // new region. The region is growing or shrinking
405 // from the start of the region.
406 resize_covered_region_by_start(new_region);
407 return;
408 }
409 if (_covered[i].start() > new_region.start()) {
410 break;
411 }
412 }
413
414 int changed_region = -1;
415 for (int j = 0; j < _cur_covered_regions; j++) {
416 if (_covered[j].end() == new_region.end()) {
417 changed_region = j;
418 // This is a case where the covered region is growing or shrinking
419 // at the start of the region.
420 assert(changed_region != -1, "Don't expect to add a covered region");
421 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
422 "The sizes should be different here");
423 resize_covered_region_by_end(changed_region, new_region);
424 return;
425 }
426 }
427 // This should only be a new covered region (where no existing
428 // covered region matches at the start or the end).
429 assert(_cur_covered_regions < _max_covered_regions,
430 "An existing region should have been found");
431 resize_covered_region_by_start(new_region);
432 }
433
434 void PSCardTable::resize_covered_region_by_start(MemRegion new_region) {
435 CardTable::resize_covered_region(new_region);
436 debug_only(verify_guard();)
437 }
438
439 void PSCardTable::resize_covered_region_by_end(int changed_region,
440 MemRegion new_region) {
441 assert(SafepointSynchronize::is_at_safepoint(),
442 "Only expect an expansion at the low end at a GC");
443 debug_only(verify_guard();)
444 #ifdef ASSERT
445 for (int k = 0; k < _cur_covered_regions; k++) {
446 if (_covered[k].end() == new_region.end()) {
447 assert(changed_region == k, "Changed region is incorrect");
448 break;
449 }
450 }
451 #endif
452
453 // Commit new or uncommit old pages, if necessary.
454 if (resize_commit_uncommit(changed_region, new_region)) {
455 // Set the new start of the committed region
456 resize_update_committed_table(changed_region, new_region);
457 }
458
459 // Update card table entries
460 resize_update_card_table_entries(changed_region, new_region);
461
462 // Update the covered region
463 resize_update_covered_table(changed_region, new_region);
464
465 int ind = changed_region;
466 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
467 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
468 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
469 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
470 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
471 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
472 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
473 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
474 p2i(addr_for((jbyte*) _committed[ind].start())), p2i(addr_for((jbyte*) _committed[ind].last())));
475
476 debug_only(verify_guard();)
477 }
478
479 bool PSCardTable::resize_commit_uncommit(int changed_region,
480 MemRegion new_region) {
481 bool result = false;
482 // Commit new or uncommit old pages, if necessary.
483 MemRegion cur_committed = _committed[changed_region];
484 assert(_covered[changed_region].end() == new_region.end(),
485 "The ends of the regions are expected to match");
486 // Extend the start of this _committed region to
487 // to cover the start of any previous _committed region.
488 // This forms overlapping regions, but never interior regions.
489 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
490 if (min_prev_start < cur_committed.start()) {
491 // Only really need to set start of "cur_committed" to
492 // the new start (min_prev_start) but assertion checking code
493 // below use cur_committed.end() so make it correct.
494 MemRegion new_committed =
495 MemRegion(min_prev_start, cur_committed.end());
496 cur_committed = new_committed;
497 }
498 #ifdef ASSERT
499 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
500 assert(cur_committed.start() == align_up(cur_committed.start(), os::vm_page_size()),
501 "Starts should have proper alignment");
502 #endif
503
504 jbyte* new_start = byte_for(new_region.start());
505 // Round down because this is for the start address
506 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
507 // The guard page is always committed and should not be committed over.
508 // This method is used in cases where the generation is growing toward
509 // lower addresses but the guard region is still at the end of the
510 // card table. That still makes sense when looking for writes
511 // off the end of the card table.
512 if (new_start_aligned < cur_committed.start()) {
513 // Expand the committed region
514 //
515 // Case A
516 // |+ guard +|
517 // |+ cur committed +++++++++|
518 // |+ new committed +++++++++++++++++|
519 //
520 // Case B
521 // |+ guard +|
522 // |+ cur committed +|
523 // |+ new committed +++++++|
524 //
525 // These are not expected because the calculation of the
526 // cur committed region and the new committed region
527 // share the same end for the covered region.
528 // Case C
529 // |+ guard +|
530 // |+ cur committed +|
531 // |+ new committed +++++++++++++++++|
532 // Case D
533 // |+ guard +|
534 // |+ cur committed +++++++++++|
535 // |+ new committed +++++++|
536
537 HeapWord* new_end_for_commit =
538 MIN2(cur_committed.end(), _guard_region.start());
539 if(new_start_aligned < new_end_for_commit) {
540 MemRegion new_committed =
541 MemRegion(new_start_aligned, new_end_for_commit);
542 os::commit_memory_or_exit((char*)new_committed.start(),
543 new_committed.byte_size(), !ExecMem,
544 "card table expansion");
545 }
546 result = true;
547 } else if (new_start_aligned > cur_committed.start()) {
548 // Shrink the committed region
549 #if 0 // uncommitting space is currently unsafe because of the interactions
550 // of growing and shrinking regions. One region A can uncommit space
551 // that it owns but which is being used by another region B (maybe).
552 // Region B has not committed the space because it was already
553 // committed by region A.
554 MemRegion uncommit_region = committed_unique_to_self(changed_region,
555 MemRegion(cur_committed.start(), new_start_aligned));
556 if (!uncommit_region.is_empty()) {
557 if (!os::uncommit_memory((char*)uncommit_region.start(),
558 uncommit_region.byte_size())) {
559 // If the uncommit fails, ignore it. Let the
560 // committed table resizing go even though the committed
561 // table will over state the committed space.
562 }
563 }
564 #else
565 assert(!result, "Should be false with current workaround");
566 #endif
567 }
568 assert(_committed[changed_region].end() == cur_committed.end(),
569 "end should not change");
570 return result;
571 }
572
573 void PSCardTable::resize_update_committed_table(int changed_region,
574 MemRegion new_region) {
575
576 jbyte* new_start = byte_for(new_region.start());
577 // Set the new start of the committed region
578 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
579 MemRegion new_committed = MemRegion(new_start_aligned,
580 _committed[changed_region].end());
581 _committed[changed_region] = new_committed;
582 _committed[changed_region].set_start(new_start_aligned);
583 }
584
585 void PSCardTable::resize_update_card_table_entries(int changed_region,
586 MemRegion new_region) {
587 debug_only(verify_guard();)
588 MemRegion original_covered = _covered[changed_region];
589 // Initialize the card entries. Only consider the
590 // region covered by the card table (_whole_heap)
591 jbyte* entry;
592 if (new_region.start() < _whole_heap.start()) {
593 entry = byte_for(_whole_heap.start());
594 } else {
595 entry = byte_for(new_region.start());
596 }
597 jbyte* end = byte_for(original_covered.start());
598 // If _whole_heap starts at the original covered regions start,
599 // this loop will not execute.
600 while (entry < end) { *entry++ = clean_card; }
601 }
602
603 void PSCardTable::resize_update_covered_table(int changed_region,
604 MemRegion new_region) {
605 // Update the covered region
606 _covered[changed_region].set_start(new_region.start());
607 _covered[changed_region].set_word_size(new_region.word_size());
608
609 // reorder regions. There should only be at most 1 out
610 // of order.
611 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
612 if (_covered[i].start() < _covered[i-1].start()) {
613 MemRegion covered_mr = _covered[i-1];
614 _covered[i-1] = _covered[i];
615 _covered[i] = covered_mr;
616 MemRegion committed_mr = _committed[i-1];
617 _committed[i-1] = _committed[i];
618 _committed[i] = committed_mr;
619 break;
620 }
621 }
622 #ifdef ASSERT
623 for (int m = 0; m < _cur_covered_regions-1; m++) {
624 assert(_covered[m].start() <= _covered[m+1].start(),
625 "Covered regions out of order");
626 assert(_committed[m].start() <= _committed[m+1].start(),
627 "Committed regions out of order");
628 }
629 #endif
630 }
631
632 // Returns the start of any committed region that is lower than
633 // the target committed region (index ind) and that intersects the
634 // target region. If none, return start of target region.
635 //
636 // -------------
637 // | |
638 // -------------
639 // ------------
640 // | target |
641 // ------------
642 // -------------
643 // | |
644 // -------------
645 // ^ returns this
646 //
647 // -------------
648 // | |
649 // -------------
650 // ------------
651 // | target |
652 // ------------
653 // -------------
654 // | |
655 // -------------
656 // ^ returns this
657
658 HeapWord* PSCardTable::lowest_prev_committed_start(int ind) const {
659 assert(_cur_covered_regions >= 0, "Expecting at least on region");
660 HeapWord* min_start = _committed[ind].start();
661 for (int j = 0; j < ind; j++) {
662 HeapWord* this_start = _committed[j].start();
663 if ((this_start < min_start) &&
664 !(_committed[j].intersection(_committed[ind])).is_empty()) {
665 min_start = this_start;
666 }
667 }
668 return min_start;
669 }
670
671 bool PSCardTable::is_in_young(oop obj) const {
672 return ParallelScavengeHeap::heap()->is_in_young(obj);
673 }