jdk-sandbox: comparison src/hotspot/share/gc/shared/oopStorage.cpp

equal deleted inserted replaced

-:13588c901957
+:9cf78a70fa4f
 #include "runtime/handles.inline.hpp"
 #include "runtime/interfaceSupport.inline.hpp"
 #include "runtime/mutex.hpp"
 #include "runtime/mutexLocker.hpp"
 #include "runtime/orderAccess.hpp"
+#include "runtime/os.hpp"
 #include "runtime/safepoint.hpp"
 #include "runtime/stubRoutines.hpp"
 #include "runtime/thread.hpp"
 #include "utilities/align.hpp"
 #include "utilities/count_trailing_zeros.hpp"
 const unsigned block_alignment = sizeof(oop) * section_size;
 OopStorage::Block::Block(const OopStorage* owner, void* memory) :
 _data(),
 _allocated_bitmask(0),
-_owner(owner),
+_owner_address(reinterpret_cast<intptr_t>(owner)),
 _memory(memory),
 _active_index(0),
 _allocation_list_entry(),
 _deferred_updates_next(NULL),
 _release_refcount(0)
 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;
-const_cast<OopStorage* volatile&>(_owner) = NULL;
+const_cast<intptr_t volatile&>(_owner_address) = 0;
 }
 size_t OopStorage::Block::allocation_size() {
 // _data must be first member, so aligning Block aligns _data.
 STATIC_ASSERT(_data_pos == 0);
 // 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
+if (SafeFetchN(&candidate->_owner_address, 0) == owner_addr) {
-= reinterpret_cast<intptr_t*>(&candidate->_owner);
-if (SafeFetchN(candidate_owner_addr, 0) == owner_addr) {
 return candidate;
 }
 }
 return NULL;
 }
 // is empty, for ease of empty block deletion processing.
 oop* OopStorage::allocate() {
 MutexLocker ml(_allocation_mutex, Mutex::_no_safepoint_check_flag);
-// Note: Without this we might never perform cleanup.  As it is,
-// cleanup is only requested here, when completing a concurrent
-// iteration, or when someone entirely else wakes up the service
-// thread, which isn't ideal.  But we can't notify in release().
-if (reduce_deferred_updates()) {
-notify_needs_cleanup();
-}
 Block* block = block_for_allocation();
 if (block == NULL) return NULL; // Block allocation failed.
 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));
+log_trace(oopstorage, blocks)("%s: block not empty " PTR_FORMAT, name(), p2i(block));
 }
 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));
+log_trace(oopstorage, blocks)("%s: block full " PTR_FORMAT, name(), p2i(block));
 _allocation_list.unlink(*block);
 }
 log_trace(oopstorage, ref)("%s: allocated " PTR_FORMAT, name(), p2i(result));
 return result;
 }
 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()) {
-MutexUnlocker ul(_allocation_mutex, Mutex::_no_safepoint_check_flag);
+// Might have added a block to the _allocation_list, so retry.
-notify_needs_cleanup();
 } else if (try_add_block()) {
-block = _allocation_list.head();
+// Successfully added a new block to the list, so retry.
-assert(block != NULL, "invariant");
+assert(_allocation_list.chead() != NULL, "invariant");
-return block;
+} else if (_allocation_list.chead() != NULL) {
-} else if (reduce_deferred_updates()) { // Once more before failure.
+// Trying to add a block failed, but some other thread added to the
-MutexUnlocker ul(_allocation_mutex, Mutex::_no_safepoint_check_flag);
+// list while we'd dropped the lock over the new block allocation.
-notify_needs_cleanup();
+} else if (!reduce_deferred_updates()) { // Once more before failure.
-} else {
 // 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());
+log_info(oopstorage, blocks)("%s: failed block allocation", name());
 return NULL;
 }
 }
 }
 static void log_release_transitions(uintx releasing,
 uintx old_allocated,
 const OopStorage* owner,
 const void* block) {
-Log(oopstorage, blocks) log;
+LogTarget(Trace, oopstorage, blocks) lt;
-LogStream ls(log.debug());
+if (lt.is_enabled()) {
-if (is_full_bitmask(old_allocated)) {
+LogStream ls(lt);
-ls.print_cr("%s: block not full " PTR_FORMAT, owner->name(), p2i(block));
+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));
+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");
 // 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);
-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.
 _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.
 }
-owner->record_needs_cleanup();
+// Only request cleanup for to-empty transitions, not for from-full.
-log_debug(oopstorage, blocks)("%s: deferred update " PTR_FORMAT,
+// There isn't any rush to process from-full transitions.  Allocation
-_owner->name(), p2i(this));
+// 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_trace(oopstorage, blocks)("%s: deferred update " PTR_FORMAT,
+owner->name(), p2i(this));
 }
 }
 // Release hold on empty block deletion.
 Atomic::dec(&_release_refcount);
 }
 // Move empty block to end of list, for possible deletion.
 if (is_empty_bitmask(allocated)) {
 _allocation_list.unlink(*block);
 _allocation_list.push_back(*block);
-notify_needs_cleanup();
+}
-}
+log_trace(oopstorage, blocks)("%s: processed deferred update " PTR_FORMAT,
-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) {
 block->release_entries(releasing, this);
 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;
-}
-// Possible values for OopStorage::_needs_cleanup.
-const uint needs_cleanup_none = 0;     // No cleanup needed.
-const uint needs_cleanup_marked = 1;   // Requested, but no notification made.
-const uint needs_cleanup_notified = 2; // Requested and Service thread notified.
 const size_t initial_active_array_size = 8;
 OopStorage::OopStorage(const char* name,
 Mutex* allocation_mutex,
 Mutex* active_mutex) :
-_name(dup_name(name)),
+_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(needs_cleanup_none)
+_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(),
 for (size_t i = _active_array->block_count(); 0 < i; ) {
 block = _active_array->at(--i);
 Block::delete_block(*block);
 }
 ActiveArray::destroy(_active_array);
-FREE_C_HEAP_ARRAY(char, _name);
+os::free(const_cast<char*>(_name));
 }
-// Called by service thread to check for pending work.
+// Managing service thread notifications.
-bool OopStorage::needs_delete_empty_blocks() const {
+//
-return Atomic::load(&_needs_cleanup) != needs_cleanup_none;
+// 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() {
-Atomic::cmpxchg(needs_cleanup_marked, &_needs_cleanup, needs_cleanup_none);
+// 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);
-// Record that cleanup is needed, and notify the Service thread.
+OrderAccess::release_store_fence(&needs_cleanup_requested, true);
-void OopStorage::notify_needs_cleanup() {
-// Avoid re-notification if already notified.
-const uint notified = needs_cleanup_notified;
-if (Atomic::xchg(notified, &_needs_cleanup) != notified) {
-MonitorLocker ml(Service_lock, Monitor::_no_safepoint_check_flag);
-ml.notify_all();
-}
 }
 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.
-Atomic::store(needs_cleanup_none, &_needs_cleanup);
+OrderAccess::release_store_fence(&_needs_cleanup, false);
-OrderAccess::fence();
 // 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.
-size_t limit = block_count();
+// We add a bit of slop because the reduce_deferred_updates clause
-if (limit == 0) return false; // Empty storage; nothing at all to do.
+// 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.
 OopStorage::BasicParState::~BasicParState() {
 _storage->relinquish_block_array(_active_array);
 update_concurrent_iteration_count(-1);
 if (_concurrent) {
-// We may have deferred some work.
+// We may have deferred some cleanup work.
-const_cast<OopStorage*>(_storage)->notify_needs_cleanup();
+const_cast<OopStorage*>(_storage)->record_needs_cleanup();
 }
 }
 void OopStorage::BasicParState::update_concurrent_iteration_count(int value) {
 if (_concurrent) {

branch	datagramsocketimpl-branch
changeset 58678	9cf78a70fa4f
parent 54663	f03d5a093093
child 58679	9c3209ff7550