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8210848: Obsolete SyncKnobs

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Reviewed-by: redestad, coleenp, dholmes, dcubed
This commit is contained in:
Mikael Vidstedt 2018-09-24 22:12:07 -07:00
parent 3edf95fc44
commit 25295df059
9 changed files with 91 additions and 532 deletions
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545
src/hotspot/share/runtime/objectMonitor.cpp
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@ -101,39 +101,15 @@
// The knob* variables are effectively final. Once set they should
// never be modified hence. Consider using __read_mostly with GCC.
int ObjectMonitor::Knob_ExitRelease = 0;
int ObjectMonitor::Knob_InlineNotify = 1;
int ObjectMonitor::Knob_Verbose = 0;
int ObjectMonitor::Knob_VerifyInUse = 0;
int ObjectMonitor::Knob_VerifyMatch = 0;
int ObjectMonitor::Knob_SpinLimit = 5000; // derived by an external tool -
static int Knob_ReportSettings = 0;
static int Knob_SpinBase = 0; // Floor AKA SpinMin
static int Knob_SpinBackOff = 0; // spin-loop backoff
static int Knob_CASPenalty = -1; // Penalty for failed CAS
static int Knob_OXPenalty = -1; // Penalty for observed _owner change
static int Knob_SpinSetSucc = 1; // spinners set the _succ field
static int Knob_SpinEarly = 1;
static int Knob_SuccEnabled = 1; // futile wake throttling
static int Knob_SuccRestrict = 0; // Limit successors + spinners to at-most-one
static int Knob_MaxSpinners = -1; // Should be a function of # CPUs
static int Knob_Bonus = 100; // spin success bonus
static int Knob_BonusB = 100; // spin success bonus
static int Knob_Penalty = 200; // spin failure penalty
static int Knob_Poverty = 1000;
static int Knob_SpinAfterFutile = 1; // Spin after returning from park()
static int Knob_FixedSpin = 0;
static int Knob_OState = 3; // Spinner checks thread state of _owner
static int Knob_UsePause = 1;
static int Knob_ExitPolicy = 0;
static int Knob_PreSpin = 10; // 20-100 likely better
static int Knob_ResetEvent = 0;
static int BackOffMask = 0;
static int Knob_FastHSSEC = 0;
static int Knob_MoveNotifyee = 2; // notify() - disposition of notifyee
static int Knob_QMode = 0; // EntryList-cxq policy - queue discipline
static volatile int InitDone = 0;
// -----------------------------------------------------------------------------
@ -299,7 +275,7 @@ void ObjectMonitor::enter(TRAPS) {
// transitions. The following spin is strictly optional ...
// Note that if we acquire the monitor from an initial spin
// we forgo posting JVMTI events and firing DTRACE probes.
if (Knob_SpinEarly && TrySpin (Self) > 0) {
if (TrySpin(Self) > 0) {
assert(_owner == Self, "invariant");
assert(_recursions == 0, "invariant");
assert(((oop)(object()))->mark() == markOopDesc::encode(this), "invariant");
@ -461,7 +437,7 @@ void ObjectMonitor::EnterI(TRAPS) {
// to the owner. This has subtle but beneficial affinity
// effects.
if (TrySpin (Self) > 0) {
if (TrySpin(Self) > 0) {
assert(_owner == Self, "invariant");
assert(_succ != Self, "invariant");
assert(_Responsible != Self, "invariant");
@ -583,20 +559,14 @@ void ObjectMonitor::EnterI(TRAPS) {
// We can defer clearing _succ until after the spin completes
// TrySpin() must tolerate being called with _succ == Self.
// Try yet another round of adaptive spinning.
if ((Knob_SpinAfterFutile & 1) && TrySpin(Self) > 0) break;
if (TrySpin(Self) > 0) break;
// We can find that we were unpark()ed and redesignated _succ while
// we were spinning. That's harmless. If we iterate and call park(),
// park() will consume the event and return immediately and we'll
// just spin again. This pattern can repeat, leaving _succ to simply
// spin on a CPU. Enable Knob_ResetEvent to clear pending unparks().
// Alternately, we can sample fired() here, and if set, forgo spinning
// in the next iteration.
// spin on a CPU.
if ((Knob_ResetEvent & 1) && Self->_ParkEvent->fired()) {
Self->_ParkEvent->reset();
OrderAccess::fence();
}
if (_succ == Self) _succ = NULL;
// Invariant: after clearing _succ a thread *must* retry _owner before parking.
@ -675,9 +645,7 @@ void ObjectMonitor::EnterI(TRAPS) {
// contended slow-path from EnterI(). We use ReenterI() only for
// monitor reentry in wait().
//
// In the future we should reconcile EnterI() and ReenterI(), adding
// Knob_Reset and Knob_SpinAfterFutile support and restructuring the
// loop accordingly.
// In the future we should reconcile EnterI() and ReenterI().
void ObjectMonitor::ReenterI(Thread * Self, ObjectWaiter * SelfNode) {
assert(Self != NULL, "invariant");
@ -929,181 +897,60 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
for (;;) {
assert(THREAD == _owner, "invariant");
if (Knob_ExitPolicy == 0) {
// release semantics: prior loads and stores from within the critical section
// must not float (reorder) past the following store that drops the lock.
// On SPARC that requires MEMBAR #loadstore|#storestore.
// But of course in TSO #loadstore|#storestore is not required.
// I'd like to write one of the following:
// A. OrderAccess::release() ; _owner = NULL
// B. OrderAccess::loadstore(); OrderAccess::storestore(); _owner = NULL;
// Unfortunately OrderAccess::release() and OrderAccess::loadstore() both
// store into a _dummy variable. That store is not needed, but can result
// in massive wasteful coherency traffic on classic SMP systems.
// Instead, I use release_store(), which is implemented as just a simple
// ST on x64, x86 and SPARC.
OrderAccess::release_store(&_owner, (void*)NULL); // drop the lock
OrderAccess::storeload(); // See if we need to wake a successor
if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
return;
}
// Other threads are blocked trying to acquire the lock.
// release semantics: prior loads and stores from within the critical section
// must not float (reorder) past the following store that drops the lock.
// On SPARC that requires MEMBAR #loadstore|#storestore.
// But of course in TSO #loadstore|#storestore is not required.
OrderAccess::release_store(&_owner, (void*)NULL); // drop the lock
OrderAccess::storeload(); // See if we need to wake a successor
if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
return;
}
// Other threads are blocked trying to acquire the lock.
// Normally the exiting thread is responsible for ensuring succession,
// but if other successors are ready or other entering threads are spinning
// then this thread can simply store NULL into _owner and exit without
// waking a successor. The existence of spinners or ready successors
// guarantees proper succession (liveness). Responsibility passes to the
// ready or running successors. The exiting thread delegates the duty.
// More precisely, if a successor already exists this thread is absolved
// of the responsibility of waking (unparking) one.
//
// The _succ variable is critical to reducing futile wakeup frequency.
// _succ identifies the "heir presumptive" thread that has been made
// ready (unparked) but that has not yet run. We need only one such
// successor thread to guarantee progress.
// See http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf
// section 3.3 "Futile Wakeup Throttling" for details.
//
// Note that spinners in Enter() also set _succ non-null.
// In the current implementation spinners opportunistically set
// _succ so that exiting threads might avoid waking a successor.
// Another less appealing alternative would be for the exiting thread
// to drop the lock and then spin briefly to see if a spinner managed
// to acquire the lock. If so, the exiting thread could exit
// immediately without waking a successor, otherwise the exiting
// thread would need to dequeue and wake a successor.
// (Note that we'd need to make the post-drop spin short, but no
// shorter than the worst-case round-trip cache-line migration time.
// The dropped lock needs to become visible to the spinner, and then
// the acquisition of the lock by the spinner must become visible to
// the exiting thread).
// Normally the exiting thread is responsible for ensuring succession,
// but if other successors are ready or other entering threads are spinning
// then this thread can simply store NULL into _owner and exit without
// waking a successor. The existence of spinners or ready successors
// guarantees proper succession (liveness). Responsibility passes to the
// ready or running successors. The exiting thread delegates the duty.
// More precisely, if a successor already exists this thread is absolved
// of the responsibility of waking (unparking) one.
//
// The _succ variable is critical to reducing futile wakeup frequency.
// _succ identifies the "heir presumptive" thread that has been made
// ready (unparked) but that has not yet run. We need only one such
// successor thread to guarantee progress.
// See http://www.usenix.org/events/jvm01/full_papers/dice/dice.pdf
// section 3.3 "Futile Wakeup Throttling" for details.
//
// Note that spinners in Enter() also set _succ non-null.
// In the current implementation spinners opportunistically set
// _succ so that exiting threads might avoid waking a successor.
// Another less appealing alternative would be for the exiting thread
// to drop the lock and then spin briefly to see if a spinner managed
// to acquire the lock. If so, the exiting thread could exit
// immediately without waking a successor, otherwise the exiting
// thread would need to dequeue and wake a successor.
// (Note that we'd need to make the post-drop spin short, but no
// shorter than the worst-case round-trip cache-line migration time.
// The dropped lock needs to become visible to the spinner, and then
// the acquisition of the lock by the spinner must become visible to
// the exiting thread).
// It appears that an heir-presumptive (successor) must be made ready.
// Only the current lock owner can manipulate the EntryList or
// drain _cxq, so we need to reacquire the lock. If we fail
// to reacquire the lock the responsibility for ensuring succession
// falls to the new owner.
//
if (!Atomic::replace_if_null(THREAD, &_owner)) {
return;
}
} else {
if ((intptr_t(_EntryList)|intptr_t(_cxq)) == 0 || _succ != NULL) {
OrderAccess::release_store(&_owner, (void*)NULL); // drop the lock
OrderAccess::storeload();
// Ratify the previously observed values.
if (_cxq == NULL || _succ != NULL) {
return;
}
// inopportune interleaving -- the exiting thread (this thread)
// in the fast-exit path raced an entering thread in the slow-enter
// path.
// We have two choices:
// A. Try to reacquire the lock.
// If the CAS() fails return immediately, otherwise
// we either restart/rerun the exit operation, or simply
// fall-through into the code below which wakes a successor.
// B. If the elements forming the EntryList|cxq are TSM
// we could simply unpark() the lead thread and return
// without having set _succ.
if (!Atomic::replace_if_null(THREAD, &_owner)) {
return;
}
}
// It appears that an heir-presumptive (successor) must be made ready.
// Only the current lock owner can manipulate the EntryList or
// drain _cxq, so we need to reacquire the lock. If we fail
// to reacquire the lock the responsibility for ensuring succession
// falls to the new owner.
//
if (!Atomic::replace_if_null(THREAD, &_owner)) {
return;
}
guarantee(_owner == THREAD, "invariant");
ObjectWaiter * w = NULL;
int QMode = Knob_QMode;
if (QMode == 2 && _cxq != NULL) {
// QMode == 2 : cxq has precedence over EntryList.
// Try to directly wake a successor from the cxq.
// If successful, the successor will need to unlink itself from cxq.
w = _cxq;
assert(w != NULL, "invariant");
assert(w->TState == ObjectWaiter::TS_CXQ, "Invariant");
ExitEpilog(Self, w);
return;
}
if (QMode == 3 && _cxq != NULL) {
// Aggressively drain cxq into EntryList at the first opportunity.
// This policy ensure that recently-run threads live at the head of EntryList.
// Drain _cxq into EntryList - bulk transfer.
// First, detach _cxq.
// The following loop is tantamount to: w = swap(&cxq, NULL)
w = _cxq;
for (;;) {
assert(w != NULL, "Invariant");
ObjectWaiter * u = Atomic::cmpxchg((ObjectWaiter*)NULL, &_cxq, w);
if (u == w) break;
w = u;
}
assert(w != NULL, "invariant");
ObjectWaiter * q = NULL;
ObjectWaiter * p;
for (p = w; p != NULL; p = p->_next) {
guarantee(p->TState == ObjectWaiter::TS_CXQ, "Invariant");
p->TState = ObjectWaiter::TS_ENTER;
p->_prev = q;
q = p;
}
// Append the RATs to the EntryList
// TODO: organize EntryList as a CDLL so we can locate the tail in constant-time.
ObjectWaiter * Tail;
for (Tail = _EntryList; Tail != NULL && Tail->_next != NULL;
Tail = Tail->_next)
/* empty */;
if (Tail == NULL) {
_EntryList = w;
} else {
Tail->_next = w;
w->_prev = Tail;
}
// Fall thru into code that tries to wake a successor from EntryList
}
if (QMode == 4 && _cxq != NULL) {
// Aggressively drain cxq into EntryList at the first opportunity.
// This policy ensure that recently-run threads live at the head of EntryList.
// Drain _cxq into EntryList - bulk transfer.
// First, detach _cxq.
// The following loop is tantamount to: w = swap(&cxq, NULL)
w = _cxq;
for (;;) {
assert(w != NULL, "Invariant");
ObjectWaiter * u = Atomic::cmpxchg((ObjectWaiter*)NULL, &_cxq, w);
if (u == w) break;
w = u;
}
assert(w != NULL, "invariant");
ObjectWaiter * q = NULL;
ObjectWaiter * p;
for (p = w; p != NULL; p = p->_next) {
guarantee(p->TState == ObjectWaiter::TS_CXQ, "Invariant");
p->TState = ObjectWaiter::TS_ENTER;
p->_prev = q;
q = p;
}
// Prepend the RATs to the EntryList
if (_EntryList != NULL) {
q->_next = _EntryList;
_EntryList->_prev = q;
}
_EntryList = w;
// Fall thru into code that tries to wake a successor from EntryList
}
w = _EntryList;
if (w != NULL) {
@ -1150,34 +997,14 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
// TODO-FIXME: consider changing EntryList from a DLL to a CDLL so
// we have faster access to the tail.
if (QMode == 1) {
// QMode == 1 : drain cxq to EntryList, reversing order
// We also reverse the order of the list.
ObjectWaiter * s = NULL;
ObjectWaiter * t = w;
ObjectWaiter * u = NULL;
while (t != NULL) {
guarantee(t->TState == ObjectWaiter::TS_CXQ, "invariant");
t->TState = ObjectWaiter::TS_ENTER;
u = t->_next;
t->_prev = u;
t->_next = s;
s = t;
t = u;
}
_EntryList = s;
assert(s != NULL, "invariant");
} else {
// QMode == 0 or QMode == 2
_EntryList = w;
ObjectWaiter * q = NULL;
ObjectWaiter * p;
for (p = w; p != NULL; p = p->_next) {
guarantee(p->TState == ObjectWaiter::TS_CXQ, "Invariant");
p->TState = ObjectWaiter::TS_ENTER;
p->_prev = q;
q = p;
}
_EntryList = w;
ObjectWaiter * q = NULL;
ObjectWaiter * p;
for (p = w; p != NULL; p = p->_next) {
guarantee(p->TState == ObjectWaiter::TS_CXQ, "Invariant");
p->TState = ObjectWaiter::TS_ENTER;
p->_prev = q;
q = p;
}
// In 1-0 mode we need: ST EntryList; MEMBAR #storestore; ST _owner = NULL
@ -1226,22 +1053,8 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
// ST Self->_suspend_equivalent = false
// MEMBAR
// LD Self_>_suspend_flags
//
// UPDATE 2007-10-6: since I've replaced the native Mutex/Monitor subsystem
// with a more efficient implementation, the need to use "FastHSSEC" has
// decreased. - Dave
bool ObjectMonitor::ExitSuspendEquivalent(JavaThread * jSelf) {
const int Mode = Knob_FastHSSEC;
if (Mode && !jSelf->is_external_suspend()) {
assert(jSelf->is_suspend_equivalent(), "invariant");
jSelf->clear_suspend_equivalent();
if (2 == Mode) OrderAccess::storeload();
if (!jSelf->is_external_suspend()) return false;
// We raced a suspension -- fall thru into the slow path
jSelf->set_suspend_equivalent();
}
return jSelf->handle_special_suspend_equivalent_condition();
}
@ -1255,7 +1068,7 @@ void ObjectMonitor::ExitEpilog(Thread * Self, ObjectWaiter * Wakee) {
// 2. ST _owner = NULL
// 3. unpark(wakee)
_succ = Knob_SuccEnabled ? Wakee->_thread : NULL;
_succ = Wakee->_thread;
ParkEvent * Trigger = Wakee->_event;
// Hygiene -- once we've set _owner = NULL we can't safely dereference Wakee again.
@ -1348,12 +1161,6 @@ void ObjectMonitor::check_slow(TRAPS) {
THROW_MSG(vmSymbols::java_lang_IllegalMonitorStateException(), "current thread not owner");
}
static int Adjust(volatile int * adr, int dx) {
int v;
for (v = *adr; Atomic::cmpxchg(v + dx, adr, v) != v; v = *adr) /* empty */;
return v;
}
static void post_monitor_wait_event(EventJavaMonitorWait* event,
ObjectMonitor* monitor,
jlong notifier_tid,
@ -1599,8 +1406,6 @@ void ObjectMonitor::wait(jlong millis, bool interruptible, TRAPS) {
// we might just dequeue a thread from the WaitSet and directly unpark() it.
void ObjectMonitor::INotify(Thread * Self) {
const int policy = Knob_MoveNotifyee;
Thread::SpinAcquire(&_WaitSetLock, "WaitSet - notify");
ObjectWaiter * iterator = DequeueWaiter();
if (iterator != NULL) {
@ -1611,9 +1416,9 @@ void ObjectMonitor::INotify(Thread * Self) {
// or head (policy == 0).
// b. push it onto the front of the _cxq (policy == 2).
// For now we use (b).
if (policy != 4) {
iterator->TState = ObjectWaiter::TS_ENTER;
}
iterator->TState = ObjectWaiter::TS_ENTER;
iterator->_notified = 1;
iterator->_notifier_tid = JFR_THREAD_ID(Self);
@ -1624,67 +1429,19 @@ void ObjectMonitor::INotify(Thread * Self) {
assert(list != iterator, "invariant");
}
if (policy == 0) { // prepend to EntryList
if (list == NULL) {
iterator->_next = iterator->_prev = NULL;
_EntryList = iterator;
} else {
list->_prev = iterator;
iterator->_next = list;
iterator->_prev = NULL;
_EntryList = iterator;
}
} else if (policy == 1) { // append to EntryList
if (list == NULL) {
iterator->_next = iterator->_prev = NULL;
_EntryList = iterator;
} else {
// CONSIDER: finding the tail currently requires a linear-time walk of
// the EntryList. We can make tail access constant-time by converting to
// a CDLL instead of using our current DLL.
ObjectWaiter * tail;
for (tail = list; tail->_next != NULL; tail = tail->_next) {}
assert(tail != NULL && tail->_next == NULL, "invariant");
tail->_next = iterator;
iterator->_prev = tail;
iterator->_next = NULL;
}
} else if (policy == 2) { // prepend to cxq
if (list == NULL) {
iterator->_next = iterator->_prev = NULL;
_EntryList = iterator;
} else {
iterator->TState = ObjectWaiter::TS_CXQ;
for (;;) {
ObjectWaiter * front = _cxq;
iterator->_next = front;
if (Atomic::cmpxchg(iterator, &_cxq, front) == front) {
break;
}
}
}
} else if (policy == 3) { // append to cxq
// prepend to cxq
if (list == NULL) {
iterator->_next = iterator->_prev = NULL;
_EntryList = iterator;
} else {
iterator->TState = ObjectWaiter::TS_CXQ;
for (;;) {
ObjectWaiter * tail = _cxq;
if (tail == NULL) {
iterator->_next = NULL;
if (Atomic::replace_if_null(iterator, &_cxq)) {
break;
}
} else {
while (tail->_next != NULL) tail = tail->_next;
tail->_next = iterator;
iterator->_prev = tail;
iterator->_next = NULL;
ObjectWaiter * front = _cxq;
iterator->_next = front;
if (Atomic::cmpxchg(iterator, &_cxq, front) == front) {
break;
}
}
} else {
ParkEvent * ev = iterator->_event;
iterator->TState = ObjectWaiter::TS_RUN;
OrderAccess::fence();
ev->unpark();
}
// _WaitSetLock protects the wait queue, not the EntryList. We could
@ -1695,9 +1452,7 @@ void ObjectMonitor::INotify(Thread * Self) {
// on _WaitSetLock so it's not profitable to reduce the length of the
// critical section.
if (policy < 4) {
iterator->wait_reenter_begin(this);
}
iterator->wait_reenter_begin(this);
}
Thread::SpinRelease(&_WaitSetLock);
}
@ -1854,33 +1609,19 @@ int ObjectMonitor::TrySpin(Thread * Self) {
// hold the duration constant but vary the frequency.
ctr = _SpinDuration;
if (ctr < Knob_SpinBase) ctr = Knob_SpinBase;
if (ctr <= 0) return 0;
if (Knob_SuccRestrict && _succ != NULL) return 0;
if (Knob_OState && NotRunnable (Self, (Thread *) _owner)) {
if (NotRunnable(Self, (Thread *) _owner)) {
return 0;
}
int MaxSpin = Knob_MaxSpinners;
if (MaxSpin >= 0) {
if (_Spinner > MaxSpin) {
return 0;
}
// Slightly racy, but benign ...
Adjust(&_Spinner, 1);
}
// We're good to spin ... spin ingress.
// CONSIDER: use Prefetch::write() to avoid RTS->RTO upgrades
// when preparing to LD...CAS _owner, etc and the CAS is likely
// to succeed.
int hits = 0;
int msk = 0;
int caspty = Knob_CASPenalty;
int oxpty = Knob_OXPenalty;
int sss = Knob_SpinSetSucc;
if (sss && _succ == NULL) _succ = Self;
if (_succ == NULL) {
_succ = Self;
}
Thread * prv = NULL;
// There are three ways to exit the following loop:
@ -1903,32 +1644,7 @@ int ObjectMonitor::TrySpin(Thread * Self) {
if (SafepointMechanism::poll(Self)) {
goto Abort; // abrupt spin egress
}
if (Knob_UsePause & 1) SpinPause();
}
if (Knob_UsePause & 2) SpinPause();
// Exponential back-off ... Stay off the bus to reduce coherency traffic.
// This is useful on classic SMP systems, but is of less utility on
// N1-style CMT platforms.
//
// Trade-off: lock acquisition latency vs coherency bandwidth.
// Lock hold times are typically short. A histogram
// of successful spin attempts shows that we usually acquire
// the lock early in the spin. That suggests we want to
// sample _owner frequently in the early phase of the spin,
// but then back-off and sample less frequently as the spin
// progresses. The back-off makes a good citizen on SMP big
// SMP systems. Oversampling _owner can consume excessive
// coherency bandwidth. Relatedly, if we _oversample _owner we
// can inadvertently interfere with the the ST m->owner=null.
// executed by the lock owner.
if (ctr & msk) continue;
++hits;
if ((hits & 0xF) == 0) {
// The 0xF, above, corresponds to the exponent.
// Consider: (msk+1)|msk
msk = ((msk << 2)|3) & BackOffMask;
SpinPause();
}
// Probe _owner with TATAS
@ -1947,10 +1663,9 @@ int ObjectMonitor::TrySpin(Thread * Self) {
if (ox == NULL) {
// The CAS succeeded -- this thread acquired ownership
// Take care of some bookkeeping to exit spin state.
if (sss && _succ == Self) {
if (_succ == Self) {
_succ = NULL;
}
if (MaxSpin > 0) Adjust(&_Spinner, -1);
// Increase _SpinDuration :
// The spin was successful (profitable) so we tend toward
@ -1968,22 +1683,17 @@ int ObjectMonitor::TrySpin(Thread * Self) {
}
// The CAS failed ... we can take any of the following actions:
// * penalize: ctr -= Knob_CASPenalty
// * penalize: ctr -= CASPenalty
// * exit spin with prejudice -- goto Abort;
// * exit spin without prejudice.
// * Since CAS is high-latency, retry again immediately.
prv = ox;
if (caspty == -2) break;
if (caspty == -1) goto Abort;
ctr -= caspty;
continue;
goto Abort;
}
// Did lock ownership change hands ?
if (ox != prv && prv != NULL) {
if (oxpty == -2) break;
if (oxpty == -1) goto Abort;
ctr -= oxpty;
goto Abort;
}
prv = ox;
@ -1991,10 +1701,12 @@ int ObjectMonitor::TrySpin(Thread * Self) {
// The owner must be executing in order to drop the lock.
// Spinning while the owner is OFFPROC is idiocy.
// Consider: ctr -= RunnablePenalty ;
if (Knob_OState && NotRunnable (Self, ox)) {
if (NotRunnable(Self, ox)) {
goto Abort;
}
if (sss && _succ == NULL) _succ = Self;
if (_succ == NULL) {
_succ = Self;
}
}
// Spin failed with prejudice -- reduce _SpinDuration.
@ -2012,8 +1724,7 @@ int ObjectMonitor::TrySpin(Thread * Self) {
}
Abort:
if (MaxSpin >= 0) Adjust(&_Spinner, -1);
if (sss && _succ == Self) {
if (_succ == Self) {
_succ = NULL;
// Invariant: after setting succ=null a contending thread
// must recheck-retry _owner before parking. This usually happens
@ -2204,29 +1915,6 @@ void ObjectMonitor::Initialize() {
}
}
static char * kvGet(char * kvList, const char * Key) {
if (kvList == NULL) return NULL;
size_t n = strlen(Key);
char * Search;
for (Search = kvList; *Search; Search += strlen(Search) + 1) {
if (strncmp (Search, Key, n) == 0) {
if (Search[n] == '=') return Search + n + 1;
if (Search[n] == 0) return(char *) "1";
}
}
return NULL;
}
static int kvGetInt(char * kvList, const char * Key, int Default) {
char * v = kvGet(kvList, Key);
int rslt = v ? ::strtol(v, NULL, 0) : Default;
if (Knob_ReportSettings && v != NULL) {
tty->print_cr("INFO: SyncKnob: %s %d(%d)", Key, rslt, Default) ;
tty->flush();
}
return rslt;
}
void ObjectMonitor::DeferredInitialize() {
if (InitDone > 0) return;
if (Atomic::cmpxchg (-1, &InitDone, 0) != 0) {
@ -2237,70 +1925,13 @@ void ObjectMonitor::DeferredInitialize() {
// One-shot global initialization ...
// The initialization is idempotent, so we don't need locks.
// In the future consider doing this via os::init_2().
// SyncKnobs consist of <Key>=<Value> pairs in the style
// of environment variables. Start by converting ':' to NUL.
if (SyncKnobs == NULL) SyncKnobs = "";
size_t sz = strlen(SyncKnobs);
char * knobs = (char *) os::malloc(sz + 2, mtInternal);
if (knobs == NULL) {
vm_exit_out_of_memory(sz + 2, OOM_MALLOC_ERROR, "Parse SyncKnobs");
guarantee(0, "invariant");
}
strcpy(knobs, SyncKnobs);
knobs[sz+1] = 0;
for (char * p = knobs; *p; p++) {
if (*p == ':') *p = 0;
}
#define SETKNOB(x) { Knob_##x = kvGetInt(knobs, #x, Knob_##x); }
SETKNOB(ReportSettings);
SETKNOB(ExitRelease);
SETKNOB(InlineNotify);
SETKNOB(Verbose);
SETKNOB(VerifyInUse);
SETKNOB(VerifyMatch);
SETKNOB(FixedSpin);
SETKNOB(SpinLimit);
SETKNOB(SpinBase);
SETKNOB(SpinBackOff);
SETKNOB(CASPenalty);
SETKNOB(OXPenalty);
SETKNOB(SpinSetSucc);
SETKNOB(SuccEnabled);
SETKNOB(SuccRestrict);
SETKNOB(Penalty);
SETKNOB(Bonus);
SETKNOB(BonusB);
SETKNOB(Poverty);
SETKNOB(SpinAfterFutile);
SETKNOB(UsePause);
SETKNOB(SpinEarly);
SETKNOB(OState);
SETKNOB(MaxSpinners);
SETKNOB(PreSpin);
SETKNOB(ExitPolicy);
SETKNOB(QMode);
SETKNOB(ResetEvent);
SETKNOB(MoveNotifyee);
SETKNOB(FastHSSEC);
#undef SETKNOB
if (os::is_MP()) {
BackOffMask = (1 << Knob_SpinBackOff) - 1;
if (Knob_ReportSettings) {
tty->print_cr("INFO: BackOffMask=0x%X", BackOffMask);
}
// CONSIDER: BackOffMask = ROUNDUP_NEXT_POWER2 (ncpus-1)
} else {
if (!os::is_MP()) {
Knob_SpinLimit = 0;
Knob_SpinBase = 0;
Knob_PreSpin = 0;
Knob_FixedSpin = -1;
}
os::free(knobs);
OrderAccess::fence();
InitDone = 1;
}