--- old/src/share/vm/memory/blockOffsetTable.hpp 2015-05-12 11:56:29.070897396 +0200 +++ /dev/null 2015-03-18 17:10:38.111854831 +0100 @@ -1,560 +0,0 @@ -/* - * Copyright (c) 2000, 2015, 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. - * - */ - -#ifndef SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP -#define SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP - -#include "memory/memRegion.hpp" -#include "memory/virtualspace.hpp" -#include "utilities/globalDefinitions.hpp" - -// The CollectedHeap type requires subtypes to implement a method -// "block_start". For some subtypes, notably generational -// systems using card-table-based write barriers, the efficiency of this -// operation may be important. Implementations of the "BlockOffsetArray" -// class may be useful in providing such efficient implementations. -// -// BlockOffsetTable (abstract) -// - BlockOffsetArray (abstract) -// - BlockOffsetArrayNonContigSpace -// - BlockOffsetArrayContigSpace -// - -class ContiguousSpace; - -////////////////////////////////////////////////////////////////////////// -// The BlockOffsetTable "interface" -////////////////////////////////////////////////////////////////////////// -class BlockOffsetTable VALUE_OBJ_CLASS_SPEC { - friend class VMStructs; -protected: - // These members describe the region covered by the table. - - // The space this table is covering. - HeapWord* _bottom; // == reserved.start - HeapWord* _end; // End of currently allocated region. - -public: - // Initialize the table to cover the given space. - // The contents of the initial table are undefined. - BlockOffsetTable(HeapWord* bottom, HeapWord* end): - _bottom(bottom), _end(end) { - assert(_bottom <= _end, "arguments out of order"); - } - - // Note that the committed size of the covered space may have changed, - // so the table size might also wish to change. - virtual void resize(size_t new_word_size) = 0; - - virtual void set_bottom(HeapWord* new_bottom) { - assert(new_bottom <= _end, "new_bottom > _end"); - _bottom = new_bottom; - resize(pointer_delta(_end, _bottom)); - } - - // Requires "addr" to be contained by a block, and returns the address of - // the start of that block. - virtual HeapWord* block_start_unsafe(const void* addr) const = 0; - - // Returns the address of the start of the block containing "addr", or - // else "null" if it is covered by no block. - HeapWord* block_start(const void* addr) const; -}; - -////////////////////////////////////////////////////////////////////////// -// One implementation of "BlockOffsetTable," the BlockOffsetArray, -// divides the covered region into "N"-word subregions (where -// "N" = 2^"LogN". An array with an entry for each such subregion -// indicates how far back one must go to find the start of the -// chunk that includes the first word of the subregion. -// -// Each BlockOffsetArray is owned by a Space. However, the actual array -// may be shared by several BlockOffsetArrays; this is useful -// when a single resizable area (such as a generation) is divided up into -// several spaces in which contiguous allocation takes place. (Consider, -// for example, the garbage-first generation.) - -// Here is the shared array type. -////////////////////////////////////////////////////////////////////////// -// BlockOffsetSharedArray -////////////////////////////////////////////////////////////////////////// -class BlockOffsetSharedArray: public CHeapObj { - friend class BlockOffsetArray; - friend class BlockOffsetArrayNonContigSpace; - friend class BlockOffsetArrayContigSpace; - friend class VMStructs; - - private: - enum SomePrivateConstants { - LogN = 9, - LogN_words = LogN - LogHeapWordSize, - N_bytes = 1 << LogN, - N_words = 1 << LogN_words - }; - - bool _init_to_zero; - - // The reserved region covered by the shared array. - MemRegion _reserved; - - // End of the current committed region. - HeapWord* _end; - - // Array for keeping offsets for retrieving object start fast given an - // address. - VirtualSpace _vs; - u_char* _offset_array; // byte array keeping backwards offsets - - protected: - // Bounds checking accessors: - // For performance these have to devolve to array accesses in product builds. - u_char offset_array(size_t index) const { - assert(index < _vs.committed_size(), "index out of range"); - return _offset_array[index]; - } - // An assertion-checking helper method for the set_offset_array() methods below. - void check_reducing_assertion(bool reducing); - - void set_offset_array(size_t index, u_char offset, bool reducing = false) { - check_reducing_assertion(reducing); - assert(index < _vs.committed_size(), "index out of range"); - assert(!reducing || _offset_array[index] >= offset, "Not reducing"); - _offset_array[index] = offset; - } - - void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) { - check_reducing_assertion(reducing); - assert(index < _vs.committed_size(), "index out of range"); - assert(high >= low, "addresses out of order"); - assert(pointer_delta(high, low) <= N_words, "offset too large"); - assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low), - "Not reducing"); - _offset_array[index] = (u_char)pointer_delta(high, low); - } - - void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) { - check_reducing_assertion(reducing); - assert(index_for(right - 1) < _vs.committed_size(), - "right address out of range"); - assert(left < right, "Heap addresses out of order"); - size_t num_cards = pointer_delta(right, left) >> LogN_words; - - // Below, we may use an explicit loop instead of memset() - // because on certain platforms memset() can give concurrent - // readers "out-of-thin-air," phantom zeros; see 6948537. - if (UseMemSetInBOT) { - memset(&_offset_array[index_for(left)], offset, num_cards); - } else { - size_t i = index_for(left); - const size_t end = i + num_cards; - for (; i < end; i++) { - // Elided until CR 6977974 is fixed properly. - // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); - _offset_array[i] = offset; - } - } - } - - void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) { - check_reducing_assertion(reducing); - assert(right < _vs.committed_size(), "right address out of range"); - assert(left <= right, "indexes out of order"); - size_t num_cards = right - left + 1; - - // Below, we may use an explicit loop instead of memset - // because on certain platforms memset() can give concurrent - // readers "out-of-thin-air," phantom zeros; see 6948537. - if (UseMemSetInBOT) { - memset(&_offset_array[left], offset, num_cards); - } else { - size_t i = left; - const size_t end = i + num_cards; - for (; i < end; i++) { - // Elided until CR 6977974 is fixed properly. - // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); - _offset_array[i] = offset; - } - } - } - - void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { - assert(index < _vs.committed_size(), "index out of range"); - assert(high >= low, "addresses out of order"); - assert(pointer_delta(high, low) <= N_words, "offset too large"); - assert(_offset_array[index] == pointer_delta(high, low), - "Wrong offset"); - } - - bool is_card_boundary(HeapWord* p) const; - - // Return the number of slots needed for an offset array - // that covers mem_region_words words. - // We always add an extra slot because if an object - // ends on a card boundary we put a 0 in the next - // offset array slot, so we want that slot always - // to be reserved. - - size_t compute_size(size_t mem_region_words) { - size_t number_of_slots = (mem_region_words / N_words) + 1; - return ReservedSpace::allocation_align_size_up(number_of_slots); - } - -public: - // Initialize the table to cover from "base" to (at least) - // "base + init_word_size". In the future, the table may be expanded - // (see "resize" below) up to the size of "_reserved" (which must be at - // least "init_word_size".) The contents of the initial table are - // undefined; it is the responsibility of the constituent - // BlockOffsetTable(s) to initialize cards. - BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); - - // Notes a change in the committed size of the region covered by the - // table. The "new_word_size" may not be larger than the size of the - // reserved region this table covers. - void resize(size_t new_word_size); - - void set_bottom(HeapWord* new_bottom); - - // Whether entries should be initialized to zero. Used currently only for - // error checking. - void set_init_to_zero(bool val) { _init_to_zero = val; } - bool init_to_zero() { return _init_to_zero; } - - // Updates all the BlockOffsetArray's sharing this shared array to - // reflect the current "top"'s of their spaces. - void update_offset_arrays(); // Not yet implemented! - - // Return the appropriate index into "_offset_array" for "p". - size_t index_for(const void* p) const; - - // Return the address indicating the start of the region corresponding to - // "index" in "_offset_array". - HeapWord* address_for_index(size_t index) const; -}; - -////////////////////////////////////////////////////////////////////////// -// The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. -////////////////////////////////////////////////////////////////////////// -class BlockOffsetArray: public BlockOffsetTable { - friend class VMStructs; - friend class G1BlockOffsetArray; // temp. until we restructure and cleanup - protected: - // The following enums are used by do_block_internal() below - enum Action { - Action_single, // BOT records a single block (see single_block()) - Action_mark, // BOT marks the start of a block (see mark_block()) - Action_check // Check that BOT records block correctly - // (see verify_single_block()). - }; - - enum SomePrivateConstants { - N_words = BlockOffsetSharedArray::N_words, - LogN = BlockOffsetSharedArray::LogN, - // entries "e" of at least N_words mean "go back by Base^(e-N_words)." - // All entries are less than "N_words + N_powers". - LogBase = 4, - Base = (1 << LogBase), - N_powers = 14 - }; - - static size_t power_to_cards_back(uint i) { - return (size_t)1 << (LogBase * i); - } - static size_t power_to_words_back(uint i) { - return power_to_cards_back(i) * N_words; - } - static size_t entry_to_cards_back(u_char entry) { - assert(entry >= N_words, "Precondition"); - return power_to_cards_back(entry - N_words); - } - static size_t entry_to_words_back(u_char entry) { - assert(entry >= N_words, "Precondition"); - return power_to_words_back(entry - N_words); - } - - // The shared array, which is shared with other BlockOffsetArray's - // corresponding to different spaces within a generation or span of - // memory. - BlockOffsetSharedArray* _array; - - // The space that owns this subregion. - Space* _sp; - - // If true, array entries are initialized to 0; otherwise, they are - // initialized to point backwards to the beginning of the covered region. - bool _init_to_zero; - - // An assertion-checking helper method for the set_remainder*() methods below. - void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); } - - // Sets the entries - // corresponding to the cards starting at "start" and ending at "end" - // to point back to the card before "start": the interval [start, end) - // is right-open. The last parameter, reducing, indicates whether the - // updates to individual entries always reduce the entry from a higher - // to a lower value. (For example this would hold true during a temporal - // regime during which only block splits were updating the BOT. - void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false); - // Same as above, except that the args here are a card _index_ interval - // that is closed: [start_index, end_index] - void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false); - - // A helper function for BOT adjustment/verification work - void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false); - - public: - // The space may not have its bottom and top set yet, which is why the - // region is passed as a parameter. If "init_to_zero" is true, the - // elements of the array are initialized to zero. Otherwise, they are - // initialized to point backwards to the beginning. - BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, - bool init_to_zero_); - - // Note: this ought to be part of the constructor, but that would require - // "this" to be passed as a parameter to a member constructor for - // the containing concrete subtype of Space. - // This would be legal C++, but MS VC++ doesn't allow it. - void set_space(Space* sp) { _sp = sp; } - - // Resets the covered region to the given "mr". - void set_region(MemRegion mr) { - _bottom = mr.start(); - _end = mr.end(); - } - - // Note that the committed size of the covered space may have changed, - // so the table size might also wish to change. - virtual void 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 - } - - // Adjust the BOT to show that it has a single block in the - // range [blk_start, blk_start + size). All necessary BOT - // cards are adjusted, but _unallocated_block isn't. - void single_block(HeapWord* blk_start, HeapWord* blk_end); - void single_block(HeapWord* blk, size_t size) { - single_block(blk, blk + size); - } - - // When the alloc_block() call returns, the block offset table should - // have enough information such that any subsequent block_start() call - // with an argument equal to an address that is within the range - // [blk_start, blk_end) would return the value blk_start, provided - // there have been no calls in between that reset this information - // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call - // for an appropriate range covering the said interval). - // These methods expect to be called with [blk_start, blk_end) - // representing a block of memory in the heap. - virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); - void alloc_block(HeapWord* blk, size_t size) { - alloc_block(blk, blk + size); - } - - // If true, initialize array slots with no allocated blocks to zero. - // Otherwise, make them point back to the front. - bool init_to_zero() { return _init_to_zero; } - // Corresponding setter - void set_init_to_zero(bool val) { - _init_to_zero = val; - assert(_array != NULL, "_array should be non-NULL"); - _array->set_init_to_zero(val); - } - - // Debugging - // Return the index of the last entry in the "active" region. - virtual size_t last_active_index() const = 0; - // Verify the block offset table - void verify() const; - void check_all_cards(size_t left_card, size_t right_card) const; -}; - -//////////////////////////////////////////////////////////////////////////// -// A subtype of BlockOffsetArray that takes advantage of the fact -// that its underlying space is a NonContiguousSpace, so that some -// specialized interfaces can be made available for spaces that -// manipulate the table. -//////////////////////////////////////////////////////////////////////////// -class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { - friend class VMStructs; - private: - // The portion [_unallocated_block, _sp.end()) of the space that - // is a single block known not to contain any objects. - // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. - HeapWord* _unallocated_block; - - public: - BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): - BlockOffsetArray(array, mr, false), - _unallocated_block(_bottom) { } - - // Accessor - HeapWord* unallocated_block() const { - assert(BlockOffsetArrayUseUnallocatedBlock, - "_unallocated_block is not being maintained"); - return _unallocated_block; - } - - void set_unallocated_block(HeapWord* block) { - assert(BlockOffsetArrayUseUnallocatedBlock, - "_unallocated_block is not being maintained"); - assert(block >= _bottom && block <= _end, "out of range"); - _unallocated_block = block; - } - - // These methods expect to be called with [blk_start, blk_end) - // representing a block of memory in the heap. - void alloc_block(HeapWord* blk_start, HeapWord* blk_end); - void alloc_block(HeapWord* blk, size_t size) { - alloc_block(blk, blk + size); - } - - // The following methods are useful and optimized for a - // non-contiguous space. - - // Given a block [blk_start, blk_start + full_blk_size), and - // a left_blk_size < full_blk_size, adjust the BOT to show two - // blocks [blk_start, blk_start + left_blk_size) and - // [blk_start + left_blk_size, blk_start + full_blk_size). - // It is assumed (and verified in the non-product VM) that the - // BOT was correct for the original block. - void split_block(HeapWord* blk_start, size_t full_blk_size, - size_t left_blk_size); - - // Adjust BOT to show that it has a block in the range - // [blk_start, blk_start + size). Only the first card - // of BOT is touched. It is assumed (and verified in the - // non-product VM) that the remaining cards of the block - // are correct. - void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false); - void mark_block(HeapWord* blk, size_t size, bool reducing = false) { - mark_block(blk, blk + size, reducing); - } - - // Adjust _unallocated_block to indicate that a particular - // block has been newly allocated or freed. It is assumed (and - // verified in the non-product VM) that the BOT is correct for - // the given block. - void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) { - // Verify that the BOT shows [blk, blk + blk_size) to be one block. - verify_single_block(blk_start, blk_end); - if (BlockOffsetArrayUseUnallocatedBlock) { - _unallocated_block = MAX2(_unallocated_block, blk_end); - } - } - - void allocated(HeapWord* blk, size_t size, bool reducing = false) { - allocated(blk, blk + size, reducing); - } - - void freed(HeapWord* blk_start, HeapWord* blk_end); - void freed(HeapWord* blk, size_t size); - - HeapWord* block_start_unsafe(const void* addr) const; - - // Requires "addr" to be the start of a card and returns the - // start of the block that contains the given address. - HeapWord* block_start_careful(const void* addr) const; - - // 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 verify_single_block(HeapWord* blk_start, HeapWord* blk_end) - PRODUCT_RETURN; - void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; - - // Verify that the given block is before _unallocated_block - void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) - const PRODUCT_RETURN; - void verify_not_unallocated(HeapWord* blk, size_t size) - const PRODUCT_RETURN; - - // Debugging support - virtual size_t last_active_index() const; -}; - -//////////////////////////////////////////////////////////////////////////// -// A subtype of BlockOffsetArray that takes advantage of the fact -// that its underlying space is a ContiguousSpace, so that its "active" -// region can be more efficiently tracked (than for a non-contiguous space). -//////////////////////////////////////////////////////////////////////////// -class BlockOffsetArrayContigSpace: public BlockOffsetArray { - friend class VMStructs; - private: - // allocation boundary at which offset array must be updated - HeapWord* _next_offset_threshold; - size_t _next_offset_index; // index corresponding to that boundary - - // Work function when allocation start crosses threshold. - void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); - - public: - BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): - BlockOffsetArray(array, mr, true) { - _next_offset_threshold = NULL; - _next_offset_index = 0; - } - - void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } - - // Initialize the threshold for an empty heap. - HeapWord* initialize_threshold(); - // Zero out the entry for _bottom (offset will be zero) - void zero_bottom_entry(); - - // Return the next threshold, the point at which the table should be - // updated. - HeapWord* threshold() const { return _next_offset_threshold; } - - // In general, these methods expect to be called with - // [blk_start, blk_end) representing a block of memory in the heap. - // In this implementation, however, we are OK even if blk_start and/or - // blk_end are NULL because NULL is represented as 0, and thus - // never exceeds the "_next_offset_threshold". - void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { - if (blk_end > _next_offset_threshold) { - alloc_block_work(blk_start, blk_end); - } - } - void alloc_block(HeapWord* blk, size_t size) { - alloc_block(blk, blk + size); - } - - HeapWord* block_start_unsafe(const void* addr) const; - - // Debugging support - virtual size_t last_active_index() const; -}; - -#endif // SHARE_VM_MEMORY_BLOCKOFFSETTABLE_HPP --- /dev/null 2015-03-18 17:10:38.111854831 +0100 +++ new/src/share/vm/gc/shared/blockOffsetTable.hpp 2015-05-12 11:56:28.843887830 +0200 @@ -0,0 +1,560 @@ +/* + * Copyright (c) 2000, 2015, 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. + * + */ + +#ifndef SHARE_VM_GC_SHARED_BLOCKOFFSETTABLE_HPP +#define SHARE_VM_GC_SHARED_BLOCKOFFSETTABLE_HPP + +#include "memory/memRegion.hpp" +#include "memory/virtualspace.hpp" +#include "utilities/globalDefinitions.hpp" + +// The CollectedHeap type requires subtypes to implement a method +// "block_start". For some subtypes, notably generational +// systems using card-table-based write barriers, the efficiency of this +// operation may be important. Implementations of the "BlockOffsetArray" +// class may be useful in providing such efficient implementations. +// +// BlockOffsetTable (abstract) +// - BlockOffsetArray (abstract) +// - BlockOffsetArrayNonContigSpace +// - BlockOffsetArrayContigSpace +// + +class ContiguousSpace; + +////////////////////////////////////////////////////////////////////////// +// The BlockOffsetTable "interface" +////////////////////////////////////////////////////////////////////////// +class BlockOffsetTable VALUE_OBJ_CLASS_SPEC { + friend class VMStructs; +protected: + // These members describe the region covered by the table. + + // The space this table is covering. + HeapWord* _bottom; // == reserved.start + HeapWord* _end; // End of currently allocated region. + +public: + // Initialize the table to cover the given space. + // The contents of the initial table are undefined. + BlockOffsetTable(HeapWord* bottom, HeapWord* end): + _bottom(bottom), _end(end) { + assert(_bottom <= _end, "arguments out of order"); + } + + // Note that the committed size of the covered space may have changed, + // so the table size might also wish to change. + virtual void resize(size_t new_word_size) = 0; + + virtual void set_bottom(HeapWord* new_bottom) { + assert(new_bottom <= _end, "new_bottom > _end"); + _bottom = new_bottom; + resize(pointer_delta(_end, _bottom)); + } + + // Requires "addr" to be contained by a block, and returns the address of + // the start of that block. + virtual HeapWord* block_start_unsafe(const void* addr) const = 0; + + // Returns the address of the start of the block containing "addr", or + // else "null" if it is covered by no block. + HeapWord* block_start(const void* addr) const; +}; + +////////////////////////////////////////////////////////////////////////// +// One implementation of "BlockOffsetTable," the BlockOffsetArray, +// divides the covered region into "N"-word subregions (where +// "N" = 2^"LogN". An array with an entry for each such subregion +// indicates how far back one must go to find the start of the +// chunk that includes the first word of the subregion. +// +// Each BlockOffsetArray is owned by a Space. However, the actual array +// may be shared by several BlockOffsetArrays; this is useful +// when a single resizable area (such as a generation) is divided up into +// several spaces in which contiguous allocation takes place. (Consider, +// for example, the garbage-first generation.) + +// Here is the shared array type. +////////////////////////////////////////////////////////////////////////// +// BlockOffsetSharedArray +////////////////////////////////////////////////////////////////////////// +class BlockOffsetSharedArray: public CHeapObj { + friend class BlockOffsetArray; + friend class BlockOffsetArrayNonContigSpace; + friend class BlockOffsetArrayContigSpace; + friend class VMStructs; + + private: + enum SomePrivateConstants { + LogN = 9, + LogN_words = LogN - LogHeapWordSize, + N_bytes = 1 << LogN, + N_words = 1 << LogN_words + }; + + bool _init_to_zero; + + // The reserved region covered by the shared array. + MemRegion _reserved; + + // End of the current committed region. + HeapWord* _end; + + // Array for keeping offsets for retrieving object start fast given an + // address. + VirtualSpace _vs; + u_char* _offset_array; // byte array keeping backwards offsets + + protected: + // Bounds checking accessors: + // For performance these have to devolve to array accesses in product builds. + u_char offset_array(size_t index) const { + assert(index < _vs.committed_size(), "index out of range"); + return _offset_array[index]; + } + // An assertion-checking helper method for the set_offset_array() methods below. + void check_reducing_assertion(bool reducing); + + void set_offset_array(size_t index, u_char offset, bool reducing = false) { + check_reducing_assertion(reducing); + assert(index < _vs.committed_size(), "index out of range"); + assert(!reducing || _offset_array[index] >= offset, "Not reducing"); + _offset_array[index] = offset; + } + + void set_offset_array(size_t index, HeapWord* high, HeapWord* low, bool reducing = false) { + check_reducing_assertion(reducing); + assert(index < _vs.committed_size(), "index out of range"); + assert(high >= low, "addresses out of order"); + assert(pointer_delta(high, low) <= N_words, "offset too large"); + assert(!reducing || _offset_array[index] >= (u_char)pointer_delta(high, low), + "Not reducing"); + _offset_array[index] = (u_char)pointer_delta(high, low); + } + + void set_offset_array(HeapWord* left, HeapWord* right, u_char offset, bool reducing = false) { + check_reducing_assertion(reducing); + assert(index_for(right - 1) < _vs.committed_size(), + "right address out of range"); + assert(left < right, "Heap addresses out of order"); + size_t num_cards = pointer_delta(right, left) >> LogN_words; + + // Below, we may use an explicit loop instead of memset() + // because on certain platforms memset() can give concurrent + // readers "out-of-thin-air," phantom zeros; see 6948537. + if (UseMemSetInBOT) { + memset(&_offset_array[index_for(left)], offset, num_cards); + } else { + size_t i = index_for(left); + const size_t end = i + num_cards; + for (; i < end; i++) { + // Elided until CR 6977974 is fixed properly. + // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); + _offset_array[i] = offset; + } + } + } + + void set_offset_array(size_t left, size_t right, u_char offset, bool reducing = false) { + check_reducing_assertion(reducing); + assert(right < _vs.committed_size(), "right address out of range"); + assert(left <= right, "indexes out of order"); + size_t num_cards = right - left + 1; + + // Below, we may use an explicit loop instead of memset + // because on certain platforms memset() can give concurrent + // readers "out-of-thin-air," phantom zeros; see 6948537. + if (UseMemSetInBOT) { + memset(&_offset_array[left], offset, num_cards); + } else { + size_t i = left; + const size_t end = i + num_cards; + for (; i < end; i++) { + // Elided until CR 6977974 is fixed properly. + // assert(!reducing || _offset_array[i] >= offset, "Not reducing"); + _offset_array[i] = offset; + } + } + } + + void check_offset_array(size_t index, HeapWord* high, HeapWord* low) const { + assert(index < _vs.committed_size(), "index out of range"); + assert(high >= low, "addresses out of order"); + assert(pointer_delta(high, low) <= N_words, "offset too large"); + assert(_offset_array[index] == pointer_delta(high, low), + "Wrong offset"); + } + + bool is_card_boundary(HeapWord* p) const; + + // Return the number of slots needed for an offset array + // that covers mem_region_words words. + // We always add an extra slot because if an object + // ends on a card boundary we put a 0 in the next + // offset array slot, so we want that slot always + // to be reserved. + + size_t compute_size(size_t mem_region_words) { + size_t number_of_slots = (mem_region_words / N_words) + 1; + return ReservedSpace::allocation_align_size_up(number_of_slots); + } + +public: + // Initialize the table to cover from "base" to (at least) + // "base + init_word_size". In the future, the table may be expanded + // (see "resize" below) up to the size of "_reserved" (which must be at + // least "init_word_size".) The contents of the initial table are + // undefined; it is the responsibility of the constituent + // BlockOffsetTable(s) to initialize cards. + BlockOffsetSharedArray(MemRegion reserved, size_t init_word_size); + + // Notes a change in the committed size of the region covered by the + // table. The "new_word_size" may not be larger than the size of the + // reserved region this table covers. + void resize(size_t new_word_size); + + void set_bottom(HeapWord* new_bottom); + + // Whether entries should be initialized to zero. Used currently only for + // error checking. + void set_init_to_zero(bool val) { _init_to_zero = val; } + bool init_to_zero() { return _init_to_zero; } + + // Updates all the BlockOffsetArray's sharing this shared array to + // reflect the current "top"'s of their spaces. + void update_offset_arrays(); // Not yet implemented! + + // Return the appropriate index into "_offset_array" for "p". + size_t index_for(const void* p) const; + + // Return the address indicating the start of the region corresponding to + // "index" in "_offset_array". + HeapWord* address_for_index(size_t index) const; +}; + +////////////////////////////////////////////////////////////////////////// +// The BlockOffsetArray whose subtypes use the BlockOffsetSharedArray. +////////////////////////////////////////////////////////////////////////// +class BlockOffsetArray: public BlockOffsetTable { + friend class VMStructs; + friend class G1BlockOffsetArray; // temp. until we restructure and cleanup + protected: + // The following enums are used by do_block_internal() below + enum Action { + Action_single, // BOT records a single block (see single_block()) + Action_mark, // BOT marks the start of a block (see mark_block()) + Action_check // Check that BOT records block correctly + // (see verify_single_block()). + }; + + enum SomePrivateConstants { + N_words = BlockOffsetSharedArray::N_words, + LogN = BlockOffsetSharedArray::LogN, + // entries "e" of at least N_words mean "go back by Base^(e-N_words)." + // All entries are less than "N_words + N_powers". + LogBase = 4, + Base = (1 << LogBase), + N_powers = 14 + }; + + static size_t power_to_cards_back(uint i) { + return (size_t)1 << (LogBase * i); + } + static size_t power_to_words_back(uint i) { + return power_to_cards_back(i) * N_words; + } + static size_t entry_to_cards_back(u_char entry) { + assert(entry >= N_words, "Precondition"); + return power_to_cards_back(entry - N_words); + } + static size_t entry_to_words_back(u_char entry) { + assert(entry >= N_words, "Precondition"); + return power_to_words_back(entry - N_words); + } + + // The shared array, which is shared with other BlockOffsetArray's + // corresponding to different spaces within a generation or span of + // memory. + BlockOffsetSharedArray* _array; + + // The space that owns this subregion. + Space* _sp; + + // If true, array entries are initialized to 0; otherwise, they are + // initialized to point backwards to the beginning of the covered region. + bool _init_to_zero; + + // An assertion-checking helper method for the set_remainder*() methods below. + void check_reducing_assertion(bool reducing) { _array->check_reducing_assertion(reducing); } + + // Sets the entries + // corresponding to the cards starting at "start" and ending at "end" + // to point back to the card before "start": the interval [start, end) + // is right-open. The last parameter, reducing, indicates whether the + // updates to individual entries always reduce the entry from a higher + // to a lower value. (For example this would hold true during a temporal + // regime during which only block splits were updating the BOT. + void set_remainder_to_point_to_start(HeapWord* start, HeapWord* end, bool reducing = false); + // Same as above, except that the args here are a card _index_ interval + // that is closed: [start_index, end_index] + void set_remainder_to_point_to_start_incl(size_t start, size_t end, bool reducing = false); + + // A helper function for BOT adjustment/verification work + void do_block_internal(HeapWord* blk_start, HeapWord* blk_end, Action action, bool reducing = false); + + public: + // The space may not have its bottom and top set yet, which is why the + // region is passed as a parameter. If "init_to_zero" is true, the + // elements of the array are initialized to zero. Otherwise, they are + // initialized to point backwards to the beginning. + BlockOffsetArray(BlockOffsetSharedArray* array, MemRegion mr, + bool init_to_zero_); + + // Note: this ought to be part of the constructor, but that would require + // "this" to be passed as a parameter to a member constructor for + // the containing concrete subtype of Space. + // This would be legal C++, but MS VC++ doesn't allow it. + void set_space(Space* sp) { _sp = sp; } + + // Resets the covered region to the given "mr". + void set_region(MemRegion mr) { + _bottom = mr.start(); + _end = mr.end(); + } + + // Note that the committed size of the covered space may have changed, + // so the table size might also wish to change. + virtual void 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 + } + + // Adjust the BOT to show that it has a single block in the + // range [blk_start, blk_start + size). All necessary BOT + // cards are adjusted, but _unallocated_block isn't. + void single_block(HeapWord* blk_start, HeapWord* blk_end); + void single_block(HeapWord* blk, size_t size) { + single_block(blk, blk + size); + } + + // When the alloc_block() call returns, the block offset table should + // have enough information such that any subsequent block_start() call + // with an argument equal to an address that is within the range + // [blk_start, blk_end) would return the value blk_start, provided + // there have been no calls in between that reset this information + // (e.g. see BlockOffsetArrayNonContigSpace::single_block() call + // for an appropriate range covering the said interval). + // These methods expect to be called with [blk_start, blk_end) + // representing a block of memory in the heap. + virtual void alloc_block(HeapWord* blk_start, HeapWord* blk_end); + void alloc_block(HeapWord* blk, size_t size) { + alloc_block(blk, blk + size); + } + + // If true, initialize array slots with no allocated blocks to zero. + // Otherwise, make them point back to the front. + bool init_to_zero() { return _init_to_zero; } + // Corresponding setter + void set_init_to_zero(bool val) { + _init_to_zero = val; + assert(_array != NULL, "_array should be non-NULL"); + _array->set_init_to_zero(val); + } + + // Debugging + // Return the index of the last entry in the "active" region. + virtual size_t last_active_index() const = 0; + // Verify the block offset table + void verify() const; + void check_all_cards(size_t left_card, size_t right_card) const; +}; + +//////////////////////////////////////////////////////////////////////////// +// A subtype of BlockOffsetArray that takes advantage of the fact +// that its underlying space is a NonContiguousSpace, so that some +// specialized interfaces can be made available for spaces that +// manipulate the table. +//////////////////////////////////////////////////////////////////////////// +class BlockOffsetArrayNonContigSpace: public BlockOffsetArray { + friend class VMStructs; + private: + // The portion [_unallocated_block, _sp.end()) of the space that + // is a single block known not to contain any objects. + // NOTE: See BlockOffsetArrayUseUnallocatedBlock flag. + HeapWord* _unallocated_block; + + public: + BlockOffsetArrayNonContigSpace(BlockOffsetSharedArray* array, MemRegion mr): + BlockOffsetArray(array, mr, false), + _unallocated_block(_bottom) { } + + // Accessor + HeapWord* unallocated_block() const { + assert(BlockOffsetArrayUseUnallocatedBlock, + "_unallocated_block is not being maintained"); + return _unallocated_block; + } + + void set_unallocated_block(HeapWord* block) { + assert(BlockOffsetArrayUseUnallocatedBlock, + "_unallocated_block is not being maintained"); + assert(block >= _bottom && block <= _end, "out of range"); + _unallocated_block = block; + } + + // These methods expect to be called with [blk_start, blk_end) + // representing a block of memory in the heap. + void alloc_block(HeapWord* blk_start, HeapWord* blk_end); + void alloc_block(HeapWord* blk, size_t size) { + alloc_block(blk, blk + size); + } + + // The following methods are useful and optimized for a + // non-contiguous space. + + // Given a block [blk_start, blk_start + full_blk_size), and + // a left_blk_size < full_blk_size, adjust the BOT to show two + // blocks [blk_start, blk_start + left_blk_size) and + // [blk_start + left_blk_size, blk_start + full_blk_size). + // It is assumed (and verified in the non-product VM) that the + // BOT was correct for the original block. + void split_block(HeapWord* blk_start, size_t full_blk_size, + size_t left_blk_size); + + // Adjust BOT to show that it has a block in the range + // [blk_start, blk_start + size). Only the first card + // of BOT is touched. It is assumed (and verified in the + // non-product VM) that the remaining cards of the block + // are correct. + void mark_block(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false); + void mark_block(HeapWord* blk, size_t size, bool reducing = false) { + mark_block(blk, blk + size, reducing); + } + + // Adjust _unallocated_block to indicate that a particular + // block has been newly allocated or freed. It is assumed (and + // verified in the non-product VM) that the BOT is correct for + // the given block. + void allocated(HeapWord* blk_start, HeapWord* blk_end, bool reducing = false) { + // Verify that the BOT shows [blk, blk + blk_size) to be one block. + verify_single_block(blk_start, blk_end); + if (BlockOffsetArrayUseUnallocatedBlock) { + _unallocated_block = MAX2(_unallocated_block, blk_end); + } + } + + void allocated(HeapWord* blk, size_t size, bool reducing = false) { + allocated(blk, blk + size, reducing); + } + + void freed(HeapWord* blk_start, HeapWord* blk_end); + void freed(HeapWord* blk, size_t size); + + HeapWord* block_start_unsafe(const void* addr) const; + + // Requires "addr" to be the start of a card and returns the + // start of the block that contains the given address. + HeapWord* block_start_careful(const void* addr) const; + + // 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 verify_single_block(HeapWord* blk_start, HeapWord* blk_end) + PRODUCT_RETURN; + void verify_single_block(HeapWord* blk, size_t size) PRODUCT_RETURN; + + // Verify that the given block is before _unallocated_block + void verify_not_unallocated(HeapWord* blk_start, HeapWord* blk_end) + const PRODUCT_RETURN; + void verify_not_unallocated(HeapWord* blk, size_t size) + const PRODUCT_RETURN; + + // Debugging support + virtual size_t last_active_index() const; +}; + +//////////////////////////////////////////////////////////////////////////// +// A subtype of BlockOffsetArray that takes advantage of the fact +// that its underlying space is a ContiguousSpace, so that its "active" +// region can be more efficiently tracked (than for a non-contiguous space). +//////////////////////////////////////////////////////////////////////////// +class BlockOffsetArrayContigSpace: public BlockOffsetArray { + friend class VMStructs; + private: + // allocation boundary at which offset array must be updated + HeapWord* _next_offset_threshold; + size_t _next_offset_index; // index corresponding to that boundary + + // Work function when allocation start crosses threshold. + void alloc_block_work(HeapWord* blk_start, HeapWord* blk_end); + + public: + BlockOffsetArrayContigSpace(BlockOffsetSharedArray* array, MemRegion mr): + BlockOffsetArray(array, mr, true) { + _next_offset_threshold = NULL; + _next_offset_index = 0; + } + + void set_contig_space(ContiguousSpace* sp) { set_space((Space*)sp); } + + // Initialize the threshold for an empty heap. + HeapWord* initialize_threshold(); + // Zero out the entry for _bottom (offset will be zero) + void zero_bottom_entry(); + + // Return the next threshold, the point at which the table should be + // updated. + HeapWord* threshold() const { return _next_offset_threshold; } + + // In general, these methods expect to be called with + // [blk_start, blk_end) representing a block of memory in the heap. + // In this implementation, however, we are OK even if blk_start and/or + // blk_end are NULL because NULL is represented as 0, and thus + // never exceeds the "_next_offset_threshold". + void alloc_block(HeapWord* blk_start, HeapWord* blk_end) { + if (blk_end > _next_offset_threshold) { + alloc_block_work(blk_start, blk_end); + } + } + void alloc_block(HeapWord* blk, size_t size) { + alloc_block(blk, blk + size); + } + + HeapWord* block_start_unsafe(const void* addr) const; + + // Debugging support + virtual size_t last_active_index() const; +}; + +#endif // SHARE_VM_GC_SHARED_BLOCKOFFSETTABLE_HPP