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8196083: Avoid locking in OopStorage::release

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Defer release list updates to later allocate/delete operations.

Reviewed-by: coleenp, eosterlund
This commit is contained in:
Kim Barrett 2018-02-08 17:23:43 -05:00
parent 789e827f1a
commit a25a95120e
5 changed files with 311 additions and 246 deletions
src/hotspot/share
gc/shared
oopStorage.cppoopStorage.hppoopStorage.inline.hpp
runtime
mutexLocker.cpp
test/hotspot/gtest/gc/shared
test_oopStorage.cpp

388
src/hotspot/share/gc/shared/oopStorage.cpp

@ -26,7 +26,9 @@
#include "gc/shared/oopStorage.inline.hpp"
#include "gc/shared/oopStorageParState.inline.hpp"
#include "logging/log.hpp"
#include "logging/logStream.hpp"
#include "memory/allocation.inline.hpp"
#include "memory/resourceArea.hpp"
#include "runtime/atomic.hpp"
#include "runtime/handles.inline.hpp"
#include "runtime/mutex.hpp"
@ -107,7 +109,7 @@ void OopStorage::BlockList::unlink(const Block& block) {
}
// Blocks start with an array of BitsPerWord oop entries. That array
// is divided into conceptual BytesPerWord sections of BitsPerWord
// is divided into conceptual BytesPerWord sections of BitsPerByte
// 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
@ -130,7 +132,9 @@ OopStorage::Block::Block(const OopStorage* owner, void* memory) :
_owner(owner),
_memory(memory),
_active_entry(),
_allocate_entry()
_allocate_entry(),
_deferred_updates_next(NULL),
_release_refcount(0)
{
STATIC_ASSERT(_data_pos == 0);
STATIC_ASSERT(section_size * section_count == ARRAY_SIZE(_data));
@ -143,6 +147,8 @@ OopStorage::Block::Block(const OopStorage* owner, void* memory) :
#endif
OopStorage::Block::~Block() {
assert(_release_refcount == 0, "deleting block while releasing");
assert(_deferred_updates_next == NULL, "deleting block with deferred update");
// 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;
@ -182,8 +188,24 @@ 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);
// A block is deletable if
// (1) It is empty.
// (2) There is not a release() operation currently operating on it.
// (3) It is not in the deferred updates list.
// The order of tests is important for proper interaction between release()
// and concurrent deletion.
bool OopStorage::Block::is_deletable() const {
return (OrderAccess::load_acquire(&_allocated_bitmask) == 0) &&
(OrderAccess::load_acquire(&_release_refcount) == 0) &&
(OrderAccess::load_acquire(&_deferred_updates_next) == NULL);
}
OopStorage::Block* OopStorage::Block::deferred_updates_next() const {
return _deferred_updates_next;
}
void OopStorage::Block::set_deferred_updates_next(Block* block) {
_deferred_updates_next = block;
}
bool OopStorage::Block::contains(const oop* ptr) const {
@ -203,7 +225,7 @@ oop* OopStorage::Block::allocate() {
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);
uintx fetched = Atomic::cmpxchg(new_value, &_allocated_bitmask, allocated);
if (fetched == allocated) {
return get_pointer(index); // CAS succeeded; return entry for index.
}
@ -261,20 +283,6 @@ OopStorage::Block::block_for_ptr(const OopStorage* owner, const oop* ptr) {
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");
@ -291,39 +299,49 @@ void OopStorage::assert_at_safepoint() {
// 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(), and delete_empty_blocks_concurrent() 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.
// loops. This prevents loss of updates even though release() performs
// its 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.
// allocations until some entries in it are released.
//
// 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:
// release() is performed lock-free. release() first looks up the block for
// the entry, using address alignment to find the enclosing block (thereby
// avoiding iteration over the _active_list). 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.
// (b) Otherwise, the _allocate_list also needs to be modified. This requires
// locking the _allocate_mutex. To keep the release() operation lock-free,
// rather than updating the _allocate_list itself, it instead performs a
// lock-free push of the block onto the _deferred_updates list. Entries on
// that list are processed by allocate() and delete_empty_blocks_XXX(), while
// they already hold the necessary lock. That processing makes the block's
// list state consistent with its current _allocated_bitmask. The block is
// added to the _allocate_list if not already present and the bitmask is not
// full. The block is moved to the end of the _allocated_list if the bitmask
// is empty, for ease of empty block deletion processing.
oop* OopStorage::allocate() {
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
// Do some deferred update processing every time we allocate.
// Continue processing deferred updates if _allocate_list is empty,
// in the hope that we'll get a block from that, rather than
// allocating a new block.
while (reduce_deferred_updates() && (_allocate_list.head() == NULL)) {}
// Use the first block in _allocate_list for the allocation.
Block* block = _allocate_list.head();
if (block == NULL) {
// No available blocks; make a new one, and add to storage.
@ -331,7 +349,17 @@ oop* OopStorage::allocate() {
MutexUnlockerEx mul(_allocate_mutex, Mutex::_no_safepoint_check_flag);
block = Block::new_block(this);
}
if (block != NULL) {
if (block == NULL) {
while (_allocate_list.head() == NULL) {
if (!reduce_deferred_updates()) {
// Failed to make new block, no other thread made a block
// available while the mutex was released, and didn't get
// one from a deferred update either, so return failure.
log_info(oopstorage, ref)("%s: failed allocation", name());
return NULL;
}
}
} else {
// Add new block to storage.
log_info(oopstorage, blocks)("%s: new block " PTR_FORMAT, name(), p2i(block));
@ -340,22 +368,14 @@ oop* OopStorage::allocate() {
// 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");
@ -363,7 +383,6 @@ oop* OopStorage::allocate() {
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");
@ -384,72 +403,115 @@ OopStorage::Block* OopStorage::find_block_or_null(const oop* ptr) const {
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();
static void log_release_transitions(uintx releasing,
uintx old_allocated,
const OopStorage* owner,
const void* block) {
ResourceMark rm;
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, Block* volatile* deferred_list) {
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 == (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.
}
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 _allocate_list. This deferral avoids 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 = *deferred_list;
while (true) {
_deferred_updates_next = (head == NULL) ? this : head;
Block* fetched = Atomic::cmpxchg(this, deferred_list, head);
if (fetched == head) break; // Successful update.
head = fetched; // Retry with updated head.
}
log_debug(oopstorage, blocks)("%s: deferred update " PTR_FORMAT,
_owner->name(), p2i(this));
}
// CAS failed; retry with latest value.
allocated = fetched;
}
// Release hold on empty block deletion.
Atomic::dec(&_release_refcount);
}
#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();
// Process one available deferred update. Returns true if one was processed.
bool OopStorage::reduce_deferred_updates() {
assert_locked_or_safepoint(_allocate_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::storeload();
// Process popped block.
uintx allocated = block->allocated_bitmask();
// Make membership in list consistent with bitmask state.
if ((_allocate_list.ctail() != NULL) &&
((_allocate_list.ctail() == block) ||
(_allocate_list.next(*block) != NULL))) {
// Block is in the allocate list.
assert(!is_full_bitmask(allocated), "invariant");
} else if (!is_full_bitmask(allocated)) {
// Block is not in the allocate list, but now should be.
_allocate_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)) {
_allocate_list.unlink(*block);
_allocate_list.push_back(*block);
}
log_debug(oopstorage, blocks)("%s: processed deferred update " PTR_FORMAT,
name(), p2i(block));
return true; // Processed one pending update.
}
#endif // ASSERT
inline void check_release_entry(const oop* entry) {
assert(entry != NULL, "Releasing NULL");
@ -459,9 +521,9 @@ inline void check_release_entry(const oop* entry) {
void OopStorage::release(const oop* ptr) {
check_release_entry(ptr);
Block* block = find_block_or_null(ptr);
check_release(block, ptr);
assert(block != NULL, "%s: invalid release " PTR_FORMAT, name(), p2i(ptr));
log_info(oopstorage, ref)("%s: released " PTR_FORMAT, name(), p2i(ptr));
release_from_block(*block, block->bitmask_for_entry(ptr));
block->release_entries(block->bitmask_for_entry(ptr), &_deferred_updates);
Atomic::dec(&_allocation_count);
}
@ -470,15 +532,15 @@ void OopStorage::release(const oop* const* ptrs, size_t size) {
while (i < size) {
check_release_entry(ptrs[i]);
Block* block = find_block_or_null(ptrs[i]);
check_release(block, ptrs[i]);
assert(block != NULL, "%s: invalid release " PTR_FORMAT, name(), p2i(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];
check_release_entry(entry);
// 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);
@ -488,7 +550,7 @@ void OopStorage::release(const oop* const* ptrs, size_t size) {
++count;
}
// Release the contiguous entries that are in block.
release_from_block(*block, releasing);
block->release_entries(releasing, &_deferred_updates);
Atomic::sub(count, &_allocation_count);
}
}
@ -506,11 +568,11 @@ OopStorage::OopStorage(const char* name,
_active_list(&Block::get_active_entry),
_allocate_list(&Block::get_allocate_entry),
_active_head(NULL),
_deferred_updates(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(),
@ -529,6 +591,10 @@ void OopStorage::delete_empty_block(const 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 = _allocate_list.head()) != NULL) {
_allocate_list.unlink(*block);
}
@ -539,43 +605,47 @@ OopStorage::~OopStorage() {
FREE_C_HEAP_ARRAY(char, _name);
}
void OopStorage::delete_empty_blocks_safepoint(size_t retain) {
void OopStorage::delete_empty_blocks_safepoint() {
assert_at_safepoint();
// Process any pending release updates, which may make more empty
// blocks available for deletion.
while (reduce_deferred_updates()) {}
// 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();
// Delete empty (and otherwise deletable) blocks from end of _allocate_list.
for (const Block* block = _allocate_list.ctail();
(block != NULL) && block->is_deletable();
block = _allocate_list.ctail()) {
_active_list.unlink(*block);
_allocate_list.unlink(*block);
delete_empty_block(*block);
--_block_count;
}
// 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) {
void OopStorage::delete_empty_blocks_concurrent() {
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) {
size_t limit = _block_count;
for (size_t i = 0; i < limit; ++i) {
// Additional updates might become available while we dropped the
// lock. But limit number processed to limit lock duration.
reduce_deferred_updates();
const Block* block = _allocate_list.ctail();
assert(block != NULL, "invariant");
assert(block->is_empty(), "invariant");
if ((block == NULL) || !block->is_deletable()) {
// No block to delete, so done. There could be more pending
// deferred updates that could give us more work to do; deal with
// that in some later call, to limit lock duration here.
return;
}
{
MutexLockerEx aml(_active_mutex, Mutex::_no_safepoint_check_flag);
// Don't interfere with a concurrent iteration.
@ -589,28 +659,31 @@ void OopStorage::delete_empty_blocks_concurrent(size_t retain) {
}
// 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);
const Block* block = find_block_or_null(ptr);
if (block != NULL) {
// Verify block is a real block. For now, simple linear search.
// Do something more clever if this is a performance bottleneck.
MutexLockerEx ml(_allocate_mutex, Mutex::_no_safepoint_check_flag);
for (const Block* check_block = _active_list.chead();
check_block != NULL;
check_block = _active_list.next(*check_block)) {
if (check_block == block) {
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 {
@ -621,10 +694,6 @@ 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;
@ -690,17 +759,12 @@ const char* OopStorage::name() const { return _name; }
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);
double alloc_percentage = percent_of((double)allocations, blocks * 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());
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_active) {
st->print(", concurrent iteration active");
}

20
src/hotspot/share/gc/shared/oopStorage.hpp

@ -84,10 +84,6 @@ public:
// The number of blocks of entries. Useful for sizing parallel iteration.
size_t block_count() const;
// The number of blocks with no allocated entries. Useful for sizing
// parallel iteration and scheduling block deletion.
size_t empty_block_count() const;
// Total number of blocks * memory allocation per block, plus
// bookkeeping overhead, including this storage object.
size_t total_memory_usage() const;
@ -107,14 +103,13 @@ public:
// postcondition: *result == NULL.
oop* allocate();
// Deallocates ptr, after setting its value to NULL. Locks _allocate_mutex.
// Deallocates ptr. No locking.
// precondition: ptr is a valid allocated entry.
// precondition: *ptr == NULL.
void release(const oop* ptr);
// Releases all the ptrs. Possibly faster than individual calls to
// release(oop*). Best if ptrs is sorted by address. Locks
// _allocate_mutex.
// release(oop*). Best if ptrs is sorted by address. No locking.
// precondition: All elements of ptrs are valid allocated entries.
// precondition: *ptrs[i] == NULL, for i in [0,size).
void release(const oop* const* ptrs, size_t size);
@ -160,8 +155,8 @@ public:
// Block cleanup functions are for the exclusive use of the GC.
// Both stop deleting if there is an in-progress concurrent iteration.
// Concurrent deletion locks both the allocate_mutex and the active_mutex.
void delete_empty_blocks_safepoint(size_t retain = 1);
void delete_empty_blocks_concurrent(size_t retain = 1);
void delete_empty_blocks_safepoint();
void delete_empty_blocks_concurrent();
// Debugging and logging support.
const char* name() const;
@ -231,6 +226,7 @@ private:
BlockList _active_list;
BlockList _allocate_list;
Block* volatile _active_head;
Block* volatile _deferred_updates;
Mutex* _allocate_mutex;
Mutex* _active_mutex;
@ -238,16 +234,12 @@ private:
// Counts are volatile for racy unlocked accesses.
volatile size_t _allocation_count;
volatile size_t _block_count;
volatile size_t _empty_block_count;
// mutable because this gets set even for const iteration.
mutable bool _concurrent_iteration_active;
Block* find_block_or_null(const oop* ptr) const;
bool is_valid_block_locked_or_safepoint(const Block* block) const;
EntryStatus allocation_status_validating_block(const Block* block, const oop* ptr) const;
void check_release(const Block* block, const oop* ptr) const NOT_DEBUG_RETURN;
void release_from_block(Block& block, uintx release_bitmask);
void delete_empty_block(const Block& block);
bool reduce_deferred_updates();
static void assert_at_safepoint() NOT_DEBUG_RETURN;

9
src/hotspot/share/gc/shared/oopStorage.inline.hpp

@ -44,6 +44,8 @@ class OopStorage::Block /* No base class, to avoid messing up alignment. */ {
void* _memory; // Unaligned storage containing block.
BlockEntry _active_entry;
BlockEntry _allocate_entry;
Block* volatile _deferred_updates_next;
volatile uintx _release_refcount;
Block(const OopStorage* owner, void* memory);
~Block();
@ -75,7 +77,10 @@ public:
bool is_full() const;
bool is_empty() const;
uintx allocated_bitmask() const;
uintx cmpxchg_allocated_bitmask(uintx new_value, uintx compare_value);
bool is_deletable() const;
Block* deferred_updates_next() const;
void set_deferred_updates_next(Block* new_next);
bool contains(const oop* ptr) const;
@ -86,6 +91,8 @@ public:
static Block* new_block(const OopStorage* owner);
static void delete_block(const Block& block);
void release_entries(uintx releasing, Block* volatile* deferred_list);
template<typename F> bool iterate(F f);
template<typename F> bool iterate(F f) const;
}; // class Block

8
src/hotspot/share/runtime/mutexLocker.cpp

@ -253,10 +253,10 @@ void mutex_init() {
// of some places which hold other locks while releasing a handle, including
// the Patching_lock, which is of "special" rank. As a temporary workaround,
// lower the JNI oopstorage lock ranks to make them super-special.
def(JNIGlobalAlloc_lock , PaddedMutex , special-1, true, Monitor::_safepoint_check_never);
def(JNIGlobalActive_lock , PaddedMutex , special-2, true, Monitor::_safepoint_check_never);
def(JNIWeakAlloc_lock , PaddedMutex , special-1, true, Monitor::_safepoint_check_never);
def(JNIWeakActive_lock , PaddedMutex , special-2, true, Monitor::_safepoint_check_never);
def(JNIGlobalAlloc_lock , PaddedMutex , nonleaf, true, Monitor::_safepoint_check_never);
def(JNIGlobalActive_lock , PaddedMutex , nonleaf-1, true, Monitor::_safepoint_check_never);
def(JNIWeakAlloc_lock , PaddedMutex , nonleaf, true, Monitor::_safepoint_check_never);
def(JNIWeakActive_lock , PaddedMutex , nonleaf-1, true, Monitor::_safepoint_check_never);
def(JNICritical_lock , PaddedMonitor, nonleaf, true, Monitor::_safepoint_check_always); // used for JNI critical regions
def(AdapterHandlerLibrary_lock , PaddedMutex , nonleaf, true, Monitor::_safepoint_check_always);

132
test/hotspot/gtest/gc/shared/test_oopStorage.cpp

@ -70,6 +70,10 @@ public:
return storage._allocate_mutex;
}
static bool reduce_deferred_updates(OopStorage& storage) {
return storage.reduce_deferred_updates();
}
static bool block_is_empty(const Block& block) {
return block.is_empty();
}
@ -127,9 +131,31 @@ static bool is_list_empty(const TestAccess::BlockList& list) {
return list.chead() == NULL;
}
static void release_entry(OopStorage& storage, oop* entry) {
static bool process_deferred_updates(OopStorage& storage) {
MutexLockerEx ml(TestAccess::allocate_mutex(storage), Mutex::_no_safepoint_check_flag);
bool result = false;
while (TestAccess::reduce_deferred_updates(storage)) {
result = true;
}
return result;
}
static void release_entry(OopStorage& storage, oop* entry, bool process_deferred = true) {
*entry = NULL;
storage.release(entry);
if (process_deferred) {
process_deferred_updates(storage);
}
}
static size_t empty_block_count(const OopStorage& storage) {
const TestAccess::BlockList& list = TestAccess::allocate_list(storage);
size_t count = 0;
for (const OopBlock* block = list.ctail();
(block != NULL) && block->is_empty();
++count, block = list.prev(*block))
{}
return count;
}
class OopStorageTest : public ::testing::Test {
@ -188,31 +214,22 @@ const size_t OopStorageTestWithAllocation::_max_entries;
class OopStorageTestWithAllocation::VM_DeleteBlocksAtSafepoint
: public VM_GTestExecuteAtSafepoint {
public:
VM_DeleteBlocksAtSafepoint(OopStorage* storage, size_t retain) :
_storage(storage), _retain(retain)
{}
VM_DeleteBlocksAtSafepoint(OopStorage* storage) : _storage(storage) {}
void doit() {
_storage->delete_empty_blocks_safepoint(_retain);
_storage->delete_empty_blocks_safepoint();
}
private:
OopStorage* _storage;
size_t _retain;
};
static bool is_allocate_list_sorted(const OopStorage& storage) {
// The allocate_list isn't strictly sorted. Rather, all empty
// blocks are segregated to the end of the list. And the number of
// empty blocks should match empty_block_count().
size_t expected_empty = storage.empty_block_count();
// blocks are segregated to the end of the list.
const TestAccess::BlockList& list = TestAccess::allocate_list(storage);
const OopBlock* block = list.ctail();
for (size_t i = 0; i < expected_empty; ++i, block = list.prev(*block)) {
if ((block == NULL) || !block->is_empty()) {
return false;
}
}
for ( ; (block != NULL) && block->is_empty(); block = list.prev(*block)) {}
for ( ; block != NULL; block = list.prev(*block)) {
if (block->is_empty()) {
return false;
@ -243,7 +260,7 @@ TEST_VM_F(OopStorageTest, allocate_one) {
EXPECT_EQ(1u, _storage.block_count());
EXPECT_EQ(1u, list_length(TestAccess::allocate_list(_storage)));
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
const OopBlock* block = TestAccess::allocate_list(_storage).chead();
EXPECT_NE(block, (OopBlock*)NULL);
@ -259,7 +276,7 @@ TEST_VM_F(OopStorageTest, allocate_one) {
EXPECT_EQ(1u, _storage.block_count());
EXPECT_EQ(1u, list_length(TestAccess::allocate_list(_storage)));
EXPECT_EQ(1u, _storage.empty_block_count());
EXPECT_EQ(1u, empty_block_count(_storage));
const OopBlock* new_block = TestAccess::allocate_list(_storage).chead();
EXPECT_EQ(block, new_block);
@ -322,14 +339,14 @@ TEST_VM_F(OopStorageTest, allocate_many) {
TestAccess::BlockList& active_list = TestAccess::active_list(_storage);
TestAccess::BlockList& allocate_list = TestAccess::allocate_list(_storage);
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
entries[0] = _storage.allocate();
ASSERT_TRUE(entries[0] != NULL);
EXPECT_EQ(1u, list_length(active_list));
EXPECT_EQ(1u, _storage.block_count());
EXPECT_EQ(1u, list_length(allocate_list));
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
const OopBlock* block = active_list.chead();
EXPECT_EQ(1u, TestAccess::block_allocation_count(*block));
@ -339,7 +356,7 @@ TEST_VM_F(OopStorageTest, allocate_many) {
entries[i] = _storage.allocate();
EXPECT_EQ(i + 1, _storage.allocation_count());
ASSERT_TRUE(entries[i] != NULL);
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
if (block == NULL) {
ASSERT_FALSE(is_list_empty(allocate_list));
@ -374,7 +391,7 @@ TEST_VM_F(OopStorageTest, allocate_many) {
EXPECT_EQ(list_length(active_list), list_length(allocate_list));
EXPECT_EQ(list_length(active_list), _storage.block_count());
EXPECT_EQ(list_length(active_list), _storage.empty_block_count());
EXPECT_EQ(list_length(active_list), empty_block_count(_storage));
for (const OopBlock* block = allocate_list.chead();
block != NULL;
block = allocate_list.next(*block)) {
@ -386,7 +403,7 @@ TEST_VM_F(OopStorageTestWithAllocation, random_release) {
static const size_t step = 11;
ASSERT_NE(0u, _max_entries % step); // max_entries and step are mutually prime
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
TestAccess::BlockList& active_list = TestAccess::active_list(_storage);
TestAccess::BlockList& allocate_list = TestAccess::allocate_list(_storage);
@ -409,7 +426,7 @@ TEST_VM_F(OopStorageTestWithAllocation, random_release) {
EXPECT_EQ(list_length(active_list), list_length(allocate_list));
EXPECT_EQ(list_length(active_list), _storage.block_count());
EXPECT_EQ(0u, total_allocation_count(active_list));
EXPECT_EQ(list_length(allocate_list), _storage.empty_block_count());
EXPECT_EQ(list_length(allocate_list), empty_block_count(_storage));
}
TEST_VM_F(OopStorageTestWithAllocation, random_allocate_release) {
@ -417,7 +434,7 @@ TEST_VM_F(OopStorageTestWithAllocation, random_allocate_release) {
static const size_t allocate_step = 5;
ASSERT_NE(0u, _max_entries % release_step); // max_entries and step are mutually prime
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
TestAccess::BlockList& active_list = TestAccess::active_list(_storage);
TestAccess::BlockList& allocate_list = TestAccess::allocate_list(_storage);
@ -449,7 +466,7 @@ TEST_VM_F(OopStorageTestWithAllocation, random_allocate_release) {
EXPECT_EQ(list_length(active_list), list_length(allocate_list));
EXPECT_EQ(list_length(active_list), _storage.block_count());
EXPECT_EQ(0u, total_allocation_count(active_list));
EXPECT_EQ(list_length(allocate_list), _storage.empty_block_count());
EXPECT_EQ(list_length(allocate_list), empty_block_count(_storage));
}
template<bool sorted>
@ -471,11 +488,12 @@ public:
EXPECT_EQ(_max_entries - nrelease, _storage.allocation_count());
for (size_t i = 0; i < nrelease; ++i) {
release_entry(_storage, _entries[2 * i + 1]);
release_entry(_storage, _entries[2 * i + 1], false);
EXPECT_EQ(_max_entries - nrelease - (i + 1), _storage.allocation_count());
}
EXPECT_TRUE(process_deferred_updates(_storage));
EXPECT_EQ(_storage.block_count(), _storage.empty_block_count());
EXPECT_EQ(_storage.block_count(), empty_block_count(_storage));
FREE_C_HEAP_ARRAY(oop*, to_release);
}
@ -607,8 +625,9 @@ TEST_VM_F(OopStorageTest, simple_iterate) {
}
while (allocated > 0) {
release_entry(_storage, entries[--allocated]);
release_entry(_storage, entries[--allocated], false);
}
process_deferred_updates(_storage);
}
class OopStorageTestIteration : public OopStorageTestWithAllocation {
@ -627,16 +646,17 @@ public:
memset(_states, 0, sizeof(_states));
size_t initial_release = 0;
for ( ; _storage.empty_block_count() < 2; ++initial_release) {
for ( ; empty_block_count(_storage) < 2; ++initial_release) {
ASSERT_GT(_max_entries, initial_release);
release_entry(_storage, _entries[initial_release]);
_states[0][initial_release] = mark_released;
}
for (size_t i = initial_release; i < _max_entries; i += 3) {
release_entry(_storage, _entries[i]);
release_entry(_storage, _entries[i], false);
_states[0][i] = mark_released;
}
process_deferred_updates(_storage);
}
class VerifyState;
@ -1006,30 +1026,21 @@ TEST_VM_F(OopStorageTestWithAllocation, delete_empty_blocks_safepoint) {
EXPECT_EQ(initial_active_size, _storage.block_count());
ASSERT_LE(3u, initial_active_size); // Need at least 3 blocks for test
for (size_t i = 0; _storage.empty_block_count() < 3; ++i) {
for (size_t i = 0; empty_block_count(_storage) < 3; ++i) {
ASSERT_GT(_max_entries, i);
release_entry(_storage, _entries[i]);
}
EXPECT_EQ(initial_active_size, list_length(active_list));
EXPECT_EQ(initial_active_size, _storage.block_count());
EXPECT_EQ(3u, _storage.empty_block_count());
EXPECT_EQ(3u, empty_block_count(_storage));
{
ThreadInVMfromNative invm(JavaThread::current());
VM_DeleteBlocksAtSafepoint op(&_storage, 2);
VM_DeleteBlocksAtSafepoint op(&_storage);
VMThread::execute(&op);
}
EXPECT_EQ(2u, _storage.empty_block_count());
EXPECT_EQ(initial_active_size - 1, list_length(active_list));
EXPECT_EQ(initial_active_size - 1, _storage.block_count());
{
ThreadInVMfromNative invm(JavaThread::current());
VM_DeleteBlocksAtSafepoint op(&_storage, 0);
VMThread::execute(&op);
}
EXPECT_EQ(0u, _storage.empty_block_count());
EXPECT_EQ(0u, empty_block_count(_storage));
EXPECT_EQ(initial_active_size - 3, list_length(active_list));
EXPECT_EQ(initial_active_size - 3, _storage.block_count());
}
@ -1041,22 +1052,17 @@ TEST_VM_F(OopStorageTestWithAllocation, delete_empty_blocks_concurrent) {
EXPECT_EQ(initial_active_size, _storage.block_count());
ASSERT_LE(3u, initial_active_size); // Need at least 3 blocks for test
for (size_t i = 0; _storage.empty_block_count() < 3; ++i) {
for (size_t i = 0; empty_block_count(_storage) < 3; ++i) {
ASSERT_GT(_max_entries, i);
release_entry(_storage, _entries[i]);
}
EXPECT_EQ(initial_active_size, list_length(active_list));
EXPECT_EQ(initial_active_size, _storage.block_count());
EXPECT_EQ(3u, _storage.empty_block_count());
EXPECT_EQ(3u, empty_block_count(_storage));
_storage.delete_empty_blocks_concurrent(2);
EXPECT_EQ(2u, _storage.empty_block_count());
EXPECT_EQ(initial_active_size - 1, list_length(active_list));
EXPECT_EQ(initial_active_size - 1, _storage.block_count());
_storage.delete_empty_blocks_concurrent(0);
EXPECT_EQ(0u, _storage.empty_block_count());
_storage.delete_empty_blocks_concurrent();
EXPECT_EQ(0u, empty_block_count(_storage));
EXPECT_EQ(initial_active_size - 3, list_length(active_list));
EXPECT_EQ(initial_active_size - 3, _storage.block_count());
}
@ -1075,13 +1081,14 @@ TEST_VM_F(OopStorageTestWithAllocation, allocation_status) {
for (size_t i = 0; i < _max_entries; ++i) {
if ((_entries[i] != retained) && (_entries[i] != released)) {
release_entry(_storage, _entries[i]);
// Leave deferred release updates to block deletion.
release_entry(_storage, _entries[i], false);
}
}
{
ThreadInVMfromNative invm(JavaThread::current());
VM_DeleteBlocksAtSafepoint op(&_storage, 0);
VM_DeleteBlocksAtSafepoint op(&_storage);
VMThread::execute(&op);
}
EXPECT_EQ(OopStorage::ALLOCATED_ENTRY, _storage.allocation_status(retained));
@ -1121,12 +1128,14 @@ TEST_VM_F(OopStorageTest, usage_info) {
TEST_VM_F(OopStorageTestWithAllocation, print_storage) {
// Release the first 1/2
for (size_t i = 0; i < (_max_entries / 2); ++i) {
release_entry(_storage, _entries[i]);
// Deferred updates don't affect print output.
release_entry(_storage, _entries[i], false);
_entries[i] = NULL;
}
// Release every other remaining
for (size_t i = _max_entries / 2; i < _max_entries; i += 2) {
release_entry(_storage, _entries[i]);
// Deferred updates don't affect print output.
release_entry(_storage, _entries[i], false);
_entries[i] = NULL;
}
@ -1137,24 +1146,17 @@ TEST_VM_F(OopStorageTestWithAllocation, print_storage) {
size_t expected_blocks = (_max_entries + entries_per_block - 1) / entries_per_block;
EXPECT_EQ(expected_blocks, _storage.block_count());
size_t expected_empties = (_max_entries / 2) / entries_per_block;
EXPECT_EQ(expected_empties, _storage.empty_block_count());
size_t expected_used = expected_blocks - expected_empties;
double expected_usage = (100.0 * expected_entries) / (expected_used * entries_per_block);
double expected_usage = (100.0 * expected_entries) / (expected_blocks * entries_per_block);
{
ResourceMark rm;
stringStream expected_st;
expected_st.print("Test Storage: " SIZE_FORMAT
" entries in " SIZE_FORMAT
" blocks (%.F%%), " SIZE_FORMAT
" empties, " SIZE_FORMAT " bytes",
" blocks (%.F%%), " SIZE_FORMAT " bytes",
expected_entries,
expected_used,
expected_blocks,
expected_usage,
expected_empties,
_storage.total_memory_usage());
stringStream st;
_storage.print_on(&st);