/* * Copyright 2001-2008 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/_g1BlockOffsetTable.cpp.incl" ////////////////////////////////////////////////////////////////////// // G1BlockOffsetSharedArray ////////////////////////////////////////////////////////////////////// G1BlockOffsetSharedArray::G1BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size) : _reserved(reserved), _end(NULL) { size_t size = compute_size(reserved.word_size()); ReservedSpace rs(ReservedSpace::allocation_align_size_up(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("G1BlockOffsetSharedArray::G1BlockOffsetSharedArray: "); 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 G1BlockOffsetSharedArray::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"); // Initialization of the contents is left to the // G1BlockOffsetArray that uses it. } 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 G1BlockOffsetSharedArray::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; } ////////////////////////////////////////////////////////////////////// // G1BlockOffsetArray ////////////////////////////////////////////////////////////////////// G1BlockOffsetArray::G1BlockOffsetArray(G1BlockOffsetSharedArray* array, MemRegion mr, bool init_to_zero) : G1BlockOffsetTable(mr.start(), mr.end()), _unallocated_block(_bottom), _array(array), _csp(NULL), _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 } } void G1BlockOffsetArray::set_space(Space* sp) { _sp = sp; _csp = sp->toContiguousSpace(); } // The arguments follow the normal convention of denoting // a right-open interval: [start, end) void G1BlockOffsetArray:: 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 G1BlockOffsetArray::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 < BlockOffsetArray::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 + (BlockOffsetArray::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 block [blk_start, blk_end) has been allocated; // adjust the block offset table to represent this information; // right-open interval: [blk_start, blk_end) void G1BlockOffsetArray::alloc_block(HeapWord* blk_start, HeapWord* blk_end) { mark_block(blk_start, blk_end); allocated(blk_start, blk_end); } // Adjust BOT to show that a previously whole block has been split // into two. void G1BlockOffsetArray::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. mark_block(blk + left_blk_size, blk + blk_size); } // 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 G1BlockOffsetArray::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 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 G1BlockOffsetArray::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 > BlockOffsetArray::power_to_cards_back(1)) { guarantee(entry > N_words, "Should be in logarithmic region"); } size_t backskip = BlockOffsetArray::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"); } } } // 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 G1BlockOffsetArray::single_block(HeapWord* blk_start, HeapWord* blk_end) { do_block_internal(blk_start, blk_end, Action_single); } // 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 G1BlockOffsetArray::mark_block(HeapWord* blk_start, HeapWord* blk_end) { do_block_internal(blk_start, blk_end, Action_mark); } void G1BlockOffsetArray::join_blocks(HeapWord* blk1, HeapWord* blk2) { HeapWord* blk1_start = Universe::heap()->block_start(blk1); HeapWord* blk2_start = Universe::heap()->block_start(blk2); assert(blk1 == blk1_start && blk2 == blk2_start, "Must be block starts."); assert(blk1 + _sp->block_size(blk1) == blk2, "Must be contiguous."); size_t blk1_start_index = _array->index_for(blk1); size_t blk2_start_index = _array->index_for(blk2); assert(blk1_start_index <= blk2_start_index, "sanity"); HeapWord* blk2_card_start = _array->address_for_index(blk2_start_index); if (blk2 == blk2_card_start) { // blk2 starts a card. Does blk1 start on the prevous card, or futher // back? assert(blk1_start_index < blk2_start_index, "must be lower card."); if (blk1_start_index + 1 == blk2_start_index) { // previous card; new value for blk2 card is size of blk1. _array->set_offset_array(blk2_start_index, (u_char) _sp->block_size(blk1)); } else { // Earlier card; go back a card. _array->set_offset_array(blk2_start_index, N_words); } } else { // blk2 does not start a card. Does it cross a card? If not, nothing // to do. size_t blk2_end_index = _array->index_for(blk2 + _sp->block_size(blk2) - 1); assert(blk2_end_index >= blk2_start_index, "sanity"); if (blk2_end_index > blk2_start_index) { // Yes, it crosses a card. The value for the next card must change. if (blk1_start_index + 1 == blk2_start_index) { // previous card; new value for second blk2 card is size of blk1. _array->set_offset_array(blk2_start_index + 1, (u_char) _sp->block_size(blk1)); } else { // Earlier card; go back a card. _array->set_offset_array(blk2_start_index + 1, N_words); } } } } HeapWord* G1BlockOffsetArray::block_start_unsafe(const void* addr) { 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. HeapWord* q = block_at_or_preceding(addr, false, 0); return forward_to_block_containing_addr(q, addr); } // This duplicates a little code from the above: unavoidable. HeapWord* G1BlockOffsetArray::block_start_unsafe_const(const void* addr) const { 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. HeapWord* q = block_at_or_preceding(addr, false, 0); HeapWord* n = q + _sp->block_size(q); return forward_to_block_containing_addr_const(q, n, addr); } HeapWord* G1BlockOffsetArray::forward_to_block_containing_addr_slow(HeapWord* q, HeapWord* n, const void* addr) { // We're not in the normal case. We need to handle an important subcase // here: LAB allocation. An allocation previously recorded in the // offset table was actually a lab allocation, and was divided into // several objects subsequently. Fix this situation as we answer the // query, by updating entries as we cross them. // If the fist object's end q is at the card boundary. Start refining // with the corresponding card (the value of the entry will be basically // set to 0). If the object crosses the boundary -- start from the next card. size_t next_index = _array->index_for(n) + !_array->is_card_boundary(n); HeapWord* next_boundary = _array->address_for_index(next_index); if (csp() != NULL) { if (addr >= csp()->top()) return csp()->top(); while (next_boundary < addr) { while (n <= next_boundary) { q = n; oop obj = oop(q); if (obj->klass() == NULL) return q; n += obj->size(); } assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); // [q, n) is the block that crosses the boundary. alloc_block_work2(&next_boundary, &next_index, q, n); } } else { while (next_boundary < addr) { while (n <= next_boundary) { q = n; oop obj = oop(q); if (obj->klass() == NULL) return q; n += _sp->block_size(q); } assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); // [q, n) is the block that crosses the boundary. alloc_block_work2(&next_boundary, &next_index, q, n); } } return forward_to_block_containing_addr_const(q, n, addr); } HeapWord* G1BlockOffsetArray::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--); q -= offset; } while (offset == N_words); assert(q <= addr, "block start should be to left of arg"); return q; } // Note that the committed size of the covered space may have changed, // so the table size might also wish to change. void G1BlockOffsetArray::resize(size_t new_word_size) { HeapWord* new_end = _bottom + new_word_size; if (_end < new_end && !init_to_zero()) { // verify that the old and new boundaries are also card boundaries assert(_array->is_card_boundary(_end), "_end not a card boundary"); assert(_array->is_card_boundary(new_end), "new _end would not be a card boundary"); // set all the newly added cards _array->set_offset_array(_end, new_end, N_words); } _end = new_end; // update _end } void G1BlockOffsetArray::set_region(MemRegion mr) { _bottom = mr.start(); _end = mr.end(); } // // threshold_ // | _index_ // v v // +-------+-------+-------+-------+-------+ // | i-1 | i | i+1 | i+2 | i+3 | // +-------+-------+-------+-------+-------+ // ( ^ ] // block-start // void G1BlockOffsetArray::alloc_block_work2(HeapWord** threshold_, size_t* index_, HeapWord* blk_start, HeapWord* blk_end) { // For efficiency, do copy-in/copy-out. HeapWord* threshold = *threshold_; size_t index = *index_; assert(blk_start != NULL && blk_end > blk_start, "phantom block"); assert(blk_end > threshold, "should be past threshold"); assert(blk_start <= threshold, "blk_start should be at or before threshold") assert(pointer_delta(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(threshold == _array->_reserved.start() + index*N_words, "index must agree with threshold"); DEBUG_ONLY(size_t orig_index = 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(index, 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 (index + 1 <= end_index) { HeapWord* rem_st = _array->address_for_index(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); } index = end_index + 1; // Calculate threshold_ this way because end_index // may be the last valid index in the covered region. threshold = _array->address_for_index(end_index) + N_words; assert(threshold >= blk_end, "Incorrect offset threshold"); // index_ and threshold_ updated here. *threshold_ = threshold; *index_ = index; #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_index) == 0 && blk_start == boundary) || (_array->offset_array(orig_index) > 0 && _array->offset_array(orig_index) <= N_words), "offset array should have been set"); for (size_t j = orig_index + 1; j <= end_index; j++) { assert(_array->offset_array(j) > 0 && _array->offset_array(j) <= (u_char) (N_words+BlockOffsetArray::N_powers-1), "offset array should have been set"); } #endif } ////////////////////////////////////////////////////////////////////// // G1BlockOffsetArrayContigSpace ////////////////////////////////////////////////////////////////////// HeapWord* G1BlockOffsetArrayContigSpace::block_start_unsafe(const void* addr) { assert(_bottom <= addr && addr < _end, "addr must be covered by this Array"); HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1); return forward_to_block_containing_addr(q, addr); } HeapWord* G1BlockOffsetArrayContigSpace:: block_start_unsafe_const(const void* addr) const { assert(_bottom <= addr && addr < _end, "addr must be covered by this Array"); HeapWord* q = block_at_or_preceding(addr, true, _next_offset_index-1); HeapWord* n = q + _sp->block_size(q); return forward_to_block_containing_addr_const(q, n, addr); } G1BlockOffsetArrayContigSpace:: G1BlockOffsetArrayContigSpace(G1BlockOffsetSharedArray* array, MemRegion mr) : G1BlockOffsetArray(array, mr, true) { _next_offset_threshold = NULL; _next_offset_index = 0; } HeapWord* G1BlockOffsetArrayContigSpace::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 G1BlockOffsetArrayContigSpace::zero_bottom_entry() { assert(!Universe::heap()->is_in_reserved(_array->_offset_array), "just checking"); size_t bottom_index = _array->index_for(_bottom); assert(_array->address_for_index(bottom_index) == _bottom, "Precondition of call"); _array->set_offset_array(bottom_index, 0); }