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8225631: Consider replacing muxAcquire/Release with PlatformMonitor

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Reviewed-by: coleenp, dcubed, kbarrett
This commit is contained in:
David Holmes 2020-11-18 22:45:49 +00:00
parent 646c20022c
commit 99eac53580
6 changed files with 26 additions and 183 deletions
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30
src/hotspot/share/runtime/synchronizer.cpp
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@ -227,8 +227,14 @@ int dtrace_waited_probe(ObjectMonitor* monitor, Handle obj, Thread* thr) {
return 0;
}
#define NINFLATIONLOCKS 256
static volatile intptr_t gInflationLocks[NINFLATIONLOCKS];
static const int NINFLATIONLOCKS = 256;
static os::PlatformMutex* gInflationLocks[NINFLATIONLOCKS];
void ObjectSynchronizer::initialize() {
for (int i = 0; i < NINFLATIONLOCKS; i++) {
gInflationLocks[i] = new os::PlatformMutex();
}
}
static MonitorList _in_use_list;
// The ratio of the current _in_use_list count to the ceiling is used
@ -749,13 +755,7 @@ static markWord read_stable_mark(oop obj) {
// The object is being inflated by some other thread.
// The caller of read_stable_mark() must wait for inflation to complete.
// Avoid live-lock
// TODO: consider calling SafepointSynchronize::do_call_back() while
// spinning to see if there's a safepoint pending. If so, immediately
// yielding or blocking would be appropriate. Avoid spinning while
// there is a safepoint pending.
// TODO: add inflation contention performance counters.
// TODO: restrict the aggregate number of spinners.
// Avoid live-lock.
++its;
if (its > 10000 || !os::is_MP()) {
@ -775,15 +775,15 @@ static markWord read_stable_mark(oop obj) {
// and calling park(). When inflation was complete the thread that accomplished inflation
// would detach the list and set the markword to inflated with a single CAS and
// then for each thread on the list, set the flag and unpark() the thread.
// This is conceptually similar to muxAcquire-muxRelease, except that muxRelease
// wakes at most one thread whereas we need to wake the entire list.
// Index into the lock array based on the current object address.
static_assert(is_power_of_2(NINFLATIONLOCKS), "must be");
int ix = (cast_from_oop<intptr_t>(obj) >> 5) & (NINFLATIONLOCKS-1);
int YieldThenBlock = 0;
assert(ix >= 0 && ix < NINFLATIONLOCKS, "invariant");
assert((NINFLATIONLOCKS & (NINFLATIONLOCKS-1)) == 0, "invariant");
Thread::muxAcquire(gInflationLocks + ix, "gInflationLock");
gInflationLocks[ix]->lock();
while (obj->mark() == markWord::INFLATING()) {
// Beware: NakedYield() is advisory and has almost no effect on some platforms
// Beware: naked_yield() is advisory and has almost no effect on some platforms
// so we periodically call self->_ParkEvent->park(1).
// We use a mixed spin/yield/block mechanism.
if ((YieldThenBlock++) >= 16) {
@ -792,7 +792,7 @@ static markWord read_stable_mark(oop obj) {
os::naked_yield();
}
}
Thread::muxRelease(gInflationLocks + ix);
gInflationLocks[ix]->unlock();
}
} else {
SpinPause(); // SMP-polite spinning