Mercurial > hg > truffle
diff src/share/vm/memory/blockOffsetTable.cpp @ 0:a61af66fc99e jdk7-b24
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author | duke |
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date | Sat, 01 Dec 2007 00:00:00 +0000 |
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children | 37f87013dfd8 |
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--- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/src/share/vm/memory/blockOffsetTable.cpp Sat Dec 01 00:00:00 2007 +0000 @@ -0,0 +1,783 @@ +/* + * Copyright 2000-2006 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara, + * CA 95054 USA or visit www.sun.com if you need additional information or + * have any questions. + * + */ + +# include "incls/_precompiled.incl" +# include "incls/_blockOffsetTable.cpp.incl" + +////////////////////////////////////////////////////////////////////// +// 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"); + } + 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, "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; +} + + +void BlockOffsetSharedArray::serialize(SerializeOopClosure* soc, + HeapWord* start, HeapWord* end) { + assert(_offset_array[0] == 0, "objects can't cross covered areas"); + assert(start <= end, "bad address range"); + size_t start_index = index_for(start); + size_t end_index = index_for(end-1)+1; + soc->do_region(&_offset_array[start_index], + (end_index - start_index) * sizeof(_offset_array[0])); +} + +////////////////////////////////////////////////////////////////////// +// BlockOffsetArray +////////////////////////////////////////////////////////////////////// + +BlockOffsetArray::BlockOffsetArray(BlockOffsetSharedArray* array, + MemRegion mr, bool init_to_zero) : + BlockOffsetTable(mr.start(), mr.end()), + _array(array), + _init_to_zero(init_to_zero) +{ + assert(_bottom <= _end, "arguments out of order"); + 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) { + + 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); // 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) { + 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-1; 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); + start_card_for_region = reach + 1; + break; + } + _array->set_offset_array(start_card_for_region, reach, offset); + 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"); + for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { + u_char entry = _array->offset_array(c); + 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"); + guarantee(_array->offset_array(landing_card) <= N_words, "Offset value"); + } + } +} + + +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) { + 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); + break; + } // Else fall through to the next case + } + case Action_single: { + _array->set_offset_array(start_index, boundary, blk_start); + // 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); + } + 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 deos 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); + // 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); + } 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); + // 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); + } 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); + 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) { + do_block_internal(blk_start, blk_end, Action_mark); +} + +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(), "Went below bottom!"); + index -= n_cards_back; + offset = _array->offset_array(index); + } + assert(offset < N_words, "offset too large"); + index--; + 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; +} + +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, "Incorrent 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); +} + + +void BlockOffsetArrayContigSpace::serialize(SerializeOopClosure* soc) { + if (soc->reading()) { + // Null these values so that the serializer won't object to updating them. + _next_offset_threshold = NULL; + _next_offset_index = 0; + } + soc->do_ptr(&_next_offset_threshold); + soc->do_size_t(&_next_offset_index); +} + +size_t BlockOffsetArrayContigSpace::last_active_index() const { + size_t result = _next_offset_index - 1; + return result >= 0 ? result : 0; +}