1 #ifdef USE_PRAGMA_IDENT_SRC
2 #pragma ident "@(#)cardTableExtension.cpp 1.35 07/09/25 16:47:41 JVM"
3 #endif
4 /*
5 * Copyright 2001-2008 Sun Microsystems, Inc. All Rights Reserved.
6 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
7 *
8 * This code is free software; you can redistribute it and/or modify it
9 * under the terms of the GNU General Public License version 2 only, as
10 * published by the Free Software Foundation.
11 *
12 * This code is distributed in the hope that it will be useful, but WITHOUT
13 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
14 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
15 * version 2 for more details (a copy is included in the LICENSE file that
16 * accompanied this code).
17 *
18 * You should have received a copy of the GNU General Public License version
19 * 2 along with this work; if not, write to the Free Software Foundation,
20 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
21 *
22 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
23 * CA 95054 USA or visit www.sun.com if you need additional information or
24 * have any questions.
25 *
26 */
27
28 # include "incls/_precompiled.incl"
29 # include "incls/_cardTableExtension.cpp.incl"
30
31 // Checks an individual oop for missing precise marks. Mark
32 // may be either dirty or newgen.
33 class CheckForUnmarkedOops : public OopClosure {
34 private:
35 PSYoungGen* _young_gen;
36 CardTableExtension* _card_table;
37 HeapWord* _unmarked_addr;
38 jbyte* _unmarked_card;
39
40 protected:
41 template <class T> void do_oop_work(T* p) {
42 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
43 if (_young_gen->is_in_reserved(obj) &&
44 !_card_table->addr_is_marked_imprecise(p)) {
45 // Don't overwrite the first missing card mark
46 if (_unmarked_addr == NULL) {
47 _unmarked_addr = (HeapWord*)p;
48 _unmarked_card = _card_table->byte_for(p);
49 }
50 }
51 }
52
53 public:
54 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) :
55 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
56
57 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); }
58 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
59
60 bool has_unmarked_oop() {
61 return _unmarked_addr != NULL;
62 }
63 };
64
65 // Checks all objects for the existance of some type of mark,
66 // precise or imprecise, dirty or newgen.
67 class CheckForUnmarkedObjects : public ObjectClosure {
68 private:
69 PSYoungGen* _young_gen;
70 CardTableExtension* _card_table;
71
72 public:
73 CheckForUnmarkedObjects() {
74 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
75 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
76
77 _young_gen = heap->young_gen();
78 _card_table = (CardTableExtension*)heap->barrier_set();
79 // No point in asserting barrier set type here. Need to make CardTableExtension
80 // a unique barrier set type.
81 }
82
83 // Card marks are not precise. The current system can leave us with
84 // a mismash of precise marks and begining of object marks. This means
85 // we test for missing precise marks first. If any are found, we don't
86 // fail unless the object head is also unmarked.
87 virtual void do_object(oop obj) {
88 CheckForUnmarkedOops object_check(_young_gen, _card_table);
89 obj->oop_iterate(&object_check);
90 if (object_check.has_unmarked_oop()) {
91 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
92 }
93 }
94 };
95
96 // Checks for precise marking of oops as newgen.
97 class CheckForPreciseMarks : public OopClosure {
98 private:
99 PSYoungGen* _young_gen;
100 CardTableExtension* _card_table;
101
102 protected:
103 template <class T> void do_oop_work(T* p) {
104 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
105 if (_young_gen->is_in_reserved(obj)) {
106 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
107 _card_table->set_card_newgen(p);
108 }
109 }
110
111 public:
112 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) :
113 _young_gen(young_gen), _card_table(card_table) { }
114
115 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); }
116 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
117 };
118
119 // We get passed the space_top value to prevent us from traversing into
120 // the old_gen promotion labs, which cannot be safely parsed.
121 void CardTableExtension::scavenge_contents(ObjectStartArray* start_array,
122 MutableSpace* sp,
123 HeapWord* space_top,
124 PSPromotionManager* pm)
125 {
126 assert(start_array != NULL && sp != NULL && pm != NULL, "Sanity");
127 assert(start_array->covered_region().contains(sp->used_region()),
128 "ObjectStartArray does not cover space");
129 bool depth_first = pm->depth_first();
130
131 if (sp->not_empty()) {
132 oop* sp_top = (oop*)space_top;
133 oop* prev_top = NULL;
134 jbyte* current_card = byte_for(sp->bottom());
135 jbyte* end_card = byte_for(sp_top - 1); // sp_top is exclusive
136 // scan card marking array
137 while (current_card <= end_card) {
138 jbyte value = *current_card;
139 // skip clean cards
140 if (card_is_clean(value)) {
141 current_card++;
142 } else {
143 // we found a non-clean card
144 jbyte* first_nonclean_card = current_card++;
145 oop* bottom = (oop*)addr_for(first_nonclean_card);
146 // find object starting on card
147 oop* bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom);
148 // bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom);
149 assert(bottom_obj <= bottom, "just checking");
150 // make sure we don't scan oops we already looked at
151 if (bottom < prev_top) bottom = prev_top;
152 // figure out when to stop scanning
153 jbyte* first_clean_card;
154 oop* top;
155 bool restart_scanning;
156 do {
157 restart_scanning = false;
158 // find a clean card
159 while (current_card <= end_card) {
160 value = *current_card;
161 if (card_is_clean(value)) break;
162 current_card++;
163 }
164 // check if we reached the end, if so we are done
165 if (current_card >= end_card) {
166 first_clean_card = end_card + 1;
167 current_card++;
168 top = sp_top;
169 } else {
170 // we have a clean card, find object starting on that card
171 first_clean_card = current_card++;
172 top = (oop*)addr_for(first_clean_card);
173 oop* top_obj = (oop*)start_array->object_start((HeapWord*)top);
174 // top_obj = (oop*)start_array->object_start((HeapWord*)top);
175 assert(top_obj <= top, "just checking");
176 if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {
177 // an arrayOop is starting on the clean card - since we do exact store
178 // checks for objArrays we are done
179 } else {
180 // otherwise, it is possible that the object starting on the clean card
181 // spans the entire card, and that the store happened on a later card.
182 // figure out where the object ends
183 top = top_obj + oop(top_obj)->size();
184 jbyte* top_card = CardTableModRefBS::byte_for(top - 1); // top is exclusive
185 if (top_card > first_clean_card) {
186 // object ends a different card
187 current_card = top_card + 1;
188 if (card_is_clean(*top_card)) {
189 // the ending card is clean, we are done
190 first_clean_card = top_card;
191 } else {
192 // the ending card is not clean, continue scanning at start of do-while
193 restart_scanning = true;
194 }
195 } else {
196 // object ends on the clean card, we are done.
197 assert(first_clean_card == top_card, "just checking");
198 }
199 }
200 }
201 } while (restart_scanning);
202 // we know which cards to scan, now clear them
203 while (first_nonclean_card < first_clean_card) {
204 *first_nonclean_card++ = clean_card;
205 }
206 // scan oops in objects
207 // hoisted the if (depth_first) check out of the loop
208 if (depth_first){
209 do {
210 oop(bottom_obj)->push_contents(pm);
211 bottom_obj += oop(bottom_obj)->size();
212 assert(bottom_obj <= sp_top, "just checking");
213 } while (bottom_obj < top);
214 pm->drain_stacks_cond_depth();
215 } else {
216 do {
217 oop(bottom_obj)->copy_contents(pm);
218 bottom_obj += oop(bottom_obj)->size();
219 assert(bottom_obj <= sp_top, "just checking");
220 } while (bottom_obj < top);
221 }
222 // remember top oop* scanned
223 prev_top = top;
224 }
225 }
226 }
227 }
228
229 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array,
230 MutableSpace* sp,
231 HeapWord* space_top,
232 PSPromotionManager* pm,
233 uint stripe_number) {
234 int ssize = 128; // Naked constant! Work unit = 64k.
235 int dirty_card_count = 0;
236 bool depth_first = pm->depth_first();
237
238 oop* sp_top = (oop*)space_top;
239 jbyte* start_card = byte_for(sp->bottom());
240 jbyte* end_card = byte_for(sp_top - 1) + 1;
241 oop* last_scanned = NULL; // Prevent scanning objects more than once
242 for (jbyte* slice = start_card; slice < end_card; slice += ssize*ParallelGCThreads) {
243 jbyte* worker_start_card = slice + stripe_number * ssize;
244 if (worker_start_card >= end_card)
245 return; // We're done.
246
247 jbyte* worker_end_card = worker_start_card + ssize;
248 if (worker_end_card > end_card)
249 worker_end_card = end_card;
250
251 // We do not want to scan objects more than once. In order to accomplish
252 // this, we assert that any object with an object head inside our 'slice'
253 // belongs to us. We may need to extend the range of scanned cards if the
254 // last object continues into the next 'slice'.
255 //
256 // Note! ending cards are exclusive!
257 HeapWord* slice_start = addr_for(worker_start_card);
258 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
259
260 // If there are not objects starting within the chunk, skip it.
261 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
262 continue;
263 }
264 // Update our begining addr
265 HeapWord* first_object = start_array->object_start(slice_start);
266 debug_only(oop* first_object_within_slice = (oop*) first_object;)
267 if (first_object < slice_start) {
268 last_scanned = (oop*)(first_object + oop(first_object)->size());
269 debug_only(first_object_within_slice = last_scanned;)
270 worker_start_card = byte_for(last_scanned);
271 }
272
273 // Update the ending addr
274 if (slice_end < (HeapWord*)sp_top) {
275 // The subtraction is important! An object may start precisely at slice_end.
276 HeapWord* last_object = start_array->object_start(slice_end - 1);
277 slice_end = last_object + oop(last_object)->size();
278 // worker_end_card is exclusive, so bump it one past the end of last_object's
279 // covered span.
280 worker_end_card = byte_for(slice_end) + 1;
281
282 if (worker_end_card > end_card)
283 worker_end_card = end_card;
284 }
285
286 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
287 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
288 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
289 // Note that worker_start_card >= worker_end_card is legal, and happens when
290 // an object spans an entire slice.
291 assert(worker_start_card <= end_card, "worker start card beyond end card");
292 assert(worker_end_card <= end_card, "worker end card beyond end card");
293
294 jbyte* current_card = worker_start_card;
295 while (current_card < worker_end_card) {
296 // Find an unclean card.
297 while (current_card < worker_end_card && card_is_clean(*current_card)) {
298 current_card++;
299 }
300 jbyte* first_unclean_card = current_card;
301
302 // Find the end of a run of contiguous unclean cards
303 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
304 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
305 current_card++;
306 }
307
308 if (current_card < worker_end_card) {
309 // Some objects may be large enough to span several cards. If such
310 // an object has more than one dirty card, separated by a clean card,
311 // we will attempt to scan it twice. The test against "last_scanned"
312 // prevents the redundant object scan, but it does not prevent newly
313 // marked cards from being cleaned.
314 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
315 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
316 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
317 jbyte* ending_card_of_last_object = byte_for(end_of_last_object);
318 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
319 if (ending_card_of_last_object > current_card) {
320 // This means the object spans the next complete card.
321 // We need to bump the current_card to ending_card_of_last_object
322 current_card = ending_card_of_last_object;
323 }
324 }
325 }
326 jbyte* following_clean_card = current_card;
327
328 if (first_unclean_card < worker_end_card) {
329 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
330 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
331 // "p" should always be >= "last_scanned" because newly GC dirtied
332 // cards are no longer scanned again (see comment at end
333 // of loop on the increment of "current_card"). Test that
334 // hypothesis before removing this code.
335 // If this code is removed, deal with the first time through
336 // the loop when the last_scanned is the object starting in
337 // the previous slice.
338 assert((p >= last_scanned) ||
339 (last_scanned == first_object_within_slice),
340 "Should no longer be possible");
341 if (p < last_scanned) {
342 // Avoid scanning more than once; this can happen because
343 // newgen cards set by GC may a different set than the
344 // originally dirty set
345 p = last_scanned;
346 }
347 oop* to = (oop*)addr_for(following_clean_card);
348
349 // Test slice_end first!
350 if ((HeapWord*)to > slice_end) {
351 to = (oop*)slice_end;
352 } else if (to > sp_top) {
353 to = sp_top;
354 }
355
356 // we know which cards to scan, now clear them
357 if (first_unclean_card <= worker_start_card+1)
358 first_unclean_card = worker_start_card+1;
359 if (following_clean_card >= worker_end_card-1)
360 following_clean_card = worker_end_card-1;
361
362 while (first_unclean_card < following_clean_card) {
363 *first_unclean_card++ = clean_card;
364 }
365
366 const int interval = PrefetchScanIntervalInBytes;
367 // scan all objects in the range
368 if (interval != 0) {
369 // hoisted the if (depth_first) check out of the loop
370 if (depth_first) {
371 while (p < to) {
372 Prefetch::write(p, interval);
373 oop m = oop(p);
374 assert(m->is_oop_or_null(), "check for header");
375 m->push_contents(pm);
376 p += m->size();
377 }
378 pm->drain_stacks_cond_depth();
379 } else {
380 while (p < to) {
381 Prefetch::write(p, interval);
382 oop m = oop(p);
383 assert(m->is_oop_or_null(), "check for header");
384 m->copy_contents(pm);
385 p += m->size();
386 }
387 }
388 } else {
389 // hoisted the if (depth_first) check out of the loop
390 if (depth_first) {
391 while (p < to) {
392 oop m = oop(p);
393 assert(m->is_oop_or_null(), "check for header");
394 m->push_contents(pm);
395 p += m->size();
396 }
397 pm->drain_stacks_cond_depth();
398 } else {
399 while (p < to) {
400 oop m = oop(p);
401 assert(m->is_oop_or_null(), "check for header");
402 m->copy_contents(pm);
403 p += m->size();
404 }
405 }
406 }
407 last_scanned = p;
408 }
409 // "current_card" is still the "following_clean_card" or
410 // the current_card is >= the worker_end_card so the
411 // loop will not execute again.
412 assert((current_card == following_clean_card) ||
413 (current_card >= worker_end_card),
414 "current_card should only be incremented if it still equals "
415 "following_clean_card");
416 // Increment current_card so that it is not processed again.
417 // It may now be dirty because a old-to-young pointer was
418 // found on it an updated. If it is now dirty, it cannot be
419 // be safely cleaned in the next iteration.
420 current_card++;
421 }
422 }
423 }
424
425 // This should be called before a scavenge.
426 void CardTableExtension::verify_all_young_refs_imprecise() {
427 CheckForUnmarkedObjects check;
428
429 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
430 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
431
432 PSOldGen* old_gen = heap->old_gen();
433 PSPermGen* perm_gen = heap->perm_gen();
434
435 old_gen->object_iterate(&check);
436 perm_gen->object_iterate(&check);
437 }
438
439 // This should be called immediately after a scavenge, before mutators resume.
440 void CardTableExtension::verify_all_young_refs_precise() {
441 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
442 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
443
444 PSOldGen* old_gen = heap->old_gen();
445 PSPermGen* perm_gen = heap->perm_gen();
446
447 CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set());
448
449 old_gen->oop_iterate(&check);
450 perm_gen->oop_iterate(&check);
451
452 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
453 verify_all_young_refs_precise_helper(perm_gen->object_space()->used_region());
454 }
455
456 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) {
457 CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set();
458 // FIX ME ASSERT HERE
459
460 jbyte* bot = card_table->byte_for(mr.start());
461 jbyte* top = card_table->byte_for(mr.end());
462 while(bot <= top) {
463 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
464 if (*bot == verify_card)
465 *bot = youngergen_card;
466 bot++;
467 }
468 }
469
470 bool CardTableExtension::addr_is_marked_imprecise(void *addr) {
471 jbyte* p = byte_for(addr);
472 jbyte val = *p;
473
474 if (card_is_dirty(val))
475 return true;
476
477 if (card_is_newgen(val))
478 return true;
479
480 if (card_is_clean(val))
481 return false;
482
483 assert(false, "Found unhandled card mark type");
484
485 return false;
486 }
487
488 // Also includes verify_card
489 bool CardTableExtension::addr_is_marked_precise(void *addr) {
490 jbyte* p = byte_for(addr);
491 jbyte val = *p;
492
493 if (card_is_newgen(val))
494 return true;
495
496 if (card_is_verify(val))
497 return true;
498
499 if (card_is_clean(val))
500 return false;
501
502 if (card_is_dirty(val))
503 return false;
504
505 assert(false, "Found unhandled card mark type");
506
507 return false;
508 }
509
510 // Assumes that only the base or the end changes. This allows indentification
511 // of the region that is being resized. The
512 // CardTableModRefBS::resize_covered_region() is used for the normal case
513 // where the covered regions are growing or shrinking at the high end.
514 // The method resize_covered_region_by_end() is analogous to
515 // CardTableModRefBS::resize_covered_region() but
516 // for regions that grow or shrink at the low end.
517 void CardTableExtension::resize_covered_region(MemRegion new_region) {
518
519 for (int i = 0; i < _cur_covered_regions; i++) {
520 if (_covered[i].start() == new_region.start()) {
521 // Found a covered region with the same start as the
522 // new region. The region is growing or shrinking
523 // from the start of the region.
524 resize_covered_region_by_start(new_region);
525 return;
526 }
527 if (_covered[i].start() > new_region.start()) {
528 break;
529 }
530 }
531
532 int changed_region = -1;
533 for (int j = 0; j < _cur_covered_regions; j++) {
534 if (_covered[j].end() == new_region.end()) {
535 changed_region = j;
536 // This is a case where the covered region is growing or shrinking
537 // at the start of the region.
538 assert(changed_region != -1, "Don't expect to add a covered region");
539 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
540 "The sizes should be different here");
541 resize_covered_region_by_end(changed_region, new_region);
542 return;
543 }
544 }
545 // This should only be a new covered region (where no existing
546 // covered region matches at the start or the end).
547 assert(_cur_covered_regions < _max_covered_regions,
548 "An existing region should have been found");
549 resize_covered_region_by_start(new_region);
550 }
551
552 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) {
553 CardTableModRefBS::resize_covered_region(new_region);
554 debug_only(verify_guard();)
555 }
556
557 void CardTableExtension::resize_covered_region_by_end(int changed_region,
558 MemRegion new_region) {
559 assert(SafepointSynchronize::is_at_safepoint(),
560 "Only expect an expansion at the low end at a GC");
561 debug_only(verify_guard();)
562 #ifdef ASSERT
563 for (int k = 0; k < _cur_covered_regions; k++) {
564 if (_covered[k].end() == new_region.end()) {
565 assert(changed_region == k, "Changed region is incorrect");
566 break;
567 }
568 }
569 #endif
570
571 // Commit new or uncommit old pages, if necessary.
572 resize_commit_uncommit(changed_region, new_region);
573
574 // Update card table entries
575 resize_update_card_table_entries(changed_region, new_region);
576
577 // Set the new start of the committed region
578 resize_update_committed_table(changed_region, new_region);
579
580 // Update the covered region
581 resize_update_covered_table(changed_region, new_region);
582
583 if (TraceCardTableModRefBS) {
584 int ind = changed_region;
585 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
586 gclog_or_tty->print_cr(" "
587 " _covered[%d].start(): " INTPTR_FORMAT
588 " _covered[%d].last(): " INTPTR_FORMAT,
589 ind, _covered[ind].start(),
590 ind, _covered[ind].last());
591 gclog_or_tty->print_cr(" "
592 " _committed[%d].start(): " INTPTR_FORMAT
593 " _committed[%d].last(): " INTPTR_FORMAT,
594 ind, _committed[ind].start(),
595 ind, _committed[ind].last());
596 gclog_or_tty->print_cr(" "
597 " byte_for(start): " INTPTR_FORMAT
598 " byte_for(last): " INTPTR_FORMAT,
599 byte_for(_covered[ind].start()),
600 byte_for(_covered[ind].last()));
601 gclog_or_tty->print_cr(" "
602 " addr_for(start): " INTPTR_FORMAT
603 " addr_for(last): " INTPTR_FORMAT,
604 addr_for((jbyte*) _committed[ind].start()),
605 addr_for((jbyte*) _committed[ind].last()));
606 }
607 debug_only(verify_guard();)
608 }
609
610 void CardTableExtension::resize_commit_uncommit(int changed_region,
611 MemRegion new_region) {
612 // Commit new or uncommit old pages, if necessary.
613 MemRegion cur_committed = _committed[changed_region];
614 assert(_covered[changed_region].end() == new_region.end(),
615 "The ends of the regions are expected to match");
616 // Extend the start of this _committed region to
617 // to cover the start of any previous _committed region.
618 // This forms overlapping regions, but never interior regions.
619 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
620 if (min_prev_start < cur_committed.start()) {
621 // Only really need to set start of "cur_committed" to
622 // the new start (min_prev_start) but assertion checking code
623 // below use cur_committed.end() so make it correct.
624 MemRegion new_committed =
625 MemRegion(min_prev_start, cur_committed.end());
626 cur_committed = new_committed;
627 }
628 #ifdef ASSERT
629 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
630 assert(cur_committed.start() ==
631 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(),
632 os::vm_page_size()),
633 "Starts should have proper alignment");
634 #endif
635
636 jbyte* new_start = byte_for(new_region.start());
637 // Round down because this is for the start address
638 HeapWord* new_start_aligned =
639 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size());
640 // The guard page is always committed and should not be committed over.
641 // This method is used in cases where the generation is growing toward
642 // lower addresses but the guard region is still at the end of the
643 // card table. That still makes sense when looking for writes
644 // off the end of the card table.
645 if (new_start_aligned < cur_committed.start()) {
646 // Expand the committed region
647 //
648 // Case A
649 // |+ guard +|
650 // |+ cur committed +++++++++|
651 // |+ new committed +++++++++++++++++|
652 //
653 // Case B
654 // |+ guard +|
655 // |+ cur committed +|
656 // |+ new committed +++++++|
657 //
658 // These are not expected because the calculation of the
659 // cur committed region and the new committed region
660 // share the same end for the covered region.
661 // Case C
662 // |+ guard +|
663 // |+ cur committed +|
664 // |+ new committed +++++++++++++++++|
665 // Case D
666 // |+ guard +|
667 // |+ cur committed +++++++++++|
668 // |+ new committed +++++++|
669
670 HeapWord* new_end_for_commit =
671 MIN2(cur_committed.end(), _guard_region.start());
672 if(new_start_aligned < new_end_for_commit) {
673 MemRegion new_committed =
674 MemRegion(new_start_aligned, new_end_for_commit);
675 if (!os::commit_memory((char*)new_committed.start(),
676 new_committed.byte_size())) {
677 vm_exit_out_of_memory(new_committed.byte_size(),
678 "card table expansion");
679 }
680 }
681 } else if (new_start_aligned > cur_committed.start()) {
682 // Shrink the committed region
683 MemRegion uncommit_region = committed_unique_to_self(changed_region,
684 MemRegion(cur_committed.start(), new_start_aligned));
685 if (!uncommit_region.is_empty()) {
686 if (!os::uncommit_memory((char*)uncommit_region.start(),
687 uncommit_region.byte_size())) {
688 vm_exit_out_of_memory(uncommit_region.byte_size(),
689 "card table contraction");
690 }
691 }
692 }
693 assert(_committed[changed_region].end() == cur_committed.end(),
694 "end should not change");
695 }
696
697 void CardTableExtension::resize_update_committed_table(int changed_region,
698 MemRegion new_region) {
699
700 jbyte* new_start = byte_for(new_region.start());
701 // Set the new start of the committed region
702 HeapWord* new_start_aligned =
703 (HeapWord*)align_size_down((uintptr_t)new_start,
704 os::vm_page_size());
705 MemRegion new_committed = MemRegion(new_start_aligned,
706 _committed[changed_region].end());
707 _committed[changed_region] = new_committed;
708 _committed[changed_region].set_start(new_start_aligned);
709 }
710
711 void CardTableExtension::resize_update_card_table_entries(int changed_region,
712 MemRegion new_region) {
713 debug_only(verify_guard();)
714 MemRegion original_covered = _covered[changed_region];
715 // Initialize the card entries. Only consider the
716 // region covered by the card table (_whole_heap)
717 jbyte* entry;
718 if (new_region.start() < _whole_heap.start()) {
719 entry = byte_for(_whole_heap.start());
720 } else {
721 entry = byte_for(new_region.start());
722 }
723 jbyte* end = byte_for(original_covered.start());
724 // If _whole_heap starts at the original covered regions start,
725 // this loop will not execute.
726 while (entry < end) { *entry++ = clean_card; }
727 }
728
729 void CardTableExtension::resize_update_covered_table(int changed_region,
730 MemRegion new_region) {
731 // Update the covered region
732 _covered[changed_region].set_start(new_region.start());
733 _covered[changed_region].set_word_size(new_region.word_size());
734
735 // reorder regions. There should only be at most 1 out
736 // of order.
737 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
738 if (_covered[i].start() < _covered[i-1].start()) {
739 MemRegion covered_mr = _covered[i-1];
740 _covered[i-1] = _covered[i];
741 _covered[i] = covered_mr;
742 MemRegion committed_mr = _committed[i-1];
743 _committed[i-1] = _committed[i];
744 _committed[i] = committed_mr;
745 break;
746 }
747 }
748 #ifdef ASSERT
749 for (int m = 0; m < _cur_covered_regions-1; m++) {
750 assert(_covered[m].start() <= _covered[m+1].start(),
751 "Covered regions out of order");
752 assert(_committed[m].start() <= _committed[m+1].start(),
753 "Committed regions out of order");
754 }
755 #endif
756 }
757
758 // Returns the start of any committed region that is lower than
759 // the target committed region (index ind) and that intersects the
760 // target region. If none, return start of target region.
761 //
762 // -------------
763 // | |
764 // -------------
765 // ------------
766 // | target |
767 // ------------
768 // -------------
769 // | |
770 // -------------
771 // ^ returns this
772 //
773 // -------------
774 // | |
775 // -------------
776 // ------------
777 // | target |
778 // ------------
779 // -------------
780 // | |
781 // -------------
782 // ^ returns this
783
784 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const {
785 assert(_cur_covered_regions >= 0, "Expecting at least on region");
786 HeapWord* min_start = _committed[ind].start();
787 for (int j = 0; j < ind; j++) {
788 HeapWord* this_start = _committed[j].start();
789 if ((this_start < min_start) &&
790 !(_committed[j].intersection(_committed[ind])).is_empty()) {
791 min_start = this_start;
792 }
793 }
794 return min_start;
795 }
796