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src/hotspot/share/runtime/synchronizer.cpp
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rev 54996 : Checkpoint latest preliminary review patches for full OpenJDK review; merge with 8222295.patch.
rev 54997 : imported patch dcubed.monitor_deflate_conc.v2.01
rev 54998 : imported patch dcubed.monitor_deflate_conc.v2.02
rev 54999 : imported patch dcubed.monitor_deflate_conc.v2.03
rev 55000 : [mq]: dcubed.monitor_deflate_conc.v2.04
@@ -123,10 +123,13 @@
// global monitor in-use list, for moribund threads,
// monitors they inflated need to be scanned for deflation
ObjectMonitor * volatile ObjectSynchronizer::gOmInUseList = NULL;
// count of entries in gOmInUseList
int ObjectSynchronizer::gOmInUseCount = 0;
+bool volatile ObjectSynchronizer::_is_async_deflation_requested = false;
+bool volatile ObjectSynchronizer::_is_special_deflation_requested = false;
+jlong ObjectSynchronizer::_last_async_deflation_time_ns = 0;
static volatile intptr_t gListLock = 0; // protects global monitor lists
static volatile int gMonitorFreeCount = 0; // # on gFreeList
static volatile int gMonitorPopulation = 0; // # Extant -- in circulation
@@ -209,14 +212,22 @@
assert(!SafepointSynchronize::is_at_safepoint(), "invariant");
assert(Self->is_Java_thread(), "invariant");
assert(((JavaThread *) Self)->thread_state() == _thread_in_Java, "invariant");
NoSafepointVerifier nsv;
if (obj == NULL) return false; // Need to throw NPE
+
+ while (true) {
const markOop mark = obj->mark();
if (mark->has_monitor()) {
- ObjectMonitor * const m = mark->monitor();
+ ObjectMonitorHandle omh;
+ if (!omh.save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ ObjectMonitor * const m = omh.om_ptr();
assert(oopDesc::equals((oop) m->object(), obj), "invariant");
Thread * const owner = (Thread *) m->_owner;
// Lock contention and Transactional Lock Elision (TLE) diagnostics
// and observability
@@ -244,10 +255,12 @@
assert(m->_recursions == 0, "invariant");
assert(m->_owner == Self, "invariant");
return true;
}
}
+ break;
+ }
// Note that we could inflate in quick_enter.
// This is likely a useful optimization
// Critically, in quick_enter() we must not:
// -- perform bias revocation, or
@@ -326,11 +339,13 @@
return;
}
}
// We have to take the slow-path of possible inflation and then exit.
- inflate(THREAD, object, inflate_cause_vm_internal)->exit(true, THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, object, inflate_cause_vm_internal);
+ omh.om_ptr()->exit(true, THREAD);
}
// -----------------------------------------------------------------------------
// Interpreter/Compiler Slow Case
// This routine is used to handle interpreter/compiler slow case
@@ -359,11 +374,13 @@
// The object header will never be displaced to this lock,
// so it does not matter what the value is, except that it
// must be non-zero to avoid looking like a re-entrant lock,
// and must not look locked either.
lock->set_displaced_header(markOopDesc::unused_mark());
- inflate(THREAD, obj(), inflate_cause_monitor_enter)->enter(THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_monitor_enter);
+ omh.om_ptr()->enter(THREAD);
}
// This routine is used to handle interpreter/compiler slow case
// We don't need to use fast path here, because it must have
// failed in the interpreter/compiler code. Simply use the heavy
@@ -388,25 +405,26 @@
if (UseBiasedLocking) {
BiasedLocking::revoke_and_rebias(obj, false, THREAD);
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
- ObjectMonitor* monitor = inflate(THREAD, obj(), inflate_cause_vm_internal);
-
- return monitor->complete_exit(THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_vm_internal);
+ intptr_t ret_code = omh.om_ptr()->complete_exit(THREAD);
+ return ret_code;
}
// NOTE: must use heavy weight monitor to handle complete_exit/reenter()
void ObjectSynchronizer::reenter(Handle obj, intptr_t recursion, TRAPS) {
if (UseBiasedLocking) {
BiasedLocking::revoke_and_rebias(obj, false, THREAD);
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
- ObjectMonitor* monitor = inflate(THREAD, obj(), inflate_cause_vm_internal);
-
- monitor->reenter(recursion, THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_vm_internal);
+ omh.om_ptr()->reenter(recursion, THREAD);
}
// -----------------------------------------------------------------------------
// JNI locks on java objects
// NOTE: must use heavy weight monitor to handle jni monitor enter
void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) {
@@ -414,11 +432,13 @@
if (UseBiasedLocking) {
BiasedLocking::revoke_and_rebias(obj, false, THREAD);
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
THREAD->set_current_pending_monitor_is_from_java(false);
- inflate(THREAD, obj(), inflate_cause_jni_enter)->enter(THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_jni_enter);
+ omh.om_ptr()->enter(THREAD);
THREAD->set_current_pending_monitor_is_from_java(true);
}
// NOTE: must use heavy weight monitor to handle jni monitor exit
void ObjectSynchronizer::jni_exit(oop obj, Thread* THREAD) {
@@ -427,11 +447,13 @@
BiasedLocking::revoke_and_rebias(h_obj, false, THREAD);
obj = h_obj();
}
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
- ObjectMonitor* monitor = inflate(THREAD, obj, inflate_cause_jni_exit);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj, inflate_cause_jni_exit);
+ ObjectMonitor * monitor = omh.om_ptr();
// If this thread has locked the object, exit the monitor. Note: can't use
// monitor->check(CHECK); must exit even if an exception is pending.
if (monitor->check(THREAD)) {
monitor->exit(true, THREAD);
}
@@ -467,31 +489,36 @@
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
if (millis < 0) {
THROW_MSG_0(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
}
- ObjectMonitor* monitor = inflate(THREAD, obj(), inflate_cause_wait);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_wait);
+ ObjectMonitor * monitor = omh.om_ptr();
DTRACE_MONITOR_WAIT_PROBE(monitor, obj(), THREAD, millis);
monitor->wait(millis, true, THREAD);
// This dummy call is in place to get around dtrace bug 6254741. Once
// that's fixed we can uncomment the following line, remove the call
// and change this function back into a "void" func.
// DTRACE_MONITOR_PROBE(waited, monitor, obj(), THREAD);
- return dtrace_waited_probe(monitor, obj, THREAD);
+ int ret_code = dtrace_waited_probe(monitor, obj, THREAD);
+ return ret_code;
}
void ObjectSynchronizer::waitUninterruptibly(Handle obj, jlong millis, TRAPS) {
if (UseBiasedLocking) {
BiasedLocking::revoke_and_rebias(obj, false, THREAD);
assert(!obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
if (millis < 0) {
THROW_MSG(vmSymbols::java_lang_IllegalArgumentException(), "timeout value is negative");
}
- inflate(THREAD, obj(), inflate_cause_wait)->wait(millis, false, THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_wait);
+ omh.om_ptr()->wait(millis, false, THREAD);
}
void ObjectSynchronizer::notify(Handle obj, TRAPS) {
if (UseBiasedLocking) {
BiasedLocking::revoke_and_rebias(obj, false, THREAD);
@@ -500,11 +527,13 @@
markOop mark = obj->mark();
if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
return;
}
- inflate(THREAD, obj(), inflate_cause_notify)->notify(THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_notify);
+ omh.om_ptr()->notify(THREAD);
}
// NOTE: see comment of notify()
void ObjectSynchronizer::notifyall(Handle obj, TRAPS) {
if (UseBiasedLocking) {
@@ -514,11 +543,13 @@
markOop mark = obj->mark();
if (mark->has_locker() && THREAD->is_lock_owned((address)mark->locker())) {
return;
}
- inflate(THREAD, obj(), inflate_cause_notify)->notifyAll(THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_notify);
+ omh.om_ptr()->notifyAll(THREAD);
}
// -----------------------------------------------------------------------------
// Hash Code handling
//
@@ -708,10 +739,11 @@
assert(Universe::verify_in_progress() || DumpSharedSpaces ||
Self->is_Java_thread() , "invariant");
assert(Universe::verify_in_progress() || DumpSharedSpaces ||
((JavaThread *)Self)->thread_state() != _thread_blocked, "invariant");
+ while (true) {
ObjectMonitor* monitor = NULL;
markOop temp, test;
intptr_t hash;
markOop mark = ReadStableMark(obj);
@@ -732,11 +764,17 @@
}
// If atomic operation failed, we must inflate the header
// into heavy weight monitor. We could add more code here
// for fast path, but it does not worth the complexity.
} else if (mark->has_monitor()) {
- monitor = mark->monitor();
+ ObjectMonitorHandle omh;
+ if (!omh.save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ monitor = omh.om_ptr();
temp = monitor->header();
assert(temp->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(temp));
hash = temp->hash();
if (hash != 0) {
return hash;
@@ -758,31 +796,39 @@
// during an inflate() call so any change to that stack memory
// may not propagate to other threads correctly.
}
// Inflate the monitor to set hash code
- monitor = inflate(Self, obj, inflate_cause_hash_code);
+ ObjectMonitorHandle omh;
+ inflate(&omh, Self, obj, inflate_cause_hash_code);
+ monitor = omh.om_ptr();
// Load displaced header and check it has hash code
mark = monitor->header();
assert(mark->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(mark));
hash = mark->hash();
if (hash == 0) {
hash = get_next_hash(Self, obj);
temp = mark->copy_set_hash(hash); // merge hash code into header
assert(temp->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(temp));
test = Atomic::cmpxchg(temp, monitor->header_addr(), mark);
if (test != mark) {
- // The only update to the ObjectMonitor's header/dmw field
- // is to merge in the hash code. If someone adds a new usage
- // of the header/dmw field, please update this code.
+ // The only non-deflation update to the ObjectMonitor's
+ // header/dmw field is to merge in the hash code. If someone
+ // adds a new usage of the header/dmw field, please update
+ // this code.
+ // ObjectMonitor::install_displaced_markword_in_object()
+ // does mark the header/dmw field as part of async deflation,
+ // but that protocol cannot happen now due to the
+ // ObjectMonitorHandle above.
hash = test->hash();
assert(test->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(test));
assert(hash != 0, "Trivial unexpected object/monitor header usage.");
}
}
// We finally get the hash
return hash;
+ }
}
// Deprecated -- use FastHashCode() instead.
intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) {
@@ -798,24 +844,32 @@
}
assert(thread == JavaThread::current(), "Can only be called on current thread");
oop obj = h_obj();
+ while (true) {
markOop mark = ReadStableMark(obj);
// Uncontended case, header points to stack
if (mark->has_locker()) {
return thread->is_lock_owned((address)mark->locker());
}
// Contended case, header points to ObjectMonitor (tagged pointer)
if (mark->has_monitor()) {
- ObjectMonitor* monitor = mark->monitor();
- return monitor->is_entered(thread) != 0;
+ ObjectMonitorHandle omh;
+ if (!omh.save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ bool ret_code = omh.om_ptr()->is_entered(thread) != 0;
+ return ret_code;
}
// Unlocked case, header in place
assert(mark->is_neutral(), "sanity check");
return false;
+ }
}
// Be aware of this method could revoke bias of the lock object.
// This method queries the ownership of the lock handle specified by 'h_obj'.
// If the current thread owns the lock, it returns owner_self. If no
@@ -837,31 +891,41 @@
"biases should be revoked by now");
}
assert(self == JavaThread::current(), "Can only be called on current thread");
oop obj = h_obj();
+
+ while (true) {
markOop mark = ReadStableMark(obj);
// CASE: stack-locked. Mark points to a BasicLock on the owner's stack.
if (mark->has_locker()) {
return self->is_lock_owned((address)mark->locker()) ?
owner_self : owner_other;
}
// CASE: inflated. Mark (tagged pointer) points to an ObjectMonitor.
// The Object:ObjectMonitor relationship is stable as long as we're
- // not at a safepoint.
+ // not at a safepoint and AsyncDeflateIdleMonitors is false.
if (mark->has_monitor()) {
- void * owner = mark->monitor()->_owner;
+ ObjectMonitorHandle omh;
+ if (!omh.save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ ObjectMonitor * monitor = omh.om_ptr();
+ void * owner = monitor->_owner;
if (owner == NULL) return owner_none;
return (owner == self ||
self->is_lock_owned((address)owner)) ? owner_self : owner_other;
}
// CASE: neutral
assert(mark->is_neutral(), "sanity check");
return owner_none; // it's unlocked
+ }
}
// FIXME: jvmti should call this
JavaThread* ObjectSynchronizer::get_lock_owner(ThreadsList * t_list, Handle h_obj) {
if (UseBiasedLocking) {
@@ -872,22 +936,29 @@
}
assert(!h_obj->mark()->has_bias_pattern(), "biases should be revoked by now");
}
oop obj = h_obj();
- address owner = NULL;
+ while (true) {
+ address owner = NULL;
markOop mark = ReadStableMark(obj);
// Uncontended case, header points to stack
if (mark->has_locker()) {
owner = (address) mark->locker();
}
// Contended case, header points to ObjectMonitor (tagged pointer)
else if (mark->has_monitor()) {
- ObjectMonitor* monitor = mark->monitor();
+ ObjectMonitorHandle omh;
+ if (!omh.save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ ObjectMonitor* monitor = omh.om_ptr();
assert(monitor != NULL, "monitor should be non-null");
owner = (address) monitor->owner();
}
if (owner != NULL) {
@@ -899,22 +970,33 @@
// Cannot have assertion since this object may have been
// locked by another thread when reaching here.
// assert(mark->is_neutral(), "sanity check");
return NULL;
+ }
}
// Visitors ...
void ObjectSynchronizer::monitors_iterate(MonitorClosure* closure) {
PaddedEnd<ObjectMonitor> * block = OrderAccess::load_acquire(&gBlockList);
while (block != NULL) {
assert(block->object() == CHAINMARKER, "must be a block header");
for (int i = _BLOCKSIZE - 1; i > 0; i--) {
ObjectMonitor* mid = (ObjectMonitor *)(block + i);
- oop object = (oop)mid->object();
- if (object != NULL) {
+ if (mid->is_active()) {
+ ObjectMonitorHandle omh(mid);
+
+ if (mid->object() == NULL ||
+ (AsyncDeflateIdleMonitors && mid->_owner == DEFLATER_MARKER)) {
+ // Only process with closure if the object is set.
+ // For async deflation, race here if monitor is not owned!
+ // The above ref_count bump (in ObjectMonitorHandle ctr)
+ // will cause subsequent async deflation to skip it.
+ // However, previous or concurrent async deflation is a race.
+ continue;
+ }
closure->do_monitor(mid);
}
}
block = (PaddedEnd<ObjectMonitor> *)block->FreeNext;
}
@@ -930,22 +1012,59 @@
static bool monitors_used_above_threshold() {
if (gMonitorPopulation == 0) {
return false;
}
+ if (MonitorUsedDeflationThreshold > 0) {
int monitors_used = gMonitorPopulation - gMonitorFreeCount;
int monitor_usage = (monitors_used * 100LL) / gMonitorPopulation;
return monitor_usage > MonitorUsedDeflationThreshold;
+ }
+ return false;
}
-bool ObjectSynchronizer::is_cleanup_needed() {
- if (MonitorUsedDeflationThreshold > 0) {
- return monitors_used_above_threshold();
+bool ObjectSynchronizer::is_async_deflation_needed() {
+ if (!AsyncDeflateIdleMonitors) {
+ return false;
+ }
+ if (is_async_deflation_requested()) {
+ // Async deflation request.
+ return true;
+ }
+ if (AsyncDeflationInterval > 0 &&
+ time_since_last_async_deflation_ms() > AsyncDeflationInterval &&
+ monitors_used_above_threshold()) {
+ // It's been longer than our specified deflate interval and there
+ // are too many monitors in use. We don't deflate more frequently
+ // than AsyncDeflationInterval (unless is_async_deflation_requested)
+ // in order to not swamp the ServiceThread.
+ _last_async_deflation_time_ns = os::javaTimeNanos();
+ return true;
}
return false;
}
+bool ObjectSynchronizer::is_safepoint_deflation_needed() {
+ if (!AsyncDeflateIdleMonitors) {
+ if (monitors_used_above_threshold()) {
+ // Too many monitors in use.
+ return true;
+ }
+ return false;
+ }
+ if (is_special_deflation_requested()) {
+ // For AsyncDeflateIdleMonitors only do a safepoint deflation
+ // if there is a special deflation request.
+ return true;
+ }
+ return false;
+}
+
+jlong ObjectSynchronizer::time_since_last_async_deflation_ms() {
+ return (os::javaTimeNanos() - _last_async_deflation_time_ns) / (NANOUNITS / MILLIUNITS);
+}
+
void ObjectSynchronizer::oops_do(OopClosure* f) {
// We only scan the global used list here (for moribund threads), and
// the thread-local monitors in Thread::oops_do().
global_used_oops_do(f);
}
@@ -1021,17 +1140,34 @@
// The VMThread will delete the op when completed.
VMThread::execute(new VM_ScavengeMonitors());
}
}
-ObjectMonitor* ObjectSynchronizer::omAlloc(Thread * Self) {
+ObjectMonitor* ObjectSynchronizer::omAlloc(Thread * Self,
+ const InflateCause cause) {
// 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
// scavenge costs. As usual, we lean toward time in space-time
// tradeoffs.
const int MAXPRIVATE = 1024;
+
+ if (AsyncDeflateIdleMonitors) {
+ JavaThread * jt = (JavaThread *)Self;
+ if (jt->omShouldDeflateIdleMonitors && jt->omInUseCount > 0 &&
+ cause != inflate_cause_vm_internal) {
+ // Deflate any per-thread idle monitors for this JavaThread if
+ // this is not an internal inflation; internal inflations can
+ // occur in places where it is not safe to pause for a safepoint.
+ // Clean up your own mess. (Gibbs Rule 45) Otherwise, skip this
+ // deflation. deflate_global_idle_monitors_using_JT() is called
+ // by the ServiceThread.
+ debug_only(jt->check_for_valid_safepoint_state(false);)
+ ObjectSynchronizer::deflate_per_thread_idle_monitors_using_JT();
+ }
+ }
+
for (;;) {
ObjectMonitor * m;
// 1: try to allocate from the thread's local omFreeList.
// Threads will attempt to allocate first from their local list, then
@@ -1042,10 +1178,11 @@
m = Self->omFreeList;
if (m != NULL) {
Self->omFreeList = m->FreeNext;
Self->omFreeCount--;
guarantee(m->object() == NULL, "invariant");
+ m->set_allocation_state(ObjectMonitor::New);
m->FreeNext = Self->omInUseList;
Self->omInUseList = m;
Self->omInUseCount++;
return m;
}
@@ -1063,12 +1200,27 @@
for (int i = Self->omFreeProvision; --i >= 0 && gFreeList != NULL;) {
gMonitorFreeCount--;
ObjectMonitor * take = gFreeList;
gFreeList = take->FreeNext;
guarantee(take->object() == NULL, "invariant");
+ if (AsyncDeflateIdleMonitors) {
+ // Clear any values we allowed to linger during async deflation.
+ take->_header = NULL;
+ take->set_owner(NULL);
+
+ if (take->ref_count() < 0) {
+ // Add back max_jint to restore the ref_count field to its
+ // proper value.
+ Atomic::add(max_jint, &take->_ref_count);
+
+ assert(take->ref_count() >= 0, "must not be negative: ref_count=%d",
+ take->ref_count());
+ }
+ }
guarantee(!take->is_busy(), "invariant");
take->Recycle();
+ assert(take->is_free(), "invariant");
omRelease(Self, take, false);
}
Thread::muxRelease(&gListLock);
Self->omFreeProvision += 1 + (Self->omFreeProvision/2);
if (Self->omFreeProvision > MAXPRIVATE) Self->omFreeProvision = MAXPRIVATE;
@@ -1117,10 +1269,11 @@
// linkage should be reconsidered. A better implementation would
// look like: class Block { Block * next; int N; ObjectMonitor Body [N] ; }
for (int i = 1; i < _BLOCKSIZE; i++) {
temp[i].FreeNext = (ObjectMonitor *)&temp[i+1];
+ assert(temp[i].is_free(), "invariant");
}
// terminate the last monitor as the end of list
temp[_BLOCKSIZE - 1].FreeNext = NULL;
@@ -1159,17 +1312,19 @@
// attempt failed. This doesn't allow unbounded #s of monitors to
// accumulate on a thread's free list.
//
// 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() -- from reclaiming them.
+// scavenger -- deflate_monitor_list() or deflate_monitor_list_using_JT()
+// -- from reclaiming them while we are trying to release them.
void ObjectSynchronizer::omRelease(Thread * Self, ObjectMonitor * m,
bool fromPerThreadAlloc) {
guarantee(m->header() == NULL, "invariant");
guarantee(m->object() == NULL, "invariant");
guarantee(((m->is_busy()|m->_recursions) == 0), "freeing in-use monitor");
+ m->set_allocation_state(ObjectMonitor::Free);
// Remove from omInUseList
if (fromPerThreadAlloc) {
ObjectMonitor* cur_mid_in_use = NULL;
bool extracted = false;
for (ObjectMonitor* mid = Self->omInUseList; mid != NULL; cur_mid_in_use = mid, mid = mid->FreeNext) {
@@ -1188,10 +1343,11 @@
assert(extracted, "Should have extracted from in-use list");
}
// FreeNext is used for both omInUseList and omFreeList, so clear old before setting new
m->FreeNext = Self->omFreeList;
+ guarantee(m->is_free(), "invariant");
Self->omFreeList = m;
Self->omFreeCount++;
}
// Return the monitors of a moribund thread's local free list to
@@ -1211,10 +1367,14 @@
// interleave with the deflate_idle_monitors scavenge operator. In particular,
// this ensures that the thread's monitors are scanned by a GC safepoint,
// either via Thread::oops_do() (if safepoint happens before omFlush()) or via
// ObjectSynchronizer::oops_do() (if it happens after omFlush() and the thread's
// monitors have been transferred to the global in-use list).
+//
+// With AsyncDeflateIdleMonitors, deflate_global_idle_monitors_using_JT()
+// and deflate_per_thread_idle_monitors_using_JT() (in another thread) can
+// run at the same time as omFlush() so we have to be careful.
void ObjectSynchronizer::omFlush(Thread * Self) {
ObjectMonitor * list = Self->omFreeList; // Null-terminated SLL
ObjectMonitor * tail = NULL;
int tally = 0;
@@ -1230,11 +1390,11 @@
guarantee(s->object() == NULL, "invariant");
guarantee(!s->is_busy(), "invariant");
s->set_owner(NULL); // redundant but good hygiene
}
guarantee(tail != NULL, "invariant");
- assert(Self->omFreeCount == tally, "free-count off");
+ ADIM_guarantee(Self->omFreeCount == tally, "free-count off");
Self->omFreeList = NULL;
Self->omFreeCount = 0;
}
ObjectMonitor * inUseList = Self->omInUseList;
@@ -1247,13 +1407,14 @@
// Link them to inUseTail, which will be linked into the global in-use list
// gOmInUseList below, under the gListLock
for (cur_om = inUseList; cur_om != NULL; cur_om = cur_om->FreeNext) {
inUseTail = cur_om;
inUseTally++;
+ ADIM_guarantee(cur_om->is_active(), "invariant");
}
guarantee(inUseTail != NULL, "invariant");
- assert(Self->omInUseCount == inUseTally, "in-use count off");
+ ADIM_guarantee(Self->omInUseCount == inUseTally, "in-use count off");
Self->omInUseList = NULL;
Self->omInUseCount = 0;
}
Thread::muxAcquire(&gListLock, "omFlush");
@@ -1297,23 +1458,32 @@
event->set_cause((u1)cause);
event->commit();
}
// Fast path code shared by multiple functions
-void ObjectSynchronizer::inflate_helper(oop obj) {
+void ObjectSynchronizer::inflate_helper(ObjectMonitorHandle * omh_p, oop obj) {
+ while (true) {
markOop mark = obj->mark();
if (mark->has_monitor()) {
- assert(ObjectSynchronizer::verify_objmon_isinpool(mark->monitor()), "monitor is invalid");
- assert(mark->monitor()->header()->is_neutral(), "monitor must record a good object header");
+ if (!omh_p->save_om_ptr(obj, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ ObjectMonitor * monitor = omh_p->om_ptr();
+ assert(ObjectSynchronizer::verify_objmon_isinpool(monitor), "monitor is invalid");
+ markOop dmw = monitor->header();
+ assert(dmw->is_neutral(), "sanity check: header=" INTPTR_FORMAT, p2i(dmw));
+ return;
+ }
+ inflate(omh_p, Thread::current(), obj, inflate_cause_vm_internal);
return;
}
- inflate(Thread::current(), obj, inflate_cause_vm_internal);
}
-ObjectMonitor* ObjectSynchronizer::inflate(Thread * Self,
- oop object,
- const InflateCause cause) {
+void ObjectSynchronizer::inflate(ObjectMonitorHandle * omh_p, Thread * Self,
+ oop object, const InflateCause cause) {
// Inflate mutates the heap ...
// Relaxing assertion for bug 6320749.
assert(Universe::verify_in_progress() ||
!SafepointSynchronize::is_at_safepoint(), "invariant");
@@ -1330,16 +1500,21 @@
// * Neutral - aggressively inflate the object.
// * BIASED - Illegal. We should never see this
// CASE: inflated
if (mark->has_monitor()) {
- ObjectMonitor * inf = mark->monitor();
+ if (!omh_p->save_om_ptr(object, mark)) {
+ // Lost a race with async deflation so try again.
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ continue;
+ }
+ ObjectMonitor * inf = omh_p->om_ptr();
markOop dmw = inf->header();
assert(dmw->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(dmw));
assert(oopDesc::equals((oop) inf->object(), object), "invariant");
assert(ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid");
- return inf;
+ return;
}
// CASE: inflation in progress - inflating over a stack-lock.
// Some other thread is converting from stack-locked to inflated.
// Only that thread can complete inflation -- other threads must wait.
@@ -1371,11 +1546,22 @@
// See the comments in omAlloc().
LogStreamHandle(Trace, monitorinflation) lsh;
if (mark->has_locker()) {
- ObjectMonitor * m = omAlloc(Self);
+ ObjectMonitor * m;
+ if (!AsyncDeflateIdleMonitors || cause == inflate_cause_vm_internal) {
+ // If !AsyncDeflateIdleMonitors or if an internal inflation, then
+ // we won't stop for a potential safepoint in omAlloc.
+ m = omAlloc(Self, cause);
+ } else {
+ // If AsyncDeflateIdleMonitors and not an internal inflation, then
+ // we may stop for a safepoint in omAlloc() so protect object.
+ Handle h_obj(Self, object);
+ m = omAlloc(Self, cause);
+ object = h_obj(); // Refresh object.
+ }
// Optimistically prepare the objectmonitor - anticipate successful CAS
// We do this before the CAS in order to minimize the length of time
// in which INFLATING appears in the mark.
m->Recycle();
m->_Responsible = NULL;
@@ -1419,11 +1605,11 @@
// object is in the mark. Furthermore the owner can't complete
// an unlock on the object, either.
markOop 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).
- assert(dmw->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(dmw));
+ ADIM_guarantee(dmw->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(dmw));
// Setup monitor fields to proper values -- prepare the monitor
m->set_header(dmw);
// Optimization: if the mark->locker stack address is associated
@@ -1433,10 +1619,14 @@
// with CAS. That is, we can avoid the xchg-NULL .... ST idiom.
m->set_owner(mark->locker());
m->set_object(object);
// TODO-FIXME: assert BasicLock->dhw != 0.
+ omh_p->set_om_ptr(m);
+ assert(m->is_new(), "freshly allocated monitor must be new");
+ m->set_allocation_state(ObjectMonitor::Old);
+
// Must preserve store ordering. The monitor state must
// be stable at the time of publishing the monitor address.
guarantee(object->mark() == markOopDesc::INFLATING(), "invariant");
object->release_set_mark(markOopDesc::encode(m));
@@ -1450,11 +1640,12 @@
p2i(object->mark()), object->klass()->external_name());
}
if (event.should_commit()) {
post_monitor_inflate_event(&event, object, cause);
}
- return m;
+ ADIM_guarantee(!m->is_free(), "inflated monitor to be returned cannot be free");
+ return;
}
// CASE: neutral
// TODO-FIXME: for entry we currently inflate and then try to CAS _owner.
// If we know we're inflating for entry it's better to inflate by swinging a
@@ -1465,25 +1656,42 @@
// An inflateTry() method that we could call from fast_enter() and slow_enter()
// would be useful.
// Catch if the object's header is not neutral (not locked and
// not marked is what we care about here).
- assert(mark->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(mark));
- ObjectMonitor * m = omAlloc(Self);
+ ADIM_guarantee(mark->is_neutral(), "invariant: header=" INTPTR_FORMAT, p2i(mark));
+ ObjectMonitor * m;
+ if (!AsyncDeflateIdleMonitors || cause == inflate_cause_vm_internal) {
+ // If !AsyncDeflateIdleMonitors or if an internal inflation, then
+ // we won't stop for a potential safepoint in omAlloc.
+ m = omAlloc(Self, cause);
+ } else {
+ // If AsyncDeflateIdleMonitors and not an internal inflation, then
+ // we may stop for a safepoint in omAlloc() so protect object.
+ Handle h_obj(Self, object);
+ m = omAlloc(Self, cause);
+ object = h_obj(); // Refresh object.
+ }
// prepare m for installation - set monitor to initial state
m->Recycle();
m->set_header(mark);
m->set_owner(NULL);
m->set_object(object);
m->_recursions = 0;
m->_Responsible = NULL;
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit; // consider: keep metastats by type/class
+ omh_p->set_om_ptr(m);
+ assert(m->is_new(), "freshly allocated monitor must be new");
+ m->set_allocation_state(ObjectMonitor::Old);
+
if (object->cas_set_mark(markOopDesc::encode(m), mark) != mark) {
m->set_header(NULL);
m->set_object(NULL);
m->Recycle();
+ omh_p->set_om_ptr(NULL);
+ // omRelease() will reset the allocation state
omRelease(Self, m, true);
m = NULL;
continue;
// interference - the markword changed - just retry.
// The state-transitions are one-way, so there's no chance of
@@ -1500,11 +1708,12 @@
p2i(object->mark()), object->klass()->external_name());
}
if (event.should_commit()) {
post_monitor_inflate_event(&event, object, cause);
}
- return m;
+ ADIM_guarantee(!m->is_free(), "inflated monitor to be returned cannot be free");
+ return;
}
}
// We maintain a list of in-use monitors for each thread.
@@ -1526,10 +1735,30 @@
// 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.
+void ObjectSynchronizer::do_safepoint_work(DeflateMonitorCounters* _counters) {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+
+ // The per-thread in-use lists are handled in
+ // ParallelSPCleanupThreadClosure::do_thread().
+
+ if (!AsyncDeflateIdleMonitors || is_special_deflation_requested()) {
+ // Use the older mechanism for the global in-use list or if a
+ // special deflation has been requested before the safepoint.
+ 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);
+ MonitorLocker ml(Service_lock, Mutex::_no_safepoint_check_flag);
+ ml.notify_all();
+}
+
// 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** freeHeadp,
ObjectMonitor** freeTailp) {
@@ -1563,10 +1792,11 @@
obj->release_set_mark(dmw);
mid->clear();
assert(mid->object() == NULL, "invariant: object=" INTPTR_FORMAT,
p2i(mid->object()));
+ assert(mid->is_free(), "invariant");
// Move the object to the working free list defined by freeHeadp, freeTailp
if (*freeHeadp == NULL) *freeHeadp = mid;
if (*freeTailp != NULL) {
ObjectMonitor * prevtail = *freeTailp;
@@ -1577,10 +1807,150 @@
deflated = true;
}
return deflated;
}
+// Deflate the specified ObjectMonitor if not in-use using a JavaThread.
+// Returns true if it was deflated and false otherwise.
+//
+// The async deflation protocol sets owner to DEFLATER_MARKER and
+// makes ref_count negative as signals to contending threads that
+// an async deflation is in progress. There are a number of checks
+// as part of the protocol to make sure that the calling thread has
+// not lost the race to a contending thread or to a thread that just
+// wants to use the ObjectMonitor*.
+//
+// The ObjectMonitor has been successfully async deflated when:
+// (owner == DEFLATER_MARKER && ref_count < 0)
+// Contending threads or ObjectMonitor* using threads that see those
+// values know to retry their operation.
+//
+bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
+ ObjectMonitor** freeHeadp,
+ ObjectMonitor** freeTailp) {
+ 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.
+ assert(mid->is_old(), "must be old: allocation_state=%d",
+ (int) mid->allocation_state());
+
+ if (mid->is_busy() || mid->ref_count() != 0) {
+ // Easy checks are first - the ObjectMonitor is busy or ObjectMonitor*
+ // is in use so no deflation.
+ return false;
+ }
+
+ if (Atomic::replace_if_null(DEFLATER_MARKER, &(mid->_owner))) {
+ // ObjectMonitor is not owned by another thread. Our setting
+ // owner to DEFLATER_MARKER forces any contending thread through
+ // the slow path. This is just the first part of the async
+ // deflation dance.
+
+ if (mid->_contentions != 0 || mid->_waiters != 0) {
+ // Another thread has raced to enter the ObjectMonitor after
+ // mid->is_busy() above or has already entered and waited on
+ // it which makes it busy so no deflation. Restore owner to
+ // NULL if it is still DEFLATER_MARKER.
+ Atomic::cmpxchg((void*)NULL, &mid->_owner, DEFLATER_MARKER);
+ return false;
+ }
+
+ if (Atomic::cmpxchg(-max_jint, &mid->_ref_count, (jint)0) == 0) {
+ // Make ref_count negative to force any contending threads or
+ // ObjectMonitor* using threads to retry. This is the second
+ // part of the async deflation dance.
+
+ if (mid->_owner == DEFLATER_MARKER) {
+ // If owner is still DEFLATER_MARKER, then we have successfully
+ // signaled any contending threads to retry. If it is not, then we
+ // have lost the race to an entering thread and the ObjectMonitor
+ // is now busy. This is the third and final part of the async
+ // deflation dance.
+ // Note: This owner check solves the ABA problem with ref_count
+ // where another thread acquired the ObjectMonitor, finished
+ // using it and restored the ref_count to zero.
+
+ // Sanity checks for the races:
+ guarantee(mid->_contentions == 0, "must be 0: contentions=%d",
+ mid->_contentions);
+ guarantee(mid->_waiters == 0, "must be 0: waiters=%d", mid->_waiters);
+ guarantee(mid->_cxq == NULL, "must be no contending threads: cxq="
+ INTPTR_FORMAT, p2i(mid->_cxq));
+ guarantee(mid->_EntryList == NULL,
+ "must be no entering threads: EntryList=" INTPTR_FORMAT,
+ p2i(mid->_EntryList));
+
+ const oop obj = (oop) mid->object();
+ if (log_is_enabled(Trace, monitorinflation)) {
+ ResourceMark rm;
+ log_trace(monitorinflation)("deflate_monitor_using_JT: "
+ "object=" INTPTR_FORMAT ", mark="
+ INTPTR_FORMAT ", type='%s'",
+ p2i(obj), p2i(obj->mark()),
+ obj->klass()->external_name());
+ }
+
+ // Install the old mark word if nobody else has already done it.
+ mid->install_displaced_markword_in_object(obj);
+ mid->clear_using_JT();
+
+ assert(mid->object() == NULL, "must be NULL: object=" INTPTR_FORMAT,
+ p2i(mid->object()));
+ assert(mid->is_free(), "must be free: allocation_state=%d",
+ (int) mid->allocation_state());
+
+ // Move the deflated ObjectMonitor to the working free list
+ // defined by freeHeadp and freeTailp.
+ if (*freeHeadp == NULL) {
+ // First one on the list.
+ *freeHeadp = mid;
+ }
+ if (*freeTailp != NULL) {
+ // We append to the list so the caller can use mid->FreeNext
+ // to fix the linkages in its context.
+ ObjectMonitor * prevtail = *freeTailp;
+ // Should have been cleaned up by the caller:
+ assert(prevtail->FreeNext == NULL, "must be NULL: FreeNext="
+ INTPTR_FORMAT, p2i(prevtail->FreeNext));
+ prevtail->FreeNext = mid;
+ }
+ *freeTailp = mid;
+
+ // At this point, mid->FreeNext still refers to its current
+ // value and another ObjectMonitor's FreeNext field still
+ // refers to this ObjectMonitor. Those linkages have to be
+ // cleaned up by the caller who has the complete context.
+
+ // We leave owner == DEFLATER_MARKER and ref_count < 0
+ // to force any racing threads to retry.
+ return true; // Success, ObjectMonitor has been deflated.
+ }
+
+ // The owner was changed from DEFLATER_MARKER so we lost the
+ // race since the ObjectMonitor is now busy.
+
+ // Add back max_jint to restore the ref_count field to its
+ // proper value (which may not be what we saw above):
+ Atomic::add(max_jint, &mid->_ref_count);
+
+ assert(mid->ref_count() >= 0, "must not be negative: ref_count=%d",
+ mid->ref_count());
+ return false;
+ }
+
+ // The ref_count was no longer 0 so we lost the race since the
+ // ObjectMonitor is now busy or the ObjectMonitor* is now is use.
+ // Restore owner to NULL if it is still DEFLATER_MARKER:
+ Atomic::cmpxchg((void*)NULL, &mid->_owner, DEFLATER_MARKER);
+ }
+
+ // The owner field is no longer NULL so we lost the race since the
+ // ObjectMonitor is now busy.
+ return false;
+}
+
// Walk a given monitor list, and deflate idle monitors
// The given list could be a per-thread list or a global list
// Caller acquires gListLock as needed.
//
// In the case of parallel processing of thread local monitor lists,
@@ -1620,20 +1990,105 @@
}
}
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.
+// Caller acquires gListLock as appropriate. If a safepoint has started,
+// then we save state via savedMidInUsep and return to the caller to
+// honor the safepoint.
+//
+int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** listHeadp,
+ ObjectMonitor** freeHeadp,
+ ObjectMonitor** freeTailp,
+ ObjectMonitor** savedMidInUsep) {
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ assert(Thread::current()->is_Java_thread(), "precondition");
+
+ ObjectMonitor* mid;
+ ObjectMonitor* next;
+ ObjectMonitor* cur_mid_in_use = NULL;
+ int deflated_count = 0;
+
+ if (*savedMidInUsep == NULL) {
+ // No saved state so start at the beginning.
+ mid = *listHeadp;
+ } else {
+ // We're restarting after a safepoint so restore the necessary state
+ // before we resume.
+ cur_mid_in_use = *savedMidInUsep;
+ mid = cur_mid_in_use->FreeNext;
+ }
+ while (mid != NULL) {
+ // Only try to deflate if there is an associated Java object and if
+ // mid is old (is not newly allocated and is not newly freed).
+ if (mid->object() != NULL && mid->is_old() &&
+ deflate_monitor_using_JT(mid, freeHeadp, freeTailp)) {
+ // Deflation succeeded so update the in-use list.
+ if (mid == *listHeadp) {
+ *listHeadp = mid->FreeNext;
+ } else if (cur_mid_in_use != NULL) {
+ // Maintain the current in-use list.
+ cur_mid_in_use->FreeNext = mid->FreeNext;
+ }
+ next = mid->FreeNext;
+ mid->FreeNext = NULL;
+ // At this point mid is disconnected from the in-use list
+ // and is the current tail in the freeHeadp list.
+ mid = next;
+ deflated_count++;
+ } else {
+ // mid is considered in-use if it does not have an associated
+ // Java object or mid is not old or deflation did not succeed.
+ // A mid->is_new() node can be seen here when it is freshly
+ // returned by omAlloc() (and skips the deflation code path).
+ // A mid->is_old() node can be seen here when deflation failed.
+ // A mid->is_free() node can be seen here when a fresh node from
+ // omAlloc() is released by omRelease() due to losing the race
+ // in inflate().
+
+ cur_mid_in_use = mid;
+ mid = mid->FreeNext;
+
+ if (SafepointSynchronize::is_synchronizing() &&
+ cur_mid_in_use != *listHeadp && cur_mid_in_use->is_old()) {
+ // If a safepoint has started and cur_mid_in_use is not the list
+ // head and is old, then it is safe to use as saved state. Return
+ // to the caller so gListLock can be dropped as appropriate
+ // before blocking.
+ *savedMidInUsep = cur_mid_in_use;
+ return deflated_count;
+ }
+ }
+ }
+ // We finished the list without a safepoint starting so there's
+ // no need to save state.
+ *savedMidInUsep = NULL;
+ return deflated_count;
+}
+
void ObjectSynchronizer::prepare_deflate_idle_monitors(DeflateMonitorCounters* counters) {
counters->nInuse = 0; // currently associated with objects
counters->nInCirculation = 0; // extant
counters->nScavenged = 0; // reclaimed (global and per-thread)
counters->perThreadScavenged = 0; // per-thread scavenge total
counters->perThreadTimes = 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 unless a special deflation has been requested.
+ if (!is_special_deflation_requested()) {
+ return;
+ }
+ }
+
bool deflated = false;
ObjectMonitor * freeHeadp = NULL; // Local SLL of scavenged monitors
ObjectMonitor * freeTailp = NULL;
elapsedTimer timer;
@@ -1682,19 +2137,150 @@
if (ls != NULL) {
ls->print_cr("deflating global idle monitors, %3.7f secs, %d monitors", timer.seconds(), deflated_count);
}
}
+// 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();
+
+ deflate_common_idle_monitors_using_JT(true /* is_global */, self);
+}
+
+// Deflate per-thread idle ObjectMonitors using a JavaThread.
+//
+void ObjectSynchronizer::deflate_per_thread_idle_monitors_using_JT() {
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+ assert(Thread::current()->is_Java_thread(), "precondition");
+ JavaThread * self = JavaThread::current();
+
+ self->omShouldDeflateIdleMonitors = false;
+
+ deflate_common_idle_monitors_using_JT(false /* !is_global */, self);
+}
+
+// Deflate global or per-thread idle ObjectMonitors using a JavaThread.
+//
+void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, JavaThread * self) {
+ int deflated_count = 0;
+ ObjectMonitor * freeHeadp = NULL; // Local SLL of scavenged ObjectMonitors
+ ObjectMonitor * freeTailp = NULL;
+ ObjectMonitor * savedMidInUsep = NULL;
+ elapsedTimer timer;
+
+ if (log_is_enabled(Info, monitorinflation)) {
+ timer.start();
+ }
+
+ if (is_global) {
+ Thread::muxAcquire(&gListLock, "deflate_global_idle_monitors_using_JT(1)");
+ OM_PERFDATA_OP(MonExtant, set_value(gOmInUseCount));
+ } else {
+ OM_PERFDATA_OP(MonExtant, inc(self->omInUseCount));
+ }
+
+ do {
+ int local_deflated_count;
+ if (is_global) {
+ local_deflated_count = deflate_monitor_list_using_JT((ObjectMonitor **)&gOmInUseList, &freeHeadp, &freeTailp, &savedMidInUsep);
+ gOmInUseCount -= local_deflated_count;
+ } else {
+ local_deflated_count = deflate_monitor_list_using_JT(self->omInUseList_addr(), &freeHeadp, &freeTailp, &savedMidInUsep);
+ self->omInUseCount -= local_deflated_count;
+ }
+ deflated_count += local_deflated_count;
+
+ if (freeHeadp != NULL) {
+ // Move the scavenged ObjectMonitors to the global free list.
+ guarantee(freeTailp != NULL && local_deflated_count > 0, "freeTailp=" INTPTR_FORMAT ", local_deflated_count=%d", p2i(freeTailp), local_deflated_count);
+ assert(freeTailp->FreeNext == NULL, "invariant");
+
+ if (!is_global) {
+ Thread::muxAcquire(&gListLock, "deflate_per_thread_idle_monitors_using_JT(2)");
+ }
+ // Constant-time list splice - prepend scavenged segment to gFreeList.
+ freeTailp->FreeNext = gFreeList;
+ gFreeList = freeHeadp;
+
+ gMonitorFreeCount += local_deflated_count;
+ OM_PERFDATA_OP(Deflations, inc(local_deflated_count));
+ if (!is_global) {
+ Thread::muxRelease(&gListLock);
+ }
+ }
+
+ if (savedMidInUsep != NULL) {
+ // deflate_monitor_list_using_JT() detected a safepoint starting.
+ if (is_global) {
+ Thread::muxRelease(&gListLock);
+ }
+ timer.stop();
+ {
+ if (is_global) {
+ log_debug(monitorinflation)("pausing deflation of global idle monitors for a safepoint.");
+ } else {
+ log_debug(monitorinflation)("jt=" INTPTR_FORMAT ": pausing deflation of per-thread idle monitors for a safepoint.", p2i(self));
+ }
+ assert(SafepointSynchronize::is_synchronizing(), "sanity check");
+ ThreadBlockInVM blocker(self);
+ }
+ // Prepare for another loop after the safepoint.
+ freeHeadp = NULL;
+ freeTailp = NULL;
+ if (log_is_enabled(Info, monitorinflation)) {
+ timer.start();
+ }
+ if (is_global) {
+ Thread::muxAcquire(&gListLock, "deflate_global_idle_monitors_using_JT(3)");
+ }
+ }
+ } while (savedMidInUsep != NULL);
+ if (is_global) {
+ Thread::muxRelease(&gListLock);
+ }
+ 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) {
+ if (is_global) {
+ ls->print_cr("async-deflating global idle monitors, %3.7f secs, %d monitors", timer.seconds(), deflated_count);
+ } else {
+ ls->print_cr("jt=" INTPTR_FORMAT ": async-deflating per-thread idle monitors, %3.7f secs, %d monitors", p2i(self), timer.seconds(), deflated_count);
+ }
+ }
+}
+
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.
+ // Note: AsyncDeflateIdleMonitors only deflates per-thread idle
+ // monitors at a safepoint when a special deflation has been requested.
log_info(safepoint, cleanup)("deflating per-thread idle monitors, %3.7f secs, monitors=%d", counters->perThreadTimes, counters->perThreadScavenged);
+ bool needs_special_deflation = is_special_deflation_requested();
+ if (!AsyncDeflateIdleMonitors || needs_special_deflation) {
+ // AsyncDeflateIdleMonitors does not use these counters unless
+ // there is a special deflation request.
+
gMonitorFreeCount += counters->nScavenged;
+ OM_PERFDATA_OP(Deflations, inc(counters->nScavenged));
+ OM_PERFDATA_OP(MonExtant, set_value(counters->nInCirculation));
+ }
+
if (log_is_enabled(Debug, monitorinflation)) {
// exit_globals()'s call to audit_and_print_stats() is done
// at the Info level.
ObjectSynchronizer::audit_and_print_stats(false /* on_exit */);
} else if (log_is_enabled(Info, monitorinflation)) {
@@ -1704,21 +2290,32 @@
gOmInUseCount, gMonitorFreeCount);
Thread::muxRelease(&gListLock);
}
ForceMonitorScavenge = 0; // Reset
-
- OM_PERFDATA_OP(Deflations, inc(counters->nScavenged));
- OM_PERFDATA_OP(MonExtant, set_value(counters->nInCirculation));
-
GVars.stwRandom = os::random();
GVars.stwCycle++;
+ if (needs_special_deflation) {
+ set_is_special_deflation_requested(false); // special deflation is done
+ }
}
void ObjectSynchronizer::deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ if (AsyncDeflateIdleMonitors) {
+ if (!is_special_deflation_requested()) {
+ // Mark the JavaThread for idle monitor deflation if a special
+ // deflation has NOT been requested.
+ if (thread->omInUseCount > 0) {
+ // This JavaThread is using monitors so mark it.
+ thread->omShouldDeflateIdleMonitors = true;
+ }
+ return;
+ }
+ }
+
ObjectMonitor * freeHeadp = NULL; // Local SLL of scavenged monitors
ObjectMonitor * freeTailp = NULL;
elapsedTimer timer;
if (log_is_enabled(Info, safepoint, cleanup) ||
@@ -1923,11 +2520,12 @@
}
// Check a free monitor entry; log any errors.
void ObjectSynchronizer::chk_free_entry(JavaThread * jt, ObjectMonitor * n,
outputStream * out, int *error_cnt_p) {
- if (n->is_busy()) {
+ if ((!AsyncDeflateIdleMonitors && n->is_busy()) ||
+ (AsyncDeflateIdleMonitors && n->is_busy_async())) {
if (jt != NULL) {
out->print_cr("ERROR: jt=" INTPTR_FORMAT ", monitor=" INTPTR_FORMAT
": free per-thread monitor must not be busy.", p2i(jt),
p2i(n));
} else {
@@ -1940,17 +2538,18 @@
if (jt != NULL) {
out->print_cr("ERROR: jt=" INTPTR_FORMAT ", monitor=" INTPTR_FORMAT
": free per-thread monitor must have NULL _header "
"field: _header=" INTPTR_FORMAT, p2i(jt), p2i(n),
p2i(n->header()));
- } else {
+ *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), p2i(n->header()));
- }
*error_cnt_p = *error_cnt_p + 1;
}
+ }
if (n->object() != NULL) {
if (jt != NULL) {
out->print_cr("ERROR: jt=" INTPTR_FORMAT ", monitor=" INTPTR_FORMAT
": free per-thread monitor must have NULL _object "
"field: _object=" INTPTR_FORMAT, p2i(jt), p2i(n),
@@ -2112,41 +2711,42 @@
}
if (gOmInUseCount > 0) {
out->print_cr("In-use global monitor info:");
out->print_cr("(B -> is_busy, H -> has hash code, L -> lock status)");
- out->print_cr("%18s %s %18s %18s",
- "monitor", "BHL", "object", "object type");
- out->print_cr("================== === ================== ==================");
+ out->print_cr("%18s %s %7s %18s %18s",
+ "monitor", "BHL", "ref_cnt", "object", "object type");
+ out->print_cr("================== === ======= ================== ==================");
for (ObjectMonitor * n = gOmInUseList; n != NULL; n = n->FreeNext) {
const oop obj = (oop) n->object();
const markOop mark = n->header();
ResourceMark rm;
- out->print_cr(INTPTR_FORMAT " %d%d%d " INTPTR_FORMAT " %s", p2i(n),
- n->is_busy() != 0, mark->hash() != 0, n->owner() != NULL,
- p2i(obj), obj->klass()->external_name());
+ out->print_cr(INTPTR_FORMAT " %d%d%d %7d " INTPTR_FORMAT " %s",
+ p2i(n), n->is_busy() != 0, mark->hash() != 0,
+ n->owner() != NULL, (int)n->ref_count(), p2i(obj),
+ obj->klass()->external_name());
}
}
if (!on_exit) {
Thread::muxRelease(&gListLock);
}
out->print_cr("In-use per-thread monitor info:");
out->print_cr("(B -> is_busy, H -> has hash code, L -> lock status)");
- out->print_cr("%18s %18s %s %18s %18s",
- "jt", "monitor", "BHL", "object", "object type");
- out->print_cr("================== ================== === ================== ==================");
+ out->print_cr("%18s %18s %s %7s %18s %18s",
+ "jt", "monitor", "BHL", "ref_cnt", "object", "object type");
+ out->print_cr("================== ================== === ======= ================== ==================");
for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
for (ObjectMonitor * n = jt->omInUseList; n != NULL; n = n->FreeNext) {
const oop obj = (oop) n->object();
const markOop mark = n->header();
ResourceMark rm;
- out->print_cr(INTPTR_FORMAT " " INTPTR_FORMAT " %d%d%d " INTPTR_FORMAT
- " %s", p2i(jt), p2i(n), n->is_busy() != 0,
- mark->hash() != 0, n->owner() != NULL, p2i(obj),
- obj->klass()->external_name());
+ out->print_cr(INTPTR_FORMAT " " INTPTR_FORMAT " %d%d%d %7d "
+ INTPTR_FORMAT " %s", p2i(jt), p2i(n), n->is_busy() != 0,
+ mark->hash() != 0, n->owner() != NULL, (int)n->ref_count(),
+ p2i(obj), obj->klass()->external_name());
}
}
out->flush();
}
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