Mercurial > hg > truffle
view src/share/vm/memory/blockOffsetTable.cpp @ 11361:07625ef93345
Merge.
author | Doug Simon <doug.simon@oracle.com> |
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date | Mon, 19 Aug 2013 14:11:10 +0200 |
parents | 746b070f5022 |
children | de6a9e811145 |
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/* * Copyright (c) 2000, 2012, Oracle and/or its affiliates. All rights reserved. * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. * * This code is free software; you can redistribute it and/or modify it * under the terms of the GNU General Public License version 2 only, as * published by the Free Software Foundation. * * This code is distributed in the hope that it will be useful, but WITHOUT * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License * version 2 for more details (a copy is included in the LICENSE file that * accompanied this code). * * You should have received a copy of the GNU General Public License version * 2 along with this work; if not, write to the Free Software Foundation, * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. * * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA * or visit www.oracle.com if you need additional information or have any * questions. * */ #include "precompiled.hpp" #include "gc_interface/collectedHeap.inline.hpp" #include "memory/blockOffsetTable.inline.hpp" #include "memory/iterator.hpp" #include "memory/space.inline.hpp" #include "memory/universe.hpp" #include "oops/oop.inline.hpp" #include "runtime/java.hpp" #include "services/memTracker.hpp" ////////////////////////////////////////////////////////////////////// // BlockOffsetSharedArray ////////////////////////////////////////////////////////////////////// BlockOffsetSharedArray::BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size): _reserved(reserved), _end(NULL) { size_t size = compute_size(reserved.word_size()); ReservedSpace rs(size); if (!rs.is_reserved()) { vm_exit_during_initialization("Could not reserve enough space for heap offset array"); } MemTracker::record_virtual_memory_type((address)rs.base(), mtGC); if (!_vs.initialize(rs, 0)) { vm_exit_during_initialization("Could not reserve enough space for heap offset array"); } _offset_array = (u_char*)_vs.low_boundary(); resize(init_word_size); if (TraceBlockOffsetTable) { gclog_or_tty->print_cr("BlockOffsetSharedArray::BlockOffsetSharedArray: "); gclog_or_tty->print_cr(" " " rs.base(): " INTPTR_FORMAT " rs.size(): " INTPTR_FORMAT " rs end(): " INTPTR_FORMAT, rs.base(), rs.size(), rs.base() + rs.size()); gclog_or_tty->print_cr(" " " _vs.low_boundary(): " INTPTR_FORMAT " _vs.high_boundary(): " INTPTR_FORMAT, _vs.low_boundary(), _vs.high_boundary()); } } void BlockOffsetSharedArray::resize(size_t new_word_size) { assert(new_word_size <= _reserved.word_size(), "Resize larger than reserved"); size_t new_size = compute_size(new_word_size); size_t old_size = _vs.committed_size(); size_t delta; char* high = _vs.high(); _end = _reserved.start() + new_word_size; if (new_size > old_size) { delta = ReservedSpace::page_align_size_up(new_size - old_size); assert(delta > 0, "just checking"); if (!_vs.expand_by(delta)) { // Do better than this for Merlin vm_exit_out_of_memory(delta, OOM_MMAP_ERROR, "offset table expansion"); } assert(_vs.high() == high + delta, "invalid expansion"); } else { delta = ReservedSpace::page_align_size_down(old_size - new_size); if (delta == 0) return; _vs.shrink_by(delta); assert(_vs.high() == high - delta, "invalid expansion"); } } bool BlockOffsetSharedArray::is_card_boundary(HeapWord* p) const { assert(p >= _reserved.start(), "just checking"); size_t delta = pointer_delta(p, _reserved.start()); return (delta & right_n_bits(LogN_words)) == (size_t)NoBits; } ////////////////////////////////////////////////////////////////////// // BlockOffsetArray ////////////////////////////////////////////////////////////////////// BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, bool init_to_zero_) : BlockOffsetTable(mr.start(), mr.end()), _array(array) { assert(_bottom <= _end, "arguments out of order"); set_init_to_zero(init_to_zero_); if (!init_to_zero_) { // initialize cards to point back to mr.start() set_remainder_to_point_to_start(mr.start() + N_words, mr.end()); _array->set_offset_array(0, 0); // set first card to 0 } } // The arguments follow the normal convention of denoting // a right-open interval: [start, end) void BlockOffsetArray:: set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing) { check_reducing_assertion(reducing); if (start >= end) { // The start address is equal to the end address (or to // the right of the end address) so there are not cards // that need to be updated.. return; } // Write the backskip value for each region. // // offset // card 2nd 3rd // | +- 1st | | // v v v v // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- // |x|0|0|0|0|0|0|0|1|1|1|1|1|1| ... |1|1|1|1|2|2|2|2|2|2| ... // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+- // 11 19 75 // 12 // // offset card is the card that points to the start of an object // x - offset value of offset card // 1st - start of first logarithmic region // 0 corresponds to logarithmic value N_words + 0 and 2**(3 * 0) = 1 // 2nd - start of second logarithmic region // 1 corresponds to logarithmic value N_words + 1 and 2**(3 * 1) = 8 // 3rd - start of third logarithmic region // 2 corresponds to logarithmic value N_words + 2 and 2**(3 * 2) = 64 // // integer below the block offset entry is an example of // the index of the entry // // Given an address, // Find the index for the address // Find the block offset table entry // Convert the entry to a back slide // (e.g., with today's, offset = 0x81 => // back slip = 2**(3*(0x81 - N_words)) = 2**3) = 8 // Move back N (e.g., 8) entries and repeat with the // value of the new entry // size_t start_card = _array->index_for(start); size_t end_card = _array->index_for(end-1); assert(start ==_array->address_for_index(start_card), "Precondition"); assert(end ==_array->address_for_index(end_card)+N_words, "Precondition"); set_remainder_to_point_to_start_incl(start_card, end_card, reducing); // closed interval } // Unlike the normal convention in this code, the argument here denotes // a closed, inclusive interval: [start_card, end_card], cf set_remainder_to_point_to_start() // above. void BlockOffsetArray::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card, bool reducing) { check_reducing_assertion(reducing); if (start_card > end_card) { return; } assert(start_card > _array->index_for(_bottom), "Cannot be first card"); assert(_array->offset_array(start_card-1) <= N_words, "Offset card has an unexpected value"); size_t start_card_for_region = start_card; u_char offset = max_jubyte; for (int i = 0; i < N_powers; i++) { // -1 so that the the card with the actual offset is counted. Another -1 // so that the reach ends in this region and not at the start // of the next. size_t reach = start_card - 1 + (power_to_cards_back(i+1) - 1); offset = N_words + i; if (reach >= end_card) { _array->set_offset_array(start_card_for_region, end_card, offset, reducing); start_card_for_region = reach + 1; break; } _array->set_offset_array(start_card_for_region, reach, offset, reducing); start_card_for_region = reach + 1; } assert(start_card_for_region > end_card, "Sanity check"); DEBUG_ONLY(check_all_cards(start_card, end_card);) } // The card-interval [start_card, end_card] is a closed interval; this // is an expensive check -- use with care and only under protection of // suitable flag. void BlockOffsetArray::check_all_cards(size_t start_card, size_t end_card) const { if (end_card < start_card) { return; } guarantee(_array->offset_array(start_card) == N_words, "Wrong value in second card"); u_char last_entry = N_words; for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { u_char entry = _array->offset_array(c); guarantee(entry >= last_entry, "Monotonicity"); if (c - start_card > power_to_cards_back(1)) { guarantee(entry > N_words, "Should be in logarithmic region"); } size_t backskip = entry_to_cards_back(entry); size_t landing_card = c - backskip; guarantee(landing_card >= (start_card - 1), "Inv"); if (landing_card >= start_card) { guarantee(_array->offset_array(landing_card) <= entry, "Monotonicity"); } else { guarantee(landing_card == (start_card - 1), "Tautology"); // Note that N_words is the maximum offset value guarantee(_array->offset_array(landing_card) <= N_words, "Offset value"); } last_entry = entry; // remember for monotonicity test } } void BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) { assert(blk_start != NULL && blk_end > blk_start, "phantom block"); single_block(blk_start, blk_end); } // Action_mark - update the BOT for the block [blk_start, blk_end). // Current typical use is for splitting a block. // Action_single - udpate the BOT for an allocation. // Action_verify - BOT verification. void BlockOffsetArray::do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing) { assert(Universe::heap()->is_in_reserved(blk_start), "reference must be into the heap"); assert(Universe::heap()->is_in_reserved(blk_end-1), "limit must be within the heap"); // This is optimized to make the test fast, assuming we only rarely // cross boundaries. uintptr_t end_ui = (uintptr_t)(blk_end - 1); uintptr_t start_ui = (uintptr_t)blk_start; // Calculate the last card boundary preceding end of blk intptr_t boundary_before_end = (intptr_t)end_ui; clear_bits(boundary_before_end, right_n_bits(LogN)); if (start_ui <= (uintptr_t)boundary_before_end) { // blk starts at or crosses a boundary // Calculate index of card on which blk begins size_t start_index = _array->index_for(blk_start); // Index of card on which blk ends size_t end_index = _array->index_for(blk_end - 1); // Start address of card on which blk begins HeapWord* boundary = _array->address_for_index(start_index); assert(boundary <= blk_start, "blk should start at or after boundary"); if (blk_start != boundary) { // blk starts strictly after boundary // adjust card boundary and start_index forward to next card boundary += N_words; start_index++; } assert(start_index <= end_index, "monotonicity of index_for()"); assert(boundary <= (HeapWord*)boundary_before_end, "tautology"); switch (action) { case Action_mark: { if (init_to_zero()) { _array->set_offset_array(start_index, boundary, blk_start, reducing); break; } // Else fall through to the next case } case Action_single: { _array->set_offset_array(start_index, boundary, blk_start, reducing); // We have finished marking the "offset card". We need to now // mark the subsequent cards that this blk spans. if (start_index < end_index) { HeapWord* rem_st = _array->address_for_index(start_index) + N_words; HeapWord* rem_end = _array->address_for_index(end_index) + N_words; set_remainder_to_point_to_start(rem_st, rem_end, reducing); } break; } case Action_check: { _array->check_offset_array(start_index, boundary, blk_start); // We have finished checking the "offset card". We need to now // check the subsequent cards that this blk spans. check_all_cards(start_index + 1, end_index); break; } default: ShouldNotReachHere(); } } } // The range [blk_start, blk_end) represents a single contiguous block // of storage; modify the block offset table to represent this // information; Right-open interval: [blk_start, blk_end) // NOTE: this method does _not_ adjust _unallocated_block. void BlockOffsetArray::single_block(HeapWord* blk_start, HeapWord* blk_end) { do_block_internal(blk_start, blk_end, Action_single); } void BlockOffsetArray::verify() const { // For each entry in the block offset table, verify that // the entry correctly finds the start of an object at the // first address covered by the block or to the left of that // first address. size_t next_index = 1; size_t last_index = last_active_index(); // Use for debugging. Initialize to NULL to distinguish the // first iteration through the while loop. HeapWord* last_p = NULL; HeapWord* last_start = NULL; oop last_o = NULL; while (next_index <= last_index) { // Use an address past the start of the address for // the entry. HeapWord* p = _array->address_for_index(next_index) + 1; if (p >= _end) { // That's all of the allocated block table. return; } // block_start() asserts that start <= p. HeapWord* start = block_start(p); // First check if the start is an allocated block and only // then if it is a valid object. oop o = oop(start); assert(!Universe::is_fully_initialized() || _sp->is_free_block(start) || o->is_oop_or_null(), "Bad object was found"); next_index++; last_p = p; last_start = start; last_o = o; } } ////////////////////////////////////////////////////////////////////// // BlockOffsetArrayNonContigSpace ////////////////////////////////////////////////////////////////////// // The block [blk_start, blk_end) has been allocated; // adjust the block offset table to represent this information; // NOTE: Clients of BlockOffsetArrayNonContigSpace: consider using // the somewhat more lightweight split_block() or // (when init_to_zero()) mark_block() wherever possible. // right-open interval: [blk_start, blk_end) void BlockOffsetArrayNonContigSpace::alloc_block(HeapWord* blk_start, HeapWord* blk_end) { assert(blk_start != NULL && blk_end > blk_start, "phantom block"); single_block(blk_start, blk_end); allocated(blk_start, blk_end); } // Adjust BOT to show that a previously whole block has been split // into two. We verify the BOT for the first part (prefix) and // update the BOT for the second part (suffix). // blk is the start of the block // blk_size is the size of the original block // left_blk_size is the size of the first part of the split void BlockOffsetArrayNonContigSpace::split_block(HeapWord* blk, size_t blk_size, size_t left_blk_size) { // Verify that the BOT shows [blk, blk + blk_size) to be one block. verify_single_block(blk, blk_size); // Update the BOT to indicate that [blk + left_blk_size, blk + blk_size) // is one single block. assert(blk_size > 0, "Should be positive"); assert(left_blk_size > 0, "Should be positive"); assert(left_blk_size < blk_size, "Not a split"); // Start addresses of prefix block and suffix block. HeapWord* pref_addr = blk; HeapWord* suff_addr = blk + left_blk_size; HeapWord* end_addr = blk + blk_size; // Indices for starts of prefix block and suffix block. size_t pref_index = _array->index_for(pref_addr); if (_array->address_for_index(pref_index) != pref_addr) { // pref_addr does not begin pref_index pref_index++; } size_t suff_index = _array->index_for(suff_addr); if (_array->address_for_index(suff_index) != suff_addr) { // suff_addr does not begin suff_index suff_index++; } // Definition: A block B, denoted [B_start, B_end) __starts__ // a card C, denoted [C_start, C_end), where C_start and C_end // are the heap addresses that card C covers, iff // B_start <= C_start < B_end. // // We say that a card C "is started by" a block B, iff // B "starts" C. // // Note that the cardinality of the set of cards {C} // started by a block B can be 0, 1, or more. // // Below, pref_index and suff_index are, respectively, the // first (least) card indices that the prefix and suffix of // the split start; end_index is one more than the index of // the last (greatest) card that blk starts. size_t end_index = _array->index_for(end_addr - 1) + 1; // Calculate the # cards that the prefix and suffix affect. size_t num_pref_cards = suff_index - pref_index; size_t num_suff_cards = end_index - suff_index; // Change the cards that need changing if (num_suff_cards > 0) { HeapWord* boundary = _array->address_for_index(suff_index); // Set the offset card for suffix block _array->set_offset_array(suff_index, boundary, suff_addr, true /* reducing */); // Change any further cards that need changing in the suffix if (num_pref_cards > 0) { if (num_pref_cards >= num_suff_cards) { // Unilaterally fix all of the suffix cards: closed card // index interval in args below. set_remainder_to_point_to_start_incl(suff_index + 1, end_index - 1, true /* reducing */); } else { // Unilaterally fix the first (num_pref_cards - 1) following // the "offset card" in the suffix block. set_remainder_to_point_to_start_incl(suff_index + 1, suff_index + num_pref_cards - 1, true /* reducing */); // Fix the appropriate cards in the remainder of the // suffix block -- these are the last num_pref_cards // cards in each power block of the "new" range plumbed // from suff_addr. bool more = true; uint i = 1; while (more && (i < N_powers)) { size_t back_by = power_to_cards_back(i); size_t right_index = suff_index + back_by - 1; size_t left_index = right_index - num_pref_cards + 1; if (right_index >= end_index - 1) { // last iteration right_index = end_index - 1; more = false; } if (back_by > num_pref_cards) { // Fill in the remainder of this "power block", if it // is non-null. if (left_index <= right_index) { _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */); } else { more = false; // we are done } i++; break; } i++; } while (more && (i < N_powers)) { size_t back_by = power_to_cards_back(i); size_t right_index = suff_index + back_by - 1; size_t left_index = right_index - num_pref_cards + 1; if (right_index >= end_index - 1) { // last iteration right_index = end_index - 1; if (left_index > right_index) { break; } more = false; } assert(left_index <= right_index, "Error"); _array->set_offset_array(left_index, right_index, N_words + i - 1, true /* reducing */); i++; } } } // else no more cards to fix in suffix } // else nothing needs to be done // Verify that we did the right thing verify_single_block(pref_addr, left_blk_size); verify_single_block(suff_addr, blk_size - left_blk_size); } // Mark the BOT such that if [blk_start, blk_end) straddles a card // boundary, the card following the first such boundary is marked // with the appropriate offset. // NOTE: this method does _not_ adjust _unallocated_block or // any cards subsequent to the first one. void BlockOffsetArrayNonContigSpace::mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing) { do_block_internal(blk_start, blk_end, Action_mark, reducing); } HeapWord* BlockOffsetArrayNonContigSpace::block_start_unsafe( const void* addr) const { assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); assert(_bottom <= addr && addr < _end, "addr must be covered by this Array"); // Must read this exactly once because it can be modified by parallel // allocation. HeapWord* ub = _unallocated_block; if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { assert(ub < _end, "tautology (see above)"); return ub; } // Otherwise, find the block start using the table. size_t index = _array->index_for(addr); HeapWord* q = _array->address_for_index(index); uint offset = _array->offset_array(index); // Extend u_char to uint. while (offset >= N_words) { // The excess of the offset from N_words indicates a power of Base // to go back by. size_t n_cards_back = entry_to_cards_back(offset); q -= (N_words * n_cards_back); assert(q >= _sp->bottom(), err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT, q, _sp->bottom())); assert(q < _sp->end(), err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT, q, _sp->end())); index -= n_cards_back; offset = _array->offset_array(index); } assert(offset < N_words, "offset too large"); index--; q -= offset; assert(q >= _sp->bottom(), err_msg("q = " PTR_FORMAT " crossed below bottom = " PTR_FORMAT, q, _sp->bottom())); assert(q < _sp->end(), err_msg("q = " PTR_FORMAT " crossed above end = " PTR_FORMAT, q, _sp->end())); HeapWord* n = q; while (n <= addr) { debug_only(HeapWord* last = q); // for debugging q = n; n += _sp->block_size(n); assert(n > q, err_msg("Looping at n = " PTR_FORMAT " with last = " PTR_FORMAT"," " while querying blk_start(" PTR_FORMAT ")" " on _sp = [" PTR_FORMAT "," PTR_FORMAT ")", n, last, addr, _sp->bottom(), _sp->end())); } assert(q <= addr, err_msg("wrong order for current (" INTPTR_FORMAT ")" " <= arg (" INTPTR_FORMAT ")", q, addr)); assert(addr <= n, err_msg("wrong order for arg (" INTPTR_FORMAT ") <= next (" INTPTR_FORMAT ")", addr, n)); return q; } HeapWord* BlockOffsetArrayNonContigSpace::block_start_careful( const void* addr) const { assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); assert(_bottom <= addr && addr < _end, "addr must be covered by this Array"); // Must read this exactly once because it can be modified by parallel // allocation. HeapWord* ub = _unallocated_block; if (BlockOffsetArrayUseUnallocatedBlock && addr >= ub) { assert(ub < _end, "tautology (see above)"); return ub; } // Otherwise, find the block start using the table, but taking // care (cf block_start_unsafe() above) not to parse any objects/blocks // on the cards themsleves. size_t index = _array->index_for(addr); assert(_array->address_for_index(index) == addr, "arg should be start of card"); HeapWord* q = (HeapWord*)addr; uint offset; do { offset = _array->offset_array(index); if (offset < N_words) { q -= offset; } else { size_t n_cards_back = entry_to_cards_back(offset); q -= (n_cards_back * N_words); index -= n_cards_back; } } while (offset >= N_words); assert(q <= addr, "block start should be to left of arg"); return q; } #ifndef PRODUCT // Verification & debugging - ensure that the offset table reflects the fact // that the block [blk_start, blk_end) or [blk, blk + size) is a // single block of storage. NOTE: can't const this because of // call to non-const do_block_internal() below. void BlockOffsetArrayNonContigSpace::verify_single_block( HeapWord* blk_start, HeapWord* blk_end) { if (VerifyBlockOffsetArray) { do_block_internal(blk_start, blk_end, Action_check); } } void BlockOffsetArrayNonContigSpace::verify_single_block( HeapWord* blk, size_t size) { verify_single_block(blk, blk + size); } // Verify that the given block is before _unallocated_block void BlockOffsetArrayNonContigSpace::verify_not_unallocated( HeapWord* blk_start, HeapWord* blk_end) const { if (BlockOffsetArrayUseUnallocatedBlock) { assert(blk_start < blk_end, "Block inconsistency?"); assert(blk_end <= _unallocated_block, "_unallocated_block problem"); } } void BlockOffsetArrayNonContigSpace::verify_not_unallocated( HeapWord* blk, size_t size) const { verify_not_unallocated(blk, blk + size); } #endif // PRODUCT size_t BlockOffsetArrayNonContigSpace::last_active_index() const { if (_unallocated_block == _bottom) { return 0; } else { return _array->index_for(_unallocated_block - 1); } } ////////////////////////////////////////////////////////////////////// // BlockOffsetArrayContigSpace ////////////////////////////////////////////////////////////////////// HeapWord* BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) const { assert(_array->offset_array(0) == 0, "objects can't cross covered areas"); // Otherwise, find the block start using the table. assert(_bottom <= addr && addr < _end, "addr must be covered by this Array"); size_t index = _array->index_for(addr); // We must make sure that the offset table entry we use is valid. If // "addr" is past the end, start at the last known one and go forward. index = MIN2(index, _next_offset_index-1); HeapWord* q = _array->address_for_index(index); uint offset = _array->offset_array(index); // Extend u_char to uint. while (offset > N_words) { // The excess of the offset from N_words indicates a power of Base // to go back by. size_t n_cards_back = entry_to_cards_back(offset); q -= (N_words * n_cards_back); assert(q >= _sp->bottom(), "Went below bottom!"); index -= n_cards_back; offset = _array->offset_array(index); } while (offset == N_words) { assert(q >= _sp->bottom(), "Went below bottom!"); q -= N_words; index--; offset = _array->offset_array(index); } assert(offset < N_words, "offset too large"); q -= offset; HeapWord* n = q; while (n <= addr) { debug_only(HeapWord* last = q); // for debugging q = n; n += _sp->block_size(n); } assert(q <= addr, "wrong order for current and arg"); assert(addr <= n, "wrong order for arg and next"); return q; } // // _next_offset_threshold // | _next_offset_index // v v // +-------+-------+-------+-------+-------+ // | i-1 | i | i+1 | i+2 | i+3 | // +-------+-------+-------+-------+-------+ // ( ^ ] // block-start // void BlockOffsetArrayContigSpace::alloc_block_work(HeapWord* blk_start, HeapWord* blk_end) { assert(blk_start != NULL && blk_end > blk_start, "phantom block"); assert(blk_end > _next_offset_threshold, "should be past threshold"); assert(blk_start <= _next_offset_threshold, "blk_start should be at or before threshold"); assert(pointer_delta(_next_offset_threshold, blk_start) <= N_words, "offset should be <= BlockOffsetSharedArray::N"); assert(Universe::heap()->is_in_reserved(blk_start), "reference must be into the heap"); assert(Universe::heap()->is_in_reserved(blk_end-1), "limit must be within the heap"); assert(_next_offset_threshold == _array->_reserved.start() + _next_offset_index*N_words, "index must agree with threshold"); debug_only(size_t orig_next_offset_index = _next_offset_index;) // Mark the card that holds the offset into the block. Note // that _next_offset_index and _next_offset_threshold are not // updated until the end of this method. _array->set_offset_array(_next_offset_index, _next_offset_threshold, blk_start); // We need to now mark the subsequent cards that this blk spans. // Index of card on which blk ends. size_t end_index = _array->index_for(blk_end - 1); // Are there more cards left to be updated? if (_next_offset_index + 1 <= end_index) { HeapWord* rem_st = _array->address_for_index(_next_offset_index + 1); // Calculate rem_end this way because end_index // may be the last valid index in the covered region. HeapWord* rem_end = _array->address_for_index(end_index) + N_words; set_remainder_to_point_to_start(rem_st, rem_end); } // _next_offset_index and _next_offset_threshold updated here. _next_offset_index = end_index + 1; // Calculate _next_offset_threshold this way because end_index // may be the last valid index in the covered region. _next_offset_threshold = _array->address_for_index(end_index) + N_words; assert(_next_offset_threshold >= blk_end, "Incorrect offset threshold"); #ifdef ASSERT // The offset can be 0 if the block starts on a boundary. That // is checked by an assertion above. size_t start_index = _array->index_for(blk_start); HeapWord* boundary = _array->address_for_index(start_index); assert((_array->offset_array(orig_next_offset_index) == 0 && blk_start == boundary) || (_array->offset_array(orig_next_offset_index) > 0 && _array->offset_array(orig_next_offset_index) <= N_words), "offset array should have been set"); for (size_t j = orig_next_offset_index + 1; j <= end_index; j++) { assert(_array->offset_array(j) > 0 && _array->offset_array(j) <= (u_char) (N_words+N_powers-1), "offset array should have been set"); } #endif } HeapWord* BlockOffsetArrayContigSpace::initialize_threshold() { assert(!Universe::heap()->is_in_reserved(_array->_offset_array), "just checking"); _next_offset_index = _array->index_for(_bottom); _next_offset_index++; _next_offset_threshold = _array->address_for_index(_next_offset_index); return _next_offset_threshold; } void BlockOffsetArrayContigSpace::zero_bottom_entry() { assert(!Universe::heap()->is_in_reserved(_array->_offset_array), "just checking"); size_t bottom_index = _array->index_for(_bottom); _array->set_offset_array(bottom_index, 0); } size_t BlockOffsetArrayContigSpace::last_active_index() const { size_t result = _next_offset_index - 1; return result >= 0 ? result : 0; }