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8153224: Monitor deflation prolong safepoints

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Add support for AsyncDeflateIdleMonitors (default true); the async deflation work is performed by the ServiceThread.

Co-authored-by: Carsten Varming <varming@gmail.com>
Reviewed-by: dcubed, rehn, rkennke, cvarming, coleenp, acorn, dholmes, eosterlund
This commit is contained in:
Daniel D. Daugherty 2020-06-01 23:37:14 -04:00
parent 30aa1b0689
commit 00f223e22f
23 changed files with 1496 additions and 250 deletions
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19
src/hotspot/share/services/threadService.cpp
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@ -1,5 +1,5 @@
/*
* Copyright (c) 2003, 2019, Oracle and/or its affiliates. All rights reserved.
* Copyright (c) 2003, 2020, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
@ -208,19 +208,27 @@ Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
assert(thread != NULL, "should be non-NULL");
debug_only(Thread::check_for_dangling_thread_pointer(thread);)
// This function can be called on a target JavaThread that is not
// the caller and we are not at a safepoint. So it is possible for
// the waiting or pending condition to be over/stale and for the
// first stage of async deflation to clear the object field in
// the ObjectMonitor. It is also possible for the object to be
// inflated again and to be associated with a completely different
// ObjectMonitor by the time this object reference is processed
// by the caller.
ObjectMonitor *wait_obj = thread->current_waiting_monitor();
oop obj = NULL;
if (wait_obj != NULL) {
// thread is doing an Object.wait() call
obj = (oop) wait_obj->object();
assert(obj != NULL, "Object.wait() should have an 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(obj != NULL, "ObjectMonitor should have an associated object!");
assert(AsyncDeflateIdleMonitors || obj != NULL, "ObjectMonitor should have an associated object!");
}
}
@ -391,6 +399,7 @@ DeadlockCycle* ThreadService::find_deadlocks_at_safepoint(ThreadsList * t_list,
cycle->reset();
// The ObjectMonitor* can't be async deflated since we are at a safepoint.
// When there is a deadlock, all the monitors involved in the dependency
// cycle must be contended and heavyweight. So we only care about the
// heavyweight monitor a thread is waiting to lock.
@ -967,13 +976,13 @@ void DeadlockCycle::print_on_with(ThreadsList * t_list, outputStream* st) const
st->print("=============================");
JavaThread* currentThread;
ObjectMonitor* waitingToLockMonitor;
JvmtiRawMonitor* waitingToLockRawMonitor;
oop waitingToLockBlocker;
int len = _threads->length();
for (int i = 0; i < len; i++) {
currentThread = _threads->at(i);
waitingToLockMonitor = currentThread->current_pending_monitor();
// The ObjectMonitor* can't be async deflated since we are at a safepoint.
ObjectMonitor* waitingToLockMonitor = currentThread->current_pending_monitor();
waitingToLockRawMonitor = currentThread->current_pending_raw_monitor();
waitingToLockBlocker = currentThread->current_park_blocker();
st->cr();