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.inline.hpp"
32#include "gc/parallel/psTasks.hpp"
33#include "gc/parallel/psYoungGen.hpp"
34#include "memory/iterator.inline.hpp"
35#include "oops/access.inline.hpp"
36#include "oops/oop.inline.hpp"
37#include "runtime/prefetch.inline.hpp"
38#include "utilities/align.hpp"
39
40// Checks an individual oop for missing precise marks. Mark
41// may be either dirty or newgen.
42class CheckForUnmarkedOops : public BasicOopIterateClosure {
43 private:
44 PSYoungGen* _young_gen;
45 PSCardTable* _card_table;
46 HeapWord* _unmarked_addr;
47
48 protected:
49 template <class T> void do_oop_work(T* p) {
50 oop obj = RawAccess<>::oop_load(p);
51 if (_young_gen->is_in_reserved(obj) &&
52 !_card_table->addr_is_marked_imprecise(p)) {
53 // Don't overwrite the first missing card mark
54 if (_unmarked_addr == NULL) {
55 _unmarked_addr = (HeapWord*)p;
56 }
57 }
58 }
59
60 public:
61 CheckForUnmarkedOops(PSYoungGen* young_gen, PSCardTable* card_table) :
62 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
63
64 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); }
65 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
66
67 bool has_unmarked_oop() {
68 return _unmarked_addr != NULL;
69 }
70};
71
72// Checks all objects for the existence of some type of mark,
73// precise or imprecise, dirty or newgen.
74class CheckForUnmarkedObjects : public ObjectClosure {
75 private:
76 PSYoungGen* _young_gen;
77 PSCardTable* _card_table;
78
79 public:
80 CheckForUnmarkedObjects() {
81 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
82 _young_gen = heap->young_gen();
83 _card_table = heap->card_table();
84 }
85
86 // Card marks are not precise. The current system can leave us with
87 // a mismatch of precise marks and beginning of object marks. This means
88 // we test for missing precise marks first. If any are found, we don't
89 // fail unless the object head is also unmarked.
90 virtual void do_object(oop obj) {
91 CheckForUnmarkedOops object_check(_young_gen, _card_table);
92 obj->oop_iterate(&object_check);
93 if (object_check.has_unmarked_oop()) {
94 guarantee(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
95 }
96 }
97};
98
99// Checks for precise marking of oops as newgen.
100class CheckForPreciseMarks : public BasicOopIterateClosure {
101 private:
102 PSYoungGen* _young_gen;
103 PSCardTable* _card_table;
104
105 protected:
106 template <class T> void do_oop_work(T* p) {
107 oop obj = RawAccess<IS_NOT_NULL>::oop_load(p);
108 if (_young_gen->is_in_reserved(obj)) {
109 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
110 _card_table->set_card_newgen(p);
111 }
112 }
113
114 public:
115 CheckForPreciseMarks(PSYoungGen* young_gen, PSCardTable* card_table) :
116 _young_gen(young_gen), _card_table(card_table) { }
117
118 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); }
119 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
120};
121
122// We get passed the space_top value to prevent us from traversing into
123// the old_gen promotion labs, which cannot be safely parsed.
124
125// Do not call this method if the space is empty.
126// It is a waste to start tasks and get here only to
127// do no work. If this method needs to be called
128// when the space is empty, fix the calculation of
129// end_card to allow sp_top == sp->bottom().
130
131void PSCardTable::scavenge_contents_parallel(ObjectStartArray* start_array,
132 MutableSpace* sp,
133 HeapWord* space_top,
134 PSPromotionManager* pm,
135 uint stripe_number,
136 uint stripe_total) {
137 int ssize = 128; // Naked constant! Work unit = 64k.
138 int dirty_card_count = 0;
139
140 // It is a waste to get here if empty.
141 assert(sp->bottom() < sp->top(), "Should not be called if empty");
142 oop* sp_top = (oop*)space_top;
143 CardValue* start_card = byte_for(sp->bottom());
144 CardValue* end_card = byte_for(sp_top - 1) + 1;
145 oop* last_scanned = NULL; // Prevent scanning objects more than once
146 // The width of the stripe ssize*stripe_total must be
147 // consistent with the number of stripes so that the complete slice
148 // is covered.
149 size_t slice_width = ssize * stripe_total;
150 for (CardValue* slice = start_card; slice < end_card; slice += slice_width) {
151 CardValue* worker_start_card = slice + stripe_number * ssize;
152 if (worker_start_card >= end_card)
153 return; // We're done.
154
155 CardValue* worker_end_card = worker_start_card + ssize;
156 if (worker_end_card > end_card)
157 worker_end_card = end_card;
158
159 // We do not want to scan objects more than once. In order to accomplish
160 // this, we assert that any object with an object head inside our 'slice'
161 // belongs to us. We may need to extend the range of scanned cards if the
162 // last object continues into the next 'slice'.
163 //
164 // Note! ending cards are exclusive!
165 HeapWord* slice_start = addr_for(worker_start_card);
166 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
167
168#ifdef ASSERT
169 if (GCWorkerDelayMillis > 0) {
170 // Delay 1 worker so that it proceeds after all the work
171 // has been completed.
172 if (stripe_number < 2) {
173 os::sleep(Thread::current(), GCWorkerDelayMillis, false);
174 }
175 }
176#endif
177
178 // If there are not objects starting within the chunk, skip it.
179 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
180 continue;
181 }
182 // Update our beginning addr
183 HeapWord* first_object = start_array->object_start(slice_start);
184 debug_only(oop* first_object_within_slice = (oop*) first_object;)
185 if (first_object < slice_start) {
186 last_scanned = (oop*)(first_object + oop(first_object)->size());
187 debug_only(first_object_within_slice = last_scanned;)
188 worker_start_card = byte_for(last_scanned);
189 }
190
191 // Update the ending addr
192 if (slice_end < (HeapWord*)sp_top) {
193 // The subtraction is important! An object may start precisely at slice_end.
194 HeapWord* last_object = start_array->object_start(slice_end - 1);
195 slice_end = last_object + oop(last_object)->size();
196 // worker_end_card is exclusive, so bump it one past the end of last_object's
197 // covered span.
198 worker_end_card = byte_for(slice_end) + 1;
199
200 if (worker_end_card > end_card)
201 worker_end_card = end_card;
202 }
203
204 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
205 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
206 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
207 // Note that worker_start_card >= worker_end_card is legal, and happens when
208 // an object spans an entire slice.
209 assert(worker_start_card <= end_card, "worker start card beyond end card");
210 assert(worker_end_card <= end_card, "worker end card beyond end card");
211
212 CardValue* current_card = worker_start_card;
213 while (current_card < worker_end_card) {
214 // Find an unclean card.
215 while (current_card < worker_end_card && card_is_clean(*current_card)) {
216 current_card++;
217 }
218 CardValue* first_unclean_card = current_card;
219
220 // Find the end of a run of contiguous unclean cards
221 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
222 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
223 current_card++;
224 }
225
226 if (current_card < worker_end_card) {
227 // Some objects may be large enough to span several cards. If such
228 // an object has more than one dirty card, separated by a clean card,
229 // we will attempt to scan it twice. The test against "last_scanned"
230 // prevents the redundant object scan, but it does not prevent newly
231 // marked cards from being cleaned.
232 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
233 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
234 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
235 CardValue* ending_card_of_last_object = byte_for(end_of_last_object);
236 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
237 if (ending_card_of_last_object > current_card) {
238 // This means the object spans the next complete card.
239 // We need to bump the current_card to ending_card_of_last_object
240 current_card = ending_card_of_last_object;
241 }
242 }
243 }
244 CardValue* following_clean_card = current_card;
245
246 if (first_unclean_card < worker_end_card) {
247 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
248 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
249 // "p" should always be >= "last_scanned" because newly GC dirtied
250 // cards are no longer scanned again (see comment at end
251 // of loop on the increment of "current_card"). Test that
252 // hypothesis before removing this code.
253 // If this code is removed, deal with the first time through
254 // the loop when the last_scanned is the object starting in
255 // the previous slice.
256 assert((p >= last_scanned) ||
257 (last_scanned == first_object_within_slice),
258 "Should no longer be possible");
259 if (p < last_scanned) {
260 // Avoid scanning more than once; this can happen because
261 // newgen cards set by GC may a different set than the
262 // originally dirty set
263 p = last_scanned;
264 }
265 oop* to = (oop*)addr_for(following_clean_card);
266
267 // Test slice_end first!
268 if ((HeapWord*)to > slice_end) {
269 to = (oop*)slice_end;
270 } else if (to > sp_top) {
271 to = sp_top;
272 }
273
274 // we know which cards to scan, now clear them
275 if (first_unclean_card <= worker_start_card+1)
276 first_unclean_card = worker_start_card+1;
277 if (following_clean_card >= worker_end_card-1)
278 following_clean_card = worker_end_card-1;
279
280 while (first_unclean_card < following_clean_card) {
281 *first_unclean_card++ = clean_card;
282 }
283
284 const int interval = PrefetchScanIntervalInBytes;
285 // scan all objects in the range
286 if (interval != 0) {
287 while (p < to) {
288 Prefetch::write(p, interval);
289 oop m = oop(p);
290 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
291 pm->push_contents(m);
292 p += m->size();
293 }
294 pm->drain_stacks_cond_depth();
295 } else {
296 while (p < to) {
297 oop m = oop(p);
298 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
299 pm->push_contents(m);
300 p += m->size();
301 }
302 pm->drain_stacks_cond_depth();
303 }
304 last_scanned = p;
305 }
306 // "current_card" is still the "following_clean_card" or
307 // the current_card is >= the worker_end_card so the
308 // loop will not execute again.
309 assert((current_card == following_clean_card) ||
310 (current_card >= worker_end_card),
311 "current_card should only be incremented if it still equals "
312 "following_clean_card");
313 // Increment current_card so that it is not processed again.
314 // It may now be dirty because a old-to-young pointer was
315 // found on it an updated. If it is now dirty, it cannot be
316 // be safely cleaned in the next iteration.
317 current_card++;
318 }
319 }
320}
321
322// This should be called before a scavenge.
323void PSCardTable::verify_all_young_refs_imprecise() {
324 CheckForUnmarkedObjects check;
325
326 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
327 PSOldGen* old_gen = heap->old_gen();
328
329 old_gen->object_iterate(&check);
330}
331
332// This should be called immediately after a scavenge, before mutators resume.
333void PSCardTable::verify_all_young_refs_precise() {
334 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
335 PSOldGen* old_gen = heap->old_gen();
336
337 CheckForPreciseMarks check(heap->young_gen(), this);
338
339 old_gen->oop_iterate(&check);
340
341 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
342}
343
344void PSCardTable::verify_all_young_refs_precise_helper(MemRegion mr) {
345 CardValue* bot = byte_for(mr.start());
346 CardValue* top = byte_for(mr.end());
347 while (bot <= top) {
348 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
349 if (*bot == verify_card)
350 *bot = youngergen_card;
351 bot++;
352 }
353}
354
355bool PSCardTable::addr_is_marked_imprecise(void *addr) {
356 CardValue* p = byte_for(addr);
357 CardValue val = *p;
358
359 if (card_is_dirty(val))
360 return true;
361
362 if (card_is_newgen(val))
363 return true;
364
365 if (card_is_clean(val))
366 return false;
367
368 assert(false, "Found unhandled card mark type");
369
370 return false;
371}
372
373// Also includes verify_card
374bool PSCardTable::addr_is_marked_precise(void *addr) {
375 CardValue* p = byte_for(addr);
376 CardValue val = *p;
377
378 if (card_is_newgen(val))
379 return true;
380
381 if (card_is_verify(val))
382 return true;
383
384 if (card_is_clean(val))
385 return false;
386
387 if (card_is_dirty(val))
388 return false;
389
390 assert(false, "Found unhandled card mark type");
391
392 return false;
393}
394
395// Assumes that only the base or the end changes. This allows indentification
396// of the region that is being resized. The
397// CardTable::resize_covered_region() is used for the normal case
398// where the covered regions are growing or shrinking at the high end.
399// The method resize_covered_region_by_end() is analogous to
400// CardTable::resize_covered_region() but
401// for regions that grow or shrink at the low end.
402void PSCardTable::resize_covered_region(MemRegion new_region) {
403 for (int i = 0; i < _cur_covered_regions; i++) {
404 if (_covered[i].start() == new_region.start()) {
405 // Found a covered region with the same start as the
406 // new region. The region is growing or shrinking
407 // from the start of the region.
408 resize_covered_region_by_start(new_region);
409 return;
410 }
411 if (_covered[i].start() > new_region.start()) {
412 break;
413 }
414 }
415
416 int changed_region = -1;
417 for (int j = 0; j < _cur_covered_regions; j++) {
418 if (_covered[j].end() == new_region.end()) {
419 changed_region = j;
420 // This is a case where the covered region is growing or shrinking
421 // at the start of the region.
422 assert(changed_region != -1, "Don't expect to add a covered region");
423 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
424 "The sizes should be different here");
425 resize_covered_region_by_end(changed_region, new_region);
426 return;
427 }
428 }
429 // This should only be a new covered region (where no existing
430 // covered region matches at the start or the end).
431 assert(_cur_covered_regions < _max_covered_regions,
432 "An existing region should have been found");
433 resize_covered_region_by_start(new_region);
434}
435
436void PSCardTable::resize_covered_region_by_start(MemRegion new_region) {
437 CardTable::resize_covered_region(new_region);
438 debug_only(verify_guard();)
439}
440
441void PSCardTable::resize_covered_region_by_end(int changed_region,
442 MemRegion new_region) {
443 assert(SafepointSynchronize::is_at_safepoint(),
444 "Only expect an expansion at the low end at a GC");
445 debug_only(verify_guard();)
446#ifdef ASSERT
447 for (int k = 0; k < _cur_covered_regions; k++) {
448 if (_covered[k].end() == new_region.end()) {
449 assert(changed_region == k, "Changed region is incorrect");
450 break;
451 }
452 }
453#endif
454
455 // Commit new or uncommit old pages, if necessary.
456 if (resize_commit_uncommit(changed_region, new_region)) {
457 // Set the new start of the committed region
458 resize_update_committed_table(changed_region, new_region);
459 }
460
461 // Update card table entries
462 resize_update_card_table_entries(changed_region, new_region);
463
464 // Update the covered region
465 resize_update_covered_table(changed_region, new_region);
466
467 int ind = changed_region;
468 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
469 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
470 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
471 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
472 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
473 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
474 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
475 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
476 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
477
478 debug_only(verify_guard();)
479}
480
481bool PSCardTable::resize_commit_uncommit(int changed_region,
482 MemRegion new_region) {
483 bool result = false;
484 // Commit new or uncommit old pages, if necessary.
485 MemRegion cur_committed = _committed[changed_region];
486 assert(_covered[changed_region].end() == new_region.end(),
487 "The ends of the regions are expected to match");
488 // Extend the start of this _committed region to
489 // to cover the start of any previous _committed region.
490 // This forms overlapping regions, but never interior regions.
491 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
492 if (min_prev_start < cur_committed.start()) {
493 // Only really need to set start of "cur_committed" to
494 // the new start (min_prev_start) but assertion checking code
495 // below use cur_committed.end() so make it correct.
496 MemRegion new_committed =
497 MemRegion(min_prev_start, cur_committed.end());
498 cur_committed = new_committed;
499 }
500#ifdef ASSERT
501 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
502 assert(cur_committed.start() == align_up(cur_committed.start(), os::vm_page_size()),
503 "Starts should have proper alignment");
504#endif
505
506 CardValue* new_start = byte_for(new_region.start());
507 // Round down because this is for the start address
508 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
509 // The guard page is always committed and should not be committed over.
510 // This method is used in cases where the generation is growing toward
511 // lower addresses but the guard region is still at the end of the
512 // card table. That still makes sense when looking for writes
513 // off the end of the card table.
514 if (new_start_aligned < cur_committed.start()) {
515 // Expand the committed region
516 //
517 // Case A
518 // |+ guard +|
519 // |+ cur committed +++++++++|
520 // |+ new committed +++++++++++++++++|
521 //
522 // Case B
523 // |+ guard +|
524 // |+ cur committed +|
525 // |+ new committed +++++++|
526 //
527 // These are not expected because the calculation of the
528 // cur committed region and the new committed region
529 // share the same end for the covered region.
530 // Case C
531 // |+ guard +|
532 // |+ cur committed +|
533 // |+ new committed +++++++++++++++++|
534 // Case D
535 // |+ guard +|
536 // |+ cur committed +++++++++++|
537 // |+ new committed +++++++|
538
539 HeapWord* new_end_for_commit =
540 MIN2(cur_committed.end(), _guard_region.start());
541 if(new_start_aligned < new_end_for_commit) {
542 MemRegion new_committed =
543 MemRegion(new_start_aligned, new_end_for_commit);
544 os::commit_memory_or_exit((char*)new_committed.start(),
545 new_committed.byte_size(), !ExecMem,
546 "card table expansion");
547 }
548 result = true;
549 } else if (new_start_aligned > cur_committed.start()) {
550 // Shrink the committed region
551#if 0 // uncommitting space is currently unsafe because of the interactions
552 // of growing and shrinking regions. One region A can uncommit space
553 // that it owns but which is being used by another region B (maybe).
554 // Region B has not committed the space because it was already
555 // committed by region A.
556 MemRegion uncommit_region = committed_unique_to_self(changed_region,
557 MemRegion(cur_committed.start(), new_start_aligned));
558 if (!uncommit_region.is_empty()) {
559 if (!os::uncommit_memory((char*)uncommit_region.start(),
560 uncommit_region.byte_size())) {
561 // If the uncommit fails, ignore it. Let the
562 // committed table resizing go even though the committed
563 // table will over state the committed space.
564 }
565 }
566#else
567 assert(!result, "Should be false with current workaround");
568#endif
569 }
570 assert(_committed[changed_region].end() == cur_committed.end(),
571 "end should not change");
572 return result;
573}
574
575void PSCardTable::resize_update_committed_table(int changed_region,
576 MemRegion new_region) {
577
578 CardValue* new_start = byte_for(new_region.start());
579 // Set the new start of the committed region
580 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
581 MemRegion new_committed = MemRegion(new_start_aligned,
582 _committed[changed_region].end());
583 _committed[changed_region] = new_committed;
584 _committed[changed_region].set_start(new_start_aligned);
585}
586
587void PSCardTable::resize_update_card_table_entries(int changed_region,
588 MemRegion new_region) {
589 debug_only(verify_guard();)
590 MemRegion original_covered = _covered[changed_region];
591 // Initialize the card entries. Only consider the
592 // region covered by the card table (_whole_heap)
593 CardValue* entry;
594 if (new_region.start() < _whole_heap.start()) {
595 entry = byte_for(_whole_heap.start());
596 } else {
597 entry = byte_for(new_region.start());
598 }
599 CardValue* end = byte_for(original_covered.start());
600 // If _whole_heap starts at the original covered regions start,
601 // this loop will not execute.
602 while (entry < end) { *entry++ = clean_card; }
603}
604
605void PSCardTable::resize_update_covered_table(int changed_region,
606 MemRegion new_region) {
607 // Update the covered region
608 _covered[changed_region].set_start(new_region.start());
609 _covered[changed_region].set_word_size(new_region.word_size());
610
611 // reorder regions. There should only be at most 1 out
612 // of order.
613 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
614 if (_covered[i].start() < _covered[i-1].start()) {
615 MemRegion covered_mr = _covered[i-1];
616 _covered[i-1] = _covered[i];
617 _covered[i] = covered_mr;
618 MemRegion committed_mr = _committed[i-1];
619 _committed[i-1] = _committed[i];
620 _committed[i] = committed_mr;
621 break;
622 }
623 }
624#ifdef ASSERT
625 for (int m = 0; m < _cur_covered_regions-1; m++) {
626 assert(_covered[m].start() <= _covered[m+1].start(),
627 "Covered regions out of order");
628 assert(_committed[m].start() <= _committed[m+1].start(),
629 "Committed regions out of order");
630 }
631#endif
632}
633
634// Returns the start of any committed region that is lower than
635// the target committed region (index ind) and that intersects the
636// target region. If none, return start of target region.
637//
638// -------------
639// | |
640// -------------
641// ------------
642// | target |
643// ------------
644// -------------
645// | |
646// -------------
647// ^ returns this
648//
649// -------------
650// | |
651// -------------
652// ------------
653// | target |
654// ------------
655// -------------
656// | |
657// -------------
658// ^ returns this
659
660HeapWord* PSCardTable::lowest_prev_committed_start(int ind) const {
661 assert(_cur_covered_regions >= 0, "Expecting at least on region");
662 HeapWord* min_start = _committed[ind].start();
663 for (int j = 0; j < ind; j++) {
664 HeapWord* this_start = _committed[j].start();
665 if ((this_start < min_start) &&
666 !(_committed[j].intersection(_committed[ind])).is_empty()) {
667 min_start = this_start;
668 }
669 }
670 return min_start;
671}
672
673bool PSCardTable::is_in_young(oop obj) const {
674 return ParallelScavengeHeap::heap()->is_in_young(obj);
675}
676