1 /*
2 * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
24
25 #include "precompiled.hpp"
26 #include "gc/parallel/objectStartArray.inline.hpp"
27 #include "gc/parallel/parallelScavengeHeap.inline.hpp"
28 #include "gc/parallel/psCardTable.hpp"
29 #include "gc/parallel/psPromotionManager.inline.hpp"
30 #include "gc/parallel/psScavenge.inline.hpp"
31 #include "gc/parallel/psYoungGen.hpp"
32 #include "memory/iterator.inline.hpp"
33 #include "oops/access.inline.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 BasicOopIterateClosure {
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 = RawAccess<>::oop_load(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(&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 BasicOopIterateClosure {
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 = RawAccess<IS_NOT_NULL>::oop_load(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 // The generation (old gen) is divided into slices, which are further
130 // subdivided into stripes, with one stripe per GC thread. The size of
131 // a stripe is a constant, ssize.
132 //
133 // +===============+ slice 0
134 // | stripe 0 |
135 // +---------------+
136 // | stripe 1 |
137 // +---------------+
138 // | stripe 2 |
139 // +---------------+
140 // | stripe 3 |
141 // +===============+ slice 1
142 // | stripe 0 |
143 // +---------------+
144 // | stripe 1 |
145 // +---------------+
146 // | stripe 2 |
147 // +---------------+
148 // | stripe 3 |
149 // +===============+ slice 2
150 // ...
151 //
152 // In this case there are 4 threads, so 4 stripes. A GC thread first works on
153 // its stripe within slice 0 and then moves to its stripe in the next slice
154 // until it has exceeded the top of the generation. The distance to stripe in
155 // the next slice is calculated based on the number of stripes. The next
156 // stripe is at ssize * number_of_stripes (= slice_stride).. So after
157 // finishing stripe 0 in slice 0, the thread finds the stripe 0 in slice1 by
158 // adding slice_stride to the start of stripe 0 in slice 0 to get to the start
159 // of stride 0 in slice 1.
160
161 void PSCardTable::scavenge_contents_parallel(ObjectStartArray* start_array,
162 MutableSpace* sp,
163 HeapWord* space_top,
164 PSPromotionManager* pm,
165 uint stripe_number,
166 uint stripe_total) {
167 int ssize = 128; // Naked constant! Work unit = 64k.
168 int dirty_card_count = 0;
169
170 // It is a waste to get here if empty.
171 assert(sp->bottom() < sp->top(), "Should not be called if empty");
172 oop* sp_top = (oop*)space_top;
173 CardValue* start_card = byte_for(sp->bottom());
174 CardValue* end_card = byte_for(sp_top - 1) + 1;
175 oop* last_scanned = NULL; // Prevent scanning objects more than once
176 // The width of the stripe ssize*stripe_total must be
177 // consistent with the number of stripes so that the complete slice
178 // is covered.
179 size_t slice_width = ssize * stripe_total;
180 for (CardValue* slice = start_card; slice < end_card; slice += slice_width) {
181 CardValue* worker_start_card = slice + stripe_number * ssize;
182 if (worker_start_card >= end_card)
183 return; // We're done.
184
185 CardValue* worker_end_card = worker_start_card + ssize;
186 if (worker_end_card > end_card)
187 worker_end_card = end_card;
188
189 // We do not want to scan objects more than once. In order to accomplish
190 // this, we assert that any object with an object head inside our 'slice'
191 // belongs to us. We may need to extend the range of scanned cards if the
192 // last object continues into the next 'slice'.
193 //
194 // Note! ending cards are exclusive!
195 HeapWord* slice_start = addr_for(worker_start_card);
196 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
197
198 #ifdef ASSERT
199 if (GCWorkerDelayMillis > 0) {
200 // Delay 1 worker so that it proceeds after all the work
201 // has been completed.
202 if (stripe_number < 2) {
203 os::sleep(Thread::current(), GCWorkerDelayMillis, false);
204 }
205 }
206 #endif
207
208 // If there are not objects starting within the chunk, skip it.
209 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
210 continue;
211 }
212 // Update our beginning addr
213 HeapWord* first_object = start_array->object_start(slice_start);
214 debug_only(oop* first_object_within_slice = (oop*) first_object;)
215 if (first_object < slice_start) {
216 last_scanned = (oop*)(first_object + oop(first_object)->size());
217 debug_only(first_object_within_slice = last_scanned;)
218 worker_start_card = byte_for(last_scanned);
219 }
220
221 // Update the ending addr
222 if (slice_end < (HeapWord*)sp_top) {
223 // The subtraction is important! An object may start precisely at slice_end.
224 HeapWord* last_object = start_array->object_start(slice_end - 1);
225 slice_end = last_object + oop(last_object)->size();
226 // worker_end_card is exclusive, so bump it one past the end of last_object's
227 // covered span.
228 worker_end_card = byte_for(slice_end) + 1;
229
230 if (worker_end_card > end_card)
231 worker_end_card = end_card;
232 }
233
234 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
235 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
236 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
237 // Note that worker_start_card >= worker_end_card is legal, and happens when
238 // an object spans an entire slice.
239 assert(worker_start_card <= end_card, "worker start card beyond end card");
240 assert(worker_end_card <= end_card, "worker end card beyond end card");
241
242 CardValue* current_card = worker_start_card;
243 while (current_card < worker_end_card) {
244 // Find an unclean card.
245 while (current_card < worker_end_card && card_is_clean(*current_card)) {
246 current_card++;
247 }
248 CardValue* first_unclean_card = current_card;
249
250 // Find the end of a run of contiguous unclean cards
251 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
252 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
253 current_card++;
254 }
255
256 if (current_card < worker_end_card) {
257 // Some objects may be large enough to span several cards. If such
258 // an object has more than one dirty card, separated by a clean card,
259 // we will attempt to scan it twice. The test against "last_scanned"
260 // prevents the redundant object scan, but it does not prevent newly
261 // marked cards from being cleaned.
262 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
263 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
264 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
265 CardValue* ending_card_of_last_object = byte_for(end_of_last_object);
266 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
267 if (ending_card_of_last_object > current_card) {
268 // This means the object spans the next complete card.
269 // We need to bump the current_card to ending_card_of_last_object
270 current_card = ending_card_of_last_object;
271 }
272 }
273 }
274 CardValue* following_clean_card = current_card;
275
276 if (first_unclean_card < worker_end_card) {
277 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
278 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
279 // "p" should always be >= "last_scanned" because newly GC dirtied
280 // cards are no longer scanned again (see comment at end
281 // of loop on the increment of "current_card"). Test that
282 // hypothesis before removing this code.
283 // If this code is removed, deal with the first time through
284 // the loop when the last_scanned is the object starting in
285 // the previous slice.
286 assert((p >= last_scanned) ||
287 (last_scanned == first_object_within_slice),
288 "Should no longer be possible");
289 if (p < last_scanned) {
290 // Avoid scanning more than once; this can happen because
291 // newgen cards set by GC may a different set than the
292 // originally dirty set
293 p = last_scanned;
294 }
295 oop* to = (oop*)addr_for(following_clean_card);
296
297 // Test slice_end first!
298 if ((HeapWord*)to > slice_end) {
299 to = (oop*)slice_end;
300 } else if (to > sp_top) {
301 to = sp_top;
302 }
303
304 // we know which cards to scan, now clear them
305 if (first_unclean_card <= worker_start_card+1)
306 first_unclean_card = worker_start_card+1;
307 if (following_clean_card >= worker_end_card-1)
308 following_clean_card = worker_end_card-1;
309
310 while (first_unclean_card < following_clean_card) {
311 *first_unclean_card++ = clean_card;
312 }
313
314 const int interval = PrefetchScanIntervalInBytes;
315 // scan all objects in the range
316 if (interval != 0) {
317 while (p < to) {
318 Prefetch::write(p, interval);
319 oop m = oop(p);
320 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
321 pm->push_contents(m);
322 p += m->size();
323 }
324 pm->drain_stacks_cond_depth();
325 } else {
326 while (p < to) {
327 oop m = oop(p);
328 assert(oopDesc::is_oop_or_null(m), "Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m));
329 pm->push_contents(m);
330 p += m->size();
331 }
332 pm->drain_stacks_cond_depth();
333 }
334 last_scanned = p;
335 }
336 // "current_card" is still the "following_clean_card" or
337 // the current_card is >= the worker_end_card so the
338 // loop will not execute again.
339 assert((current_card == following_clean_card) ||
340 (current_card >= worker_end_card),
341 "current_card should only be incremented if it still equals "
342 "following_clean_card");
343 // Increment current_card so that it is not processed again.
344 // It may now be dirty because a old-to-young pointer was
345 // found on it an updated. If it is now dirty, it cannot be
346 // be safely cleaned in the next iteration.
347 current_card++;
348 }
349 }
350 }
351
352 // This should be called before a scavenge.
353 void PSCardTable::verify_all_young_refs_imprecise() {
354 CheckForUnmarkedObjects check;
355
356 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
357 PSOldGen* old_gen = heap->old_gen();
358
359 old_gen->object_iterate(&check);
360 }
361
362 // This should be called immediately after a scavenge, before mutators resume.
363 void PSCardTable::verify_all_young_refs_precise() {
364 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
365 PSOldGen* old_gen = heap->old_gen();
366
367 CheckForPreciseMarks check(heap->young_gen(), this);
368
369 old_gen->oop_iterate(&check);
370
371 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
372 }
373
374 void PSCardTable::verify_all_young_refs_precise_helper(MemRegion mr) {
375 CardValue* bot = byte_for(mr.start());
376 CardValue* top = byte_for(mr.end());
377 while (bot <= top) {
378 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
379 if (*bot == verify_card)
380 *bot = youngergen_card;
381 bot++;
382 }
383 }
384
385 bool PSCardTable::addr_is_marked_imprecise(void *addr) {
386 CardValue* p = byte_for(addr);
387 CardValue val = *p;
388
389 if (card_is_dirty(val))
390 return true;
391
392 if (card_is_newgen(val))
393 return true;
394
395 if (card_is_clean(val))
396 return false;
397
398 assert(false, "Found unhandled card mark type");
399
400 return false;
401 }
402
403 // Also includes verify_card
404 bool PSCardTable::addr_is_marked_precise(void *addr) {
405 CardValue* p = byte_for(addr);
406 CardValue val = *p;
407
408 if (card_is_newgen(val))
409 return true;
410
411 if (card_is_verify(val))
412 return true;
413
414 if (card_is_clean(val))
415 return false;
416
417 if (card_is_dirty(val))
418 return false;
419
420 assert(false, "Found unhandled card mark type");
421
422 return false;
423 }
424
425 // Assumes that only the base or the end changes. This allows indentification
426 // of the region that is being resized. The
427 // CardTable::resize_covered_region() is used for the normal case
428 // where the covered regions are growing or shrinking at the high end.
429 // The method resize_covered_region_by_end() is analogous to
430 // CardTable::resize_covered_region() but
431 // for regions that grow or shrink at the low end.
432 void PSCardTable::resize_covered_region(MemRegion new_region) {
433 for (int i = 0; i < _cur_covered_regions; i++) {
434 if (_covered[i].start() == new_region.start()) {
435 // Found a covered region with the same start as the
436 // new region. The region is growing or shrinking
437 // from the start of the region.
438 resize_covered_region_by_start(new_region);
439 return;
440 }
441 if (_covered[i].start() > new_region.start()) {
442 break;
443 }
444 }
445
446 int changed_region = -1;
447 for (int j = 0; j < _cur_covered_regions; j++) {
448 if (_covered[j].end() == new_region.end()) {
449 changed_region = j;
450 // This is a case where the covered region is growing or shrinking
451 // at the start of the region.
452 assert(changed_region != -1, "Don't expect to add a covered region");
453 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
454 "The sizes should be different here");
455 resize_covered_region_by_end(changed_region, new_region);
456 return;
457 }
458 }
459 // This should only be a new covered region (where no existing
460 // covered region matches at the start or the end).
461 assert(_cur_covered_regions < _max_covered_regions,
462 "An existing region should have been found");
463 resize_covered_region_by_start(new_region);
464 }
465
466 void PSCardTable::resize_covered_region_by_start(MemRegion new_region) {
467 CardTable::resize_covered_region(new_region);
468 debug_only(verify_guard();)
469 }
470
471 void PSCardTable::resize_covered_region_by_end(int changed_region,
472 MemRegion new_region) {
473 assert(SafepointSynchronize::is_at_safepoint(),
474 "Only expect an expansion at the low end at a GC");
475 debug_only(verify_guard();)
476 #ifdef ASSERT
477 for (int k = 0; k < _cur_covered_regions; k++) {
478 if (_covered[k].end() == new_region.end()) {
479 assert(changed_region == k, "Changed region is incorrect");
480 break;
481 }
482 }
483 #endif
484
485 // Commit new or uncommit old pages, if necessary.
486 if (resize_commit_uncommit(changed_region, new_region)) {
487 // Set the new start of the committed region
488 resize_update_committed_table(changed_region, new_region);
489 }
490
491 // Update card table entries
492 resize_update_card_table_entries(changed_region, new_region);
493
494 // Update the covered region
495 resize_update_covered_table(changed_region, new_region);
496
497 int ind = changed_region;
498 log_trace(gc, barrier)("CardTable::resize_covered_region: ");
499 log_trace(gc, barrier)(" _covered[%d].start(): " INTPTR_FORMAT " _covered[%d].last(): " INTPTR_FORMAT,
500 ind, p2i(_covered[ind].start()), ind, p2i(_covered[ind].last()));
501 log_trace(gc, barrier)(" _committed[%d].start(): " INTPTR_FORMAT " _committed[%d].last(): " INTPTR_FORMAT,
502 ind, p2i(_committed[ind].start()), ind, p2i(_committed[ind].last()));
503 log_trace(gc, barrier)(" byte_for(start): " INTPTR_FORMAT " byte_for(last): " INTPTR_FORMAT,
504 p2i(byte_for(_covered[ind].start())), p2i(byte_for(_covered[ind].last())));
505 log_trace(gc, barrier)(" addr_for(start): " INTPTR_FORMAT " addr_for(last): " INTPTR_FORMAT,
506 p2i(addr_for((CardValue*) _committed[ind].start())), p2i(addr_for((CardValue*) _committed[ind].last())));
507
508 debug_only(verify_guard();)
509 }
510
511 bool PSCardTable::resize_commit_uncommit(int changed_region,
512 MemRegion new_region) {
513 bool result = false;
514 // Commit new or uncommit old pages, if necessary.
515 MemRegion cur_committed = _committed[changed_region];
516 assert(_covered[changed_region].end() == new_region.end(),
517 "The ends of the regions are expected to match");
518 // Extend the start of this _committed region to
519 // to cover the start of any previous _committed region.
520 // This forms overlapping regions, but never interior regions.
521 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
522 if (min_prev_start < cur_committed.start()) {
523 // Only really need to set start of "cur_committed" to
524 // the new start (min_prev_start) but assertion checking code
525 // below use cur_committed.end() so make it correct.
526 MemRegion new_committed =
527 MemRegion(min_prev_start, cur_committed.end());
528 cur_committed = new_committed;
529 }
530 #ifdef ASSERT
531 ParallelScavengeHeap* heap = ParallelScavengeHeap::heap();
532 assert(cur_committed.start() == align_up(cur_committed.start(), os::vm_page_size()),
533 "Starts should have proper alignment");
534 #endif
535
536 CardValue* new_start = byte_for(new_region.start());
537 // Round down because this is for the start address
538 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
539 // The guard page is always committed and should not be committed over.
540 // This method is used in cases where the generation is growing toward
541 // lower addresses but the guard region is still at the end of the
542 // card table. That still makes sense when looking for writes
543 // off the end of the card table.
544 if (new_start_aligned < cur_committed.start()) {
545 // Expand the committed region
546 //
547 // Case A
548 // |+ guard +|
549 // |+ cur committed +++++++++|
550 // |+ new committed +++++++++++++++++|
551 //
552 // Case B
553 // |+ guard +|
554 // |+ cur committed +|
555 // |+ new committed +++++++|
556 //
557 // These are not expected because the calculation of the
558 // cur committed region and the new committed region
559 // share the same end for the covered region.
560 // Case C
561 // |+ guard +|
562 // |+ cur committed +|
563 // |+ new committed +++++++++++++++++|
564 // Case D
565 // |+ guard +|
566 // |+ cur committed +++++++++++|
567 // |+ new committed +++++++|
568
569 HeapWord* new_end_for_commit =
570 MIN2(cur_committed.end(), _guard_region.start());
571 if(new_start_aligned < new_end_for_commit) {
572 MemRegion new_committed =
573 MemRegion(new_start_aligned, new_end_for_commit);
574 os::commit_memory_or_exit((char*)new_committed.start(),
575 new_committed.byte_size(), !ExecMem,
576 "card table expansion");
577 }
578 result = true;
579 } else if (new_start_aligned > cur_committed.start()) {
580 // Shrink the committed region
581 #if 0 // uncommitting space is currently unsafe because of the interactions
582 // of growing and shrinking regions. One region A can uncommit space
583 // that it owns but which is being used by another region B (maybe).
584 // Region B has not committed the space because it was already
585 // committed by region A.
586 MemRegion uncommit_region = committed_unique_to_self(changed_region,
587 MemRegion(cur_committed.start(), new_start_aligned));
588 if (!uncommit_region.is_empty()) {
589 if (!os::uncommit_memory((char*)uncommit_region.start(),
590 uncommit_region.byte_size())) {
591 // If the uncommit fails, ignore it. Let the
592 // committed table resizing go even though the committed
593 // table will over state the committed space.
594 }
595 }
596 #else
597 assert(!result, "Should be false with current workaround");
598 #endif
599 }
600 assert(_committed[changed_region].end() == cur_committed.end(),
601 "end should not change");
602 return result;
603 }
604
605 void PSCardTable::resize_update_committed_table(int changed_region,
606 MemRegion new_region) {
607
608 CardValue* new_start = byte_for(new_region.start());
609 // Set the new start of the committed region
610 HeapWord* new_start_aligned = align_down((HeapWord*)new_start, os::vm_page_size());
611 MemRegion new_committed = MemRegion(new_start_aligned,
612 _committed[changed_region].end());
613 _committed[changed_region] = new_committed;
614 _committed[changed_region].set_start(new_start_aligned);
615 }
616
617 void PSCardTable::resize_update_card_table_entries(int changed_region,
618 MemRegion new_region) {
619 debug_only(verify_guard();)
620 MemRegion original_covered = _covered[changed_region];
621 // Initialize the card entries. Only consider the
622 // region covered by the card table (_whole_heap)
623 CardValue* entry;
624 if (new_region.start() < _whole_heap.start()) {
625 entry = byte_for(_whole_heap.start());
626 } else {
627 entry = byte_for(new_region.start());
628 }
629 CardValue* end = byte_for(original_covered.start());
630 // If _whole_heap starts at the original covered regions start,
631 // this loop will not execute.
632 while (entry < end) { *entry++ = clean_card; }
633 }
634
635 void PSCardTable::resize_update_covered_table(int changed_region,
636 MemRegion new_region) {
637 // Update the covered region
638 _covered[changed_region].set_start(new_region.start());
639 _covered[changed_region].set_word_size(new_region.word_size());
640
641 // reorder regions. There should only be at most 1 out
642 // of order.
643 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
644 if (_covered[i].start() < _covered[i-1].start()) {
645 MemRegion covered_mr = _covered[i-1];
646 _covered[i-1] = _covered[i];
647 _covered[i] = covered_mr;
648 MemRegion committed_mr = _committed[i-1];
649 _committed[i-1] = _committed[i];
650 _committed[i] = committed_mr;
651 break;
652 }
653 }
654 #ifdef ASSERT
655 for (int m = 0; m < _cur_covered_regions-1; m++) {
656 assert(_covered[m].start() <= _covered[m+1].start(),
657 "Covered regions out of order");
658 assert(_committed[m].start() <= _committed[m+1].start(),
659 "Committed regions out of order");
660 }
661 #endif
662 }
663
664 // Returns the start of any committed region that is lower than
665 // the target committed region (index ind) and that intersects the
666 // target region. If none, return start of target region.
667 //
668 // -------------
669 // | |
670 // -------------
671 // ------------
672 // | target |
673 // ------------
674 // -------------
675 // | |
676 // -------------
677 // ^ returns this
678 //
679 // -------------
680 // | |
681 // -------------
682 // ------------
683 // | target |
684 // ------------
685 // -------------
686 // | |
687 // -------------
688 // ^ returns this
689
690 HeapWord* PSCardTable::lowest_prev_committed_start(int ind) const {
691 assert(_cur_covered_regions >= 0, "Expecting at least on region");
692 HeapWord* min_start = _committed[ind].start();
693 for (int j = 0; j < ind; j++) {
694 HeapWord* this_start = _committed[j].start();
695 if ((this_start < min_start) &&
696 !(_committed[j].intersection(_committed[ind])).is_empty()) {
697 min_start = this_start;
698 }
699 }
700 return min_start;
701 }
702
703 bool PSCardTable::is_in_young(oop obj) const {
704 return ParallelScavengeHeap::heap()->is_in_young(obj);
705 }