1060 lines
42 KiB
C++
1060 lines
42 KiB
C++
/*
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* Copyright (c) 2018, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*
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*/
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#include "precompiled.hpp"
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#include "gc/shared/oopStorage.inline.hpp"
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#include "gc/shared/oopStorageParState.inline.hpp"
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#include "logging/log.hpp"
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#include "logging/logStream.hpp"
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#include "memory/allocation.inline.hpp"
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#include "runtime/atomic.hpp"
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#include "runtime/globals.hpp"
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#include "runtime/handles.inline.hpp"
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#include "runtime/interfaceSupport.inline.hpp"
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#include "runtime/mutex.hpp"
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#include "runtime/mutexLocker.hpp"
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#include "runtime/orderAccess.hpp"
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#include "runtime/os.hpp"
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#include "runtime/safepoint.hpp"
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#include "runtime/stubRoutines.hpp"
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#include "runtime/thread.hpp"
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#include "utilities/align.hpp"
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#include "utilities/count_trailing_zeros.hpp"
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#include "utilities/debug.hpp"
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#include "utilities/globalDefinitions.hpp"
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#include "utilities/macros.hpp"
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#include "utilities/ostream.hpp"
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OopStorage::AllocationListEntry::AllocationListEntry() : _prev(NULL), _next(NULL) {}
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OopStorage::AllocationListEntry::~AllocationListEntry() {
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assert(_prev == NULL, "deleting attached block");
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assert(_next == NULL, "deleting attached block");
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}
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OopStorage::AllocationList::AllocationList() : _head(NULL), _tail(NULL) {}
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OopStorage::AllocationList::~AllocationList() {
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// ~OopStorage() empties its lists before destroying them.
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assert(_head == NULL, "deleting non-empty block list");
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assert(_tail == NULL, "deleting non-empty block list");
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}
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void OopStorage::AllocationList::push_front(const Block& block) {
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const Block* old = _head;
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if (old == NULL) {
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assert(_tail == NULL, "invariant");
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_head = _tail = █
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} else {
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block.allocation_list_entry()._next = old;
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old->allocation_list_entry()._prev = █
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_head = █
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}
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}
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void OopStorage::AllocationList::push_back(const Block& block) {
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const Block* old = _tail;
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if (old == NULL) {
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assert(_head == NULL, "invariant");
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_head = _tail = █
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} else {
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old->allocation_list_entry()._next = █
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block.allocation_list_entry()._prev = old;
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_tail = █
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}
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}
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void OopStorage::AllocationList::unlink(const Block& block) {
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const AllocationListEntry& block_entry = block.allocation_list_entry();
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const Block* prev_blk = block_entry._prev;
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const Block* next_blk = block_entry._next;
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block_entry._prev = NULL;
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block_entry._next = NULL;
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if ((prev_blk == NULL) && (next_blk == NULL)) {
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assert(_head == &block, "invariant");
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assert(_tail == &block, "invariant");
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_head = _tail = NULL;
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} else if (prev_blk == NULL) {
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assert(_head == &block, "invariant");
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next_blk->allocation_list_entry()._prev = NULL;
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_head = next_blk;
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} else if (next_blk == NULL) {
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assert(_tail == &block, "invariant");
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prev_blk->allocation_list_entry()._next = NULL;
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_tail = prev_blk;
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} else {
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next_blk->allocation_list_entry()._prev = prev_blk;
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prev_blk->allocation_list_entry()._next = next_blk;
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}
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}
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OopStorage::ActiveArray::ActiveArray(size_t size) :
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_size(size),
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_block_count(0),
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_refcount(0)
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{}
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OopStorage::ActiveArray::~ActiveArray() {
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assert(_refcount == 0, "precondition");
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}
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OopStorage::ActiveArray* OopStorage::ActiveArray::create(size_t size, AllocFailType alloc_fail) {
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size_t size_in_bytes = blocks_offset() + sizeof(Block*) * size;
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void* mem = NEW_C_HEAP_ARRAY3(char, size_in_bytes, mtGC, CURRENT_PC, alloc_fail);
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if (mem == NULL) return NULL;
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return new (mem) ActiveArray(size);
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}
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void OopStorage::ActiveArray::destroy(ActiveArray* ba) {
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ba->~ActiveArray();
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FREE_C_HEAP_ARRAY(char, ba);
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}
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size_t OopStorage::ActiveArray::size() const {
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return _size;
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}
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size_t OopStorage::ActiveArray::block_count() const {
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return _block_count;
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}
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size_t OopStorage::ActiveArray::block_count_acquire() const {
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return OrderAccess::load_acquire(&_block_count);
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}
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void OopStorage::ActiveArray::increment_refcount() const {
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int new_value = Atomic::add(1, &_refcount);
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assert(new_value >= 1, "negative refcount %d", new_value - 1);
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}
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bool OopStorage::ActiveArray::decrement_refcount() const {
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int new_value = Atomic::sub(1, &_refcount);
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assert(new_value >= 0, "negative refcount %d", new_value);
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return new_value == 0;
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}
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bool OopStorage::ActiveArray::push(Block* block) {
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size_t index = _block_count;
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if (index < _size) {
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block->set_active_index(index);
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*block_ptr(index) = block;
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// Use a release_store to ensure all the setup is complete before
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// making the block visible.
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OrderAccess::release_store(&_block_count, index + 1);
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return true;
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} else {
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return false;
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}
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}
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void OopStorage::ActiveArray::remove(Block* block) {
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assert(_block_count > 0, "array is empty");
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size_t index = block->active_index();
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assert(*block_ptr(index) == block, "block not present");
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size_t last_index = _block_count - 1;
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Block* last_block = *block_ptr(last_index);
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last_block->set_active_index(index);
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*block_ptr(index) = last_block;
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_block_count = last_index;
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}
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void OopStorage::ActiveArray::copy_from(const ActiveArray* from) {
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assert(_block_count == 0, "array must be empty");
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size_t count = from->_block_count;
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assert(count <= _size, "precondition");
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Block* const* from_ptr = from->block_ptr(0);
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Block** to_ptr = block_ptr(0);
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for (size_t i = 0; i < count; ++i) {
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Block* block = *from_ptr++;
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assert(block->active_index() == i, "invariant");
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*to_ptr++ = block;
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}
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_block_count = count;
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}
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// Blocks start with an array of BitsPerWord oop entries. That array
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// is divided into conceptual BytesPerWord sections of BitsPerByte
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// entries. Blocks are allocated aligned on section boundaries, for
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// the convenience of mapping from an entry to the containing block;
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// see block_for_ptr(). Aligning on section boundary rather than on
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// the full _data wastes a lot less space, but makes for a bit more
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// work in block_for_ptr().
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const unsigned section_size = BitsPerByte;
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const unsigned section_count = BytesPerWord;
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const unsigned block_alignment = sizeof(oop) * section_size;
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OopStorage::Block::Block(const OopStorage* owner, void* memory) :
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_data(),
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_allocated_bitmask(0),
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_owner(owner),
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_memory(memory),
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_active_index(0),
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_allocation_list_entry(),
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_deferred_updates_next(NULL),
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_release_refcount(0)
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{
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STATIC_ASSERT(_data_pos == 0);
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STATIC_ASSERT(section_size * section_count == ARRAY_SIZE(_data));
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assert(offset_of(Block, _data) == _data_pos, "invariant");
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assert(owner != NULL, "NULL owner");
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assert(is_aligned(this, block_alignment), "misaligned block");
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}
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OopStorage::Block::~Block() {
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assert(_release_refcount == 0, "deleting block while releasing");
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assert(_deferred_updates_next == NULL, "deleting block with deferred update");
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// Clear fields used by block_for_ptr and entry validation, which
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// might help catch bugs. Volatile to prevent dead-store elimination.
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const_cast<uintx volatile&>(_allocated_bitmask) = 0;
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const_cast<OopStorage* volatile&>(_owner) = NULL;
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}
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size_t OopStorage::Block::allocation_size() {
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// _data must be first member, so aligning Block aligns _data.
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STATIC_ASSERT(_data_pos == 0);
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return sizeof(Block) + block_alignment - sizeof(void*);
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}
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size_t OopStorage::Block::allocation_alignment_shift() {
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return exact_log2(block_alignment);
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}
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inline bool is_full_bitmask(uintx bitmask) { return ~bitmask == 0; }
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inline bool is_empty_bitmask(uintx bitmask) { return bitmask == 0; }
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bool OopStorage::Block::is_full() const {
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return is_full_bitmask(allocated_bitmask());
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}
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bool OopStorage::Block::is_empty() const {
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return is_empty_bitmask(allocated_bitmask());
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}
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uintx OopStorage::Block::bitmask_for_entry(const oop* ptr) const {
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return bitmask_for_index(get_index(ptr));
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}
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// An empty block is not yet deletable if either:
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// (1) There is a release() operation currently operating on it.
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// (2) It is in the deferred updates list.
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// For interaction with release(), these must follow the empty check,
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// and the order of these checks is important.
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bool OopStorage::Block::is_safe_to_delete() const {
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assert(is_empty(), "precondition");
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OrderAccess::loadload();
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return (OrderAccess::load_acquire(&_release_refcount) == 0) &&
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(OrderAccess::load_acquire(&_deferred_updates_next) == NULL);
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}
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OopStorage::Block* OopStorage::Block::deferred_updates_next() const {
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return _deferred_updates_next;
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}
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void OopStorage::Block::set_deferred_updates_next(Block* block) {
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_deferred_updates_next = block;
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}
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bool OopStorage::Block::contains(const oop* ptr) const {
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const oop* base = get_pointer(0);
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return (base <= ptr) && (ptr < (base + ARRAY_SIZE(_data)));
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}
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size_t OopStorage::Block::active_index() const {
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return _active_index;
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}
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void OopStorage::Block::set_active_index(size_t index) {
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_active_index = index;
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}
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size_t OopStorage::Block::active_index_safe(const Block* block) {
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STATIC_ASSERT(sizeof(intptr_t) == sizeof(block->_active_index));
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assert(CanUseSafeFetchN(), "precondition");
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return SafeFetchN((intptr_t*)&block->_active_index, 0);
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}
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unsigned OopStorage::Block::get_index(const oop* ptr) const {
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assert(contains(ptr), PTR_FORMAT " not in block " PTR_FORMAT, p2i(ptr), p2i(this));
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return static_cast<unsigned>(ptr - get_pointer(0));
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}
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oop* OopStorage::Block::allocate() {
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// Use CAS loop because release may change bitmask outside of lock.
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uintx allocated = allocated_bitmask();
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while (true) {
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assert(!is_full_bitmask(allocated), "attempt to allocate from full block");
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unsigned index = count_trailing_zeros(~allocated);
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uintx new_value = allocated | bitmask_for_index(index);
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uintx fetched = Atomic::cmpxchg(new_value, &_allocated_bitmask, allocated);
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if (fetched == allocated) {
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return get_pointer(index); // CAS succeeded; return entry for index.
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}
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allocated = fetched; // CAS failed; retry with latest value.
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}
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}
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OopStorage::Block* OopStorage::Block::new_block(const OopStorage* owner) {
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// _data must be first member: aligning block => aligning _data.
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STATIC_ASSERT(_data_pos == 0);
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size_t size_needed = allocation_size();
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void* memory = NEW_C_HEAP_ARRAY_RETURN_NULL(char, size_needed, mtGC);
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if (memory == NULL) {
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return NULL;
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}
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void* block_mem = align_up(memory, block_alignment);
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assert(sizeof(Block) + pointer_delta(block_mem, memory, 1) <= size_needed,
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"allocated insufficient space for aligned block");
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return ::new (block_mem) Block(owner, memory);
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}
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void OopStorage::Block::delete_block(const Block& block) {
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void* memory = block._memory;
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block.Block::~Block();
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FREE_C_HEAP_ARRAY(char, memory);
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}
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// This can return a false positive if ptr is not contained by some
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// block. For some uses, it is a precondition that ptr is valid,
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// e.g. contained in some block in owner's _active_array. Other uses
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// require additional validation of the result.
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OopStorage::Block*
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OopStorage::Block::block_for_ptr(const OopStorage* owner, const oop* ptr) {
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assert(CanUseSafeFetchN(), "precondition");
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STATIC_ASSERT(_data_pos == 0);
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// Const-ness of ptr is not related to const-ness of containing block.
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// Blocks are allocated section-aligned, so get the containing section.
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oop* section_start = align_down(const_cast<oop*>(ptr), block_alignment);
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// Start with a guess that the containing section is the last section,
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// so the block starts section_count-1 sections earlier.
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oop* section = section_start - (section_size * (section_count - 1));
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// Walk up through the potential block start positions, looking for
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// the owner in the expected location. If we're below the actual block
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// start position, the value at the owner position will be some oop
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// (possibly NULL), which can never match the owner.
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intptr_t owner_addr = reinterpret_cast<intptr_t>(owner);
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for (unsigned i = 0; i < section_count; ++i, section += section_size) {
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Block* candidate = reinterpret_cast<Block*>(section);
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intptr_t* candidate_owner_addr
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= reinterpret_cast<intptr_t*>(&candidate->_owner);
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if (SafeFetchN(candidate_owner_addr, 0) == owner_addr) {
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return candidate;
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}
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}
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return NULL;
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}
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//////////////////////////////////////////////////////////////////////////////
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// Allocation
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//
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// Allocation involves the _allocation_list, which contains a subset of the
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// blocks owned by a storage object. This is a doubly-linked list, linked
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// through dedicated fields in the blocks. Full blocks are removed from this
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// list, though they are still present in the _active_array. Empty blocks are
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// kept at the end of the _allocation_list, to make it easy for empty block
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// deletion to find them.
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//
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// allocate(), and delete_empty_blocks() lock the
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// _allocation_mutex while performing any list and array modifications.
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//
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// allocate() and release() update a block's _allocated_bitmask using CAS
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// loops. This prevents loss of updates even though release() performs
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// its updates without any locking.
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//
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// allocate() obtains the entry from the first block in the _allocation_list,
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// and updates that block's _allocated_bitmask to indicate the entry is in
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// use. If this makes the block full (all entries in use), the block is
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// removed from the _allocation_list so it won't be considered by future
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// allocations until some entries in it are released.
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//
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// release() is performed lock-free. (Note: This means it can't notify the
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// service thread of pending cleanup work. It must be lock-free because
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// it is called in all kinds of contexts where even quite low ranked locks
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// may be held.) release() first looks up the block for
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// the entry, using address alignment to find the enclosing block (thereby
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// avoiding iteration over the _active_array). Once the block has been
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// determined, its _allocated_bitmask needs to be updated, and its position in
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// the _allocation_list may need to be updated. There are two cases:
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//
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// (a) If the block is neither full nor would become empty with the release of
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// the entry, only its _allocated_bitmask needs to be updated. But if the CAS
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// update fails, the applicable case may change for the retry.
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//
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// (b) Otherwise, the _allocation_list also needs to be modified. This requires
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// locking the _allocation_mutex. To keep the release() operation lock-free,
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// rather than updating the _allocation_list itself, it instead performs a
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// lock-free push of the block onto the _deferred_updates list. Entries on
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// that list are processed by allocate() and delete_empty_blocks(), while
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// they already hold the necessary lock. That processing makes the block's
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// list state consistent with its current _allocated_bitmask. The block is
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// added to the _allocation_list if not already present and the bitmask is not
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// full. The block is moved to the end of the _allocation_list if the bitmask
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// is empty, for ease of empty block deletion processing.
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oop* OopStorage::allocate() {
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MutexLocker ml(_allocation_mutex, Mutex::_no_safepoint_check_flag);
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Block* block = block_for_allocation();
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if (block == NULL) return NULL; // Block allocation failed.
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assert(!block->is_full(), "invariant");
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if (block->is_empty()) {
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// Transitioning from empty to not empty.
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log_debug(oopstorage, blocks)("%s: block not empty " PTR_FORMAT, name(), p2i(block));
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}
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oop* result = block->allocate();
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assert(result != NULL, "allocation failed");
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assert(!block->is_empty(), "postcondition");
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Atomic::inc(&_allocation_count); // release updates outside lock.
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if (block->is_full()) {
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// Transitioning from not full to full.
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// Remove full blocks from consideration by future allocates.
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log_debug(oopstorage, blocks)("%s: block full " PTR_FORMAT, name(), p2i(block));
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_allocation_list.unlink(*block);
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}
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log_trace(oopstorage, ref)("%s: allocated " PTR_FORMAT, name(), p2i(result));
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return result;
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}
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bool OopStorage::try_add_block() {
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assert_lock_strong(_allocation_mutex);
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Block* block;
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{
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MutexUnlocker ul(_allocation_mutex, Mutex::_no_safepoint_check_flag);
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block = Block::new_block(this);
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}
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if (block == NULL) return false;
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// Add new block to the _active_array, growing if needed.
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if (!_active_array->push(block)) {
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if (expand_active_array()) {
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guarantee(_active_array->push(block), "push failed after expansion");
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} else {
|
|
log_debug(oopstorage, blocks)("%s: failed active array expand", name());
|
|
Block::delete_block(*block);
|
|
return false;
|
|
}
|
|
}
|
|
// Add to end of _allocation_list. The mutex release allowed other
|
|
// threads to add blocks to the _allocation_list. We prefer to
|
|
// allocate from non-empty blocks, to allow empty blocks to be
|
|
// deleted. But we don't bother notifying about the empty block
|
|
// because we're (probably) about to allocate an entry from it.
|
|
_allocation_list.push_back(*block);
|
|
log_debug(oopstorage, blocks)("%s: new block " PTR_FORMAT, name(), p2i(block));
|
|
return true;
|
|
}
|
|
|
|
OopStorage::Block* OopStorage::block_for_allocation() {
|
|
assert_lock_strong(_allocation_mutex);
|
|
while (true) {
|
|
// Use the first block in _allocation_list for the allocation.
|
|
Block* block = _allocation_list.head();
|
|
if (block != NULL) {
|
|
return block;
|
|
} else if (reduce_deferred_updates()) {
|
|
// Might have added a block to the _allocation_list, so retry.
|
|
} else if (try_add_block()) {
|
|
// Successfully added a new block to the list, so retry.
|
|
assert(_allocation_list.chead() != NULL, "invariant");
|
|
} else if (_allocation_list.chead() != NULL) {
|
|
// Trying to add a block failed, but some other thread added to the
|
|
// list while we'd dropped the lock over the new block allocation.
|
|
} else if (!reduce_deferred_updates()) { // Once more before failure.
|
|
// Attempt to add a block failed, no other thread added a block,
|
|
// and no deferred updated added a block, then allocation failed.
|
|
log_debug(oopstorage, blocks)("%s: failed block allocation", name());
|
|
return NULL;
|
|
}
|
|
}
|
|
}
|
|
|
|
// Create a new, larger, active array with the same content as the
|
|
// current array, and then replace, relinquishing the old array.
|
|
// Return true if the array was successfully expanded, false to
|
|
// indicate allocation failure.
|
|
bool OopStorage::expand_active_array() {
|
|
assert_lock_strong(_allocation_mutex);
|
|
ActiveArray* old_array = _active_array;
|
|
size_t new_size = 2 * old_array->size();
|
|
log_debug(oopstorage, blocks)("%s: expand active array " SIZE_FORMAT,
|
|
name(), new_size);
|
|
ActiveArray* new_array = ActiveArray::create(new_size, AllocFailStrategy::RETURN_NULL);
|
|
if (new_array == NULL) return false;
|
|
new_array->copy_from(old_array);
|
|
replace_active_array(new_array);
|
|
relinquish_block_array(old_array);
|
|
return true;
|
|
}
|
|
|
|
// Make new_array the _active_array. Increments new_array's refcount
|
|
// to account for the new reference. The assignment is atomic wrto
|
|
// obtain_active_array; once this function returns, it is safe for the
|
|
// caller to relinquish the old array.
|
|
void OopStorage::replace_active_array(ActiveArray* new_array) {
|
|
// Caller has the old array that is the current value of _active_array.
|
|
// Update new_array refcount to account for the new reference.
|
|
new_array->increment_refcount();
|
|
// Install new_array, ensuring its initialization is complete first.
|
|
OrderAccess::release_store(&_active_array, new_array);
|
|
// Wait for any readers that could read the old array from _active_array.
|
|
// Can't use GlobalCounter here, because this is called from allocate(),
|
|
// which may be called in the scope of a GlobalCounter critical section
|
|
// when inserting a StringTable entry.
|
|
_protect_active.synchronize();
|
|
// All obtain critical sections that could see the old array have
|
|
// completed, having incremented the refcount of the old array. The
|
|
// caller can now safely relinquish the old array.
|
|
}
|
|
|
|
// Atomically (wrto replace_active_array) get the active array and
|
|
// increment its refcount. This provides safe access to the array,
|
|
// even if an allocate operation expands and replaces the value of
|
|
// _active_array. The caller must relinquish the array when done
|
|
// using it.
|
|
OopStorage::ActiveArray* OopStorage::obtain_active_array() const {
|
|
SingleWriterSynchronizer::CriticalSection cs(&_protect_active);
|
|
ActiveArray* result = OrderAccess::load_acquire(&_active_array);
|
|
result->increment_refcount();
|
|
return result;
|
|
}
|
|
|
|
// Decrement refcount of array and destroy if refcount is zero.
|
|
void OopStorage::relinquish_block_array(ActiveArray* array) const {
|
|
if (array->decrement_refcount()) {
|
|
assert(array != _active_array, "invariant");
|
|
ActiveArray::destroy(array);
|
|
}
|
|
}
|
|
|
|
class OopStorage::WithActiveArray : public StackObj {
|
|
const OopStorage* _storage;
|
|
ActiveArray* _active_array;
|
|
|
|
public:
|
|
WithActiveArray(const OopStorage* storage) :
|
|
_storage(storage),
|
|
_active_array(storage->obtain_active_array())
|
|
{}
|
|
|
|
~WithActiveArray() {
|
|
_storage->relinquish_block_array(_active_array);
|
|
}
|
|
|
|
ActiveArray& active_array() const {
|
|
return *_active_array;
|
|
}
|
|
};
|
|
|
|
OopStorage::Block* OopStorage::find_block_or_null(const oop* ptr) const {
|
|
assert(ptr != NULL, "precondition");
|
|
return Block::block_for_ptr(this, ptr);
|
|
}
|
|
|
|
static void log_release_transitions(uintx releasing,
|
|
uintx old_allocated,
|
|
const OopStorage* owner,
|
|
const void* block) {
|
|
Log(oopstorage, blocks) log;
|
|
LogStream ls(log.debug());
|
|
if (is_full_bitmask(old_allocated)) {
|
|
ls.print_cr("%s: block not full " PTR_FORMAT, owner->name(), p2i(block));
|
|
}
|
|
if (releasing == old_allocated) {
|
|
ls.print_cr("%s: block empty " PTR_FORMAT, owner->name(), p2i(block));
|
|
}
|
|
}
|
|
|
|
void OopStorage::Block::release_entries(uintx releasing, OopStorage* owner) {
|
|
assert(releasing != 0, "preconditon");
|
|
// Prevent empty block deletion when transitioning to empty.
|
|
Atomic::inc(&_release_refcount);
|
|
|
|
// Atomically update allocated bitmask.
|
|
uintx old_allocated = _allocated_bitmask;
|
|
while (true) {
|
|
assert((releasing & ~old_allocated) == 0, "releasing unallocated entries");
|
|
uintx new_value = old_allocated ^ releasing;
|
|
uintx fetched = Atomic::cmpxchg(new_value, &_allocated_bitmask, old_allocated);
|
|
if (fetched == old_allocated) break; // Successful update.
|
|
old_allocated = fetched; // Retry with updated bitmask.
|
|
}
|
|
|
|
// Now that the bitmask has been updated, if we have a state transition
|
|
// (updated bitmask is empty or old bitmask was full), atomically push
|
|
// this block onto the deferred updates list. Some future call to
|
|
// reduce_deferred_updates will make any needed changes related to this
|
|
// block and _allocation_list. This deferral avoids _allocation_list
|
|
// updates and the associated locking here.
|
|
if ((releasing == old_allocated) || is_full_bitmask(old_allocated)) {
|
|
// Log transitions. Both transitions are possible in a single update.
|
|
if (log_is_enabled(Debug, oopstorage, blocks)) {
|
|
log_release_transitions(releasing, old_allocated, _owner, this);
|
|
}
|
|
// Attempt to claim responsibility for adding this block to the deferred
|
|
// list, by setting the link to non-NULL by self-looping. If this fails,
|
|
// then someone else has made such a claim and the deferred update has not
|
|
// yet been processed and will include our change, so we don't need to do
|
|
// anything further.
|
|
if (Atomic::replace_if_null(this, &_deferred_updates_next)) {
|
|
// Successfully claimed. Push, with self-loop for end-of-list.
|
|
Block* head = owner->_deferred_updates;
|
|
while (true) {
|
|
_deferred_updates_next = (head == NULL) ? this : head;
|
|
Block* fetched = Atomic::cmpxchg(this, &owner->_deferred_updates, head);
|
|
if (fetched == head) break; // Successful update.
|
|
head = fetched; // Retry with updated head.
|
|
}
|
|
// Only request cleanup for to-empty transitions, not for from-full.
|
|
// There isn't any rush to process from-full transitions. Allocation
|
|
// will reduce deferrals before allocating new blocks, so may process
|
|
// some. And the service thread will drain the entire deferred list
|
|
// if there are any pending to-empty transitions.
|
|
if (releasing == old_allocated) {
|
|
owner->record_needs_cleanup();
|
|
}
|
|
log_debug(oopstorage, blocks)("%s: deferred update " PTR_FORMAT,
|
|
_owner->name(), p2i(this));
|
|
}
|
|
}
|
|
// Release hold on empty block deletion.
|
|
Atomic::dec(&_release_refcount);
|
|
}
|
|
|
|
// Process one available deferred update. Returns true if one was processed.
|
|
bool OopStorage::reduce_deferred_updates() {
|
|
assert_lock_strong(_allocation_mutex);
|
|
// Atomically pop a block off the list, if any available.
|
|
// No ABA issue because this is only called by one thread at a time.
|
|
// The atomicity is wrto pushes by release().
|
|
Block* block = OrderAccess::load_acquire(&_deferred_updates);
|
|
while (true) {
|
|
if (block == NULL) return false;
|
|
// Try atomic pop of block from list.
|
|
Block* tail = block->deferred_updates_next();
|
|
if (block == tail) tail = NULL; // Handle self-loop end marker.
|
|
Block* fetched = Atomic::cmpxchg(tail, &_deferred_updates, block);
|
|
if (fetched == block) break; // Update successful.
|
|
block = fetched; // Retry with updated block.
|
|
}
|
|
block->set_deferred_updates_next(NULL); // Clear tail after updating head.
|
|
// Ensure bitmask read after pop is complete, including clearing tail, for
|
|
// ordering with release(). Without this, we may be processing a stale
|
|
// bitmask state here while blocking a release() operation from recording
|
|
// the deferred update needed for its bitmask change.
|
|
OrderAccess::fence();
|
|
// Process popped block.
|
|
uintx allocated = block->allocated_bitmask();
|
|
|
|
// Make membership in list consistent with bitmask state.
|
|
if ((_allocation_list.ctail() != NULL) &&
|
|
((_allocation_list.ctail() == block) ||
|
|
(_allocation_list.next(*block) != NULL))) {
|
|
// Block is in the _allocation_list.
|
|
assert(!is_full_bitmask(allocated), "invariant");
|
|
} else if (!is_full_bitmask(allocated)) {
|
|
// Block is not in the _allocation_list, but now should be.
|
|
_allocation_list.push_front(*block);
|
|
} // Else block is full and not in list, which is correct.
|
|
|
|
// Move empty block to end of list, for possible deletion.
|
|
if (is_empty_bitmask(allocated)) {
|
|
_allocation_list.unlink(*block);
|
|
_allocation_list.push_back(*block);
|
|
}
|
|
|
|
log_debug(oopstorage, blocks)("%s: processed deferred update " PTR_FORMAT,
|
|
name(), p2i(block));
|
|
return true; // Processed one pending update.
|
|
}
|
|
|
|
inline void check_release_entry(const oop* entry) {
|
|
assert(entry != NULL, "Releasing NULL");
|
|
assert(*entry == NULL, "Releasing uncleared entry: " PTR_FORMAT, p2i(entry));
|
|
}
|
|
|
|
void OopStorage::release(const oop* ptr) {
|
|
check_release_entry(ptr);
|
|
Block* block = find_block_or_null(ptr);
|
|
assert(block != NULL, "%s: invalid release " PTR_FORMAT, name(), p2i(ptr));
|
|
log_trace(oopstorage, ref)("%s: released " PTR_FORMAT, name(), p2i(ptr));
|
|
block->release_entries(block->bitmask_for_entry(ptr), this);
|
|
Atomic::dec(&_allocation_count);
|
|
}
|
|
|
|
void OopStorage::release(const oop* const* ptrs, size_t size) {
|
|
size_t i = 0;
|
|
while (i < size) {
|
|
check_release_entry(ptrs[i]);
|
|
Block* block = find_block_or_null(ptrs[i]);
|
|
assert(block != NULL, "%s: invalid release " PTR_FORMAT, name(), p2i(ptrs[i]));
|
|
log_trace(oopstorage, ref)("%s: released " PTR_FORMAT, name(), p2i(ptrs[i]));
|
|
size_t count = 0;
|
|
uintx releasing = 0;
|
|
for ( ; i < size; ++i) {
|
|
const oop* entry = ptrs[i];
|
|
check_release_entry(entry);
|
|
// If entry not in block, finish block and resume outer loop with entry.
|
|
if (!block->contains(entry)) break;
|
|
// Add entry to releasing bitmap.
|
|
log_trace(oopstorage, ref)("%s: released " PTR_FORMAT, name(), p2i(entry));
|
|
uintx entry_bitmask = block->bitmask_for_entry(entry);
|
|
assert((releasing & entry_bitmask) == 0,
|
|
"Duplicate entry: " PTR_FORMAT, p2i(entry));
|
|
releasing |= entry_bitmask;
|
|
++count;
|
|
}
|
|
// Release the contiguous entries that are in block.
|
|
block->release_entries(releasing, this);
|
|
Atomic::sub(count, &_allocation_count);
|
|
}
|
|
}
|
|
|
|
const size_t initial_active_array_size = 8;
|
|
|
|
OopStorage::OopStorage(const char* name,
|
|
Mutex* allocation_mutex,
|
|
Mutex* active_mutex) :
|
|
_name(os::strdup(name)),
|
|
_active_array(ActiveArray::create(initial_active_array_size)),
|
|
_allocation_list(),
|
|
_deferred_updates(NULL),
|
|
_allocation_mutex(allocation_mutex),
|
|
_active_mutex(active_mutex),
|
|
_allocation_count(0),
|
|
_concurrent_iteration_count(0),
|
|
_needs_cleanup(false)
|
|
{
|
|
_active_array->increment_refcount();
|
|
assert(_active_mutex->rank() < _allocation_mutex->rank(),
|
|
"%s: active_mutex must have lower rank than allocation_mutex", _name);
|
|
assert(Service_lock->rank() < _active_mutex->rank(),
|
|
"%s: active_mutex must have higher rank than Service_lock", _name);
|
|
assert(_active_mutex->_safepoint_check_required == Mutex::_safepoint_check_never,
|
|
"%s: active mutex requires never safepoint check", _name);
|
|
assert(_allocation_mutex->_safepoint_check_required == Mutex::_safepoint_check_never,
|
|
"%s: allocation mutex requires never safepoint check", _name);
|
|
}
|
|
|
|
void OopStorage::delete_empty_block(const Block& block) {
|
|
assert(block.is_empty(), "discarding non-empty block");
|
|
log_debug(oopstorage, blocks)("%s: delete empty block " PTR_FORMAT, name(), p2i(&block));
|
|
Block::delete_block(block);
|
|
}
|
|
|
|
OopStorage::~OopStorage() {
|
|
Block* block;
|
|
while ((block = _deferred_updates) != NULL) {
|
|
_deferred_updates = block->deferred_updates_next();
|
|
block->set_deferred_updates_next(NULL);
|
|
}
|
|
while ((block = _allocation_list.head()) != NULL) {
|
|
_allocation_list.unlink(*block);
|
|
}
|
|
bool unreferenced = _active_array->decrement_refcount();
|
|
assert(unreferenced, "deleting storage while _active_array is referenced");
|
|
for (size_t i = _active_array->block_count(); 0 < i; ) {
|
|
block = _active_array->at(--i);
|
|
Block::delete_block(*block);
|
|
}
|
|
ActiveArray::destroy(_active_array);
|
|
os::free(const_cast<char*>(_name));
|
|
}
|
|
|
|
// Managing service thread notifications.
|
|
//
|
|
// We don't want cleanup work to linger indefinitely, but we also don't want
|
|
// to run the service thread too often. We're also very limited in what we
|
|
// can do in a release operation, where cleanup work is created.
|
|
//
|
|
// When a release operation changes a block's state to empty, it records the
|
|
// need for cleanup in both the associated storage object and in the global
|
|
// request state. A safepoint cleanup task notifies the service thread when
|
|
// there may be cleanup work for any storage object, based on the global
|
|
// request state. But that notification is deferred if the service thread
|
|
// has run recently, and we also avoid duplicate notifications. The service
|
|
// thread updates the timestamp and resets the state flags on every iteration.
|
|
|
|
// Global cleanup request state.
|
|
static volatile bool needs_cleanup_requested = false;
|
|
|
|
// Flag for avoiding duplicate notifications.
|
|
static bool needs_cleanup_triggered = false;
|
|
|
|
// Time after which a notification can be made.
|
|
static jlong cleanup_trigger_permit_time = 0;
|
|
|
|
// Minimum time since last service thread check before notification is
|
|
// permitted. The value of 500ms was an arbitrary choice; frequent, but not
|
|
// too frequent.
|
|
const jlong cleanup_trigger_defer_period = 500 * NANOSECS_PER_MILLISEC;
|
|
|
|
void OopStorage::trigger_cleanup_if_needed() {
|
|
MonitorLocker ml(Service_lock, Monitor::_no_safepoint_check_flag);
|
|
if (Atomic::load(&needs_cleanup_requested) &&
|
|
!needs_cleanup_triggered &&
|
|
(os::javaTimeNanos() > cleanup_trigger_permit_time)) {
|
|
needs_cleanup_triggered = true;
|
|
ml.notify_all();
|
|
}
|
|
}
|
|
|
|
bool OopStorage::has_cleanup_work_and_reset() {
|
|
assert_lock_strong(Service_lock);
|
|
cleanup_trigger_permit_time =
|
|
os::javaTimeNanos() + cleanup_trigger_defer_period;
|
|
needs_cleanup_triggered = false;
|
|
// Set the request flag false and return its old value.
|
|
// Needs to be atomic to avoid dropping a concurrent request.
|
|
// Can't use Atomic::xchg, which may not support bool.
|
|
return Atomic::cmpxchg(false, &needs_cleanup_requested, true);
|
|
}
|
|
|
|
// Record that cleanup is needed, without notifying the Service thread.
|
|
// Used by release(), where we can't lock even Service_lock.
|
|
void OopStorage::record_needs_cleanup() {
|
|
// Set local flag first, else service thread could wake up and miss
|
|
// the request. This order may instead (rarely) unnecessarily notify.
|
|
OrderAccess::release_store(&_needs_cleanup, true);
|
|
OrderAccess::release_store_fence(&needs_cleanup_requested, true);
|
|
}
|
|
|
|
bool OopStorage::delete_empty_blocks() {
|
|
// Service thread might have oopstorage work, but not for this object.
|
|
// Check for deferred updates even though that's not a service thread
|
|
// trigger; since we're here, we might as well process them.
|
|
if (!OrderAccess::load_acquire(&_needs_cleanup) &&
|
|
(OrderAccess::load_acquire(&_deferred_updates) == NULL)) {
|
|
return false;
|
|
}
|
|
|
|
MutexLocker ml(_allocation_mutex, Mutex::_no_safepoint_check_flag);
|
|
|
|
// Clear the request before processing.
|
|
OrderAccess::release_store_fence(&_needs_cleanup, false);
|
|
|
|
// Other threads could be adding to the empty block count or the
|
|
// deferred update list while we're working. Set an upper bound on
|
|
// how many updates we'll process and blocks we'll try to release,
|
|
// so other threads can't cause an unbounded stay in this function.
|
|
// We add a bit of slop because the reduce_deferred_updates clause
|
|
// can cause blocks to be double counted. If there are few blocks
|
|
// and many of them are deferred and empty, we might hit the limit
|
|
// and spin the caller without doing very much work. Otherwise,
|
|
// we don't normally hit the limit anyway, instead running out of
|
|
// work to do.
|
|
size_t limit = block_count() + 10;
|
|
|
|
for (size_t i = 0; i < limit; ++i) {
|
|
// Process deferred updates, which might make empty blocks available.
|
|
// Continue checking once deletion starts, since additional updates
|
|
// might become available while we're working.
|
|
if (reduce_deferred_updates()) {
|
|
// Be safepoint-polite while looping.
|
|
MutexUnlocker ul(_allocation_mutex, Mutex::_no_safepoint_check_flag);
|
|
ThreadBlockInVM tbiv(JavaThread::current());
|
|
} else {
|
|
Block* block = _allocation_list.tail();
|
|
if ((block == NULL) || !block->is_empty()) {
|
|
return false;
|
|
} else if (!block->is_safe_to_delete()) {
|
|
// Look for other work while waiting for block to be deletable.
|
|
break;
|
|
}
|
|
|
|
// Try to delete the block. First, try to remove from _active_array.
|
|
{
|
|
MutexLocker aml(_active_mutex, Mutex::_no_safepoint_check_flag);
|
|
// Don't interfere with an active concurrent iteration.
|
|
// Instead, give up immediately. There is more work to do,
|
|
// but don't re-notify, to avoid useless spinning of the
|
|
// service thread. Instead, iteration completion notifies.
|
|
if (_concurrent_iteration_count > 0) return true;
|
|
_active_array->remove(block);
|
|
}
|
|
// Remove block from _allocation_list and delete it.
|
|
_allocation_list.unlink(*block);
|
|
// Be safepoint-polite while deleting and looping.
|
|
MutexUnlocker ul(_allocation_mutex, Mutex::_no_safepoint_check_flag);
|
|
delete_empty_block(*block);
|
|
ThreadBlockInVM tbiv(JavaThread::current());
|
|
}
|
|
}
|
|
// Exceeded work limit or can't delete last block. This will
|
|
// cause the service thread to loop, giving other subtasks an
|
|
// opportunity to run too. There's no need for a notification,
|
|
// because we are part of the service thread (unless gtesting).
|
|
record_needs_cleanup();
|
|
return true;
|
|
}
|
|
|
|
OopStorage::EntryStatus OopStorage::allocation_status(const oop* ptr) const {
|
|
const Block* block = find_block_or_null(ptr);
|
|
if (block != NULL) {
|
|
// Prevent block deletion and _active_array modification.
|
|
MutexLocker ml(_allocation_mutex, Mutex::_no_safepoint_check_flag);
|
|
// Block could be a false positive, so get index carefully.
|
|
size_t index = Block::active_index_safe(block);
|
|
if ((index < _active_array->block_count()) &&
|
|
(block == _active_array->at(index)) &&
|
|
block->contains(ptr)) {
|
|
if ((block->allocated_bitmask() & block->bitmask_for_entry(ptr)) != 0) {
|
|
return ALLOCATED_ENTRY;
|
|
} else {
|
|
return UNALLOCATED_ENTRY;
|
|
}
|
|
}
|
|
}
|
|
return INVALID_ENTRY;
|
|
}
|
|
|
|
size_t OopStorage::allocation_count() const {
|
|
return _allocation_count;
|
|
}
|
|
|
|
size_t OopStorage::block_count() const {
|
|
WithActiveArray wab(this);
|
|
// Count access is racy, but don't care.
|
|
return wab.active_array().block_count();
|
|
}
|
|
|
|
size_t OopStorage::total_memory_usage() const {
|
|
size_t total_size = sizeof(OopStorage);
|
|
total_size += strlen(name()) + 1;
|
|
total_size += sizeof(ActiveArray);
|
|
WithActiveArray wab(this);
|
|
const ActiveArray& blocks = wab.active_array();
|
|
// Count access is racy, but don't care.
|
|
total_size += blocks.block_count() * Block::allocation_size();
|
|
total_size += blocks.size() * sizeof(Block*);
|
|
return total_size;
|
|
}
|
|
|
|
// Parallel iteration support
|
|
|
|
uint OopStorage::BasicParState::default_estimated_thread_count(bool concurrent) {
|
|
uint configured = concurrent ? ConcGCThreads : ParallelGCThreads;
|
|
return MAX2(1u, configured); // Never estimate zero threads.
|
|
}
|
|
|
|
OopStorage::BasicParState::BasicParState(const OopStorage* storage,
|
|
uint estimated_thread_count,
|
|
bool concurrent) :
|
|
_storage(storage),
|
|
_active_array(_storage->obtain_active_array()),
|
|
_block_count(0), // initialized properly below
|
|
_next_block(0),
|
|
_estimated_thread_count(estimated_thread_count),
|
|
_concurrent(concurrent)
|
|
{
|
|
assert(estimated_thread_count > 0, "estimated thread count must be positive");
|
|
update_concurrent_iteration_count(1);
|
|
// Get the block count *after* iteration state updated, so concurrent
|
|
// empty block deletion is suppressed and can't reduce the count. But
|
|
// ensure the count we use was written after the block with that count
|
|
// was fully initialized; see ActiveArray::push.
|
|
_block_count = _active_array->block_count_acquire();
|
|
}
|
|
|
|
OopStorage::BasicParState::~BasicParState() {
|
|
_storage->relinquish_block_array(_active_array);
|
|
update_concurrent_iteration_count(-1);
|
|
if (_concurrent) {
|
|
// We may have deferred some cleanup work.
|
|
const_cast<OopStorage*>(_storage)->record_needs_cleanup();
|
|
}
|
|
}
|
|
|
|
void OopStorage::BasicParState::update_concurrent_iteration_count(int value) {
|
|
if (_concurrent) {
|
|
MutexLocker ml(_storage->_active_mutex, Mutex::_no_safepoint_check_flag);
|
|
_storage->_concurrent_iteration_count += value;
|
|
assert(_storage->_concurrent_iteration_count >= 0, "invariant");
|
|
}
|
|
}
|
|
|
|
bool OopStorage::BasicParState::claim_next_segment(IterationData* data) {
|
|
data->_processed += data->_segment_end - data->_segment_start;
|
|
size_t start = OrderAccess::load_acquire(&_next_block);
|
|
if (start >= _block_count) {
|
|
return finish_iteration(data); // No more blocks available.
|
|
}
|
|
// Try to claim several at a time, but not *too* many. We want to
|
|
// avoid deciding there are many available and selecting a large
|
|
// quantity, get delayed, and then end up claiming most or all of
|
|
// the remaining largish amount of work, leaving nothing for other
|
|
// threads to do. But too small a step can lead to contention
|
|
// over _next_block, esp. when the work per block is small.
|
|
size_t max_step = 10;
|
|
size_t remaining = _block_count - start;
|
|
size_t step = MIN2(max_step, 1 + (remaining / _estimated_thread_count));
|
|
// Atomic::add with possible overshoot. This can perform better
|
|
// than a CAS loop on some platforms when there is contention.
|
|
// We can cope with the uncertainty by recomputing start/end from
|
|
// the result of the add, and dealing with potential overshoot.
|
|
size_t end = Atomic::add(step, &_next_block);
|
|
// _next_block may have changed, so recompute start from result of add.
|
|
start = end - step;
|
|
// _next_block may have changed so much that end has overshot.
|
|
end = MIN2(end, _block_count);
|
|
// _next_block may have changed so much that even start has overshot.
|
|
if (start < _block_count) {
|
|
// Record claimed segment for iteration.
|
|
data->_segment_start = start;
|
|
data->_segment_end = end;
|
|
return true; // Success.
|
|
} else {
|
|
// No more blocks to claim.
|
|
return finish_iteration(data);
|
|
}
|
|
}
|
|
|
|
bool OopStorage::BasicParState::finish_iteration(const IterationData* data) const {
|
|
log_info(oopstorage, blocks, stats)
|
|
("Parallel iteration on %s: blocks = " SIZE_FORMAT
|
|
", processed = " SIZE_FORMAT " (%2.f%%)",
|
|
_storage->name(), _block_count, data->_processed,
|
|
percent_of(data->_processed, _block_count));
|
|
return false;
|
|
}
|
|
|
|
const char* OopStorage::name() const { return _name; }
|
|
|
|
#ifndef PRODUCT
|
|
|
|
void OopStorage::print_on(outputStream* st) const {
|
|
size_t allocations = _allocation_count;
|
|
size_t blocks = _active_array->block_count();
|
|
|
|
double data_size = section_size * section_count;
|
|
double alloc_percentage = percent_of((double)allocations, blocks * data_size);
|
|
|
|
st->print("%s: " SIZE_FORMAT " entries in " SIZE_FORMAT " blocks (%.F%%), " SIZE_FORMAT " bytes",
|
|
name(), allocations, blocks, alloc_percentage, total_memory_usage());
|
|
if (_concurrent_iteration_count > 0) {
|
|
st->print(", concurrent iteration active");
|
|
}
|
|
}
|
|
|
|
#endif // !PRODUCT
|