/* * Copyright (c) 2001, 2017, 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/g1/g1BlockOffsetTable.inline.hpp" #include "gc/g1/g1CollectedHeap.inline.hpp" #include "gc/g1/heapRegion.hpp" #include "gc/shared/space.hpp" #include "logging/log.hpp" #include "oops/oop.inline.hpp" #include "runtime/java.hpp" #include "services/memTracker.hpp" ////////////////////////////////////////////////////////////////////// // G1BlockOffsetTable ////////////////////////////////////////////////////////////////////// G1BlockOffsetTable::G1BlockOffsetTable(MemRegion heap, G1RegionToSpaceMapper* storage) : _reserved(heap), _offset_array(NULL) { MemRegion bot_reserved = storage->reserved(); _offset_array = (u_char*)bot_reserved.start(); log_trace(gc, bot)("G1BlockOffsetTable::G1BlockOffsetTable: "); log_trace(gc, bot)(" rs.base(): " PTR_FORMAT " rs.size(): " SIZE_FORMAT " rs end(): " PTR_FORMAT, p2i(bot_reserved.start()), bot_reserved.byte_size(), p2i(bot_reserved.end())); } bool G1BlockOffsetTable::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((int)BOTConstants::LogN_words)) == (size_t)NoBits; } #ifdef ASSERT void G1BlockOffsetTable::check_index(size_t index, const char* msg) const { assert((index) < (_reserved.word_size() >> BOTConstants::LogN_words), "%s - index: " SIZE_FORMAT ", _vs.committed_size: " SIZE_FORMAT, msg, (index), (_reserved.word_size() >> BOTConstants::LogN_words)); assert(G1CollectedHeap::heap()->is_in_exact(address_for_index_raw(index)), "Index " SIZE_FORMAT " corresponding to " PTR_FORMAT " (%u) is not in committed area.", (index), p2i(address_for_index_raw(index)), G1CollectedHeap::heap()->addr_to_region(address_for_index_raw(index))); } #endif // ASSERT ////////////////////////////////////////////////////////////////////// // G1BlockOffsetTablePart ////////////////////////////////////////////////////////////////////// G1BlockOffsetTablePart::G1BlockOffsetTablePart(G1BlockOffsetTable* array, G1ContiguousSpace* gsp) : _bot(array), _space(gsp), _next_offset_threshold(NULL), _next_offset_index(0) { debug_only(_object_can_span = false;) } // The arguments follow the normal convention of denoting // a right-open interval: [start, end) void G1BlockOffsetTablePart:: 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 = _bot->index_for(start); size_t end_card = _bot->index_for(end-1); assert(start ==_bot->address_for_index(start_card), "Precondition"); assert(end ==_bot->address_for_index(end_card)+BOTConstants::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 G1BlockOffsetTablePart::set_remainder_to_point_to_start_incl(size_t start_card, size_t end_card) { if (start_card > end_card) { return; } assert(start_card > _bot->index_for(_space->bottom()), "Cannot be first card"); assert(_bot->offset_array(start_card-1) <= BOTConstants::N_words, "Offset card has an unexpected value"); size_t start_card_for_region = start_card; u_char offset = max_jubyte; for (uint i = 0; i < BOTConstants::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 + (BOTConstants::power_to_cards_back(i+1) - 1); offset = BOTConstants::N_words + i; if (reach >= end_card) { _bot->set_offset_array(start_card_for_region, end_card, offset); start_card_for_region = reach + 1; break; } _bot->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 G1BlockOffsetTablePart::check_all_cards(size_t start_card, size_t end_card) const { if (end_card < start_card) { return; } guarantee(_bot->offset_array(start_card) == BOTConstants::N_words, "Wrong value in second card"); for (size_t c = start_card + 1; c <= end_card; c++ /* yeah! */) { u_char entry = _bot->offset_array(c); if (c - start_card > BOTConstants::power_to_cards_back(1)) { guarantee(entry > BOTConstants::N_words, "Should be in logarithmic region - " "entry: %u, " "_array->offset_array(c): %u, " "N_words: %u", (uint)entry, (uint)_bot->offset_array(c), BOTConstants::N_words); } size_t backskip = BOTConstants::entry_to_cards_back(entry); size_t landing_card = c - backskip; guarantee(landing_card >= (start_card - 1), "Inv"); if (landing_card >= start_card) { guarantee(_bot->offset_array(landing_card) <= entry, "Monotonicity - landing_card offset: %u, " "entry: %u", (uint)_bot->offset_array(landing_card), (uint)entry); } else { guarantee(landing_card == start_card - 1, "Tautology"); // Note that N_words is the maximum offset value guarantee(_bot->offset_array(landing_card) <= BOTConstants::N_words, "landing card offset: %u, " "N_words: %u", (uint)_bot->offset_array(landing_card), (uint)BOTConstants::N_words); } } } HeapWord* G1BlockOffsetTablePart::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 n_index = _bot->index_for(n); size_t next_index = _bot->index_for(n) + !_bot->is_card_boundary(n); // Calculate a consistent next boundary. If "n" is not at the boundary // already, step to the boundary. HeapWord* next_boundary = _bot->address_for_index(n_index) + (n_index == next_index ? 0 : BOTConstants::N_words); assert(next_boundary <= _bot->_reserved.end(), "next_boundary is beyond the end of the covered region " " next_boundary " PTR_FORMAT " _array->_end " PTR_FORMAT, p2i(next_boundary), p2i(_bot->_reserved.end())); if (addr >= _space->top()) return _space->top(); while (next_boundary < addr) { while (n <= next_boundary) { q = n; oop obj = oop(q); if (obj->klass_or_null_acquire() == NULL) return q; n += block_size(q); } assert(q <= next_boundary && n > next_boundary, "Consequence of loop"); // [q, n) is the block that crosses the boundary. alloc_block_work(&next_boundary, &next_index, q, n); } return forward_to_block_containing_addr_const(q, n, addr); } // // threshold_ // | _index_ // v v // +-------+-------+-------+-------+-------+ // | i-1 | i | i+1 | i+2 | i+3 | // +-------+-------+-------+-------+-------+ // ( ^ ] // block-start // void G1BlockOffsetTablePart::alloc_block_work(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) <= BOTConstants::N_words, "offset should be <= BlockOffsetSharedArray::N"); assert(G1CollectedHeap::heap()->is_in_reserved(blk_start), "reference must be into the heap"); assert(G1CollectedHeap::heap()->is_in_reserved(blk_end-1), "limit must be within the heap"); assert(threshold == _bot->_reserved.start() + index*BOTConstants::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. _bot->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 = _bot->index_for(blk_end - 1); // Are there more cards left to be updated? if (index + 1 <= end_index) { HeapWord* rem_st = _bot->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 = _bot->address_for_index(end_index) + BOTConstants::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 = _bot->address_for_index(end_index) + BOTConstants::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 = _bot->index_for(blk_start); HeapWord* boundary = _bot->address_for_index(start_index); assert((_bot->offset_array(orig_index) == 0 && blk_start == boundary) || (_bot->offset_array(orig_index) > 0 && _bot->offset_array(orig_index) <= BOTConstants::N_words), "offset array should have been set - " "orig_index offset: %u, " "blk_start: " PTR_FORMAT ", " "boundary: " PTR_FORMAT, (uint)_bot->offset_array(orig_index), p2i(blk_start), p2i(boundary)); for (size_t j = orig_index + 1; j <= end_index; j++) { assert(_bot->offset_array(j) > 0 && _bot->offset_array(j) <= (u_char) (BOTConstants::N_words+BOTConstants::N_powers-1), "offset array should have been set - " "%u not > 0 OR %u not <= %u", (uint) _bot->offset_array(j), (uint) _bot->offset_array(j), (uint) (BOTConstants::N_words+BOTConstants::N_powers-1)); } #endif } void G1BlockOffsetTablePart::verify() const { assert(_space->bottom() < _space->top(), "Only non-empty regions should be verified."); size_t start_card = _bot->index_for(_space->bottom()); size_t end_card = _bot->index_for(_space->top() - 1); for (size_t current_card = start_card; current_card < end_card; current_card++) { u_char entry = _bot->offset_array(current_card); if (entry < BOTConstants::N_words) { // The entry should point to an object before the current card. Verify that // it is possible to walk from that object in to the current card by just // iterating over the objects following it. HeapWord* card_address = _bot->address_for_index(current_card); HeapWord* obj_end = card_address - entry; while (obj_end < card_address) { HeapWord* obj = obj_end; size_t obj_size = block_size(obj); obj_end = obj + obj_size; guarantee(obj_end > obj && obj_end <= _space->top(), "Invalid object end. obj: " PTR_FORMAT " obj_size: " SIZE_FORMAT " obj_end: " PTR_FORMAT " top: " PTR_FORMAT, p2i(obj), obj_size, p2i(obj_end), p2i(_space->top())); } } else { // Because we refine the BOT based on which cards are dirty there is not much we can verify here. // We need to make sure that we are going backwards and that we don't pass the start of the // corresponding heap region. But that is about all we can verify. size_t backskip = BOTConstants::entry_to_cards_back(entry); guarantee(backskip >= 1, "Must be going back at least one card."); size_t max_backskip = current_card - start_card; guarantee(backskip <= max_backskip, "Going backwards beyond the start_card. start_card: " SIZE_FORMAT " current_card: " SIZE_FORMAT " backskip: " SIZE_FORMAT, start_card, current_card, backskip); HeapWord* backskip_address = _bot->address_for_index(current_card - backskip); guarantee(backskip_address >= _space->bottom(), "Going backwards beyond bottom of the region: bottom: " PTR_FORMAT ", backskip_address: " PTR_FORMAT, p2i(_space->bottom()), p2i(backskip_address)); } } } #ifdef ASSERT void G1BlockOffsetTablePart::set_object_can_span(bool can_span) { _object_can_span = can_span; } #endif #ifndef PRODUCT void G1BlockOffsetTablePart::print_on(outputStream* out) { size_t from_index = _bot->index_for(_space->bottom()); size_t to_index = _bot->index_for(_space->end()); out->print_cr(">> BOT for area [" PTR_FORMAT "," PTR_FORMAT ") " "cards [" SIZE_FORMAT "," SIZE_FORMAT ")", p2i(_space->bottom()), p2i(_space->end()), from_index, to_index); for (size_t i = from_index; i < to_index; ++i) { out->print_cr(" entry " SIZE_FORMAT_W(8) " | " PTR_FORMAT " : %3u", i, p2i(_bot->address_for_index(i)), (uint) _bot->offset_array(i)); } out->print_cr(" next offset threshold: " PTR_FORMAT, p2i(_next_offset_threshold)); out->print_cr(" next offset index: " SIZE_FORMAT, _next_offset_index); } #endif // !PRODUCT HeapWord* G1BlockOffsetTablePart::initialize_threshold_raw() { assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), "just checking"); _next_offset_index = _bot->index_for_raw(_space->bottom()); _next_offset_index++; _next_offset_threshold = _bot->address_for_index_raw(_next_offset_index); return _next_offset_threshold; } void G1BlockOffsetTablePart::zero_bottom_entry_raw() { assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), "just checking"); size_t bottom_index = _bot->index_for_raw(_space->bottom()); assert(_bot->address_for_index_raw(bottom_index) == _space->bottom(), "Precondition of call"); _bot->set_offset_array_raw(bottom_index, 0); } HeapWord* G1BlockOffsetTablePart::initialize_threshold() { assert(!G1CollectedHeap::heap()->is_in_reserved(_bot->_offset_array), "just checking"); _next_offset_index = _bot->index_for(_space->bottom()); _next_offset_index++; _next_offset_threshold = _bot->address_for_index(_next_offset_index); return _next_offset_threshold; } void G1BlockOffsetTablePart::set_for_starts_humongous(HeapWord* obj_top, size_t fill_size) { // The first BOT entry should have offset 0. reset_bot(); alloc_block(_space->bottom(), obj_top); if (fill_size > 0) { alloc_block(obj_top, fill_size); } }