1 /*
2 * Copyright (c) 2001, 2015, 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_implementation/parallelScavenge/cardTableExtension.hpp"
27 #include "gc_implementation/parallelScavenge/gcTaskManager.hpp"
28 #include "gc_implementation/parallelScavenge/parallelScavengeHeap.hpp"
29 #include "gc_implementation/parallelScavenge/psPromotionManager.hpp"
30 #include "gc_implementation/parallelScavenge/psScavenge.hpp"
31 #include "gc_implementation/parallelScavenge/psTasks.hpp"
32 #include "gc_implementation/parallelScavenge/psYoungGen.hpp"
33 #include "oops/oop.inline.hpp"
34 #include "oops/oop.psgc.inline.hpp"
35 #include "runtime/prefetch.inline.hpp"
36
37 // Checks an individual oop for missing precise marks. Mark
38 // may be either dirty or newgen.
39 class CheckForUnmarkedOops : public OopClosure {
40 private:
41 PSYoungGen* _young_gen;
42 CardTableExtension* _card_table;
43 HeapWord* _unmarked_addr;
44 jbyte* _unmarked_card;
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 _unmarked_card = _card_table->byte_for(p);
55 }
56 }
57 }
58
59 public:
60 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) :
61 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
62
63 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); }
64 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
65
66 bool has_unmarked_oop() {
67 return _unmarked_addr != NULL;
68 }
69 };
70
71 // Checks all objects for the existence of some type of mark,
72 // precise or imprecise, dirty or newgen.
73 class CheckForUnmarkedObjects : public ObjectClosure {
74 private:
75 PSYoungGen* _young_gen;
76 CardTableExtension* _card_table;
77
78 public:
79 CheckForUnmarkedObjects() {
80 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
81 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
82
83 _young_gen = heap->young_gen();
84 _card_table = barrier_set_cast<CardTableExtension>(heap->barrier_set());
85 // No point in asserting barrier set type here. Need to make CardTableExtension
86 // a unique barrier set type.
87 }
88
89 // Card marks are not precise. The current system can leave us with
90 // a mismatch of precise marks and beginning of object marks. This means
91 // we test for missing precise marks first. If any are found, we don't
92 // fail unless the object head is also unmarked.
93 virtual void do_object(oop obj) {
94 CheckForUnmarkedOops object_check(_young_gen, _card_table);
95 obj->oop_iterate_no_header(&object_check);
96 if (object_check.has_unmarked_oop()) {
97 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
98 }
99 }
100 };
101
102 // Checks for precise marking of oops as newgen.
103 class CheckForPreciseMarks : public OopClosure {
104 private:
105 PSYoungGen* _young_gen;
106 CardTableExtension* _card_table;
107
108 protected:
109 template <class T> void do_oop_work(T* p) {
110 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
111 if (_young_gen->is_in_reserved(obj)) {
112 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
113 _card_table->set_card_newgen(p);
114 }
115 }
116
117 public:
118 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) :
119 _young_gen(young_gen), _card_table(card_table) { }
120
121 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); }
122 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
123 };
124
125 // We get passed the space_top value to prevent us from traversing into
126 // the old_gen promotion labs, which cannot be safely parsed.
127
128 // Do not call this method if the space is empty.
129 // It is a waste to start tasks and get here only to
130 // do no work. If this method needs to be called
131 // when the space is empty, fix the calculation of
132 // end_card to allow sp_top == sp->bottom().
133
134 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array,
135 MutableSpace* sp,
136 HeapWord* space_top,
137 PSPromotionManager* pm,
138 uint stripe_number,
139 uint stripe_total) {
140 int ssize = 128; // Naked constant! Work unit = 64k.
141 int dirty_card_count = 0;
142
143 // It is a waste to get here if empty.
144 assert(sp->bottom() < sp->top(), "Should not be called if empty");
145 oop* sp_top = (oop*)space_top;
146 jbyte* start_card = byte_for(sp->bottom());
147 jbyte* end_card = byte_for(sp_top - 1) + 1;
148 oop* last_scanned = NULL; // Prevent scanning objects more than once
149 // The width of the stripe ssize*stripe_total must be
150 // consistent with the number of stripes so that the complete slice
151 // is covered.
152 size_t slice_width = ssize * stripe_total;
153 for (jbyte* slice = start_card; slice < end_card; slice += slice_width) {
154 jbyte* worker_start_card = slice + stripe_number * ssize;
155 if (worker_start_card >= end_card)
156 return; // We're done.
157
158 jbyte* worker_end_card = worker_start_card + ssize;
159 if (worker_end_card > end_card)
160 worker_end_card = end_card;
161
162 // We do not want to scan objects more than once. In order to accomplish
163 // this, we assert that any object with an object head inside our 'slice'
164 // belongs to us. We may need to extend the range of scanned cards if the
165 // last object continues into the next 'slice'.
166 //
167 // Note! ending cards are exclusive!
168 HeapWord* slice_start = addr_for(worker_start_card);
169 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
170
171 #ifdef ASSERT
172 if (GCWorkerDelayMillis > 0) {
173 // Delay 1 worker so that it proceeds after all the work
174 // has been completed.
175 if (stripe_number < 2) {
176 os::sleep(Thread::current(), GCWorkerDelayMillis, false);
177 }
178 }
179 #endif
180
181 // If there are not objects starting within the chunk, skip it.
182 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
183 continue;
184 }
185 // Update our beginning addr
186 HeapWord* first_object = start_array->object_start(slice_start);
187 debug_only(oop* first_object_within_slice = (oop*) first_object;)
188 if (first_object < slice_start) {
189 last_scanned = (oop*)(first_object + oop(first_object)->size());
190 debug_only(first_object_within_slice = last_scanned;)
191 worker_start_card = byte_for(last_scanned);
192 }
193
194 // Update the ending addr
195 if (slice_end < (HeapWord*)sp_top) {
196 // The subtraction is important! An object may start precisely at slice_end.
197 HeapWord* last_object = start_array->object_start(slice_end - 1);
198 slice_end = last_object + oop(last_object)->size();
199 // worker_end_card is exclusive, so bump it one past the end of last_object's
200 // covered span.
201 worker_end_card = byte_for(slice_end) + 1;
202
203 if (worker_end_card > end_card)
204 worker_end_card = end_card;
205 }
206
207 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
208 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
209 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
210 // Note that worker_start_card >= worker_end_card is legal, and happens when
211 // an object spans an entire slice.
212 assert(worker_start_card <= end_card, "worker start card beyond end card");
213 assert(worker_end_card <= end_card, "worker end card beyond end card");
214
215 jbyte* current_card = worker_start_card;
216 while (current_card < worker_end_card) {
217 // Find an unclean card.
218 while (current_card < worker_end_card && card_is_clean(*current_card)) {
219 current_card++;
220 }
221 jbyte* first_unclean_card = current_card;
222
223 // Find the end of a run of contiguous unclean cards
224 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
225 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
226 current_card++;
227 }
228
229 if (current_card < worker_end_card) {
230 // Some objects may be large enough to span several cards. If such
231 // an object has more than one dirty card, separated by a clean card,
232 // we will attempt to scan it twice. The test against "last_scanned"
233 // prevents the redundant object scan, but it does not prevent newly
234 // marked cards from being cleaned.
235 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
236 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
237 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
238 jbyte* ending_card_of_last_object = byte_for(end_of_last_object);
239 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
240 if (ending_card_of_last_object > current_card) {
241 // This means the object spans the next complete card.
242 // We need to bump the current_card to ending_card_of_last_object
243 current_card = ending_card_of_last_object;
244 }
245 }
246 }
247 jbyte* following_clean_card = current_card;
248
249 if (first_unclean_card < worker_end_card) {
250 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
251 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
252 // "p" should always be >= "last_scanned" because newly GC dirtied
253 // cards are no longer scanned again (see comment at end
254 // of loop on the increment of "current_card"). Test that
255 // hypothesis before removing this code.
256 // If this code is removed, deal with the first time through
257 // the loop when the last_scanned is the object starting in
258 // the previous slice.
259 assert((p >= last_scanned) ||
260 (last_scanned == first_object_within_slice),
261 "Should no longer be possible");
262 if (p < last_scanned) {
263 // Avoid scanning more than once; this can happen because
264 // newgen cards set by GC may a different set than the
265 // originally dirty set
266 p = last_scanned;
267 }
268 oop* to = (oop*)addr_for(following_clean_card);
269
270 // Test slice_end first!
271 if ((HeapWord*)to > slice_end) {
272 to = (oop*)slice_end;
273 } else if (to > sp_top) {
274 to = sp_top;
275 }
276
277 // we know which cards to scan, now clear them
278 if (first_unclean_card <= worker_start_card+1)
279 first_unclean_card = worker_start_card+1;
280 if (following_clean_card >= worker_end_card-1)
281 following_clean_card = worker_end_card-1;
282
283 while (first_unclean_card < following_clean_card) {
284 *first_unclean_card++ = clean_card;
285 }
286
287 const int interval = PrefetchScanIntervalInBytes;
288 // scan all objects in the range
289 if (interval != 0) {
290 while (p < to) {
291 Prefetch::write(p, interval);
292 oop m = oop(p);
293 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m)));
294 m->push_contents(pm);
295 p += m->size();
296 }
297 pm->drain_stacks_cond_depth();
298 } else {
299 while (p < to) {
300 oop m = oop(p);
301 assert(m->is_oop_or_null(), err_msg("Expected an oop or NULL for header field at " PTR_FORMAT, p2i(m)));
302 m->push_contents(pm);
303 p += m->size();
304 }
305 pm->drain_stacks_cond_depth();
306 }
307 last_scanned = p;
308 }
309 // "current_card" is still the "following_clean_card" or
310 // the current_card is >= the worker_end_card so the
311 // loop will not execute again.
312 assert((current_card == following_clean_card) ||
313 (current_card >= worker_end_card),
314 "current_card should only be incremented if it still equals "
315 "following_clean_card");
316 // Increment current_card so that it is not processed again.
317 // It may now be dirty because a old-to-young pointer was
318 // found on it an updated. If it is now dirty, it cannot be
319 // be safely cleaned in the next iteration.
320 current_card++;
321 }
322 }
323 }
324
325 // This should be called before a scavenge.
326 void CardTableExtension::verify_all_young_refs_imprecise() {
327 CheckForUnmarkedObjects check;
328
329 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
330 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
331
332 PSOldGen* old_gen = heap->old_gen();
333
334 old_gen->object_iterate(&check);
335 }
336
337 // This should be called immediately after a scavenge, before mutators resume.
338 void CardTableExtension::verify_all_young_refs_precise() {
339 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
340 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
341
342 PSOldGen* old_gen = heap->old_gen();
343
344 CheckForPreciseMarks check(
345 heap->young_gen(),
346 barrier_set_cast<CardTableExtension>(heap->barrier_set()));
347
348 old_gen->oop_iterate_no_header(&check);
349
350 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
351 }
352
353 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) {
354 CardTableExtension* card_table =
355 barrier_set_cast<CardTableExtension>(Universe::heap()->barrier_set());
356
357 jbyte* bot = card_table->byte_for(mr.start());
358 jbyte* top = card_table->byte_for(mr.end());
359 while(bot <= top) {
360 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
361 if (*bot == verify_card)
362 *bot = youngergen_card;
363 bot++;
364 }
365 }
366
367 bool CardTableExtension::addr_is_marked_imprecise(void *addr) {
368 jbyte* p = byte_for(addr);
369 jbyte val = *p;
370
371 if (card_is_dirty(val))
372 return true;
373
374 if (card_is_newgen(val))
375 return true;
376
377 if (card_is_clean(val))
378 return false;
379
380 assert(false, "Found unhandled card mark type");
381
382 return false;
383 }
384
385 // Also includes verify_card
386 bool CardTableExtension::addr_is_marked_precise(void *addr) {
387 jbyte* p = byte_for(addr);
388 jbyte val = *p;
389
390 if (card_is_newgen(val))
391 return true;
392
393 if (card_is_verify(val))
394 return true;
395
396 if (card_is_clean(val))
397 return false;
398
399 if (card_is_dirty(val))
400 return false;
401
402 assert(false, "Found unhandled card mark type");
403
404 return false;
405 }
406
407 // Assumes that only the base or the end changes. This allows indentification
408 // of the region that is being resized. The
409 // CardTableModRefBS::resize_covered_region() is used for the normal case
410 // where the covered regions are growing or shrinking at the high end.
411 // The method resize_covered_region_by_end() is analogous to
412 // CardTableModRefBS::resize_covered_region() but
413 // for regions that grow or shrink at the low end.
414 void CardTableExtension::resize_covered_region(MemRegion new_region) {
415
416 for (int i = 0; i < _cur_covered_regions; i++) {
417 if (_covered[i].start() == new_region.start()) {
418 // Found a covered region with the same start as the
419 // new region. The region is growing or shrinking
420 // from the start of the region.
421 resize_covered_region_by_start(new_region);
422 return;
423 }
424 if (_covered[i].start() > new_region.start()) {
425 break;
426 }
427 }
428
429 int changed_region = -1;
430 for (int j = 0; j < _cur_covered_regions; j++) {
431 if (_covered[j].end() == new_region.end()) {
432 changed_region = j;
433 // This is a case where the covered region is growing or shrinking
434 // at the start of the region.
435 assert(changed_region != -1, "Don't expect to add a covered region");
436 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
437 "The sizes should be different here");
438 resize_covered_region_by_end(changed_region, new_region);
439 return;
440 }
441 }
442 // This should only be a new covered region (where no existing
443 // covered region matches at the start or the end).
444 assert(_cur_covered_regions < _max_covered_regions,
445 "An existing region should have been found");
446 resize_covered_region_by_start(new_region);
447 }
448
449 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) {
450 CardTableModRefBS::resize_covered_region(new_region);
451 debug_only(verify_guard();)
452 }
453
454 void CardTableExtension::resize_covered_region_by_end(int changed_region,
455 MemRegion new_region) {
456 assert(SafepointSynchronize::is_at_safepoint(),
457 "Only expect an expansion at the low end at a GC");
458 debug_only(verify_guard();)
459 #ifdef ASSERT
460 for (int k = 0; k < _cur_covered_regions; k++) {
461 if (_covered[k].end() == new_region.end()) {
462 assert(changed_region == k, "Changed region is incorrect");
463 break;
464 }
465 }
466 #endif
467
468 // Commit new or uncommit old pages, if necessary.
469 if (resize_commit_uncommit(changed_region, new_region)) {
470 // Set the new start of the committed region
471 resize_update_committed_table(changed_region, new_region);
472 }
473
474 // Update card table entries
475 resize_update_card_table_entries(changed_region, new_region);
476
477 // Update the covered region
478 resize_update_covered_table(changed_region, new_region);
479
480 if (TraceCardTableModRefBS) {
481 int ind = changed_region;
482 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
483 gclog_or_tty->print_cr(" "
484 " _covered[%d].start(): " INTPTR_FORMAT
485 " _covered[%d].last(): " INTPTR_FORMAT,
486 ind, p2i(_covered[ind].start()),
487 ind, p2i(_covered[ind].last()));
488 gclog_or_tty->print_cr(" "
489 " _committed[%d].start(): " INTPTR_FORMAT
490 " _committed[%d].last(): " INTPTR_FORMAT,
491 ind, p2i(_committed[ind].start()),
492 ind, p2i(_committed[ind].last()));
493 gclog_or_tty->print_cr(" "
494 " byte_for(start): " INTPTR_FORMAT
495 " byte_for(last): " INTPTR_FORMAT,
496 p2i(byte_for(_covered[ind].start())),
497 p2i(byte_for(_covered[ind].last())));
498 gclog_or_tty->print_cr(" "
499 " addr_for(start): " INTPTR_FORMAT
500 " addr_for(last): " INTPTR_FORMAT,
501 p2i(addr_for((jbyte*) _committed[ind].start())),
502 p2i(addr_for((jbyte*) _committed[ind].last())));
503 }
504 debug_only(verify_guard();)
505 }
506
507 bool CardTableExtension::resize_commit_uncommit(int changed_region,
508 MemRegion new_region) {
509 bool result = false;
510 // Commit new or uncommit old pages, if necessary.
511 MemRegion cur_committed = _committed[changed_region];
512 assert(_covered[changed_region].end() == new_region.end(),
513 "The ends of the regions are expected to match");
514 // Extend the start of this _committed region to
515 // to cover the start of any previous _committed region.
516 // This forms overlapping regions, but never interior regions.
517 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
518 if (min_prev_start < cur_committed.start()) {
519 // Only really need to set start of "cur_committed" to
520 // the new start (min_prev_start) but assertion checking code
521 // below use cur_committed.end() so make it correct.
522 MemRegion new_committed =
523 MemRegion(min_prev_start, cur_committed.end());
524 cur_committed = new_committed;
525 }
526 #ifdef ASSERT
527 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
528 assert(cur_committed.start() ==
529 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(),
530 os::vm_page_size()),
531 "Starts should have proper alignment");
532 #endif
533
534 jbyte* new_start = byte_for(new_region.start());
535 // Round down because this is for the start address
536 HeapWord* new_start_aligned =
537 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size());
538 // The guard page is always committed and should not be committed over.
539 // This method is used in cases where the generation is growing toward
540 // lower addresses but the guard region is still at the end of the
541 // card table. That still makes sense when looking for writes
542 // off the end of the card table.
543 if (new_start_aligned < cur_committed.start()) {
544 // Expand the committed region
545 //
546 // Case A
547 // |+ guard +|
548 // |+ cur committed +++++++++|
549 // |+ new committed +++++++++++++++++|
550 //
551 // Case B
552 // |+ guard +|
553 // |+ cur committed +|
554 // |+ new committed +++++++|
555 //
556 // These are not expected because the calculation of the
557 // cur committed region and the new committed region
558 // share the same end for the covered region.
559 // Case C
560 // |+ guard +|
561 // |+ cur committed +|
562 // |+ new committed +++++++++++++++++|
563 // Case D
564 // |+ guard +|
565 // |+ cur committed +++++++++++|
566 // |+ new committed +++++++|
567
568 HeapWord* new_end_for_commit =
569 MIN2(cur_committed.end(), _guard_region.start());
570 if(new_start_aligned < new_end_for_commit) {
571 MemRegion new_committed =
572 MemRegion(new_start_aligned, new_end_for_commit);
573 os::commit_memory_or_exit((char*)new_committed.start(),
574 new_committed.byte_size(), !ExecMem,
575 "card table expansion");
576 }
577 result = true;
578 } else if (new_start_aligned > cur_committed.start()) {
579 // Shrink the committed region
580 #if 0 // uncommitting space is currently unsafe because of the interactions
581 // of growing and shrinking regions. One region A can uncommit space
582 // that it owns but which is being used by another region B (maybe).
583 // Region B has not committed the space because it was already
584 // committed by region A.
585 MemRegion uncommit_region = committed_unique_to_self(changed_region,
586 MemRegion(cur_committed.start(), new_start_aligned));
587 if (!uncommit_region.is_empty()) {
588 if (!os::uncommit_memory((char*)uncommit_region.start(),
589 uncommit_region.byte_size())) {
590 // If the uncommit fails, ignore it. Let the
591 // committed table resizing go even though the committed
592 // table will over state the committed space.
593 }
594 }
595 #else
596 assert(!result, "Should be false with current workaround");
597 #endif
598 }
599 assert(_committed[changed_region].end() == cur_committed.end(),
600 "end should not change");
601 return result;
602 }
603
604 void CardTableExtension::resize_update_committed_table(int changed_region,
605 MemRegion new_region) {
606
607 jbyte* new_start = byte_for(new_region.start());
608 // Set the new start of the committed region
609 HeapWord* new_start_aligned =
610 (HeapWord*)align_size_down((uintptr_t)new_start,
611 os::vm_page_size());
612 MemRegion new_committed = MemRegion(new_start_aligned,
613 _committed[changed_region].end());
614 _committed[changed_region] = new_committed;
615 _committed[changed_region].set_start(new_start_aligned);
616 }
617
618 void CardTableExtension::resize_update_card_table_entries(int changed_region,
619 MemRegion new_region) {
620 debug_only(verify_guard();)
621 MemRegion original_covered = _covered[changed_region];
622 // Initialize the card entries. Only consider the
623 // region covered by the card table (_whole_heap)
624 jbyte* entry;
625 if (new_region.start() < _whole_heap.start()) {
626 entry = byte_for(_whole_heap.start());
627 } else {
628 entry = byte_for(new_region.start());
629 }
630 jbyte* end = byte_for(original_covered.start());
631 // If _whole_heap starts at the original covered regions start,
632 // this loop will not execute.
633 while (entry < end) { *entry++ = clean_card; }
634 }
635
636 void CardTableExtension::resize_update_covered_table(int changed_region,
637 MemRegion new_region) {
638 // Update the covered region
639 _covered[changed_region].set_start(new_region.start());
640 _covered[changed_region].set_word_size(new_region.word_size());
641
642 // reorder regions. There should only be at most 1 out
643 // of order.
644 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
645 if (_covered[i].start() < _covered[i-1].start()) {
646 MemRegion covered_mr = _covered[i-1];
647 _covered[i-1] = _covered[i];
648 _covered[i] = covered_mr;
649 MemRegion committed_mr = _committed[i-1];
650 _committed[i-1] = _committed[i];
651 _committed[i] = committed_mr;
652 break;
653 }
654 }
655 #ifdef ASSERT
656 for (int m = 0; m < _cur_covered_regions-1; m++) {
657 assert(_covered[m].start() <= _covered[m+1].start(),
658 "Covered regions out of order");
659 assert(_committed[m].start() <= _committed[m+1].start(),
660 "Committed regions out of order");
661 }
662 #endif
663 }
664
665 // Returns the start of any committed region that is lower than
666 // the target committed region (index ind) and that intersects the
667 // target region. If none, return start of target region.
668 //
669 // -------------
670 // | |
671 // -------------
672 // ------------
673 // | target |
674 // ------------
675 // -------------
676 // | |
677 // -------------
678 // ^ returns this
679 //
680 // -------------
681 // | |
682 // -------------
683 // ------------
684 // | target |
685 // ------------
686 // -------------
687 // | |
688 // -------------
689 // ^ returns this
690
691 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const {
692 assert(_cur_covered_regions >= 0, "Expecting at least on region");
693 HeapWord* min_start = _committed[ind].start();
694 for (int j = 0; j < ind; j++) {
695 HeapWord* this_start = _committed[j].start();
696 if ((this_start < min_start) &&
697 !(_committed[j].intersection(_committed[ind])).is_empty()) {
698 min_start = this_start;
699 }
700 }
701 return min_start;
702 }