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/*
* Copyright (c) 2018, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
* questions.
*
*/
#include "precompiled.hpp"
#include "gc/shared/oopStorage.inline.hpp"
#include "gc/shared/oopStorageParState.inline.hpp"
#include "logging/log.hpp"
#include "memory/allocation.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/mutex.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/orderAccess.inline.hpp"
#include "runtime/safepoint.hpp"
#include "runtime/stubRoutines.hpp"
#include "utilities/align.hpp"
#include "utilities/count_trailing_zeros.hpp"
#include "utilities/debug.hpp"
#include "utilities/globalDefinitions.hpp"
#include "utilities/macros.hpp"
#include "utilities/ostream.hpp"
OopStorage::BlockEntry::BlockEntry() : _prev(NULL), _next(NULL) {}
OopStorage::BlockEntry::~BlockEntry() {
assert(_prev == NULL, "deleting attached block");
assert(_next == NULL, "deleting attached block");
}
OopStorage::BlockList::BlockList(const BlockEntry& (*get_entry)(const Block& block)) :
_head(NULL), _tail(NULL), _get_entry(get_entry)
{}
OopStorage::BlockList::~BlockList() {
// ~OopStorage() empties its lists before destroying them.
assert(_head == NULL, "deleting non-empty block list");
assert(_tail == NULL, "deleting non-empty block list");
}
void OopStorage::BlockList::push_front(const Block& block) {
const Block* old = _head;
if (old == NULL) {
assert(_tail == NULL, "invariant");
_head = _tail = █
} else {
_get_entry(block)._next = old;
_get_entry(*old)._prev = █
_head = █
}
}
void OopStorage::BlockList::push_back(const Block& block) {
const Block* old = _tail;
if (old == NULL) {
assert(_head == NULL, "invariant");
_head = _tail = █
} else {
_get_entry(*old)._next = █
_get_entry(block)._prev = old;
_tail = █
}
}
void OopStorage::BlockList::unlink(const Block& block) {
const BlockEntry& block_entry = _get_entry(block);
const Block* prev_blk = block_entry._prev;
const Block* next_blk = block_entry._next;
block_entry._prev = NULL;
block_entry._next = NULL;
if ((prev_blk == NULL) && (next_blk == NULL)) {
assert(_head == &block, "invariant");
assert(_tail == &block, "invariant");
_head = _tail = NULL;
} else if (prev_blk == NULL) {
assert(_head == &block, "invariant");
_get_entry(*next_blk)._prev = NULL;
_head = next_blk;
} else if (next_blk == NULL) {
assert(_tail == &block, "invariant");
_get_entry(*prev_blk)._next = NULL;
_tail = prev_blk;
} else {
_get_entry(*next_blk)._prev = prev_blk;
_get_entry(*prev_blk)._next = next_blk;
}
}
// Blocks start with an array of BitsPerWord oop entries. That array
// is divided into conceptual BytesPerWord sections of BitsPerWord
// entries. Blocks are allocated aligned on section boundaries, for
// the convenience of mapping from an entry to the containing block;
// see block_for_ptr(). Aligning on section boundary rather than on
// the full _data wastes a lot less space, but makes for a bit more
// work in block_for_ptr().
const unsigned section_size = BitsPerByte;
const unsigned section_count = BytesPerWord;
const unsigned block_alignment = sizeof(oop) * section_size;
// VS2013 warns (C4351) that elements of _data will be *correctly* default
// initialized, unlike earlier versions that *incorrectly* did not do so.
#ifdef _WINDOWS
#pragma warning(push)
#pragma warning(disable: 4351)
#endif // _WINDOWS
OopStorage::Block::Block(const OopStorage* owner, void* memory) :
_data(),
_allocated_bitmask(0),
_owner(owner),
_memory(memory),
_active_entry(),
_allocate_entry()
{
STATIC_ASSERT(_data_pos == 0);
STATIC_ASSERT(section_size * section_count == ARRAY_SIZE(_data));
assert(offset_of(Block, _data) == _data_pos, "invariant");
assert(owner != NULL, "NULL owner");
assert(is_aligned(this, block_alignment), "misaligned block");
}
#ifdef _WINDOWS
#pragma warning(pop)
#endif
OopStorage::Block::~Block() {
// Clear fields used by block_for_ptr and entry validation, which
// might help catch bugs. Volatile to prevent dead-store elimination.
const_cast<uintx volatile&>(_allocated_bitmask) = 0;
const_cast<OopStorage* volatile&>(_owner) = NULL;
}
const OopStorage::BlockEntry& OopStorage::Block::get_active_entry(const Block& block) {
return block._active_entry;
}
const OopStorage::BlockEntry& OopStorage::Block::get_allocate_entry(const Block& block) {
return block._allocate_entry;
}
size_t OopStorage::Block::allocation_size() {
// _data must be first member, so aligning Block aligns _data.
STATIC_ASSERT(_data_pos == 0);
return sizeof(Block) + block_alignment - sizeof(void*);
}
size_t OopStorage::Block::allocation_alignment_shift() {
return exact_log2(block_alignment);
}
inline bool is_full_bitmask(uintx bitmask) { return ~bitmask == 0; }
inline bool is_empty_bitmask(uintx bitmask) { return bitmask == 0; }
bool OopStorage::Block::is_full() const {
return is_full_bitmask(allocated_bitmask());
}
bool OopStorage::Block::is_empty() const {
return is_empty_bitmask(allocated_bitmask());
}
uintx OopStorage::Block::bitmask_for_entry(const oop* ptr) const {
return bitmask_for_index(get_index(ptr));
}
uintx OopStorage::Block::cmpxchg_allocated_bitmask(uintx new_value, uintx compare_value) {
return Atomic::cmpxchg(new_value, &_allocated_bitmask, compare_value);
}
bool OopStorage::Block::contains(const oop* ptr) const {
const oop* base = get_pointer(0);
return (base <= ptr) && (ptr < (base + ARRAY_SIZE(_data)));
}
unsigned OopStorage::Block::get_index(const oop* ptr) const {
assert(contains(ptr), PTR_FORMAT " not in block " PTR_FORMAT, p2i(ptr), p2i(this));
return static_cast<unsigned>(ptr - get_pointer(0));
}
oop* OopStorage::Block::allocate() {
// Use CAS loop because release may change bitmask outside of lock.
uintx allocated = allocated_bitmask();
while (true) {
assert(!is_full_bitmask(allocated), "attempt to allocate from full block");
unsigned index = count_trailing_zeros(~allocated);
uintx new_value = allocated | bitmask_for_index(index);
uintx fetched = cmpxchg_allocated_bitmask(new_value, allocated);
if (fetched == allocated) {
return get_pointer(index); // CAS succeeded; return entry for index.
}
allocated = fetched; // CAS failed; retry with latest value.
}
}
OopStorage::Block* OopStorage::Block::new_block(const OopStorage* owner) {
// _data must be first member: aligning block => aligning _data.
STATIC_ASSERT(_data_pos == 0);
size_t size_needed = allocation_size();
void* memory = NEW_C_HEAP_ARRAY_RETURN_NULL(char, size_needed, mtGC);
if (memory == NULL) {
return NULL;
}
void* block_mem = align_up(memory, block_alignment);
assert(sizeof(Block) + pointer_delta(block_mem, memory, 1) <= size_needed,
"allocated insufficient space for aligned block");
return ::new (block_mem) Block(owner, memory);
}
void OopStorage::Block::delete_block(const Block& block) {
void* memory = block._memory;
block.Block::~Block();
FREE_C_HEAP_ARRAY(char, memory);
}
// This can return a false positive if ptr is not contained by some
// block. For some uses, it is a precondition that ptr is valid,
// e.g. contained in some block in owner's _active_list. Other uses
// require additional validation of the result.
OopStorage::Block*
OopStorage::Block::block_for_ptr(const OopStorage* owner, const oop* ptr) {
assert(CanUseSafeFetchN(), "precondition");
STATIC_ASSERT(_data_pos == 0);
// Const-ness of ptr is not related to const-ness of containing block.
// Blocks are allocated section-aligned, so get the containing section.
oop* section_start = align_down(const_cast<oop*>(ptr), block_alignment);
// Start with a guess that the containing section is the last section,
// so the block starts section_count-1 sections earlier.
oop* section = section_start - (section_size * (section_count - 1));
// Walk up through the potential block start positions, looking for
// the owner in the expected location. If we're below the actual block
// start position, the value at the owner position will be some oop
// (possibly NULL), which can never match the owner.
intptr_t owner_addr = reinterpret_cast<intptr_t>(owner);
for (unsigned i = 0; i < section_count; ++i, section += section_size) {
Block* candidate = reinterpret_cast<Block*>(section);
intptr_t* candidate_owner_addr
= reinterpret_cast<intptr_t*>(&candidate->_owner);
if (SafeFetchN(candidate_owner_addr, 0) == owner_addr) {
return candidate;
}
}
return NULL;
}
bool OopStorage::is_valid_block_locked_or_safepoint(const Block* check_block) const {
assert_locked_or_safepoint(_allocate_mutex);
// For now, simple linear search. Do something more clever if this
// is a performance bottleneck, particularly for allocation_status.
for (const Block* block = _active_list.chead();
block != NULL;
block = _active_list.next(*block)) {
if (check_block == block) {
return true;
}
}
return false;
}
#ifdef ASSERT
void OopStorage::assert_at_safepoint() {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
}
#endif // ASSERT
//////////////////////////////////////////////////////////////////////////////
// Allocation
//
// Allocation involves the _allocate_list, which contains a subset of the
// blocks owned by a storage object. This is a doubly-linked list, linked
// through dedicated fields in the blocks. Full blocks are removed from this
// list, though they are still present in the _active_list. Empty blocks are
// kept at the end of the _allocate_list, to make it easy for empty block
// deletion to find them.
//
// allocate(), release(), and delete_empty_blocks_concurrent() all lock the
// _allocate_mutex while performing any list modifications.
//
// allocate() and release() update a block's _allocated_bitmask using CAS
// loops. This prevents loss of updates even though release() may perform
// some updates without any locking.
//
// allocate() obtains the entry from the first block in the _allocate_list,
// and updates that block's _allocated_bitmask to indicate the entry is in
// use. If this makes the block full (all entries in use), the block is
// removed from the _allocate_list so it won't be considered by future
// allocations until some entries in it are relased.
//
// release() looks up the block for the entry without locking. Once the block
// has been determined, its _allocated_bitmask needs to be updated, and its
// position in the _allocate_list may need to be updated. There are two
// cases:
//
// (a) If the block is neither full nor would become empty with the release of
// the entry, only its _allocated_bitmask needs to be updated. But if the CAS
// update fails, the applicable case may change for the retry.
//
// (b) Otherwise, the _allocate_list will also need to be modified. This
// requires locking the _allocate_mutex, and then attempting to CAS the
// _allocated_bitmask. If the CAS fails, the applicable case may change for
// the retry. If the CAS succeeds, then update the _allocate_list according
// to the the state changes. If the block changed from full to not full, then
// it needs to be added to the _allocate_list, for use in future allocations.
// If the block changed from not empty to empty, then it is moved to the end
// of the _allocate_list, for ease of empty block deletion processing.
oop* OopStorage::allocate() {
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
Block* block = _allocate_list.head();
if (block == NULL) {
// No available blocks; make a new one, and add to storage.
{
MutexUnlockerEx mul(_allocate_mutex, Mutex::_no_safepoint_check_flag);
block = Block::new_block(this);
}
if (block != NULL) {
// Add new block to storage.
log_info(oopstorage, blocks)("%s: new block " PTR_FORMAT, name(), p2i(block));
// Add to end of _allocate_list. The mutex release allowed
// other threads to add blocks to the _allocate_list. We prefer
// to allocate from non-empty blocks, to allow empty blocks to
// be deleted.
_allocate_list.push_back(*block);
++_empty_block_count;
// Add to front of _active_list, and then record as the head
// block, for concurrent iteration protocol.
_active_list.push_front(*block);
++_block_count;
// Ensure all setup of block is complete before making it visible.
OrderAccess::release_store(&_active_head, block);
} else {
log_info(oopstorage, blocks)("%s: failed new block allocation", name());
}
block = _allocate_list.head();
if (block == NULL) {
// Failed to make new block, and no other thread made a block
// available while the mutex was released, so return failure.
return NULL;
}
}
// Allocate from first block.
assert(block != NULL, "invariant");
assert(!block->is_full(), "invariant");
if (block->is_empty()) {
// Transitioning from empty to not empty.
log_debug(oopstorage, blocks)("%s: block not empty " PTR_FORMAT, name(), p2i(block));
--_empty_block_count;
}
oop* result = block->allocate();
assert(result != NULL, "allocation failed");
assert(!block->is_empty(), "postcondition");
Atomic::inc(&_allocation_count); // release updates outside lock.
if (block->is_full()) {
// Transitioning from not full to full.
// Remove full blocks from consideration by future allocates.
log_debug(oopstorage, blocks)("%s: block full " PTR_FORMAT, name(), p2i(block));
_allocate_list.unlink(*block);
}
log_info(oopstorage, ref)("%s: allocated " PTR_FORMAT, name(), p2i(result));
return result;
}
OopStorage::Block* OopStorage::find_block_or_null(const oop* ptr) const {
assert(ptr != NULL, "precondition");
return Block::block_for_ptr(this, ptr);
}
void OopStorage::release_from_block(Block& block, uintx releasing) {
assert(releasing != 0, "invariant");
uintx allocated = block.allocated_bitmask();
while (true) {
assert(releasing == (allocated & releasing), "invariant");
uintx new_value = allocated ^ releasing;
// CAS new_value into block's allocated bitmask, retrying with
// updated allocated bitmask until the CAS succeeds.
uintx fetched;
if (!is_full_bitmask(allocated) && !is_empty_bitmask(new_value)) {
fetched = block.cmpxchg_allocated_bitmask(new_value, allocated);
if (fetched == allocated) return;
} else {
// Need special handling if transitioning from full to not full,
// or from not empty to empty. For those cases, must hold the
// _allocation_mutex when updating the allocated bitmask, to
// ensure the associated list manipulations will be consistent
// with the allocation bitmask that is visible to other threads
// in allocate() or deleting empty blocks.
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
fetched = block.cmpxchg_allocated_bitmask(new_value, allocated);
if (fetched == allocated) {
// CAS succeeded; handle special cases, which might no longer apply.
if (is_full_bitmask(allocated)) {
// Transitioning from full to not-full; add to _allocate_list.
log_debug(oopstorage, blocks)("%s: block not full " PTR_FORMAT, name(), p2i(&block));
_allocate_list.push_front(block);
assert(!block.is_full(), "invariant"); // Still not full.
}
if (is_empty_bitmask(new_value)) {
// Transitioning from not-empty to empty; move to end of
// _allocate_list, to make it a deletion candidate.
log_debug(oopstorage, blocks)("%s: block empty " PTR_FORMAT, name(), p2i(&block));
_allocate_list.unlink(block);
_allocate_list.push_back(block);
++_empty_block_count;
assert(block.is_empty(), "invariant"); // Still empty.
}
return; // Successful CAS and transitions handled.
}
}
// CAS failed; retry with latest value.
allocated = fetched;
}
}
#ifdef ASSERT
void OopStorage::check_release(const Block* block, const oop* ptr) const {
switch (allocation_status_validating_block(block, ptr)) {
case INVALID_ENTRY:
fatal("Releasing invalid entry: " PTR_FORMAT, p2i(ptr));
break;
case UNALLOCATED_ENTRY:
fatal("Releasing unallocated entry: " PTR_FORMAT, p2i(ptr));
break;
case ALLOCATED_ENTRY:
assert(block->contains(ptr), "invariant");
break;
default:
ShouldNotReachHere();
}
}
#endif // ASSERT
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);
check_release(block, ptr);
log_info(oopstorage, ref)("%s: released " PTR_FORMAT, name(), p2i(ptr));
release_from_block(*block, block->bitmask_for_entry(ptr));
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]);
check_release(block, ptrs[i]);
log_info(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];
// If entry not in block, finish block and resume outer loop with entry.
if (!block->contains(entry)) break;
check_release_entry(entry);
// Add entry to releasing bitmap.
log_info(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.
release_from_block(*block, releasing);
Atomic::sub(count, &_allocation_count);
}
}
const char* dup_name(const char* name) {
char* dup = NEW_C_HEAP_ARRAY(char, strlen(name) + 1, mtGC);
strcpy(dup, name);
return dup;
}
OopStorage::OopStorage(const char* name,
Mutex* allocate_mutex,
Mutex* active_mutex) :
_name(dup_name(name)),
_active_list(&Block::get_active_entry),
_allocate_list(&Block::get_allocate_entry),
_active_head(NULL),
_allocate_mutex(allocate_mutex),
_active_mutex(active_mutex),
_allocation_count(0),
_block_count(0),
_empty_block_count(0),
_concurrent_iteration_active(false)
{
assert(_active_mutex->rank() < _allocate_mutex->rank(),
"%s: active_mutex must have lower rank than allocate_mutex", _name);
assert(_active_mutex->_safepoint_check_required != Mutex::_safepoint_check_always,
"%s: active mutex requires safepoint check", _name);
assert(_allocate_mutex->_safepoint_check_required != Mutex::_safepoint_check_always,
"%s: allocate mutex requires safepoint check", _name);
}
void OopStorage::delete_empty_block(const Block& block) {
assert(block.is_empty(), "discarding non-empty block");
log_info(oopstorage, blocks)("%s: delete empty block " PTR_FORMAT, name(), p2i(&block));
Block::delete_block(block);
}
OopStorage::~OopStorage() {
Block* block;
while ((block = _allocate_list.head()) != NULL) {
_allocate_list.unlink(*block);
}
while ((block = _active_list.head()) != NULL) {
_active_list.unlink(*block);
Block::delete_block(*block);
}
FREE_C_HEAP_ARRAY(char, _name);
}
void OopStorage::delete_empty_blocks_safepoint(size_t retain) {
assert_at_safepoint();
// Don't interfere with a concurrent iteration.
if (_concurrent_iteration_active) return;
// Compute the number of blocks to remove, to minimize volatile accesses.
size_t empty_blocks = _empty_block_count;
if (retain < empty_blocks) {
size_t remove_count = empty_blocks - retain;
// Update volatile counters once.
_block_count -= remove_count;
_empty_block_count -= remove_count;
do {
const Block* block = _allocate_list.ctail();
assert(block != NULL, "invariant");
assert(block->is_empty(), "invariant");
// Remove block from lists, and delete it.
_active_list.unlink(*block);
_allocate_list.unlink(*block);
delete_empty_block(*block);
} while (--remove_count > 0);
// Update _active_head, in case current value was in deleted set.
_active_head = _active_list.head();
}
}
void OopStorage::delete_empty_blocks_concurrent(size_t retain) {
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
// Other threads could be adding to the empty block count while we
// release the mutex across the block deletions. Set an upper bound
// on how many blocks we'll try to release, so other threads can't
// cause an unbounded stay in this function.
if (_empty_block_count <= retain) return;
size_t limit = _empty_block_count - retain;
for (size_t i = 0; (i < limit) && (retain < _empty_block_count); ++i) {
const Block* block = _allocate_list.ctail();
assert(block != NULL, "invariant");
assert(block->is_empty(), "invariant");
{
MutexLockerEx aml(_active_mutex, Mutex::_no_safepoint_check_flag);
// Don't interfere with a concurrent iteration.
if (_concurrent_iteration_active) return;
// Remove block from _active_list, updating head if needed.
_active_list.unlink(*block);
--_block_count;
if (block == _active_head) {
_active_head = _active_list.head();
}
}
// Remove block from _allocate_list and delete it.
_allocate_list.unlink(*block);
--_empty_block_count;
// Release mutex while deleting block.
MutexUnlockerEx ul(_allocate_mutex, Mutex::_no_safepoint_check_flag);
delete_empty_block(*block);
}
}
OopStorage::EntryStatus
OopStorage::allocation_status_validating_block(const Block* block,
const oop* ptr) const {
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
if ((block == NULL) || !is_valid_block_locked_or_safepoint(block)) {
return INVALID_ENTRY;
} else if ((block->allocated_bitmask() & block->bitmask_for_entry(ptr)) != 0) {
return ALLOCATED_ENTRY;
} else {
return UNALLOCATED_ENTRY;
}
}
OopStorage::EntryStatus OopStorage::allocation_status(const oop* ptr) const {
return allocation_status_validating_block(find_block_or_null(ptr), ptr);
}
size_t OopStorage::allocation_count() const {
return _allocation_count;
}
size_t OopStorage::block_count() const {
return _block_count;
}
size_t OopStorage::empty_block_count() const {
return _empty_block_count;
}
size_t OopStorage::total_memory_usage() const {
size_t total_size = sizeof(OopStorage);
total_size += strlen(name()) + 1;
total_size += block_count() * Block::allocation_size();
return total_size;
}
// Parallel iteration support
#if INCLUDE_ALL_GCS
static char* not_started_marker_dummy = NULL;
static void* const not_started_marker = &not_started_marker_dummy;
OopStorage::BasicParState::BasicParState(OopStorage* storage, bool concurrent) :
_storage(storage),
_next_block(not_started_marker),
_concurrent(concurrent)
{
update_iteration_state(true);
}
OopStorage::BasicParState::~BasicParState() {
update_iteration_state(false);
}
void OopStorage::BasicParState::update_iteration_state(bool value) {
if (_concurrent) {
MutexLockerEx ml(_storage->_active_mutex, Mutex::_no_safepoint_check_flag);
assert(_storage->_concurrent_iteration_active != value, "precondition");
_storage->_concurrent_iteration_active = value;
}
}
void OopStorage::BasicParState::ensure_iteration_started() {
if (!_concurrent) assert_at_safepoint();
assert(!_concurrent || _storage->_concurrent_iteration_active, "invariant");
// Ensure _next_block is not the not_started_marker, setting it to
// the _active_head to start the iteration if necessary.
if (OrderAccess::load_acquire(&_next_block) == not_started_marker) {
Atomic::cmpxchg(_storage->_active_head, &_next_block, not_started_marker);
}
assert(_next_block != not_started_marker, "postcondition");
}
OopStorage::Block* OopStorage::BasicParState::claim_next_block() {
assert(_next_block != not_started_marker, "Iteration not started");
void* next = _next_block;
while (next != NULL) {
void* new_next = _storage->_active_list.next(*static_cast<Block*>(next));
void* fetched = Atomic::cmpxchg(new_next, &_next_block, next);
if (fetched == next) break; // Claimed.
next = fetched;
}
return static_cast<Block*>(next);
}
#endif // INCLUDE_ALL_GCS
const char* OopStorage::name() const { return _name; }
#ifndef PRODUCT
void OopStorage::print_on(outputStream* st) const {
size_t allocations = _allocation_count;
size_t blocks = _block_count;
size_t empties = _empty_block_count;
// Comparison is being careful about racy accesses.
size_t used = (blocks < empties) ? 0 : (blocks - empties);
double data_size = section_size * section_count;
double alloc_percentage = percent_of((double)allocations, used * data_size);
st->print("%s: " SIZE_FORMAT " entries in " SIZE_FORMAT " blocks (%.F%%), "
SIZE_FORMAT " empties, " SIZE_FORMAT " bytes",
name(), allocations, used, alloc_percentage,
empties, total_memory_usage());
if (_concurrent_iteration_active) {
st->print(", concurrent iteration active");
}
}
#endif // !PRODUCT