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8246476: remove AsyncDeflateIdleMonitors option and the safepoint based deflation mechanism

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Reviewed-by: dholmes, pchilanomate, coleenp
This commit is contained in:
Daniel D. Daugherty 2020-07-13 16:36:01 -04:00
parent 231a8408b2
commit 7436ef236e
14 changed files with 144 additions and 630 deletions

3
src/hotspot/share/runtime/globals.hpp

@ -688,9 +688,6 @@ const size_t minimumSymbolTableSize = 1024;
"Disable the use of stack guard pages if the JVM is loaded " \
"on the primordial process thread") \
\
diagnostic(bool, AsyncDeflateIdleMonitors, true, \
"Deflate idle monitors using the ServiceThread.") \
\
/* notice: the max range value here is max_jint, not max_intx */ \
/* because of overflow issue */ \
diagnostic(intx, AsyncDeflationInterval, 250, \

4
src/hotspot/share/runtime/init.cpp

@ -170,10 +170,8 @@ void exit_globals() {
if (log_is_enabled(Info, monitorinflation)) {
// The ObjectMonitor subsystem uses perf counters so
// do this before perfMemory_exit().
// These other two audit_and_print_stats() calls are done at the
// This other audit_and_print_stats() call is done at the
// Debug level at a safepoint:
// - for safepoint based deflation auditing:
// ObjectSynchronizer::finish_deflate_idle_monitors()
// - for async deflation auditing:
// ObjectSynchronizer::do_safepoint_work()
ObjectSynchronizer::audit_and_print_stats(true /* on_exit */);

37
src/hotspot/share/runtime/objectMonitor.cpp

@ -290,8 +290,6 @@ bool ObjectMonitor::enter(TRAPS) {
JavaThread * jt = (JavaThread *) Self;
assert(!SafepointSynchronize::is_at_safepoint(), "invariant");
assert(jt->thread_state() != _thread_blocked, "invariant");
assert(AsyncDeflateIdleMonitors || this->object() != NULL, "invariant");
assert(AsyncDeflateIdleMonitors || contentions() >= 0, "must not be negative: contentions=%d", contentions());
// Keep track of contention for JVM/TI and M&M queries.
add_to_contentions(1);
@ -455,12 +453,12 @@ void ObjectMonitor::install_displaced_markword_in_object(const oop obj) {
// deflation so we're done here.
return;
}
ADIM_guarantee(l_object == obj, "object=" INTPTR_FORMAT " must equal obj="
INTPTR_FORMAT, p2i(l_object), p2i(obj));
assert(l_object == obj, "object=" INTPTR_FORMAT " must equal obj="
INTPTR_FORMAT, p2i(l_object), p2i(obj));
markWord dmw = header();
// The dmw has to be neutral (not NULL, not locked and not marked).
ADIM_guarantee(dmw.is_neutral(), "must be neutral: dmw=" INTPTR_FORMAT, dmw.value());
assert(dmw.is_neutral(), "must be neutral: dmw=" INTPTR_FORMAT, dmw.value());
// Install displaced mark word if the object's header still points
// to this ObjectMonitor. More than one racing caller to this function
@ -487,22 +485,17 @@ void ObjectMonitor::install_displaced_markword_in_object(const oop obj) {
// used for diagnostic output.
const char* ObjectMonitor::is_busy_to_string(stringStream* ss) {
ss->print("is_busy: waiters=%d, ", _waiters);
if (!AsyncDeflateIdleMonitors) {
if (contentions() > 0) {
ss->print("contentions=%d, ", contentions());
} else {
ss->print("contentions=0");
}
if (_owner != DEFLATER_MARKER) {
ss->print("owner=" INTPTR_FORMAT, p2i(_owner));
} else {
if (contentions() > 0) {
ss->print("contentions=%d, ", contentions());
} else {
ss->print("contentions=0");
}
if (_owner != DEFLATER_MARKER) {
ss->print("owner=" INTPTR_FORMAT, p2i(_owner));
} else {
// We report NULL instead of DEFLATER_MARKER here because is_busy()
// ignores DEFLATER_MARKER values.
ss->print("owner=" INTPTR_FORMAT, NULL);
}
// We report NULL instead of DEFLATER_MARKER here because is_busy()
// ignores DEFLATER_MARKER values.
ss->print("owner=" INTPTR_FORMAT, NULL);
}
ss->print(", cxq=" INTPTR_FORMAT ", EntryList=" INTPTR_FORMAT, p2i(_cxq),
p2i(_EntryList));
@ -524,8 +517,7 @@ void ObjectMonitor::EnterI(TRAPS) {
return;
}
if (AsyncDeflateIdleMonitors &&
try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
if (try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
// Cancelled the in-progress async deflation by changing owner from
// DEFLATER_MARKER to Self. As part of the contended enter protocol,
// contentions was incremented to a positive value before EnterI()
@ -659,8 +651,7 @@ void ObjectMonitor::EnterI(TRAPS) {
if (TryLock(Self) > 0) break;
if (AsyncDeflateIdleMonitors &&
try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
if (try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
// Cancelled the in-progress async deflation by changing owner from
// DEFLATER_MARKER to Self. As part of the contended enter protocol,
// contentions was incremented to a positive value before EnterI()
@ -1007,8 +998,8 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
" is exiting an ObjectMonitor it does not own.", p2i(THREAD));
lsh.print_cr("The imbalance is possibly caused by JNI locking.");
print_debug_style_on(&lsh);
#endif
assert(false, "Non-balanced monitor enter/exit!");
#endif
return;
}
}

29
src/hotspot/share/runtime/objectMonitor.hpp

@ -175,7 +175,7 @@ class ObjectMonitor {
jint _contentions; // Number of active contentions in enter(). It is used by is_busy()
// along with other fields to determine if an ObjectMonitor can be
// deflated. It is also used by the async deflation protocol. See
// ObjectSynchronizer::deflate_monitor() and deflate_monitor_using_JT().
// ObjectSynchronizer::deflate_monitor_using_JT().
protected:
ObjectWaiter* volatile _WaitSet; // LL of threads wait()ing on the monitor
volatile jint _waiters; // number of waiting threads
@ -243,15 +243,11 @@ class ObjectMonitor {
intptr_t is_busy() const {
// TODO-FIXME: assert _owner == null implies _recursions = 0
intptr_t ret_code = _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
if (!AsyncDeflateIdleMonitors) {
ret_code |= contentions() | intptr_t(_owner);
} else {
if (contentions() > 0) {
ret_code |= contentions();
}
if (_owner != DEFLATER_MARKER) {
ret_code |= intptr_t(_owner);
}
if (contentions() > 0) {
ret_code |= contentions();
}
if (_owner != DEFLATER_MARKER) {
ret_code |= intptr_t(_owner);
}
return ret_code;
}
@ -315,9 +311,9 @@ class ObjectMonitor {
// _recursions == 0 _WaitSet == NULL
#ifdef ASSERT
stringStream ss;
#endif
assert((is_busy() | _recursions) == 0, "freeing in-use monitor: %s, "
"recursions=" INTX_FORMAT, is_busy_to_string(&ss), _recursions);
#endif
_succ = NULL;
_EntryList = NULL;
_cxq = NULL;
@ -374,15 +370,4 @@ class ObjectMonitor {
void install_displaced_markword_in_object(const oop obj);
};
// Macro to use guarantee() for more strict AsyncDeflateIdleMonitors
// checks and assert() otherwise.
#define ADIM_guarantee(p, ...) \
do { \
if (AsyncDeflateIdleMonitors) { \
guarantee(p, __VA_ARGS__); \
} else { \
assert(p, __VA_ARGS__); \
} \
} while (0)
#endif // SHARE_RUNTIME_OBJECTMONITOR_HPP

48
src/hotspot/share/runtime/objectMonitor.inline.hpp

@ -67,7 +67,7 @@ inline bool ObjectMonitor::owner_is_DEFLATER_MARKER() {
// Returns true if 'this' is being async deflated and false otherwise.
inline bool ObjectMonitor::is_being_async_deflated() {
return AsyncDeflateIdleMonitors && contentions() < 0;
return contentions() < 0;
}
inline void ObjectMonitor::clear() {
@ -80,17 +80,15 @@ inline void ObjectMonitor::clear() {
}
inline void ObjectMonitor::clear_common() {
if (AsyncDeflateIdleMonitors) {
// Async deflation protocol uses the header, owner and contentions
// fields. While the ObjectMonitor being deflated is on the global
// free list, we leave those three fields alone; contentions < 0
// will force any racing threads to retry. The header field is used
// by install_displaced_markword_in_object() to restore the object's
// header so we cannot check its value here.
guarantee(_owner == NULL || _owner == DEFLATER_MARKER,
"must be NULL or DEFLATER_MARKER: owner=" INTPTR_FORMAT,
p2i(_owner));
}
// Async deflation protocol uses the header, owner and contentions
// fields. While the ObjectMonitor being deflated is on the global
// free list, we leave those three fields alone; contentions < 0
// will force any racing threads to retry. The header field is used
// by install_displaced_markword_in_object() to restore the object's
// header so we cannot check its value here.
guarantee(_owner == NULL || _owner == DEFLATER_MARKER,
"must be NULL or DEFLATER_MARKER: owner=" INTPTR_FORMAT,
p2i(_owner));
assert(contentions() <= 0, "must not be positive: contentions=%d", contentions());
assert(_waiters == 0, "must be 0: waiters=%d", _waiters);
assert(_recursions == 0, "must be 0: recursions=" INTX_FORMAT, _recursions);
@ -124,9 +122,11 @@ inline void ObjectMonitor::add_to_contentions(jint value) {
// Clear _owner field; current value must match old_value.
inline void ObjectMonitor::release_clear_owner(void* old_value) {
#ifdef ASSERT
void* prev = Atomic::load(&_owner);
ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
assert(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
#endif
Atomic::release_store(&_owner, (void*)NULL);
log_trace(monitorinflation, owner)("release_clear_owner(): mid="
INTPTR_FORMAT ", old_value=" INTPTR_FORMAT,
@ -136,9 +136,11 @@ inline void ObjectMonitor::release_clear_owner(void* old_value) {
// Simply set _owner field to new_value; current value must match old_value.
// (Simple means no memory sync needed.)
inline void ObjectMonitor::set_owner_from(void* old_value, void* new_value) {
#ifdef ASSERT
void* prev = Atomic::load(&_owner);
ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
assert(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
#endif
Atomic::store(&_owner, new_value);
log_trace(monitorinflation, owner)("set_owner_from(): mid="
INTPTR_FORMAT ", old_value=" INTPTR_FORMAT
@ -150,10 +152,10 @@ inline void ObjectMonitor::set_owner_from(void* old_value, void* new_value) {
// (Simple means no memory sync needed.)
inline void ObjectMonitor::set_owner_from(void* old_value1, void* old_value2, void* new_value) {
void* prev = Atomic::load(&_owner);
ADIM_guarantee(prev == old_value1 || prev == old_value2,
"unexpected prev owner=" INTPTR_FORMAT ", expected1="
INTPTR_FORMAT " or expected2=" INTPTR_FORMAT, p2i(prev),
p2i(old_value1), p2i(old_value2));
assert(prev == old_value1 || prev == old_value2,
"unexpected prev owner=" INTPTR_FORMAT ", expected1="
INTPTR_FORMAT " or expected2=" INTPTR_FORMAT, p2i(prev),
p2i(old_value1), p2i(old_value2));
_owner = new_value;
log_trace(monitorinflation, owner)("set_owner_from(old1=" INTPTR_FORMAT
", old2=" INTPTR_FORMAT "): mid="
@ -165,9 +167,11 @@ inline void ObjectMonitor::set_owner_from(void* old_value1, void* old_value2, vo
// Simply set _owner field to self; current value must match basic_lock_p.
inline void ObjectMonitor::set_owner_from_BasicLock(void* basic_lock_p, Thread* self) {
#ifdef ASSERT
void* prev = Atomic::load(&_owner);
ADIM_guarantee(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(basic_lock_p));
assert(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
", expected=" INTPTR_FORMAT, p2i(prev), p2i(basic_lock_p));
#endif
// Non-null owner field to non-null owner field is safe without
// cmpxchg() as long as all readers can tolerate either flavor.
Atomic::store(&_owner, self);

51
src/hotspot/share/runtime/safepoint.cpp

@ -490,9 +490,6 @@ void SafepointSynchronize::end() {
}
bool SafepointSynchronize::is_cleanup_needed() {
// Need a cleanup safepoint if there are too many monitors in use
// and the monitor deflation needs to be done at a safepoint.
if (ObjectSynchronizer::is_safepoint_deflation_needed()) return true;
// Need a safepoint if some inline cache buffers is non-empty
if (!InlineCacheBuffer::is_empty()) return true;
if (StringTable::needs_rehashing()) return true;
@ -500,51 +497,24 @@ bool SafepointSynchronize::is_cleanup_needed() {
return false;
}
class ParallelSPCleanupThreadClosure : public ThreadClosure {
private:
DeflateMonitorCounters* _counters;
public:
ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
_counters(counters) {}
void do_thread(Thread* thread) {
// deflate_thread_local_monitors() handles or requests deflation of
// this thread's idle monitors. If !AsyncDeflateIdleMonitors or if
// there is a special cleanup request, deflation is handled now.
// Otherwise, async deflation is requested via a flag.
ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
}
};
class ParallelSPCleanupTask : public AbstractGangTask {
private:
SubTasksDone _subtasks;
ParallelSPCleanupThreadClosure _cleanup_threads_cl;
uint _num_workers;
DeflateMonitorCounters* _counters;
public:
ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
ParallelSPCleanupTask(uint num_workers) :
AbstractGangTask("Parallel Safepoint Cleanup"),
_subtasks(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS),
_cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
_num_workers(num_workers),
_counters(counters) {}
_num_workers(num_workers) {}
void work(uint worker_id) {
uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
// All threads deflate monitors and mark nmethods (if necessary).
Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
const char* name = "deflating global idle monitors";
const char* name = "deflating idle monitors";
EventSafepointCleanupTask event;
TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
// AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
// when a special cleanup has been requested.
// Note: This logging output will include global idle monitor
// elapsed times, but not global idle monitor deflation count.
ObjectSynchronizer::do_safepoint_work(_counters);
ObjectSynchronizer::do_safepoint_work();
post_safepoint_cleanup_task_event(event, safepoint_id, name);
}
@ -615,23 +585,17 @@ void SafepointSynchronize::do_cleanup_tasks() {
TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
// Prepare for monitor deflation.
DeflateMonitorCounters deflate_counters;
ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
CollectedHeap* heap = Universe::heap();
assert(heap != NULL, "heap not initialized yet?");
WorkGang* cleanup_workers = heap->get_safepoint_workers();
if (cleanup_workers != NULL) {
// Parallel cleanup using GC provided thread pool.
uint num_cleanup_workers = cleanup_workers->active_workers();
ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
StrongRootsScope srs(num_cleanup_workers);
ParallelSPCleanupTask cleanup(num_cleanup_workers);
cleanup_workers->run_task(&cleanup);
} else {
// Serial cleanup using VMThread.
ParallelSPCleanupTask cleanup(1, &deflate_counters);
StrongRootsScope srs(1);
ParallelSPCleanupTask cleanup(1);
cleanup.work(0);
}
@ -644,9 +608,6 @@ void SafepointSynchronize::do_cleanup_tasks() {
ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
}
// Finish monitor deflation.
ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
}

7
src/hotspot/share/runtime/serviceThread.cpp

@ -142,10 +142,9 @@ void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
(deflate_idle_monitors = ObjectSynchronizer::is_async_deflation_needed())
) == 0) {
// Wait until notified that there is some work to do.
// If AsyncDeflateIdleMonitors, then we wait for
// GuaranteedSafepointInterval so that is_async_deflation_needed()
// is checked at the same interval.
ml.wait(AsyncDeflateIdleMonitors ? GuaranteedSafepointInterval : 0);
// We wait for GuaranteedSafepointInterval so that
// is_async_deflation_needed() is checked at the same interval.
ml.wait(GuaranteedSafepointInterval);
}
if (has_jvmti_events) {

511
src/hotspot/share/runtime/synchronizer.cpp

@ -491,15 +491,11 @@ bool ObjectSynchronizer::quick_enter(oop obj, Thread* self,
if (mark.has_monitor()) {
ObjectMonitor* const m = mark.monitor();
if (AsyncDeflateIdleMonitors) {
// An async deflation can race us before we manage to make the
// ObjectMonitor busy by setting the owner below. If we detect
// that race we just bail out to the slow-path here.
if (m->object() == NULL) {
return false;
}
} else {
assert(m->object() == obj, "invariant");
// An async deflation can race us before we manage to make the
// ObjectMonitor busy by setting the owner below. If we detect
// that race we just bail out to the slow-path here.
if (m->object() == NULL) {
return false;
}
Thread* const owner = (Thread *) m->_owner;
@ -986,9 +982,8 @@ static inline intptr_t get_next_hash(Thread* self, oop obj) {
intptr_t ObjectSynchronizer::FastHashCode(Thread* self, oop obj) {
if (UseBiasedLocking) {
// NOTE: many places throughout the JVM do not expect a safepoint
// to be taken here, in particular most operations on perm gen
// objects. However, we only ever bias Java instances and all of
// the call sites of identity_hash that might revoke biases have
// to be taken here. However, we only ever bias Java instances and all
// of the call sites of identity_hash that might revoke biases have
// been checked to make sure they can handle a safepoint. The
// added check of the bias pattern is to avoid useless calls to
// thread-local storage.
@ -1193,8 +1188,6 @@ ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership
}
// CASE: inflated. Mark (tagged pointer) points to an ObjectMonitor.
// The Object:ObjectMonitor relationship is stable as long as we're
// not at a safepoint and AsyncDeflateIdleMonitors is false.
if (mark.has_monitor()) {
// The first stage of async deflation does not affect any field
// used by this comparison so the ObjectMonitor* is usable here.
@ -1294,9 +1287,6 @@ static bool monitors_used_above_threshold() {
}
bool ObjectSynchronizer::is_async_deflation_needed() {
if (!AsyncDeflateIdleMonitors) {
return false;
}
if (is_async_deflation_requested()) {
// Async deflation request.
return true;
@ -1313,48 +1303,33 @@ bool ObjectSynchronizer::is_async_deflation_needed() {
return false;
}
bool ObjectSynchronizer::is_safepoint_deflation_needed() {
return !AsyncDeflateIdleMonitors &&
monitors_used_above_threshold(); // Too many monitors in use.
}
bool ObjectSynchronizer::request_deflate_idle_monitors() {
bool is_JavaThread = Thread::current()->is_Java_thread();
bool ret_code = false;
if (AsyncDeflateIdleMonitors) {
jlong last_time = last_async_deflation_time_ns();
set_is_async_deflation_requested(true);
{
MonitorLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
ml.notify_all();
jlong last_time = last_async_deflation_time_ns();
set_is_async_deflation_requested(true);
{
MonitorLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
ml.notify_all();
}
const int N_CHECKS = 5;
for (int i = 0; i < N_CHECKS; i++) { // sleep for at most 5 seconds
if (last_async_deflation_time_ns() > last_time) {
log_info(monitorinflation)("Async Deflation happened after %d check(s).", i);
ret_code = true;
break;
}
const int N_CHECKS = 5;
for (int i = 0; i < N_CHECKS; i++) { // sleep for at most 5 seconds
if (last_async_deflation_time_ns() > last_time) {
log_info(monitorinflation)("Async Deflation happened after %d check(s).", i);
ret_code = true;
break;
}
if (is_JavaThread) {
// JavaThread has to honor the blocking protocol.
ThreadBlockInVM tbivm(JavaThread::current());
os::naked_short_sleep(999); // sleep for almost 1 second
} else {
os::naked_short_sleep(999); // sleep for almost 1 second
}
if (is_JavaThread) {
// JavaThread has to honor the blocking protocol.
ThreadBlockInVM tbivm(JavaThread::current());
os::naked_short_sleep(999); // sleep for almost 1 second
} else {
os::naked_short_sleep(999); // sleep for almost 1 second
}
if (!ret_code) {
log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS);
}
} else {
// Only need to force this safepoint if we are not using async
// deflation. The VMThread won't call this function before the
// final safepoint if we are not using async deflation so we
// don't have to reason about the VMThread executing a VM-op here.
VM_ForceSafepoint force_safepoint_op;
VMThread::execute(&force_safepoint_op);
ret_code = true;
}
if (!ret_code) {
log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS);
}
return ret_code;
@ -1396,9 +1371,9 @@ void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
// ObjectMonitor Lifecycle
// -----------------------
// Inflation unlinks monitors from om_list_globals._free_list or a per-thread
// free list and associates them with objects. Deflation -- which occurs at
// STW-time or asynchronously -- disassociates idle monitors from objects.
// Such scavenged monitors are returned to the om_list_globals._free_list.
// free list and associates them with objects. Async deflation disassociates
// idle monitors from objects. Such scavenged monitors are returned to the
// om_list_globals._free_list.
//
// ObjectMonitors reside in type-stable memory (TSM) and are immortal.
//
@ -1411,7 +1386,7 @@ void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
// A large MAXPRIVATE value reduces both list lock contention
// and list coherency traffic, but also tends to increase the
// number of ObjectMonitors in circulation as well as the STW
// number of ObjectMonitors in circulation as well as the
// scavenge costs. As usual, we lean toward time in space-time
// tradeoffs.
const int MAXPRIVATE = 1024;
@ -1447,23 +1422,21 @@ ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
break; // No more are available.
}
guarantee(take->object() == NULL, "invariant");
if (AsyncDeflateIdleMonitors) {
// We allowed 3 field values to linger during async deflation.
// Clear or restore them as appropriate.
take->set_header(markWord::zero());
// DEFLATER_MARKER is the only non-NULL value we should see here.
take->try_set_owner_from(DEFLATER_MARKER, NULL);
if (take->contentions() < 0) {
// Add back max_jint to restore the contentions field to its
// proper value.
take->add_to_contentions(max_jint);
// We allowed 3 field values to linger during async deflation.
// Clear or restore them as appropriate.
take->set_header(markWord::zero());
// DEFLATER_MARKER is the only non-NULL value we should see here.
take->try_set_owner_from(DEFLATER_MARKER, NULL);
if (take->contentions() < 0) {
// Add back max_jint to restore the contentions field to its
// proper value.
take->add_to_contentions(max_jint);
#ifdef ASSERT
jint l_contentions = take->contentions();
jint l_contentions = take->contentions();
assert(l_contentions >= 0, "must not be negative: l_contentions=%d, contentions=%d",
l_contentions, take->contentions());
#endif
assert(l_contentions >= 0, "must not be negative: l_contentions=%d, contentions=%d",
l_contentions, take->contentions());
}
}
take->Recycle();
// Since we're taking from the global free-list, take must be Free.
@ -1529,8 +1502,8 @@ ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
//
// Key constraint: all ObjectMonitors on a thread's free list and the global
// free list must have their object field set to null. This prevents the
// scavenger -- deflate_monitor_list() or deflate_monitor_list_using_JT()
// -- from reclaiming them while we are trying to release them.
// scavenger -- deflate_monitor_list_using_JT() -- from reclaiming them
// while we are trying to release them.
void ObjectSynchronizer::om_release(Thread* self, ObjectMonitor* m,
bool from_per_thread_alloc) {
@ -1639,15 +1612,13 @@ void ObjectSynchronizer::om_release(Thread* self, ObjectMonitor* m,
//
// We currently call om_flush() from Threads::remove() before the
// thread has been excised from the thread list and is no longer a
// mutator. This means that om_flush() cannot run concurrently with
// a safepoint and interleave with deflate_idle_monitors(). In
// particular, this ensures that the thread's in-use monitors are
// scanned by a GC safepoint, either via Thread::oops_do() (before
// om_flush() is called) or via ObjectSynchronizer::oops_do() (after
// om_flush() is called).
// mutator. In particular, this ensures that the thread's in-use
// monitors are scanned by a GC safepoint, either via Thread::oops_do()
// (before om_flush() is called) or via ObjectSynchronizer::oops_do()
// (after om_flush() is called).
//
// With AsyncDeflateIdleMonitors, deflate_global_idle_monitors_using_JT()
// and deflate_per_thread_idle_monitors_using_JT() (in another thread) can
// deflate_global_idle_monitors_using_JT() and
// deflate_per_thread_idle_monitors_using_JT() (in another thread) can
// run at the same time as om_flush() so we have to follow a careful
// protocol to prevent list corruption.
@ -1701,9 +1672,11 @@ void ObjectSynchronizer::om_flush(Thread* self) {
cur_om = unmarked_next(cur_om);
}
guarantee(in_use_tail != NULL, "invariant");
#ifdef ASSERT
int l_om_in_use_count = Atomic::load(&self->om_in_use_count);
ADIM_guarantee(l_om_in_use_count == in_use_count, "in-use counts don't match: "
"l_om_in_use_count=%d, in_use_count=%d", l_om_in_use_count, in_use_count);
assert(l_om_in_use_count == in_use_count, "in-use counts don't match: "
"l_om_in_use_count=%d, in_use_count=%d", l_om_in_use_count, in_use_count);
#endif
Atomic::store(&self->om_in_use_count, 0);
// Clear the in-use list head (which also unlocks it):
Atomic::store(&self->om_in_use_list, (ObjectMonitor*)NULL);
@ -1744,9 +1717,11 @@ void ObjectSynchronizer::om_flush(Thread* self) {
}
}
guarantee(free_tail != NULL, "invariant");
#ifdef ASSERT
int l_om_free_count = Atomic::load(&self->om_free_count);
ADIM_guarantee(l_om_free_count == free_count, "free counts don't match: "
"l_om_free_count=%d, free_count=%d", l_om_free_count, free_count);
assert(l_om_free_count == free_count, "free counts don't match: "
"l_om_free_count=%d, free_count=%d", l_om_free_count, free_count);
#endif
Atomic::store(&self->om_free_count, 0);
Atomic::store(&self->om_free_list, (ObjectMonitor*)NULL);
om_unlock(free_list);
@ -1825,7 +1800,6 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
ObjectMonitor* inf = mark.monitor();
markWord dmw = inf->header();
assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
assert(AsyncDeflateIdleMonitors || inf->object() == object, "invariant");
assert(ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid");
return inf;
}
@ -1911,7 +1885,7 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
markWord dmw = mark.displaced_mark_helper();
// Catch if the object's header is not neutral (not locked and
// not marked is what we care about here).
ADIM_guarantee(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
// Setup monitor fields to proper values -- prepare the monitor
m->set_header(dmw);
@ -1921,11 +1895,7 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
// Note that a thread can inflate an object
// that it has stack-locked -- as might happen in wait() -- directly
// with CAS. That is, we can avoid the xchg-NULL .... ST idiom.
if (AsyncDeflateIdleMonitors) {
m->set_owner_from(NULL, DEFLATER_MARKER, mark.locker());
} else {
m->set_owner_from(NULL, mark.locker());
}
m->set_owner_from(NULL, DEFLATER_MARKER, mark.locker());
m->set_object(object);
// TODO-FIXME: assert BasicLock->dhw != 0.
@ -1965,15 +1935,13 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
// Catch if the object's header is not neutral (not locked and
// not marked is what we care about here).
ADIM_guarantee(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
ObjectMonitor* m = om_alloc(self);
// prepare m for installation - set monitor to initial state
m->Recycle();
m->set_header(mark);
if (AsyncDeflateIdleMonitors) {
// DEFLATER_MARKER is the only non-NULL value we should see here.
m->try_set_owner_from(DEFLATER_MARKER, NULL);
}
// DEFLATER_MARKER is the only non-NULL value we should see here.
m->try_set_owner_from(DEFLATER_MARKER, NULL);
m->set_object(object);
m->_Responsible = NULL;
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit; // consider: keep metastats by type/class
@ -2013,45 +1981,11 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
}
// We maintain a list of in-use monitors for each thread.
//
// For safepoint based deflation:
// deflate_thread_local_monitors() scans a single thread's in-use list, while
// deflate_idle_monitors() scans only a global list of in-use monitors which
// is populated only as a thread dies (see om_flush()).
//
// These operations are called at all safepoints, immediately after mutators
// are stopped, but before any objects have moved. Collectively they traverse
// the population of in-use monitors, deflating where possible. The scavenged
// monitors are returned to the global monitor free list.
//
// Beware that we scavenge at *every* stop-the-world point. Having a large
// number of monitors in-use could negatively impact performance. We also want
// to minimize the total # of monitors in circulation, as they incur a small
// footprint penalty.
//
// Perversely, the heap size -- and thus the STW safepoint rate --
// typically drives the scavenge rate. Large heaps can mean infrequent GC,
// which in turn can mean large(r) numbers of ObjectMonitors in circulation.
// This is an unfortunate aspect of this design.
//
// For async deflation:
// If a special deflation request is made, then the safepoint based
// deflation mechanism is used. Otherwise, an async deflation request
// is registered with the ServiceThread and it is notified.
void ObjectSynchronizer::do_safepoint_work(DeflateMonitorCounters* counters) {
// An async deflation request is registered with the ServiceThread
// and it is notified.
void ObjectSynchronizer::do_safepoint_work() {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
// The per-thread in-use lists are handled in
// ParallelSPCleanupThreadClosure::do_thread().
if (!AsyncDeflateIdleMonitors) {
// Use the older mechanism for the global in-use list.
ObjectSynchronizer::deflate_idle_monitors(counters);
return;
}
log_debug(monitorinflation)("requesting async deflation of idle monitors.");
// Request deflation of idle monitors by the ServiceThread:
set_is_async_deflation_requested(true);
@ -2061,85 +1995,10 @@ void ObjectSynchronizer::do_safepoint_work(DeflateMonitorCounters* counters) {
if (log_is_enabled(Debug, monitorinflation)) {
// exit_globals()'s call to audit_and_print_stats() is done
// at the Info level and not at a safepoint.
// For safepoint based deflation, audit_and_print_stats() is called
// in ObjectSynchronizer::finish_deflate_idle_monitors() at the
// Debug level at a safepoint.
ObjectSynchronizer::audit_and_print_stats(false /* on_exit */);
}
}
// Deflate a single monitor if not in-use
// Return true if deflated, false if in-use
bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p) {
bool deflated;
// Normal case ... The monitor is associated with obj.
const markWord mark = obj->mark();
guarantee(mark == markWord::encode(mid), "should match: mark="
INTPTR_FORMAT ", encoded mid=" INTPTR_FORMAT, mark.value(),
markWord::encode(mid).value());
// Make sure that mark.monitor() and markWord::encode() agree:
guarantee(mark.monitor() == mid, "should match: monitor()=" INTPTR_FORMAT
", mid=" INTPTR_FORMAT, p2i(mark.monitor()), p2i(mid));
const markWord dmw = mid->header();
guarantee(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
if (mid->is_busy()) {
// Easy checks are first - the ObjectMonitor is busy so no deflation.
deflated = false;
} else {
// Deflate the monitor if it is no longer being used
// It's idle - scavenge and return to the global free list
// plain old deflation ...
if (log_is_enabled(Trace, monitorinflation)) {
ResourceMark rm;
log_trace(monitorinflation)("deflate_monitor: "
"object=" INTPTR_FORMAT ", mark="
INTPTR_FORMAT ", type='%s'", p2i(obj),
mark.value(), obj->klass()->external_name());
}
// Restore the header back to obj
obj->release_set_mark(dmw);
if (AsyncDeflateIdleMonitors) {
// clear() expects the owner field to be NULL.
// DEFLATER_MARKER is the only non-NULL value we should see here.
mid->try_set_owner_from(DEFLATER_MARKER, NULL);
}
mid->clear();
assert(mid->object() == NULL, "invariant: object=" INTPTR_FORMAT,
p2i(mid->object()));
assert(mid->is_free(), "invariant");
// Move the deflated ObjectMonitor to the working free list
// defined by free_head_p and free_tail_p.
if (*free_head_p == NULL) *free_head_p = mid;
if (*free_tail_p != NULL) {
// We append to the list so the caller can use mid->_next_om
// to fix the linkages in its context.
ObjectMonitor* prevtail = *free_tail_p;
// Should have been cleaned up by the caller:
// Note: Should not have to lock prevtail here since we're at a
// safepoint and ObjectMonitors on the local free list should
// not be accessed in parallel.
#ifdef ASSERT
ObjectMonitor* l_next_om = prevtail->next_om();
#endif
assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
prevtail->set_next_om(mid);
}
*free_tail_p = mid;
// At this point, mid->_next_om still refers to its current
// value and another ObjectMonitor's _next_om field still
// refers to this ObjectMonitor. Those linkages have to be
// cleaned up by the caller who has the complete context.
deflated = true;
}
return deflated;
}
// Deflate the specified ObjectMonitor if not in-use using a JavaThread.
// Returns true if it was deflated and false otherwise.
//
@ -2156,7 +2015,6 @@ bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj,
bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p) {
assert(AsyncDeflateIdleMonitors, "sanity check");
assert(Thread::current()->is_Java_thread(), "precondition");
// A newly allocated ObjectMonitor should not be seen here so we
// avoid an endless inflate/deflate cycle.
@ -2245,8 +2103,8 @@ bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
// prevtail should have been cleaned up by the caller:
#ifdef ASSERT
ObjectMonitor* l_next_om = unmarked_next(prevtail);
#endif
assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
#endif
om_lock(prevtail);
prevtail->set_next_om(mid); // prevtail now points to mid (and is unlocked)
}
@ -2262,56 +2120,6 @@ bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
return true; // Success, ObjectMonitor has been deflated.
}
// Walk a given monitor list, and deflate idle monitors.
// The given list could be a per-thread list or a global list.
//
// In the case of parallel processing of thread local monitor lists,
// work is done by Threads::parallel_threads_do() which ensures that
// each Java thread is processed by exactly one worker thread, and
// thus avoid conflicts that would arise when worker threads would
// process the same monitor lists concurrently.
//
// See also ParallelSPCleanupTask and
// SafepointSynchronize::do_cleanup_tasks() in safepoint.cpp and
// Threads::parallel_java_threads_do() in thread.cpp.
int ObjectSynchronizer::deflate_monitor_list(ObjectMonitor** list_p,
int* count_p,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p) {
ObjectMonitor* cur_mid_in_use = NULL;
ObjectMonitor* mid = NULL;
ObjectMonitor* next = NULL;
int deflated_count = 0;
// This list walk executes at a safepoint and does not race with any
// other list walkers.
for (mid = Atomic::load(list_p); mid != NULL; mid = next) {
next = unmarked_next(mid);
oop obj = (oop) mid->object();
if (obj != NULL && deflate_monitor(mid, obj, free_head_p, free_tail_p)) {
// Deflation succeeded and already updated free_head_p and
// free_tail_p as needed. Finish the move to the local free list
// by unlinking mid from the global or per-thread in-use list.
if (cur_mid_in_use == NULL) {
// mid is the list head so switch the list head to next:
Atomic::store(list_p, next);
} else {
// Switch cur_mid_in_use's next field to next:
cur_mid_in_use->set_next_om(next);
}
// At this point mid is disconnected from the in-use list.
deflated_count++;
Atomic::dec(count_p);
// mid is current tail in the free_head_p list so NULL terminate it:
mid->set_next_om(NULL);
} else {
cur_mid_in_use = mid;
}
}
return deflated_count;
}
// Walk a given ObjectMonitor list and deflate idle ObjectMonitors using
// a JavaThread. Returns the number of deflated ObjectMonitors. The given
// list could be a per-thread in-use list or the global in-use list.
@ -2323,7 +2131,6 @@ int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** list_p,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p,
ObjectMonitor** saved_mid_in_use_p) {
assert(AsyncDeflateIdleMonitors, "sanity check");
JavaThread* self = JavaThread::current();
ObjectMonitor* cur_mid_in_use = NULL;
@ -2453,75 +2260,6 @@ int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** list_p,
return deflated_count;
}
void ObjectSynchronizer::prepare_deflate_idle_monitors(DeflateMonitorCounters* counters) {
counters->n_in_use = 0; // currently associated with objects
counters->n_in_circulation = 0; // extant
counters->n_scavenged = 0; // reclaimed (global and per-thread)
counters->per_thread_scavenged = 0; // per-thread scavenge total
counters->per_thread_times = 0.0; // per-thread scavenge times
}
void ObjectSynchronizer::deflate_idle_monitors(DeflateMonitorCounters* counters) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
if (AsyncDeflateIdleMonitors) {
// Nothing to do when global idle ObjectMonitors are deflated using
// a JavaThread.
return;
}
bool deflated = false;
ObjectMonitor* free_head_p = NULL; // Local SLL of scavenged monitors
ObjectMonitor* free_tail_p = NULL;
elapsedTimer timer;
if (log_is_enabled(Info, monitorinflation)) {
timer.start();
}
// Note: the thread-local monitors lists get deflated in
// a separate pass. See deflate_thread_local_monitors().
// For moribund threads, scan om_list_globals._in_use_list
int deflated_count = 0;
if (Atomic::load(&om_list_globals._in_use_list) != NULL) {
// Update n_in_circulation before om_list_globals._in_use_count is
// updated by deflation.
Atomic::add(&counters->n_in_circulation,
Atomic::load(&om_list_globals._in_use_count));
deflated_count = deflate_monitor_list(&om_list_globals._in_use_list,
&om_list_globals._in_use_count,
&free_head_p, &free_tail_p);
Atomic::add(&counters->n_in_use, Atomic::load(&om_list_globals._in_use_count));
}
if (free_head_p != NULL) {
// Move the deflated ObjectMonitors back to the global free list.
guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
#ifdef ASSERT
ObjectMonitor* l_next_om = free_tail_p->next_om();
#endif
assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
prepend_list_to_global_free_list(free_head_p, free_tail_p, deflated_count);
Atomic::add(&counters->n_scavenged, deflated_count);
}
timer.stop();
LogStreamHandle(Debug, monitorinflation) lsh_debug;
LogStreamHandle(Info, monitorinflation) lsh_info;
LogStream* ls = NULL;
if (log_is_enabled(Debug, monitorinflation)) {
ls = &lsh_debug;
} else if (deflated_count != 0 && log_is_enabled(Info, monitorinflation)) {
ls = &lsh_info;
}
if (ls != NULL) {
ls->print_cr("deflating global idle monitors, %3.7f secs, %d monitors", timer.seconds(), deflated_count);
}
}
class HandshakeForDeflation : public HandshakeClosure {
public:
HandshakeForDeflation() : HandshakeClosure("HandshakeForDeflation") {}
@ -2533,8 +2271,6 @@ class HandshakeForDeflation : public HandshakeClosure {
};
void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
assert(AsyncDeflateIdleMonitors, "sanity check");
// Deflate any global idle monitors.
deflate_global_idle_monitors_using_JT();
@ -2568,7 +2304,7 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
// (or a safepoint) for safety.
ObjectMonitor* list = Atomic::load(&om_list_globals._wait_list);
ADIM_guarantee(list != NULL, "om_list_globals._wait_list must not be NULL");
assert(list != NULL, "om_list_globals._wait_list must not be NULL");
int count = Atomic::load(&om_list_globals._wait_count);
Atomic::store(&om_list_globals._wait_count, 0);
Atomic::store(&om_list_globals._wait_list, (ObjectMonitor*)NULL);
@ -2576,13 +2312,17 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
// Find the tail for prepend_list_to_common(). No need to mark
// ObjectMonitors for this list walk since only the deflater
// thread manages the wait list.
#ifdef ASSERT
int l_count = 0;
#endif
ObjectMonitor* tail = NULL;
for (ObjectMonitor* n = list; n != NULL; n = unmarked_next(n)) {
tail = n;
#ifdef ASSERT
l_count++;
#endif
}
ADIM_guarantee(count == l_count, "count=%d != l_count=%d", count, l_count);
assert(count == l_count, "count=%d != l_count=%d", count, l_count);
// Will execute a safepoint if !ThreadLocalHandshakes:
HandshakeForDeflation hfd_hc;
@ -2598,7 +2338,6 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
// Deflate global idle ObjectMonitors using a JavaThread.
//
void ObjectSynchronizer::deflate_global_idle_monitors_using_JT() {
assert(AsyncDeflateIdleMonitors, "sanity check");
assert(Thread::current()->is_Java_thread(), "precondition");
JavaThread* self = JavaThread::current();
@ -2608,7 +2347,6 @@ void ObjectSynchronizer::deflate_global_idle_monitors_using_JT() {
// Deflate the specified JavaThread's idle ObjectMonitors using a JavaThread.
//
void ObjectSynchronizer::deflate_per_thread_idle_monitors_using_JT(JavaThread* target) {
assert(AsyncDeflateIdleMonitors, "sanity check");
assert(Thread::current()->is_Java_thread(), "precondition");
deflate_common_idle_monitors_using_JT(false /* !is_global */, target);
@ -2664,8 +2402,8 @@ void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, J
// all out.
#ifdef ASSERT
ObjectMonitor* l_next_om = unmarked_next(free_tail_p);
#endif
assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
#endif
prepend_list_to_global_wait_list(free_head_p, free_tail_p, local_deflated_count);
@ -2711,94 +2449,6 @@ void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, J
}
}
void ObjectSynchronizer::finish_deflate_idle_monitors(DeflateMonitorCounters* counters) {
// Report the cumulative time for deflating each thread's idle
// monitors. Note: if the work is split among more than one
// worker thread, then the reported time will likely be more
// than a beginning to end measurement of the phase.
log_info(safepoint, cleanup)("deflating per-thread idle monitors, %3.7f secs, monitors=%d", counters->per_thread_times, counters->per_thread_scavenged);
if (AsyncDeflateIdleMonitors) {
// Nothing to do when idle ObjectMonitors are deflated using
// a JavaThread.
return;
}
if (log_is_enabled(Debug, monitorinflation)) {
// exit_globals()'s call to audit_and_print_stats() is done
// at the Info level and not at a safepoint.
// For async deflation, audit_and_print_stats() is called in
// ObjectSynchronizer::do_safepoint_work() at the Debug level
// at a safepoint.
ObjectSynchronizer::audit_and_print_stats(false /* on_exit */);
} else if (log_is_enabled(Info, monitorinflation)) {
log_info(monitorinflation)("global_population=%d, global_in_use_count=%d, "
"global_free_count=%d, global_wait_count=%d",
Atomic::load(&om_list_globals._population),
Atomic::load(&om_list_globals._in_use_count),
Atomic::load(&om_list_globals._free_count),
Atomic::load(&om_list_globals._wait_count));
}
OM_PERFDATA_OP(Deflations, inc(counters->n_scavenged));
OM_PERFDATA_OP(MonExtant, set_value(counters->n_in_circulation));
GVars.stw_random = os::random();
GVars.stw_cycle++;
}
void ObjectSynchronizer::deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
if (AsyncDeflateIdleMonitors) {
// Nothing to do when per-thread idle ObjectMonitors are deflated
// using a JavaThread.
return;
}
ObjectMonitor* free_head_p = NULL; // Local SLL of scavenged monitors
ObjectMonitor* free_tail_p = NULL;
elapsedTimer timer;
if (log_is_enabled(Info, safepoint, cleanup) ||
log_is_enabled(Info, monitorinflation)) {
timer.start();
}
// Update n_in_circulation before om_in_use_count is updated by deflation.
Atomic::add(&counters->n_in_circulation, Atomic::load(&thread->om_in_use_count));
int deflated_count = deflate_monitor_list(&thread->om_in_use_list, &thread->om_in_use_count, &free_head_p, &free_tail_p);
Atomic::add(&counters->n_in_use, Atomic::load(&thread->om_in_use_count));
if (free_head_p != NULL) {
// Move the deflated ObjectMonitors back to the global free list.
guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
#ifdef ASSERT
ObjectMonitor* l_next_om = free_tail_p->next_om();
#endif
assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
prepend_list_to_global_free_list(free_head_p, free_tail_p, deflated_count);
Atomic::add(&counters->n_scavenged, deflated_count);
Atomic::add(&counters->per_thread_scavenged, deflated_count);
}
timer.stop();
counters->per_thread_times += timer.seconds();
LogStreamHandle(Debug, monitorinflation) lsh_debug;
LogStreamHandle(Info, monitorinflation) lsh_info;
LogStream* ls = NULL;
if (log_is_enabled(Debug, monitorinflation)) {
ls = &lsh_debug;
} else if (deflated_count != 0 && log_is_enabled(Info, monitorinflation)) {
ls = &lsh_info;
}
if (ls != NULL) {
ls->print_cr("jt=" INTPTR_FORMAT ": deflating per-thread idle monitors, %3.7f secs, %d monitors", p2i(thread), timer.seconds(), deflated_count);
}
}
// Monitor cleanup on JavaThread::exit
// Iterate through monitor cache and attempt to release thread's monitors
@ -2824,7 +2474,7 @@ class ReleaseJavaMonitorsClosure: public MonitorClosure {
// A simple optimization is to add a per-thread flag that indicates a thread
// called jni_monitorenter() during its lifetime.
//
// Instead of No_Savepoint_Verifier it might be cheaper to
// Instead of NoSafepointVerifier it might be cheaper to
// use an idiom of the form:
// auto int tmp = SafepointSynchronize::_safepoint_counter ;
// <code that must not run at safepoint>
@ -2883,8 +2533,6 @@ u_char* ObjectSynchronizer::get_gvars_stw_random_addr() {
// aid; pass 'true' for the 'on_exit' parameter to have in-use monitor
// details logged at the Info level and 'false' for the 'on_exit'
// parameter to have in-use monitor details logged at the Trace level.
// deflate_monitor_list() no longer uses spin-locking so be careful
// when adding audit_and_print_stats() calls at a safepoint.
//
void ObjectSynchronizer::audit_and_print_stats(bool on_exit) {
assert(on_exit || SafepointSynchronize::is_at_safepoint(), "invariant");
@ -2983,11 +2631,6 @@ void ObjectSynchronizer::chk_free_entry(JavaThread* jt, ObjectMonitor* n,
"field: _header=" INTPTR_FORMAT, p2i(jt), p2i(n),
n->header().value());
*error_cnt_p = *error_cnt_p + 1;
} else if (!AsyncDeflateIdleMonitors) {
out->print_cr("ERROR: monitor=" INTPTR_FORMAT ": free global monitor "
"must have NULL _header field: _header=" INTPTR_FORMAT,
p2i(n), n->header().value());
*error_cnt_p = *error_cnt_p + 1;
}
}
if (n->object() != NULL) {

23
src/hotspot/share/runtime/synchronizer.hpp

@ -42,14 +42,6 @@ class ThreadsList;
typedef PaddedEnd<ObjectMonitor, OM_CACHE_LINE_SIZE> PaddedObjectMonitor;
struct DeflateMonitorCounters {
volatile int n_in_use; // currently associated with objects
volatile int n_in_circulation; // extant
volatile int n_scavenged; // reclaimed (global and per-thread)
volatile int per_thread_scavenged; // per-thread scavenge total
double per_thread_times; // per-thread scavenge times
};
class ObjectSynchronizer : AllStatic {
friend class VMStructs;
public:
@ -131,20 +123,11 @@ class ObjectSynchronizer : AllStatic {
// GC: we current use aggressive monitor deflation policy
// Basically we deflate all monitors that are not busy.
// An adaptive profile-based deflation policy could be used if needed
static void deflate_idle_monitors(DeflateMonitorCounters* counters);
static void deflate_idle_monitors_using_JT();
static void deflate_global_idle_monitors_using_JT();
static void deflate_per_thread_idle_monitors_using_JT(JavaThread* target);
static void deflate_common_idle_monitors_using_JT(bool is_global, JavaThread* target);
static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
// For a given monitor list: global or per-thread, deflate idle monitors
static int deflate_monitor_list(ObjectMonitor** list_p,
int* count_p,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p);
// For a given in-use monitor list: global or per-thread, deflate idle
// monitors using a JavaThread.
static int deflate_monitor_list_using_JT(ObjectMonitor** list_p,
@ -152,14 +135,10 @@ class ObjectSynchronizer : AllStatic {
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p,
ObjectMonitor** saved_mid_in_use_p);
static bool deflate_monitor(ObjectMonitor* mid, oop obj,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p);
static bool deflate_monitor_using_JT(ObjectMonitor* mid,
ObjectMonitor** free_head_p,
ObjectMonitor** free_tail_p);
static bool is_async_deflation_needed();
static bool is_safepoint_deflation_needed();
static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
static bool request_deflate_idle_monitors(); // for whitebox test support and VM exit logging
@ -191,7 +170,7 @@ class ObjectSynchronizer : AllStatic {
static int log_monitor_list_counts(outputStream * out);
static int verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
static void do_safepoint_work(DeflateMonitorCounters* counters);
static void do_safepoint_work();
private:
friend class SynchronizerTest;

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

@ -431,10 +431,10 @@ int VM_Exit::wait_for_threads_in_native_to_block() {
}
bool VM_Exit::doit_prologue() {
if (AsyncDeflateIdleMonitors && log_is_enabled(Info, monitorinflation)) {
// AsyncDeflateIdleMonitors does a special deflation in order
// to reduce the in-use monitor population that is reported by
// ObjectSynchronizer::log_in_use_monitor_details() at VM exit.
if (log_is_enabled(Info, monitorinflation)) {
// Do a deflation in order to reduce the in-use monitor population
// that is reported by ObjectSynchronizer::log_in_use_monitor_details()
// at VM exit.
ObjectSynchronizer::request_deflate_idle_monitors();
}
return true;

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

@ -260,10 +260,10 @@ void VMThread::run() {
assert(should_terminate(), "termination flag must be set");
}
if (AsyncDeflateIdleMonitors && log_is_enabled(Info, monitorinflation)) {
// AsyncDeflateIdleMonitors does a special deflation in order
// to reduce the in-use monitor population that is reported by
// ObjectSynchronizer::log_in_use_monitor_details() at VM exit.
if (log_is_enabled(Info, monitorinflation)) {
// Do a deflation in order to reduce the in-use monitor population
// that is reported by ObjectSynchronizer::log_in_use_monitor_details()
// at VM exit.
ObjectSynchronizer::request_deflate_idle_monitors();
}

2
src/hotspot/share/services/threadService.cpp

@ -222,13 +222,11 @@ Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
if (wait_obj != NULL) {
// thread is doing an Object.wait() call
obj = (oop) wait_obj->object();
assert(AsyncDeflateIdleMonitors || obj != NULL, "Object.wait() should have an object");
} else {
ObjectMonitor *enter_obj = thread->current_pending_monitor();
if (enter_obj != NULL) {
// thread is trying to enter() an ObjectMonitor.
obj = (oop) enter_obj->object();
assert(AsyncDeflateIdleMonitors || obj != NULL, "ObjectMonitor should have an associated object!");
}
}

14
test/hotspot/gtest/oops/test_markWord.cpp

@ -138,19 +138,5 @@ TEST_VM(markWord, printing) {
assert_test_pattern(h_obj, "monitor");
done.wait_with_safepoint_check(THREAD); // wait till the thread is done.
}
if (!AsyncDeflateIdleMonitors) {
// With AsyncDeflateIdleMonitors, the collect() call below
// does not guarantee monitor deflation.
// Make the object older. Not all GCs use this field.
Universe::heap()->collect(GCCause::_java_lang_system_gc);
if (UseParallelGC) {
assert_test_pattern(h_obj, "is_neutral no_hash age 1");
}
// Hash the object then print it.
intx hash = h_obj->identity_hash();
assert_test_pattern(h_obj, "is_neutral hash=0x");
}
}
#endif // PRODUCT

29
test/hotspot/jtreg/runtime/logging/SafepointCleanupTest.java

@ -29,23 +29,17 @@
* @modules java.base/jdk.internal.misc
* java.management
* @run driver SafepointCleanupTest
* @run driver SafepointCleanupTest -XX:+AsyncDeflateIdleMonitors
*/
import jdk.test.lib.process.OutputAnalyzer;
import jdk.test.lib.process.ProcessTools;
public class SafepointCleanupTest {
static final String ASYNC_DISABLE_OPTION = "-XX:-AsyncDeflateIdleMonitors";
static final String ASYNC_ENABLE_OPTION = "-XX:+AsyncDeflateIdleMonitors";
static final String UNLOCK_DIAG_OPTION = "-XX:+UnlockDiagnosticVMOptions";
static void analyzeOutputOn(ProcessBuilder pb) throws Exception {
OutputAnalyzer output = new OutputAnalyzer(pb.start());
output.shouldContain("[safepoint,cleanup]");
output.shouldContain("safepoint cleanup tasks");
output.shouldContain("deflating global idle monitors");
output.shouldContain("deflating per-thread idle monitors");
output.shouldContain("deflating idle monitors");
output.shouldContain("updating inline caches");
output.shouldContain("compilation policy safepoint handler");
output.shouldHaveExitValue(0);
@ -58,40 +52,19 @@ public class SafepointCleanupTest {
}
public static void main(String[] args) throws Exception {
String async_option;
if (args.length == 0) {
// By default test deflating idle monitors at a safepoint.
async_option = ASYNC_DISABLE_OPTION;
} else {
async_option = args[0];
}
if (!async_option.equals(ASYNC_DISABLE_OPTION) &&
!async_option.equals(ASYNC_ENABLE_OPTION)) {
throw new RuntimeException("Unknown async_option value: '"
+ async_option + "'");
}
ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-Xlog:safepoint+cleanup=info",
UNLOCK_DIAG_OPTION,
async_option,
InnerClass.class.getName());
analyzeOutputOn(pb);
pb = ProcessTools.createJavaProcessBuilder("-XX:+TraceSafepointCleanupTime",
UNLOCK_DIAG_OPTION,
async_option,
InnerClass.class.getName());
analyzeOutputOn(pb);
pb = ProcessTools.createJavaProcessBuilder("-Xlog:safepoint+cleanup=off",
UNLOCK_DIAG_OPTION,
async_option,
InnerClass.class.getName());
analyzeOutputOff(pb);
pb = ProcessTools.createJavaProcessBuilder("-XX:-TraceSafepointCleanupTime",
UNLOCK_DIAG_OPTION,
async_option,
InnerClass.class.getName());
analyzeOutputOff(pb);
}