Fri, 27 Feb 2009 13:27:09 -0800
6810672: Comment typos
Summary: I have collected some typos I have found while looking at the code.
Reviewed-by: kvn, never
1 /*
2 * Copyright 2001-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any questions.
22 *
23 */
25 # include "incls/_precompiled.incl"
26 # include "incls/_cardTableExtension.cpp.incl"
28 // Checks an individual oop for missing precise marks. Mark
29 // may be either dirty or newgen.
30 class CheckForUnmarkedOops : public OopClosure {
31 private:
32 PSYoungGen* _young_gen;
33 CardTableExtension* _card_table;
34 HeapWord* _unmarked_addr;
35 jbyte* _unmarked_card;
37 protected:
38 template <class T> void do_oop_work(T* p) {
39 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
40 if (_young_gen->is_in_reserved(obj) &&
41 !_card_table->addr_is_marked_imprecise(p)) {
42 // Don't overwrite the first missing card mark
43 if (_unmarked_addr == NULL) {
44 _unmarked_addr = (HeapWord*)p;
45 _unmarked_card = _card_table->byte_for(p);
46 }
47 }
48 }
50 public:
51 CheckForUnmarkedOops(PSYoungGen* young_gen, CardTableExtension* card_table) :
52 _young_gen(young_gen), _card_table(card_table), _unmarked_addr(NULL) { }
54 virtual void do_oop(oop* p) { CheckForUnmarkedOops::do_oop_work(p); }
55 virtual void do_oop(narrowOop* p) { CheckForUnmarkedOops::do_oop_work(p); }
57 bool has_unmarked_oop() {
58 return _unmarked_addr != NULL;
59 }
60 };
62 // Checks all objects for the existance of some type of mark,
63 // precise or imprecise, dirty or newgen.
64 class CheckForUnmarkedObjects : public ObjectClosure {
65 private:
66 PSYoungGen* _young_gen;
67 CardTableExtension* _card_table;
69 public:
70 CheckForUnmarkedObjects() {
71 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
72 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
74 _young_gen = heap->young_gen();
75 _card_table = (CardTableExtension*)heap->barrier_set();
76 // No point in asserting barrier set type here. Need to make CardTableExtension
77 // a unique barrier set type.
78 }
80 // Card marks are not precise. The current system can leave us with
81 // a mismash of precise marks and beginning of object marks. This means
82 // we test for missing precise marks first. If any are found, we don't
83 // fail unless the object head is also unmarked.
84 virtual void do_object(oop obj) {
85 CheckForUnmarkedOops object_check(_young_gen, _card_table);
86 obj->oop_iterate(&object_check);
87 if (object_check.has_unmarked_oop()) {
88 assert(_card_table->addr_is_marked_imprecise(obj), "Found unmarked young_gen object");
89 }
90 }
91 };
93 // Checks for precise marking of oops as newgen.
94 class CheckForPreciseMarks : public OopClosure {
95 private:
96 PSYoungGen* _young_gen;
97 CardTableExtension* _card_table;
99 protected:
100 template <class T> void do_oop_work(T* p) {
101 oop obj = oopDesc::load_decode_heap_oop_not_null(p);
102 if (_young_gen->is_in_reserved(obj)) {
103 assert(_card_table->addr_is_marked_precise(p), "Found unmarked precise oop");
104 _card_table->set_card_newgen(p);
105 }
106 }
108 public:
109 CheckForPreciseMarks( PSYoungGen* young_gen, CardTableExtension* card_table ) :
110 _young_gen(young_gen), _card_table(card_table) { }
112 virtual void do_oop(oop* p) { CheckForPreciseMarks::do_oop_work(p); }
113 virtual void do_oop(narrowOop* p) { CheckForPreciseMarks::do_oop_work(p); }
114 };
116 // We get passed the space_top value to prevent us from traversing into
117 // the old_gen promotion labs, which cannot be safely parsed.
118 void CardTableExtension::scavenge_contents(ObjectStartArray* start_array,
119 MutableSpace* sp,
120 HeapWord* space_top,
121 PSPromotionManager* pm)
122 {
123 assert(start_array != NULL && sp != NULL && pm != NULL, "Sanity");
124 assert(start_array->covered_region().contains(sp->used_region()),
125 "ObjectStartArray does not cover space");
126 bool depth_first = pm->depth_first();
128 if (sp->not_empty()) {
129 oop* sp_top = (oop*)space_top;
130 oop* prev_top = NULL;
131 jbyte* current_card = byte_for(sp->bottom());
132 jbyte* end_card = byte_for(sp_top - 1); // sp_top is exclusive
133 // scan card marking array
134 while (current_card <= end_card) {
135 jbyte value = *current_card;
136 // skip clean cards
137 if (card_is_clean(value)) {
138 current_card++;
139 } else {
140 // we found a non-clean card
141 jbyte* first_nonclean_card = current_card++;
142 oop* bottom = (oop*)addr_for(first_nonclean_card);
143 // find object starting on card
144 oop* bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom);
145 // bottom_obj = (oop*)start_array->object_start((HeapWord*)bottom);
146 assert(bottom_obj <= bottom, "just checking");
147 // make sure we don't scan oops we already looked at
148 if (bottom < prev_top) bottom = prev_top;
149 // figure out when to stop scanning
150 jbyte* first_clean_card;
151 oop* top;
152 bool restart_scanning;
153 do {
154 restart_scanning = false;
155 // find a clean card
156 while (current_card <= end_card) {
157 value = *current_card;
158 if (card_is_clean(value)) break;
159 current_card++;
160 }
161 // check if we reached the end, if so we are done
162 if (current_card >= end_card) {
163 first_clean_card = end_card + 1;
164 current_card++;
165 top = sp_top;
166 } else {
167 // we have a clean card, find object starting on that card
168 first_clean_card = current_card++;
169 top = (oop*)addr_for(first_clean_card);
170 oop* top_obj = (oop*)start_array->object_start((HeapWord*)top);
171 // top_obj = (oop*)start_array->object_start((HeapWord*)top);
172 assert(top_obj <= top, "just checking");
173 if (oop(top_obj)->is_objArray() || oop(top_obj)->is_typeArray()) {
174 // an arrayOop is starting on the clean card - since we do exact store
175 // checks for objArrays we are done
176 } else {
177 // otherwise, it is possible that the object starting on the clean card
178 // spans the entire card, and that the store happened on a later card.
179 // figure out where the object ends
180 top = top_obj + oop(top_obj)->size();
181 jbyte* top_card = CardTableModRefBS::byte_for(top - 1); // top is exclusive
182 if (top_card > first_clean_card) {
183 // object ends a different card
184 current_card = top_card + 1;
185 if (card_is_clean(*top_card)) {
186 // the ending card is clean, we are done
187 first_clean_card = top_card;
188 } else {
189 // the ending card is not clean, continue scanning at start of do-while
190 restart_scanning = true;
191 }
192 } else {
193 // object ends on the clean card, we are done.
194 assert(first_clean_card == top_card, "just checking");
195 }
196 }
197 }
198 } while (restart_scanning);
199 // we know which cards to scan, now clear them
200 while (first_nonclean_card < first_clean_card) {
201 *first_nonclean_card++ = clean_card;
202 }
203 // scan oops in objects
204 // hoisted the if (depth_first) check out of the loop
205 if (depth_first){
206 do {
207 oop(bottom_obj)->push_contents(pm);
208 bottom_obj += oop(bottom_obj)->size();
209 assert(bottom_obj <= sp_top, "just checking");
210 } while (bottom_obj < top);
211 pm->drain_stacks_cond_depth();
212 } else {
213 do {
214 oop(bottom_obj)->copy_contents(pm);
215 bottom_obj += oop(bottom_obj)->size();
216 assert(bottom_obj <= sp_top, "just checking");
217 } while (bottom_obj < top);
218 }
219 // remember top oop* scanned
220 prev_top = top;
221 }
222 }
223 }
224 }
226 void CardTableExtension::scavenge_contents_parallel(ObjectStartArray* start_array,
227 MutableSpace* sp,
228 HeapWord* space_top,
229 PSPromotionManager* pm,
230 uint stripe_number) {
231 int ssize = 128; // Naked constant! Work unit = 64k.
232 int dirty_card_count = 0;
233 bool depth_first = pm->depth_first();
235 oop* sp_top = (oop*)space_top;
236 jbyte* start_card = byte_for(sp->bottom());
237 jbyte* end_card = byte_for(sp_top - 1) + 1;
238 oop* last_scanned = NULL; // Prevent scanning objects more than once
239 for (jbyte* slice = start_card; slice < end_card; slice += ssize*ParallelGCThreads) {
240 jbyte* worker_start_card = slice + stripe_number * ssize;
241 if (worker_start_card >= end_card)
242 return; // We're done.
244 jbyte* worker_end_card = worker_start_card + ssize;
245 if (worker_end_card > end_card)
246 worker_end_card = end_card;
248 // We do not want to scan objects more than once. In order to accomplish
249 // this, we assert that any object with an object head inside our 'slice'
250 // belongs to us. We may need to extend the range of scanned cards if the
251 // last object continues into the next 'slice'.
252 //
253 // Note! ending cards are exclusive!
254 HeapWord* slice_start = addr_for(worker_start_card);
255 HeapWord* slice_end = MIN2((HeapWord*) sp_top, addr_for(worker_end_card));
257 // If there are not objects starting within the chunk, skip it.
258 if (!start_array->object_starts_in_range(slice_start, slice_end)) {
259 continue;
260 }
261 // Update our beginning addr
262 HeapWord* first_object = start_array->object_start(slice_start);
263 debug_only(oop* first_object_within_slice = (oop*) first_object;)
264 if (first_object < slice_start) {
265 last_scanned = (oop*)(first_object + oop(first_object)->size());
266 debug_only(first_object_within_slice = last_scanned;)
267 worker_start_card = byte_for(last_scanned);
268 }
270 // Update the ending addr
271 if (slice_end < (HeapWord*)sp_top) {
272 // The subtraction is important! An object may start precisely at slice_end.
273 HeapWord* last_object = start_array->object_start(slice_end - 1);
274 slice_end = last_object + oop(last_object)->size();
275 // worker_end_card is exclusive, so bump it one past the end of last_object's
276 // covered span.
277 worker_end_card = byte_for(slice_end) + 1;
279 if (worker_end_card > end_card)
280 worker_end_card = end_card;
281 }
283 assert(slice_end <= (HeapWord*)sp_top, "Last object in slice crosses space boundary");
284 assert(is_valid_card_address(worker_start_card), "Invalid worker start card");
285 assert(is_valid_card_address(worker_end_card), "Invalid worker end card");
286 // Note that worker_start_card >= worker_end_card is legal, and happens when
287 // an object spans an entire slice.
288 assert(worker_start_card <= end_card, "worker start card beyond end card");
289 assert(worker_end_card <= end_card, "worker end card beyond end card");
291 jbyte* current_card = worker_start_card;
292 while (current_card < worker_end_card) {
293 // Find an unclean card.
294 while (current_card < worker_end_card && card_is_clean(*current_card)) {
295 current_card++;
296 }
297 jbyte* first_unclean_card = current_card;
299 // Find the end of a run of contiguous unclean cards
300 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
301 while (current_card < worker_end_card && !card_is_clean(*current_card)) {
302 current_card++;
303 }
305 if (current_card < worker_end_card) {
306 // Some objects may be large enough to span several cards. If such
307 // an object has more than one dirty card, separated by a clean card,
308 // we will attempt to scan it twice. The test against "last_scanned"
309 // prevents the redundant object scan, but it does not prevent newly
310 // marked cards from being cleaned.
311 HeapWord* last_object_in_dirty_region = start_array->object_start(addr_for(current_card)-1);
312 size_t size_of_last_object = oop(last_object_in_dirty_region)->size();
313 HeapWord* end_of_last_object = last_object_in_dirty_region + size_of_last_object;
314 jbyte* ending_card_of_last_object = byte_for(end_of_last_object);
315 assert(ending_card_of_last_object <= worker_end_card, "ending_card_of_last_object is greater than worker_end_card");
316 if (ending_card_of_last_object > current_card) {
317 // This means the object spans the next complete card.
318 // We need to bump the current_card to ending_card_of_last_object
319 current_card = ending_card_of_last_object;
320 }
321 }
322 }
323 jbyte* following_clean_card = current_card;
325 if (first_unclean_card < worker_end_card) {
326 oop* p = (oop*) start_array->object_start(addr_for(first_unclean_card));
327 assert((HeapWord*)p <= addr_for(first_unclean_card), "checking");
328 // "p" should always be >= "last_scanned" because newly GC dirtied
329 // cards are no longer scanned again (see comment at end
330 // of loop on the increment of "current_card"). Test that
331 // hypothesis before removing this code.
332 // If this code is removed, deal with the first time through
333 // the loop when the last_scanned is the object starting in
334 // the previous slice.
335 assert((p >= last_scanned) ||
336 (last_scanned == first_object_within_slice),
337 "Should no longer be possible");
338 if (p < last_scanned) {
339 // Avoid scanning more than once; this can happen because
340 // newgen cards set by GC may a different set than the
341 // originally dirty set
342 p = last_scanned;
343 }
344 oop* to = (oop*)addr_for(following_clean_card);
346 // Test slice_end first!
347 if ((HeapWord*)to > slice_end) {
348 to = (oop*)slice_end;
349 } else if (to > sp_top) {
350 to = sp_top;
351 }
353 // we know which cards to scan, now clear them
354 if (first_unclean_card <= worker_start_card+1)
355 first_unclean_card = worker_start_card+1;
356 if (following_clean_card >= worker_end_card-1)
357 following_clean_card = worker_end_card-1;
359 while (first_unclean_card < following_clean_card) {
360 *first_unclean_card++ = clean_card;
361 }
363 const int interval = PrefetchScanIntervalInBytes;
364 // scan all objects in the range
365 if (interval != 0) {
366 // hoisted the if (depth_first) check out of the loop
367 if (depth_first) {
368 while (p < to) {
369 Prefetch::write(p, interval);
370 oop m = oop(p);
371 assert(m->is_oop_or_null(), "check for header");
372 m->push_contents(pm);
373 p += m->size();
374 }
375 pm->drain_stacks_cond_depth();
376 } else {
377 while (p < to) {
378 Prefetch::write(p, interval);
379 oop m = oop(p);
380 assert(m->is_oop_or_null(), "check for header");
381 m->copy_contents(pm);
382 p += m->size();
383 }
384 }
385 } else {
386 // hoisted the if (depth_first) check out of the loop
387 if (depth_first) {
388 while (p < to) {
389 oop m = oop(p);
390 assert(m->is_oop_or_null(), "check for header");
391 m->push_contents(pm);
392 p += m->size();
393 }
394 pm->drain_stacks_cond_depth();
395 } else {
396 while (p < to) {
397 oop m = oop(p);
398 assert(m->is_oop_or_null(), "check for header");
399 m->copy_contents(pm);
400 p += m->size();
401 }
402 }
403 }
404 last_scanned = p;
405 }
406 // "current_card" is still the "following_clean_card" or
407 // the current_card is >= the worker_end_card so the
408 // loop will not execute again.
409 assert((current_card == following_clean_card) ||
410 (current_card >= worker_end_card),
411 "current_card should only be incremented if it still equals "
412 "following_clean_card");
413 // Increment current_card so that it is not processed again.
414 // It may now be dirty because a old-to-young pointer was
415 // found on it an updated. If it is now dirty, it cannot be
416 // be safely cleaned in the next iteration.
417 current_card++;
418 }
419 }
420 }
422 // This should be called before a scavenge.
423 void CardTableExtension::verify_all_young_refs_imprecise() {
424 CheckForUnmarkedObjects check;
426 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
427 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
429 PSOldGen* old_gen = heap->old_gen();
430 PSPermGen* perm_gen = heap->perm_gen();
432 old_gen->object_iterate(&check);
433 perm_gen->object_iterate(&check);
434 }
436 // This should be called immediately after a scavenge, before mutators resume.
437 void CardTableExtension::verify_all_young_refs_precise() {
438 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
439 assert(heap->kind() == CollectedHeap::ParallelScavengeHeap, "Sanity");
441 PSOldGen* old_gen = heap->old_gen();
442 PSPermGen* perm_gen = heap->perm_gen();
444 CheckForPreciseMarks check(heap->young_gen(), (CardTableExtension*)heap->barrier_set());
446 old_gen->oop_iterate(&check);
447 perm_gen->oop_iterate(&check);
449 verify_all_young_refs_precise_helper(old_gen->object_space()->used_region());
450 verify_all_young_refs_precise_helper(perm_gen->object_space()->used_region());
451 }
453 void CardTableExtension::verify_all_young_refs_precise_helper(MemRegion mr) {
454 CardTableExtension* card_table = (CardTableExtension*)Universe::heap()->barrier_set();
455 // FIX ME ASSERT HERE
457 jbyte* bot = card_table->byte_for(mr.start());
458 jbyte* top = card_table->byte_for(mr.end());
459 while(bot <= top) {
460 assert(*bot == clean_card || *bot == verify_card, "Found unwanted or unknown card mark");
461 if (*bot == verify_card)
462 *bot = youngergen_card;
463 bot++;
464 }
465 }
467 bool CardTableExtension::addr_is_marked_imprecise(void *addr) {
468 jbyte* p = byte_for(addr);
469 jbyte val = *p;
471 if (card_is_dirty(val))
472 return true;
474 if (card_is_newgen(val))
475 return true;
477 if (card_is_clean(val))
478 return false;
480 assert(false, "Found unhandled card mark type");
482 return false;
483 }
485 // Also includes verify_card
486 bool CardTableExtension::addr_is_marked_precise(void *addr) {
487 jbyte* p = byte_for(addr);
488 jbyte val = *p;
490 if (card_is_newgen(val))
491 return true;
493 if (card_is_verify(val))
494 return true;
496 if (card_is_clean(val))
497 return false;
499 if (card_is_dirty(val))
500 return false;
502 assert(false, "Found unhandled card mark type");
504 return false;
505 }
507 // Assumes that only the base or the end changes. This allows indentification
508 // of the region that is being resized. The
509 // CardTableModRefBS::resize_covered_region() is used for the normal case
510 // where the covered regions are growing or shrinking at the high end.
511 // The method resize_covered_region_by_end() is analogous to
512 // CardTableModRefBS::resize_covered_region() but
513 // for regions that grow or shrink at the low end.
514 void CardTableExtension::resize_covered_region(MemRegion new_region) {
516 for (int i = 0; i < _cur_covered_regions; i++) {
517 if (_covered[i].start() == new_region.start()) {
518 // Found a covered region with the same start as the
519 // new region. The region is growing or shrinking
520 // from the start of the region.
521 resize_covered_region_by_start(new_region);
522 return;
523 }
524 if (_covered[i].start() > new_region.start()) {
525 break;
526 }
527 }
529 int changed_region = -1;
530 for (int j = 0; j < _cur_covered_regions; j++) {
531 if (_covered[j].end() == new_region.end()) {
532 changed_region = j;
533 // This is a case where the covered region is growing or shrinking
534 // at the start of the region.
535 assert(changed_region != -1, "Don't expect to add a covered region");
536 assert(_covered[changed_region].byte_size() != new_region.byte_size(),
537 "The sizes should be different here");
538 resize_covered_region_by_end(changed_region, new_region);
539 return;
540 }
541 }
542 // This should only be a new covered region (where no existing
543 // covered region matches at the start or the end).
544 assert(_cur_covered_regions < _max_covered_regions,
545 "An existing region should have been found");
546 resize_covered_region_by_start(new_region);
547 }
549 void CardTableExtension::resize_covered_region_by_start(MemRegion new_region) {
550 CardTableModRefBS::resize_covered_region(new_region);
551 debug_only(verify_guard();)
552 }
554 void CardTableExtension::resize_covered_region_by_end(int changed_region,
555 MemRegion new_region) {
556 assert(SafepointSynchronize::is_at_safepoint(),
557 "Only expect an expansion at the low end at a GC");
558 debug_only(verify_guard();)
559 #ifdef ASSERT
560 for (int k = 0; k < _cur_covered_regions; k++) {
561 if (_covered[k].end() == new_region.end()) {
562 assert(changed_region == k, "Changed region is incorrect");
563 break;
564 }
565 }
566 #endif
568 // Commit new or uncommit old pages, if necessary.
569 resize_commit_uncommit(changed_region, new_region);
571 // Update card table entries
572 resize_update_card_table_entries(changed_region, new_region);
574 // Set the new start of the committed region
575 resize_update_committed_table(changed_region, new_region);
577 // Update the covered region
578 resize_update_covered_table(changed_region, new_region);
580 if (TraceCardTableModRefBS) {
581 int ind = changed_region;
582 gclog_or_tty->print_cr("CardTableModRefBS::resize_covered_region: ");
583 gclog_or_tty->print_cr(" "
584 " _covered[%d].start(): " INTPTR_FORMAT
585 " _covered[%d].last(): " INTPTR_FORMAT,
586 ind, _covered[ind].start(),
587 ind, _covered[ind].last());
588 gclog_or_tty->print_cr(" "
589 " _committed[%d].start(): " INTPTR_FORMAT
590 " _committed[%d].last(): " INTPTR_FORMAT,
591 ind, _committed[ind].start(),
592 ind, _committed[ind].last());
593 gclog_or_tty->print_cr(" "
594 " byte_for(start): " INTPTR_FORMAT
595 " byte_for(last): " INTPTR_FORMAT,
596 byte_for(_covered[ind].start()),
597 byte_for(_covered[ind].last()));
598 gclog_or_tty->print_cr(" "
599 " addr_for(start): " INTPTR_FORMAT
600 " addr_for(last): " INTPTR_FORMAT,
601 addr_for((jbyte*) _committed[ind].start()),
602 addr_for((jbyte*) _committed[ind].last()));
603 }
604 debug_only(verify_guard();)
605 }
607 void CardTableExtension::resize_commit_uncommit(int changed_region,
608 MemRegion new_region) {
609 // Commit new or uncommit old pages, if necessary.
610 MemRegion cur_committed = _committed[changed_region];
611 assert(_covered[changed_region].end() == new_region.end(),
612 "The ends of the regions are expected to match");
613 // Extend the start of this _committed region to
614 // to cover the start of any previous _committed region.
615 // This forms overlapping regions, but never interior regions.
616 HeapWord* min_prev_start = lowest_prev_committed_start(changed_region);
617 if (min_prev_start < cur_committed.start()) {
618 // Only really need to set start of "cur_committed" to
619 // the new start (min_prev_start) but assertion checking code
620 // below use cur_committed.end() so make it correct.
621 MemRegion new_committed =
622 MemRegion(min_prev_start, cur_committed.end());
623 cur_committed = new_committed;
624 }
625 #ifdef ASSERT
626 ParallelScavengeHeap* heap = (ParallelScavengeHeap*)Universe::heap();
627 assert(cur_committed.start() ==
628 (HeapWord*) align_size_up((uintptr_t) cur_committed.start(),
629 os::vm_page_size()),
630 "Starts should have proper alignment");
631 #endif
633 jbyte* new_start = byte_for(new_region.start());
634 // Round down because this is for the start address
635 HeapWord* new_start_aligned =
636 (HeapWord*)align_size_down((uintptr_t)new_start, os::vm_page_size());
637 // The guard page is always committed and should not be committed over.
638 // This method is used in cases where the generation is growing toward
639 // lower addresses but the guard region is still at the end of the
640 // card table. That still makes sense when looking for writes
641 // off the end of the card table.
642 if (new_start_aligned < cur_committed.start()) {
643 // Expand the committed region
644 //
645 // Case A
646 // |+ guard +|
647 // |+ cur committed +++++++++|
648 // |+ new committed +++++++++++++++++|
649 //
650 // Case B
651 // |+ guard +|
652 // |+ cur committed +|
653 // |+ new committed +++++++|
654 //
655 // These are not expected because the calculation of the
656 // cur committed region and the new committed region
657 // share the same end for the covered region.
658 // Case C
659 // |+ guard +|
660 // |+ cur committed +|
661 // |+ new committed +++++++++++++++++|
662 // Case D
663 // |+ guard +|
664 // |+ cur committed +++++++++++|
665 // |+ new committed +++++++|
667 HeapWord* new_end_for_commit =
668 MIN2(cur_committed.end(), _guard_region.start());
669 if(new_start_aligned < new_end_for_commit) {
670 MemRegion new_committed =
671 MemRegion(new_start_aligned, new_end_for_commit);
672 if (!os::commit_memory((char*)new_committed.start(),
673 new_committed.byte_size())) {
674 vm_exit_out_of_memory(new_committed.byte_size(),
675 "card table expansion");
676 }
677 }
678 } else if (new_start_aligned > cur_committed.start()) {
679 // Shrink the committed region
680 MemRegion uncommit_region = committed_unique_to_self(changed_region,
681 MemRegion(cur_committed.start(), new_start_aligned));
682 if (!uncommit_region.is_empty()) {
683 if (!os::uncommit_memory((char*)uncommit_region.start(),
684 uncommit_region.byte_size())) {
685 vm_exit_out_of_memory(uncommit_region.byte_size(),
686 "card table contraction");
687 }
688 }
689 }
690 assert(_committed[changed_region].end() == cur_committed.end(),
691 "end should not change");
692 }
694 void CardTableExtension::resize_update_committed_table(int changed_region,
695 MemRegion new_region) {
697 jbyte* new_start = byte_for(new_region.start());
698 // Set the new start of the committed region
699 HeapWord* new_start_aligned =
700 (HeapWord*)align_size_down((uintptr_t)new_start,
701 os::vm_page_size());
702 MemRegion new_committed = MemRegion(new_start_aligned,
703 _committed[changed_region].end());
704 _committed[changed_region] = new_committed;
705 _committed[changed_region].set_start(new_start_aligned);
706 }
708 void CardTableExtension::resize_update_card_table_entries(int changed_region,
709 MemRegion new_region) {
710 debug_only(verify_guard();)
711 MemRegion original_covered = _covered[changed_region];
712 // Initialize the card entries. Only consider the
713 // region covered by the card table (_whole_heap)
714 jbyte* entry;
715 if (new_region.start() < _whole_heap.start()) {
716 entry = byte_for(_whole_heap.start());
717 } else {
718 entry = byte_for(new_region.start());
719 }
720 jbyte* end = byte_for(original_covered.start());
721 // If _whole_heap starts at the original covered regions start,
722 // this loop will not execute.
723 while (entry < end) { *entry++ = clean_card; }
724 }
726 void CardTableExtension::resize_update_covered_table(int changed_region,
727 MemRegion new_region) {
728 // Update the covered region
729 _covered[changed_region].set_start(new_region.start());
730 _covered[changed_region].set_word_size(new_region.word_size());
732 // reorder regions. There should only be at most 1 out
733 // of order.
734 for (int i = _cur_covered_regions-1 ; i > 0; i--) {
735 if (_covered[i].start() < _covered[i-1].start()) {
736 MemRegion covered_mr = _covered[i-1];
737 _covered[i-1] = _covered[i];
738 _covered[i] = covered_mr;
739 MemRegion committed_mr = _committed[i-1];
740 _committed[i-1] = _committed[i];
741 _committed[i] = committed_mr;
742 break;
743 }
744 }
745 #ifdef ASSERT
746 for (int m = 0; m < _cur_covered_regions-1; m++) {
747 assert(_covered[m].start() <= _covered[m+1].start(),
748 "Covered regions out of order");
749 assert(_committed[m].start() <= _committed[m+1].start(),
750 "Committed regions out of order");
751 }
752 #endif
753 }
755 // Returns the start of any committed region that is lower than
756 // the target committed region (index ind) and that intersects the
757 // target region. If none, return start of target region.
758 //
759 // -------------
760 // | |
761 // -------------
762 // ------------
763 // | target |
764 // ------------
765 // -------------
766 // | |
767 // -------------
768 // ^ returns this
769 //
770 // -------------
771 // | |
772 // -------------
773 // ------------
774 // | target |
775 // ------------
776 // -------------
777 // | |
778 // -------------
779 // ^ returns this
781 HeapWord* CardTableExtension::lowest_prev_committed_start(int ind) const {
782 assert(_cur_covered_regions >= 0, "Expecting at least on region");
783 HeapWord* min_start = _committed[ind].start();
784 for (int j = 0; j < ind; j++) {
785 HeapWord* this_start = _committed[j].start();
786 if ((this_start < min_start) &&
787 !(_committed[j].intersection(_committed[ind])).is_empty()) {
788 min_start = this_start;
789 }
790 }
791 return min_start;
792 }