70 _end = _reserved.start() + new_word_size;
71 if (new_size > old_size) {
72 delta = ReservedSpace::page_align_size_up(new_size - old_size);
73 assert(delta > 0, "just checking");
74 if (!_vs.expand_by(delta)) {
75 // Do better than this for Merlin
76 vm_exit_out_of_memory(delta, OOM_MMAP_ERROR, "offset table expansion");
77 }
78 assert(_vs.high() == high + delta, "invalid expansion");
79 } else {
80 delta = ReservedSpace::page_align_size_down(old_size - new_size);
81 if (delta == 0) return;
82 _vs.shrink_by(delta);
83 assert(_vs.high() == high - delta, "invalid expansion");
84 }
85 }
86
87 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
88 assert(p >= _reserved.start(), "just checking");
89 size_t delta = pointer_delta(p, _reserved.start());
90 return (delta & right_n_bits(LogN_words)) == (size_t)NoBits;
91 }
92
93
94 //////////////////////////////////////////////////////////////////////
95 // BlockOffsetArray
96 //////////////////////////////////////////////////////////////////////
97
98 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
99 MemRegion mr, bool init_to_zero_) :
100 BlockOffsetTable(mr.start(), mr.end()),
101 _array(array)
102 {
103 assert(_bottom <= _end, "arguments out of order");
104 set_init_to_zero(init_to_zero_);
105 if (!init_to_zero_) {
106 // initialize cards to point back to mr.start()
107 set_remainder_to_point_to_start(mr.start() + N_words, mr.end());
108 _array->set_offset_array(0, 0); // set first card to 0
109 }
110 }
111
112
113 // The arguments follow the normal convention of denoting
114 // a right-open interval: [start, end)
115 void
116 BlockOffsetArray::
117 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) {
118
119 check_reducing_assertion(reducing);
120 if (start >= end) {
121 // The start address is equal to the end address (or to
122 // the right of the end address) so there are not cards
123 // that need to be updated..
124 return;
125 }
126
127 // Write the backskip value for each region.
143 // 2nd - start of second logarithmic region
144 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
145 // 3rd - start of third logarithmic region
146 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
147 //
148 // integer below the block offset entry is an example of
149 // the index of the entry
150 //
151 // Given an address,
152 // Find the index for the address
153 // Find the block offset table entry
154 // Convert the entry to a back slide
155 // (e.g., with today's, offset = 0x81 =>
156 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
157 // Move back N (e.g., 8) entries and repeat with the
158 // value of the new entry
159 //
160 size_t start_card = _array->index_for(start);
161 size_t end_card = _array->index_for(end-1);
162 assert(start ==_array->address_for_index(start_card), "Precondition");
163 assert(end ==_array->address_for_index(end_card)+N_words, "Precondition");
164 set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval
165 }
166
167
168 // Unlike the normal convention in this code, the argument here denotes
169 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
170 // above.
171 void
172 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) {
173
174 check_reducing_assertion(reducing);
175 if (start_card > end_card) {
176 return;
177 }
178 assert(start_card > _array->index_for(_bottom), "Cannot be first card");
179 assert(_array->offset_array(start_card-1) <= N_words,
180 "Offset card has an unexpected value");
181 size_t start_card_for_region = start_card;
182 u_char offset = max_jubyte;
183 for (int i = 0; i < N_powers; i++) {
184 // -1 so that the the card with the actual offset is counted. Another -1
185 // so that the reach ends in this region and not at the start
186 // of the next.
187 size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1);
188 offset = N_words + i;
189 if (reach >= end_card) {
190 _array->set_offset_array(start_card_for_region, end_card, offset, reducing);
191 start_card_for_region = reach + 1;
192 break;
193 }
194 _array->set_offset_array(start_card_for_region, reach, offset, reducing);
195 start_card_for_region = reach + 1;
196 }
197 assert(start_card_for_region > end_card, "Sanity check");
198 DEBUG_ONLY(check_all_cards(start_card, end_card);)
199 }
200
201 // The card-interval [start_card, end_card] is a closed interval; this
202 // is an expensive check -- use with care and only under protection of
203 // suitable flag.
204 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
205
206 if (end_card < start_card) {
207 return;
208 }
209 guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card");
210 u_char last_entry = N_words;
211 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
212 u_char entry = _array->offset_array(c);
213 guarantee(entry >= last_entry, "Monotonicity");
214 if (c - start_card > power_to_cards_back(1)) {
215 guarantee(entry > N_words, "Should be in logarithmic region");
216 }
217 size_t backskip = entry_to_cards_back(entry);
218 size_t landing_card = c - backskip;
219 guarantee(landing_card >= (start_card - 1), "Inv");
220 if (landing_card >= start_card) {
221 guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity");
222 } else {
223 guarantee(landing_card == (start_card - 1), "Tautology");
224 // Note that N_words is the maximum offset value
225 guarantee(_array->offset_array(landing_card) <= N_words, "Offset value");
226 }
227 last_entry = entry; // remember for monotonicity test
228 }
229 }
230
231
232 void
233 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
234 assert(blk_start != NULL && blk_end > blk_start,
235 "phantom block");
236 single_block(blk_start, blk_end);
237 }
238
239 // Action_mark - update the BOT for the block [blk_start, blk_end).
240 // Current typical use is for splitting a block.
241 // Action_single - udpate the BOT for an allocation.
242 // Action_verify - BOT verification.
243 void
244 BlockOffsetArray::do_block_internal(HeapWord* blk_start,
245 HeapWord* blk_end,
246 Action action, bool reducing) {
247 assert(Universe::heap()->is_in_reserved(blk_start),
248 "reference must be into the heap");
249 assert(Universe::heap()->is_in_reserved(blk_end-1),
250 "limit must be within the heap");
251 // This is optimized to make the test fast, assuming we only rarely
252 // cross boundaries.
253 uintptr_t end_ui = (uintptr_t)(blk_end - 1);
254 uintptr_t start_ui = (uintptr_t)blk_start;
255 // Calculate the last card boundary preceding end of blk
256 intptr_t boundary_before_end = (intptr_t)end_ui;
257 clear_bits(boundary_before_end, right_n_bits(LogN));
258 if (start_ui <= (uintptr_t)boundary_before_end) {
259 // blk starts at or crosses a boundary
260 // Calculate index of card on which blk begins
261 size_t start_index = _array->index_for(blk_start);
262 // Index of card on which blk ends
263 size_t end_index = _array->index_for(blk_end - 1);
264 // Start address of card on which blk begins
265 HeapWord* boundary = _array->address_for_index(start_index);
266 assert(boundary <= blk_start, "blk should start at or after boundary");
267 if (blk_start != boundary) {
268 // blk starts strictly after boundary
269 // adjust card boundary and start_index forward to next card
270 boundary += N_words;
271 start_index++;
272 }
273 assert(start_index <= end_index, "monotonicity of index_for()");
274 assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
275 switch (action) {
276 case Action_mark: {
277 if (init_to_zero()) {
278 _array->set_offset_array(start_index, boundary, blk_start, reducing);
279 break;
280 } // Else fall through to the next case
281 }
282 case Action_single: {
283 _array->set_offset_array(start_index, boundary, blk_start, reducing);
284 // We have finished marking the "offset card". We need to now
285 // mark the subsequent cards that this blk spans.
286 if (start_index < end_index) {
287 HeapWord* rem_st = _array->address_for_index(start_index) + N_words;
288 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
289 set_remainder_to_point_to_start(rem_st, rem_end, reducing);
290 }
291 break;
292 }
293 case Action_check: {
294 _array->check_offset_array(start_index, boundary, blk_start);
295 // We have finished checking the "offset card". We need to now
296 // check the subsequent cards that this blk spans.
297 check_all_cards(start_index + 1, end_index);
298 break;
299 }
300 default:
301 ShouldNotReachHere();
302 }
303 }
304 }
305
306 // The range [blk_start, blk_end) represents a single contiguous block
307 // of storage; modify the block offset table to represent this
308 // information; Right-open interval: [blk_start, blk_end)
433 _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */);
434 // Change any further cards that need changing in the suffix
435 if (num_pref_cards > 0) {
436 if (num_pref_cards >= num_suff_cards) {
437 // Unilaterally fix all of the suffix cards: closed card
438 // index interval in args below.
439 set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */);
440 } else {
441 // Unilaterally fix the first (num_pref_cards - 1) following
442 // the "offset card" in the suffix block.
443 const size_t right_most_fixed_index = suff_index + num_pref_cards - 1;
444 set_remainder_to_point_to_start_incl(suff_index + 1,
445 right_most_fixed_index, true /* reducing */);
446 // Fix the appropriate cards in the remainder of the
447 // suffix block -- these are the last num_pref_cards
448 // cards in each power block of the "new" range plumbed
449 // from suff_addr.
450 bool more = true;
451 uint i = 1;
452 // Fix the first power block with back_by > num_pref_cards.
453 while (more && (i < N_powers)) {
454 size_t back_by = power_to_cards_back(i);
455 size_t right_index = suff_index + back_by - 1;
456 size_t left_index = right_index - num_pref_cards + 1;
457 if (right_index >= end_index - 1) { // last iteration
458 right_index = end_index - 1;
459 more = false;
460 }
461 if (left_index <= right_most_fixed_index) {
462 left_index = right_most_fixed_index + 1;
463 }
464 if (back_by > num_pref_cards) {
465 // Fill in the remainder of this "power block", if it
466 // is non-null.
467 if (left_index <= right_index) {
468 _array->set_offset_array(left_index, right_index,
469 N_words + i - 1, true /* reducing */);
470 } else {
471 more = false; // we are done
472 assert((end_index - 1) == right_index, "Must be at the end.");
473 }
474 i++;
475 break;
476 }
477 i++;
478 }
479 // Fix the rest of the power blocks.
480 while (more && (i < N_powers)) {
481 size_t back_by = power_to_cards_back(i);
482 size_t right_index = suff_index + back_by - 1;
483 size_t left_index = right_index - num_pref_cards + 1;
484 if (right_index >= end_index - 1) { // last iteration
485 right_index = end_index - 1;
486 if (left_index > right_index) {
487 break;
488 }
489 more = false;
490 }
491 assert(left_index <= right_index, "Error");
492 _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */);
493 i++;
494 }
495 }
496 } // else no more cards to fix in suffix
497 } // else nothing needs to be done
498 // Verify that we did the right thing
499 verify_single_block(pref_addr, left_blk_size);
500 verify_single_block(suff_addr, blk_size - left_blk_size);
501 }
502
503
504 // Mark the BOT such that if [blk_start, blk_end) straddles a card
505 // boundary, the card following the first such boundary is marked
506 // with the appropriate offset.
507 // NOTE: this method does _not_ adjust _unallocated_block or
508 // any cards subsequent to the first one.
509 void
510 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start,
511 HeapWord* blk_end, bool reducing) {
512 do_block_internal(blk_start, blk_end, Action_mark, reducing);
513 }
514
515 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe(
516 const void* addr) const {
517 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
518 assert(_bottom <= addr && addr < _end,
519 "addr must be covered by this Array");
520 // Must read this exactly once because it can be modified by parallel
521 // allocation.
522 HeapWord* ub = _unallocated_block;
523 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
524 assert(ub < _end, "tautology (see above)");
525 return ub;
526 }
527
528 // Otherwise, find the block start using the table.
529 size_t index = _array->index_for(addr);
530 HeapWord* q = _array->address_for_index(index);
531
532 uint offset = _array->offset_array(index); // Extend u_char to uint.
533 while (offset >= N_words) {
534 // The excess of the offset from N_words indicates a power of Base
535 // to go back by.
536 size_t n_cards_back = entry_to_cards_back(offset);
537 q -= (N_words * n_cards_back);
538 assert(q >= _sp->bottom(),
539 "q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
540 p2i(q), p2i(_sp->bottom()));
541 assert(q < _sp->end(),
542 "q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
543 p2i(q), p2i(_sp->end()));
544 index -= n_cards_back;
545 offset = _array->offset_array(index);
546 }
547 assert(offset < N_words, "offset too large");
548 index--;
549 q -= offset;
550 assert(q >= _sp->bottom(),
551 "q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
552 p2i(q), p2i(_sp->bottom()));
553 assert(q < _sp->end(),
554 "q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
555 p2i(q), p2i(_sp->end()));
556 HeapWord* n = q;
557
558 while (n <= addr) {
559 debug_only(HeapWord* last = q); // for debugging
560 q = n;
561 n += _sp->block_size(n);
562 assert(n > q,
563 "Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT ","
564 " while querying blk_start(" PTR_FORMAT ")"
565 " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")",
566 p2i(n), p2i(last), p2i(addr), p2i(_sp->bottom()), p2i(_sp->end()));
567 }
582 "addr must be covered by this Array");
583 // Must read this exactly once because it can be modified by parallel
584 // allocation.
585 HeapWord* ub = _unallocated_block;
586 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
587 assert(ub < _end, "tautology (see above)");
588 return ub;
589 }
590
591 // Otherwise, find the block start using the table, but taking
592 // care (cf block_start_unsafe() above) not to parse any objects/blocks
593 // on the cards themselves.
594 size_t index = _array->index_for(addr);
595 assert(_array->address_for_index(index) == addr,
596 "arg should be start of card");
597
598 HeapWord* q = (HeapWord*)addr;
599 uint offset;
600 do {
601 offset = _array->offset_array(index);
602 if (offset < N_words) {
603 q -= offset;
604 } else {
605 size_t n_cards_back = entry_to_cards_back(offset);
606 q -= (n_cards_back * N_words);
607 index -= n_cards_back;
608 }
609 } while (offset >= N_words);
610 assert(q <= addr, "block start should be to left of arg");
611 return q;
612 }
613
614 #ifndef PRODUCT
615 // Verification & debugging - ensure that the offset table reflects the fact
616 // that the block [blk_start, blk_end) or [blk, blk + size) is a
617 // single block of storage. NOTE: can't const this because of
618 // call to non-const do_block_internal() below.
619 void BlockOffsetArrayNonContigSpace::verify_single_block(
620 HeapWord* blk_start, HeapWord* blk_end) {
621 if (VerifyBlockOffsetArray) {
622 do_block_internal(blk_start, blk_end, Action_check);
623 }
624 }
625
626 void BlockOffsetArrayNonContigSpace::verify_single_block(
627 HeapWord* blk, size_t size) {
628 verify_single_block(blk, blk + size);
629 }
651 }
652 }
653
654 //////////////////////////////////////////////////////////////////////
655 // BlockOffsetArrayContigSpace
656 //////////////////////////////////////////////////////////////////////
657
658 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const {
659 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
660
661 // Otherwise, find the block start using the table.
662 assert(_bottom <= addr && addr < _end,
663 "addr must be covered by this Array");
664 size_t index = _array->index_for(addr);
665 // We must make sure that the offset table entry we use is valid. If
666 // "addr" is past the end, start at the last known one and go forward.
667 index = MIN2(index, _next_offset_index-1);
668 HeapWord* q = _array->address_for_index(index);
669
670 uint offset = _array->offset_array(index); // Extend u_char to uint.
671 while (offset > N_words) {
672 // The excess of the offset from N_words indicates a power of Base
673 // to go back by.
674 size_t n_cards_back = entry_to_cards_back(offset);
675 q -= (N_words * n_cards_back);
676 assert(q >= _sp->bottom(), "Went below bottom!");
677 index -= n_cards_back;
678 offset = _array->offset_array(index);
679 }
680 while (offset == N_words) {
681 assert(q >= _sp->bottom(), "Went below bottom!");
682 q -= N_words;
683 index--;
684 offset = _array->offset_array(index);
685 }
686 assert(offset < N_words, "offset too large");
687 q -= offset;
688 HeapWord* n = q;
689
690 while (n <= addr) {
691 debug_only(HeapWord* last = q); // for debugging
692 q = n;
693 n += _sp->block_size(n);
694 }
695 assert(q <= addr, "wrong order for current and arg");
696 assert(addr <= n, "wrong order for arg and next");
697 return q;
698 }
699
700 //
701 // _next_offset_threshold
702 // | _next_offset_index
703 // v v
704 // +-------+-------+-------+-------+-------+
705 // | i-1 | i | i+1 | i+2 | i+3 |
706 // +-------+-------+-------+-------+-------+
707 // ( ^ ]
708 // block-start
709 //
710
711 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start,
712 HeapWord* blk_end) {
713 assert(blk_start != NULL && blk_end > blk_start,
714 "phantom block");
715 assert(blk_end > _next_offset_threshold,
716 "should be past threshold");
717 assert(blk_start <= _next_offset_threshold,
718 "blk_start should be at or before threshold");
719 assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words,
720 "offset should be <= BlockOffsetSharedArray::N");
721 assert(Universe::heap()->is_in_reserved(blk_start),
722 "reference must be into the heap");
723 assert(Universe::heap()->is_in_reserved(blk_end-1),
724 "limit must be within the heap");
725 assert(_next_offset_threshold ==
726 _array->_reserved.start() + _next_offset_index*N_words,
727 "index must agree with threshold");
728
729 debug_only(size_t orig_next_offset_index = _next_offset_index;)
730
731 // Mark the card that holds the offset into the block. Note
732 // that _next_offset_index and _next_offset_threshold are not
733 // updated until the end of this method.
734 _array->set_offset_array(_next_offset_index,
735 _next_offset_threshold,
736 blk_start);
737
738 // We need to now mark the subsequent cards that this blk spans.
739
740 // Index of card on which blk ends.
741 size_t end_index = _array->index_for(blk_end - 1);
742
743 // Are there more cards left to be updated?
744 if (_next_offset_index + 1 <= end_index) {
745 HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1);
746 // Calculate rem_end this way because end_index
747 // may be the last valid index in the covered region.
748 HeapWord* rem_end = _array->address_for_index(end_index) + N_words;
749 set_remainder_to_point_to_start(rem_st, rem_end);
750 }
751
752 // _next_offset_index and _next_offset_threshold updated here.
753 _next_offset_index = end_index + 1;
754 // Calculate _next_offset_threshold this way because end_index
755 // may be the last valid index in the covered region.
756 _next_offset_threshold = _array->address_for_index(end_index) + N_words;
757 assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold");
758
759 #ifdef ASSERT
760 // The offset can be 0 if the block starts on a boundary. That
761 // is checked by an assertion above.
762 size_t start_index = _array->index_for(blk_start);
763 HeapWord* boundary = _array->address_for_index(start_index);
764 assert((_array->offset_array(orig_next_offset_index) == 0 &&
765 blk_start == boundary) ||
766 (_array->offset_array(orig_next_offset_index) > 0 &&
767 _array->offset_array(orig_next_offset_index) <= N_words),
768 "offset array should have been set");
769 for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) {
770 assert(_array->offset_array(j) > 0 &&
771 _array->offset_array(j) <= (u_char) (N_words+N_powers-1),
772 "offset array should have been set");
773 }
774 #endif
775 }
776
777 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {
778 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
779 "just checking");
780 _next_offset_index = _array->index_for(_bottom);
781 _next_offset_index++;
782 _next_offset_threshold =
783 _array->address_for_index(_next_offset_index);
784 return _next_offset_threshold;
785 }
786
787 void BlockOffsetArrayContigSpace::zero_bottom_entry() {
788 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
789 "just checking");
790 size_t bottom_index = _array->index_for(_bottom);
791 _array->set_offset_array(bottom_index, 0);
|
70 _end = _reserved.start() + new_word_size;
71 if (new_size > old_size) {
72 delta = ReservedSpace::page_align_size_up(new_size - old_size);
73 assert(delta > 0, "just checking");
74 if (!_vs.expand_by(delta)) {
75 // Do better than this for Merlin
76 vm_exit_out_of_memory(delta, OOM_MMAP_ERROR, "offset table expansion");
77 }
78 assert(_vs.high() == high + delta, "invalid expansion");
79 } else {
80 delta = ReservedSpace::page_align_size_down(old_size - new_size);
81 if (delta == 0) return;
82 _vs.shrink_by(delta);
83 assert(_vs.high() == high - delta, "invalid expansion");
84 }
85 }
86
87 bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const {
88 assert(p >= _reserved.start(), "just checking");
89 size_t delta = pointer_delta(p, _reserved.start());
90 return (delta & right_n_bits((int)BOTConstants::LogN_words)) == (size_t)NoBits;
91 }
92
93
94 //////////////////////////////////////////////////////////////////////
95 // BlockOffsetArray
96 //////////////////////////////////////////////////////////////////////
97
98 BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array,
99 MemRegion mr, bool init_to_zero_) :
100 BlockOffsetTable(mr.start(), mr.end()),
101 _array(array)
102 {
103 assert(_bottom <= _end, "arguments out of order");
104 set_init_to_zero(init_to_zero_);
105 if (!init_to_zero_) {
106 // initialize cards to point back to mr.start()
107 set_remainder_to_point_to_start(mr.start() + BOTConstants::N_words, mr.end());
108 _array->set_offset_array(0, 0); // set first card to 0
109 }
110 }
111
112
113 // The arguments follow the normal convention of denoting
114 // a right-open interval: [start, end)
115 void
116 BlockOffsetArray::
117 set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) {
118
119 check_reducing_assertion(reducing);
120 if (start >= end) {
121 // The start address is equal to the end address (or to
122 // the right of the end address) so there are not cards
123 // that need to be updated..
124 return;
125 }
126
127 // Write the backskip value for each region.
143 // 2nd - start of second logarithmic region
144 // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8
145 // 3rd - start of third logarithmic region
146 // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64
147 //
148 // integer below the block offset entry is an example of
149 // the index of the entry
150 //
151 // Given an address,
152 // Find the index for the address
153 // Find the block offset table entry
154 // Convert the entry to a back slide
155 // (e.g., with today's, offset = 0x81 =>
156 // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8
157 // Move back N (e.g., 8) entries and repeat with the
158 // value of the new entry
159 //
160 size_t start_card = _array->index_for(start);
161 size_t end_card = _array->index_for(end-1);
162 assert(start ==_array->address_for_index(start_card), "Precondition");
163 assert(end ==_array->address_for_index(end_card)+BOTConstants::N_words, "Precondition");
164 set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval
165 }
166
167
168 // Unlike the normal convention in this code, the argument here denotes
169 // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start()
170 // above.
171 void
172 BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) {
173
174 check_reducing_assertion(reducing);
175 if (start_card > end_card) {
176 return;
177 }
178 assert(start_card > _array->index_for(_bottom), "Cannot be first card");
179 assert(_array->offset_array(start_card-1) <= BOTConstants::N_words,
180 "Offset card has an unexpected value");
181 size_t start_card_for_region = start_card;
182 u_char offset = max_jubyte;
183 for (uint i = 0; i < BOTConstants::N_powers; i++) {
184 // -1 so that the the card with the actual offset is counted. Another -1
185 // so that the reach ends in this region and not at the start
186 // of the next.
187 size_t reach = start_card - 1 + (BOTConstants::power_to_cards_back(i+1) - 1);
188 offset = BOTConstants::N_words + i;
189 if (reach >= end_card) {
190 _array->set_offset_array(start_card_for_region, end_card, offset, reducing);
191 start_card_for_region = reach + 1;
192 break;
193 }
194 _array->set_offset_array(start_card_for_region, reach, offset, reducing);
195 start_card_for_region = reach + 1;
196 }
197 assert(start_card_for_region > end_card, "Sanity check");
198 DEBUG_ONLY(check_all_cards(start_card, end_card);)
199 }
200
201 // The card-interval [start_card, end_card] is a closed interval; this
202 // is an expensive check -- use with care and only under protection of
203 // suitable flag.
204 void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const {
205
206 if (end_card < start_card) {
207 return;
208 }
209 guarantee(_array->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card");
210 u_char last_entry = BOTConstants::N_words;
211 for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) {
212 u_char entry = _array->offset_array(c);
213 guarantee(entry >= last_entry, "Monotonicity");
214 if (c - start_card > BOTConstants::power_to_cards_back(1)) {
215 guarantee(entry > BOTConstants::N_words, "Should be in logarithmic region");
216 }
217 size_t backskip = BOTConstants::entry_to_cards_back(entry);
218 size_t landing_card = c - backskip;
219 guarantee(landing_card >= (start_card - 1), "Inv");
220 if (landing_card >= start_card) {
221 guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity");
222 } else {
223 guarantee(landing_card == (start_card - 1), "Tautology");
224 // Note that N_words is the maximum offset value
225 guarantee(_array->offset_array(landing_card) <= BOTConstants::N_words, "Offset value");
226 }
227 last_entry = entry; // remember for monotonicity test
228 }
229 }
230
231
232 void
233 BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) {
234 assert(blk_start != NULL && blk_end > blk_start,
235 "phantom block");
236 single_block(blk_start, blk_end);
237 }
238
239 // Action_mark - update the BOT for the block [blk_start, blk_end).
240 // Current typical use is for splitting a block.
241 // Action_single - udpate the BOT for an allocation.
242 // Action_verify - BOT verification.
243 void
244 BlockOffsetArray::do_block_internal(HeapWord* blk_start,
245 HeapWord* blk_end,
246 Action action, bool reducing) {
247 assert(Universe::heap()->is_in_reserved(blk_start),
248 "reference must be into the heap");
249 assert(Universe::heap()->is_in_reserved(blk_end-1),
250 "limit must be within the heap");
251 // This is optimized to make the test fast, assuming we only rarely
252 // cross boundaries.
253 uintptr_t end_ui = (uintptr_t)(blk_end - 1);
254 uintptr_t start_ui = (uintptr_t)blk_start;
255 // Calculate the last card boundary preceding end of blk
256 intptr_t boundary_before_end = (intptr_t)end_ui;
257 clear_bits(boundary_before_end, right_n_bits((int)BOTConstants::LogN));
258 if (start_ui <= (uintptr_t)boundary_before_end) {
259 // blk starts at or crosses a boundary
260 // Calculate index of card on which blk begins
261 size_t start_index = _array->index_for(blk_start);
262 // Index of card on which blk ends
263 size_t end_index = _array->index_for(blk_end - 1);
264 // Start address of card on which blk begins
265 HeapWord* boundary = _array->address_for_index(start_index);
266 assert(boundary <= blk_start, "blk should start at or after boundary");
267 if (blk_start != boundary) {
268 // blk starts strictly after boundary
269 // adjust card boundary and start_index forward to next card
270 boundary += BOTConstants::N_words;
271 start_index++;
272 }
273 assert(start_index <= end_index, "monotonicity of index_for()");
274 assert(boundary <= (HeapWord*)boundary_before_end, "tautology");
275 switch (action) {
276 case Action_mark: {
277 if (init_to_zero()) {
278 _array->set_offset_array(start_index, boundary, blk_start, reducing);
279 break;
280 } // Else fall through to the next case
281 }
282 case Action_single: {
283 _array->set_offset_array(start_index, boundary, blk_start, reducing);
284 // We have finished marking the "offset card". We need to now
285 // mark the subsequent cards that this blk spans.
286 if (start_index < end_index) {
287 HeapWord* rem_st = _array->address_for_index(start_index) + BOTConstants::N_words;
288 HeapWord* rem_end = _array->address_for_index(end_index) + BOTConstants::N_words;
289 set_remainder_to_point_to_start(rem_st, rem_end, reducing);
290 }
291 break;
292 }
293 case Action_check: {
294 _array->check_offset_array(start_index, boundary, blk_start);
295 // We have finished checking the "offset card". We need to now
296 // check the subsequent cards that this blk spans.
297 check_all_cards(start_index + 1, end_index);
298 break;
299 }
300 default:
301 ShouldNotReachHere();
302 }
303 }
304 }
305
306 // The range [blk_start, blk_end) represents a single contiguous block
307 // of storage; modify the block offset table to represent this
308 // information; Right-open interval: [blk_start, blk_end)
433 _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */);
434 // Change any further cards that need changing in the suffix
435 if (num_pref_cards > 0) {
436 if (num_pref_cards >= num_suff_cards) {
437 // Unilaterally fix all of the suffix cards: closed card
438 // index interval in args below.
439 set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */);
440 } else {
441 // Unilaterally fix the first (num_pref_cards - 1) following
442 // the "offset card" in the suffix block.
443 const size_t right_most_fixed_index = suff_index + num_pref_cards - 1;
444 set_remainder_to_point_to_start_incl(suff_index + 1,
445 right_most_fixed_index, true /* reducing */);
446 // Fix the appropriate cards in the remainder of the
447 // suffix block -- these are the last num_pref_cards
448 // cards in each power block of the "new" range plumbed
449 // from suff_addr.
450 bool more = true;
451 uint i = 1;
452 // Fix the first power block with back_by > num_pref_cards.
453 while (more && (i < BOTConstants::N_powers)) {
454 size_t back_by = BOTConstants::power_to_cards_back(i);
455 size_t right_index = suff_index + back_by - 1;
456 size_t left_index = right_index - num_pref_cards + 1;
457 if (right_index >= end_index - 1) { // last iteration
458 right_index = end_index - 1;
459 more = false;
460 }
461 if (left_index <= right_most_fixed_index) {
462 left_index = right_most_fixed_index + 1;
463 }
464 if (back_by > num_pref_cards) {
465 // Fill in the remainder of this "power block", if it
466 // is non-null.
467 if (left_index <= right_index) {
468 _array->set_offset_array(left_index, right_index,
469 BOTConstants::N_words + i - 1, true /* reducing */);
470 } else {
471 more = false; // we are done
472 assert((end_index - 1) == right_index, "Must be at the end.");
473 }
474 i++;
475 break;
476 }
477 i++;
478 }
479 // Fix the rest of the power blocks.
480 while (more && (i < BOTConstants::N_powers)) {
481 size_t back_by = BOTConstants::power_to_cards_back(i);
482 size_t right_index = suff_index + back_by - 1;
483 size_t left_index = right_index - num_pref_cards + 1;
484 if (right_index >= end_index - 1) { // last iteration
485 right_index = end_index - 1;
486 if (left_index > right_index) {
487 break;
488 }
489 more = false;
490 }
491 assert(left_index <= right_index, "Error");
492 _array->set_offset_array(left_index, right_index, BOTConstants::N_words + i - 1, true /* reducing */);
493 i++;
494 }
495 }
496 } // else no more cards to fix in suffix
497 } // else nothing needs to be done
498 // Verify that we did the right thing
499 verify_single_block(pref_addr, left_blk_size);
500 verify_single_block(suff_addr, blk_size - left_blk_size);
501 }
502
503
504 // Mark the BOT such that if [blk_start, blk_end) straddles a card
505 // boundary, the card following the first such boundary is marked
506 // with the appropriate offset.
507 // NOTE: this method does _not_ adjust _unallocated_block or
508 // any cards subsequent to the first one.
509 void
510 BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start,
511 HeapWord* blk_end, bool reducing) {
512 do_block_internal(blk_start, blk_end, Action_mark, reducing);
513 }
514
515 HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe(
516 const void* addr) const {
517 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
518 assert(_bottom <= addr && addr < _end,
519 "addr must be covered by this Array");
520 // Must read this exactly once because it can be modified by parallel
521 // allocation.
522 HeapWord* ub = _unallocated_block;
523 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
524 assert(ub < _end, "tautology (see above)");
525 return ub;
526 }
527
528 // Otherwise, find the block start using the table.
529 size_t index = _array->index_for(addr);
530 HeapWord* q = _array->address_for_index(index);
531
532 uint offset = _array->offset_array(index); // Extend u_char to uint.
533 while (offset >= BOTConstants::N_words) {
534 // The excess of the offset from N_words indicates a power of Base
535 // to go back by.
536 size_t n_cards_back = BOTConstants::entry_to_cards_back(offset);
537 q -= (BOTConstants::N_words * n_cards_back);
538 assert(q >= _sp->bottom(),
539 "q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
540 p2i(q), p2i(_sp->bottom()));
541 assert(q < _sp->end(),
542 "q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
543 p2i(q), p2i(_sp->end()));
544 index -= n_cards_back;
545 offset = _array->offset_array(index);
546 }
547 assert(offset < BOTConstants::N_words, "offset too large");
548 index--;
549 q -= offset;
550 assert(q >= _sp->bottom(),
551 "q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT,
552 p2i(q), p2i(_sp->bottom()));
553 assert(q < _sp->end(),
554 "q = " PTR_FORMAT " crossed above end = " PTR_FORMAT,
555 p2i(q), p2i(_sp->end()));
556 HeapWord* n = q;
557
558 while (n <= addr) {
559 debug_only(HeapWord* last = q); // for debugging
560 q = n;
561 n += _sp->block_size(n);
562 assert(n > q,
563 "Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT ","
564 " while querying blk_start(" PTR_FORMAT ")"
565 " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")",
566 p2i(n), p2i(last), p2i(addr), p2i(_sp->bottom()), p2i(_sp->end()));
567 }
582 "addr must be covered by this Array");
583 // Must read this exactly once because it can be modified by parallel
584 // allocation.
585 HeapWord* ub = _unallocated_block;
586 if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) {
587 assert(ub < _end, "tautology (see above)");
588 return ub;
589 }
590
591 // Otherwise, find the block start using the table, but taking
592 // care (cf block_start_unsafe() above) not to parse any objects/blocks
593 // on the cards themselves.
594 size_t index = _array->index_for(addr);
595 assert(_array->address_for_index(index) == addr,
596 "arg should be start of card");
597
598 HeapWord* q = (HeapWord*)addr;
599 uint offset;
600 do {
601 offset = _array->offset_array(index);
602 if (offset < BOTConstants::N_words) {
603 q -= offset;
604 } else {
605 size_t n_cards_back = BOTConstants::entry_to_cards_back(offset);
606 q -= (n_cards_back * BOTConstants::N_words);
607 index -= n_cards_back;
608 }
609 } while (offset >= BOTConstants::N_words);
610 assert(q <= addr, "block start should be to left of arg");
611 return q;
612 }
613
614 #ifndef PRODUCT
615 // Verification & debugging - ensure that the offset table reflects the fact
616 // that the block [blk_start, blk_end) or [blk, blk + size) is a
617 // single block of storage. NOTE: can't const this because of
618 // call to non-const do_block_internal() below.
619 void BlockOffsetArrayNonContigSpace::verify_single_block(
620 HeapWord* blk_start, HeapWord* blk_end) {
621 if (VerifyBlockOffsetArray) {
622 do_block_internal(blk_start, blk_end, Action_check);
623 }
624 }
625
626 void BlockOffsetArrayNonContigSpace::verify_single_block(
627 HeapWord* blk, size_t size) {
628 verify_single_block(blk, blk + size);
629 }
651 }
652 }
653
654 //////////////////////////////////////////////////////////////////////
655 // BlockOffsetArrayContigSpace
656 //////////////////////////////////////////////////////////////////////
657
658 HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const {
659 assert(_array->offset_array(0) == 0, "objects can't cross covered areas");
660
661 // Otherwise, find the block start using the table.
662 assert(_bottom <= addr && addr < _end,
663 "addr must be covered by this Array");
664 size_t index = _array->index_for(addr);
665 // We must make sure that the offset table entry we use is valid. If
666 // "addr" is past the end, start at the last known one and go forward.
667 index = MIN2(index, _next_offset_index-1);
668 HeapWord* q = _array->address_for_index(index);
669
670 uint offset = _array->offset_array(index); // Extend u_char to uint.
671 while (offset > BOTConstants::N_words) {
672 // The excess of the offset from N_words indicates a power of Base
673 // to go back by.
674 size_t n_cards_back = BOTConstants::entry_to_cards_back(offset);
675 q -= (BOTConstants::N_words * n_cards_back);
676 assert(q >= _sp->bottom(), "Went below bottom!");
677 index -= n_cards_back;
678 offset = _array->offset_array(index);
679 }
680 while (offset == BOTConstants::N_words) {
681 assert(q >= _sp->bottom(), "Went below bottom!");
682 q -= BOTConstants::N_words;
683 index--;
684 offset = _array->offset_array(index);
685 }
686 assert(offset < BOTConstants::N_words, "offset too large");
687 q -= offset;
688 HeapWord* n = q;
689
690 while (n <= addr) {
691 debug_only(HeapWord* last = q); // for debugging
692 q = n;
693 n += _sp->block_size(n);
694 }
695 assert(q <= addr, "wrong order for current and arg");
696 assert(addr <= n, "wrong order for arg and next");
697 return q;
698 }
699
700 //
701 // _next_offset_threshold
702 // | _next_offset_index
703 // v v
704 // +-------+-------+-------+-------+-------+
705 // | i-1 | i | i+1 | i+2 | i+3 |
706 // +-------+-------+-------+-------+-------+
707 // ( ^ ]
708 // block-start
709 //
710
711 void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start,
712 HeapWord* blk_end) {
713 assert(blk_start != NULL && blk_end > blk_start,
714 "phantom block");
715 assert(blk_end > _next_offset_threshold,
716 "should be past threshold");
717 assert(blk_start <= _next_offset_threshold,
718 "blk_start should be at or before threshold");
719 assert(pointer_delta(_next_offset_threshold, blk_start) <= BOTConstants::N_words,
720 "offset should be <= BlockOffsetSharedArray::N");
721 assert(Universe::heap()->is_in_reserved(blk_start),
722 "reference must be into the heap");
723 assert(Universe::heap()->is_in_reserved(blk_end-1),
724 "limit must be within the heap");
725 assert(_next_offset_threshold ==
726 _array->_reserved.start() + _next_offset_index*BOTConstants::N_words,
727 "index must agree with threshold");
728
729 debug_only(size_t orig_next_offset_index = _next_offset_index;)
730
731 // Mark the card that holds the offset into the block. Note
732 // that _next_offset_index and _next_offset_threshold are not
733 // updated until the end of this method.
734 _array->set_offset_array(_next_offset_index,
735 _next_offset_threshold,
736 blk_start);
737
738 // We need to now mark the subsequent cards that this blk spans.
739
740 // Index of card on which blk ends.
741 size_t end_index = _array->index_for(blk_end - 1);
742
743 // Are there more cards left to be updated?
744 if (_next_offset_index + 1 <= end_index) {
745 HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1);
746 // Calculate rem_end this way because end_index
747 // may be the last valid index in the covered region.
748 HeapWord* rem_end = _array->address_for_index(end_index) + BOTConstants::N_words;
749 set_remainder_to_point_to_start(rem_st, rem_end);
750 }
751
752 // _next_offset_index and _next_offset_threshold updated here.
753 _next_offset_index = end_index + 1;
754 // Calculate _next_offset_threshold this way because end_index
755 // may be the last valid index in the covered region.
756 _next_offset_threshold = _array->address_for_index(end_index) + BOTConstants::N_words;
757 assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold");
758
759 #ifdef ASSERT
760 // The offset can be 0 if the block starts on a boundary. That
761 // is checked by an assertion above.
762 size_t start_index = _array->index_for(blk_start);
763 HeapWord* boundary = _array->address_for_index(start_index);
764 assert((_array->offset_array(orig_next_offset_index) == 0 &&
765 blk_start == boundary) ||
766 (_array->offset_array(orig_next_offset_index) > 0 &&
767 _array->offset_array(orig_next_offset_index) <= BOTConstants::N_words),
768 "offset array should have been set");
769 for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) {
770 assert(_array->offset_array(j) > 0 &&
771 _array->offset_array(j) <= (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1),
772 "offset array should have been set");
773 }
774 #endif
775 }
776
777 HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() {
778 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
779 "just checking");
780 _next_offset_index = _array->index_for(_bottom);
781 _next_offset_index++;
782 _next_offset_threshold =
783 _array->address_for_index(_next_offset_index);
784 return _next_offset_threshold;
785 }
786
787 void BlockOffsetArrayContigSpace::zero_bottom_entry() {
788 assert(!Universe::heap()->is_in_reserved(_array->_offset_array),
789 "just checking");
790 size_t bottom_index = _array->index_for(_bottom);
791 _array->set_offset_array(bottom_index, 0);
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