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src/hotspot/share/runtime/synchronizer.cpp
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rev 57232 : v2.00 -> v2.08 (CR8/v2.08/11-for-jdk14) patches combined into one; merge with jdk-14+25 snapshot; merge with jdk-14+26 snapshot.
rev 57233 : See CR8-to-CR9-changes; merge with 8230876.patch (2019.11.15); merge with jdk-14+25 snapshot; fuzzy merge with jdk-14+26 snapshot.
@@ -35,15 +35,17 @@
#include "oops/markWord.hpp"
#include "oops/oop.inline.hpp"
#include "runtime/atomic.hpp"
#include "runtime/biasedLocking.hpp"
#include "runtime/handles.inline.hpp"
+#include "runtime/handshake.hpp"
#include "runtime/interfaceSupport.inline.hpp"
#include "runtime/mutexLocker.hpp"
#include "runtime/objectMonitor.hpp"
#include "runtime/objectMonitor.inline.hpp"
#include "runtime/osThread.hpp"
+#include "runtime/safepointMechanism.inline.hpp"
#include "runtime/safepointVerifiers.hpp"
#include "runtime/sharedRuntime.hpp"
#include "runtime/stubRoutines.hpp"
#include "runtime/synchronizer.hpp"
#include "runtime/thread.inline.hpp"
@@ -115,26 +117,299 @@
#define NINFLATIONLOCKS 256
static volatile intptr_t gInflationLocks[NINFLATIONLOCKS];
// global list of blocks of monitors
-PaddedObjectMonitor* volatile ObjectSynchronizer::g_block_list = NULL;
-// Global ObjectMonitor free list. Newly allocated and deflated
-// ObjectMonitors are prepended here.
-ObjectMonitor* volatile ObjectSynchronizer::g_free_list = NULL;
-// Global ObjectMonitor in-use list. When a JavaThread is exiting,
-// ObjectMonitors on its per-thread in-use list are prepended here.
-ObjectMonitor* volatile ObjectSynchronizer::g_om_in_use_list = NULL;
-int ObjectSynchronizer::g_om_in_use_count = 0; // # on g_om_in_use_list
-
-static volatile intptr_t gListLock = 0; // protects global monitor lists
-static volatile int g_om_free_count = 0; // # on g_free_list
-static volatile int g_om_population = 0; // # Extant -- in circulation
+PaddedObjectMonitor* ObjectSynchronizer::g_block_list = NULL;
+bool volatile ObjectSynchronizer::_is_async_deflation_requested = false;
+bool volatile ObjectSynchronizer::_is_special_deflation_requested = false;
+jlong ObjectSynchronizer::_last_async_deflation_time_ns = 0;
+
+struct ListGlobals {
+ char _pad_prefix[OM_CACHE_LINE_SIZE];
+ // These are highly shared list related variables.
+ // To avoid false-sharing they need to be the sole occupants of a cache line.
+
+ // Global ObjectMonitor free list. Newly allocated and deflated
+ // ObjectMonitors are prepended here.
+ ObjectMonitor* free_list;
+ DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(ObjectMonitor*));
+
+ // Global ObjectMonitor in-use list. When a JavaThread is exiting,
+ // ObjectMonitors on its per-thread in-use list are prepended here.
+ ObjectMonitor* in_use_list;
+ DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(ObjectMonitor*));
+
+ // Global ObjectMonitor wait list. If HandshakeAfterDeflateIdleMonitors
+ // is true, deflated ObjectMonitors wait on this list until after a
+ // handshake or a safepoint for platforms that don't support handshakes.
+ // After the handshake or safepoint, the deflated ObjectMonitors are
+ // prepended to free_list.
+ ObjectMonitor* wait_list;
+ DEFINE_PAD_MINUS_SIZE(3, OM_CACHE_LINE_SIZE, sizeof(ObjectMonitor*));
+
+ int free_count; // # on free_list
+ DEFINE_PAD_MINUS_SIZE(4, OM_CACHE_LINE_SIZE, sizeof(int));
+
+ int in_use_count; // # on in_use_list
+ DEFINE_PAD_MINUS_SIZE(5, OM_CACHE_LINE_SIZE, sizeof(int));
+
+ int population; // # Extant -- in circulation
+ DEFINE_PAD_MINUS_SIZE(6, OM_CACHE_LINE_SIZE, sizeof(int));
+
+ int wait_count; // # on wait_list
+ DEFINE_PAD_MINUS_SIZE(7, OM_CACHE_LINE_SIZE, sizeof(int));
+};
+static ListGlobals LVars;
#define CHAINMARKER (cast_to_oop<intptr_t>(-1))
+// =====================> Spinlock functions
+
+// ObjectMonitors are not lockable outside of this file. We use spinlocks
+// implemented using a bit in the _next_om field instead of the heavier
+// weight locking mechanisms for faster list management.
+
+#define OM_LOCK_BIT 0x1
+
+// Return true if the ObjectMonitor is locked.
+// Otherwise returns false.
+static bool is_locked(ObjectMonitor* om) {
+ return ((intptr_t)Atomic::load(&om->_next_om) & OM_LOCK_BIT) == OM_LOCK_BIT;
+}
+
+// Mark an ObjectMonitor* with OM_LOCK_BIT and return it.
+// Note: the om parameter may or may not have been marked originally.
+static ObjectMonitor* mark_om_ptr(ObjectMonitor* om) {
+ return (ObjectMonitor*)((intptr_t)om | OM_LOCK_BIT);
+}
+
+// Try to lock an ObjectMonitor. Returns true if locking was successful.
+// Otherwise returns false.
+static bool try_om_lock(ObjectMonitor* om) {
+ // Get current next field without any OM_LOCK_BIT value.
+ ObjectMonitor* next = (ObjectMonitor*)((intptr_t)Atomic::load(&om->_next_om) & ~OM_LOCK_BIT);
+ if (Atomic::cmpxchg(&om->_next_om, next, mark_om_ptr(next)) != next) {
+ return false; // Cannot lock the ObjectMonitor.
+ }
+ return true;
+}
+
+// Lock an ObjectMonitor.
+static void om_lock(ObjectMonitor* om) {
+ while (true) {
+ if (try_om_lock(om)) {
+ return;
+ }
+ }
+}
+
+// Unlock an ObjectMonitor.
+static void om_unlock(ObjectMonitor* om) {
+ ObjectMonitor* next = Atomic::load(&om->_next_om);
+ guarantee(((intptr_t)next & OM_LOCK_BIT) == OM_LOCK_BIT, "next=" INTPTR_FORMAT
+ " must have OM_LOCK_BIT=%x set.", p2i(next), OM_LOCK_BIT);
+
+ next = (ObjectMonitor*)((intptr_t)next & ~OM_LOCK_BIT); // Clear OM_LOCK_BIT.
+ Atomic::store(&om->_next_om, next);
+}
+
+// Get the list head after locking it. Returns the list head or NULL
+// if the list is empty.
+static ObjectMonitor* get_list_head_locked(ObjectMonitor** list_p) {
+ while (true) {
+ ObjectMonitor* mid = Atomic::load(list_p);
+ if (mid == NULL) {
+ return NULL; // The list is empty.
+ }
+ if (try_om_lock(mid)) {
+ if (Atomic::load(list_p) != mid) {
+ // The list head changed so we have to retry.
+ om_unlock(mid);
+ continue;
+ }
+ return mid;
+ }
+ }
+}
+
+// Return the unmarked next field in an ObjectMonitor. Note: the next
+// field may or may not have been marked with OM_LOCK_BIT originally.
+static ObjectMonitor* unmarked_next(ObjectMonitor* om) {
+ return (ObjectMonitor*)((intptr_t)Atomic::load(&om->_next_om) & ~OM_LOCK_BIT);
+}
+
+#undef OM_LOCK_BIT
+
+
+// =====================> List Management functions
+
+// Set the next field in an ObjectMonitor to the specified value.
+static void set_next(ObjectMonitor* om, ObjectMonitor* value) {
+ Atomic::store(&om->_next_om, value);
+}
+
+// Prepend a list of ObjectMonitors to the specified *list_p. 'tail' is
+// the last ObjectMonitor in the list and there are 'count' on the list.
+// Also updates the specified *count_p.
+static void prepend_list_to_common(ObjectMonitor* list, ObjectMonitor* tail,
+ int count, ObjectMonitor** list_p,
+ int* count_p) {
+ while (true) {
+ ObjectMonitor* cur = Atomic::load(list_p);
+ // Prepend list to *list_p.
+ if (!try_om_lock(tail)) {
+ continue; // failed to lock tail so try it all again
+ }
+ set_next(tail, cur); // tail now points to cur (and unlocks tail)
+ if (cur == NULL) {
+ // No potential race with takers or other prependers since
+ // *list_p is empty.
+ if (Atomic::cmpxchg(list_p, cur, list) == cur) {
+ // Successfully switched *list_p to the list value.
+ Atomic::add(count_p, count);
+ break;
+ }
+ // Implied else: try it all again
+ } else {
+ if (!try_om_lock(cur)) {
+ continue; // failed to lock cur so try it all again
+ }
+ // We locked cur so try to switch *list_p to the list value.
+ if (Atomic::cmpxchg(list_p, cur, list) != cur) {
+ // The list head has changed so unlock cur and try again:
+ om_unlock(cur);
+ continue;
+ }
+ Atomic::add(count_p, count);
+ om_unlock(cur);
+ break;
+ }
+ }
+}
+
+// Prepend a newly allocated block of ObjectMonitors to g_block_list and
+// LVars.free_list. Also updates LVars.population and LVars.free_count.
+void ObjectSynchronizer::prepend_block_to_lists(PaddedObjectMonitor* new_blk) {
+ // First we handle g_block_list:
+ while (true) {
+ PaddedObjectMonitor* cur = Atomic::load(&g_block_list);
+ // Prepend new_blk to g_block_list. The first ObjectMonitor in
+ // a block is reserved for use as linkage to the next block.
+ new_blk[0]._next_om = cur;
+ if (Atomic::cmpxchg(&g_block_list, cur, new_blk) == cur) {
+ // Successfully switched g_block_list to the new_blk value.
+ Atomic::add(&LVars.population, _BLOCKSIZE - 1);
+ break;
+ }
+ // Implied else: try it all again
+ }
+
+ // Second we handle LVars.free_list:
+ prepend_list_to_common(new_blk + 1, &new_blk[_BLOCKSIZE - 1], _BLOCKSIZE - 1,
+ &LVars.free_list, &LVars.free_count);
+}
+
+// Prepend a list of ObjectMonitors to LVars.free_list. 'tail' is the last
+// ObjectMonitor in the list and there are 'count' on the list. Also
+// updates LVars.free_count.
+static void prepend_list_to_global_free_list(ObjectMonitor* list,
+ ObjectMonitor* tail, int count) {
+ prepend_list_to_common(list, tail, count, &LVars.free_list, &LVars.free_count);
+}
+
+// Prepend a list of ObjectMonitors to LVars.wait_list. 'tail' is the last
+// ObjectMonitor in the list and there are 'count' on the list. Also
+// updates LVars.wait_count.
+static void prepend_list_to_global_wait_list(ObjectMonitor* list,
+ ObjectMonitor* tail, int count) {
+ assert(HandshakeAfterDeflateIdleMonitors, "sanity check");
+ prepend_list_to_common(list, tail, count, &LVars.wait_list, &LVars.wait_count);
+}
+
+// Prepend a list of ObjectMonitors to LVars.in_use_list. 'tail' is the last
+// ObjectMonitor in the list and there are 'count' on the list. Also
+// updates LVars.in_use_list.
+static void prepend_list_to_global_in_use_list(ObjectMonitor* list,
+ ObjectMonitor* tail, int count) {
+ prepend_list_to_common(list, tail, count, &LVars.in_use_list, &LVars.in_use_count);
+}
+
+// Prepend an ObjectMonitor to the specified list. Also updates
+// the specified counter.
+static void prepend_to_common(ObjectMonitor* m, ObjectMonitor** list_p,
+ int* count_p) {
+ while (true) {
+ om_lock(m); // Lock m so we can safely update its next field.
+ ObjectMonitor* cur = NULL;
+ // Lock the list head to guard against A-B-A race:
+ if ((cur = get_list_head_locked(list_p)) != NULL) {
+ // List head is now locked so we can safely switch it.
+ set_next(m, cur); // m now points to cur (and unlocks m)
+ Atomic::store(list_p, m); // Switch list head to unlocked m.
+ om_unlock(cur);
+ break;
+ }
+ // The list is empty so try to set the list head.
+ assert(cur == NULL, "cur must be NULL: cur=" INTPTR_FORMAT, p2i(cur));
+ set_next(m, cur); // m now points to NULL (and unlocks m)
+ if (Atomic::cmpxchg(list_p, cur, m) == cur) {
+ // List head is now unlocked m.
+ break;
+ }
+ // Implied else: try it all again
+ }
+ Atomic::inc(count_p);
+}
+
+// Prepend an ObjectMonitor to a per-thread om_free_list.
+// Also updates the per-thread om_free_count.
+static void prepend_to_om_free_list(Thread* self, ObjectMonitor* m) {
+ prepend_to_common(m, &self->om_free_list, &self->om_free_count);
+}
+
+// Prepend an ObjectMonitor to a per-thread om_in_use_list.
+// Also updates the per-thread om_in_use_count.
+static void prepend_to_om_in_use_list(Thread* self, ObjectMonitor* m) {
+ prepend_to_common(m, &self->om_in_use_list, &self->om_in_use_count);
+}
+
+// Take an ObjectMonitor from the start of the specified list. Also
+// decrements the specified counter. Returns NULL if none are available.
+static ObjectMonitor* take_from_start_of_common(ObjectMonitor** list_p,
+ int* count_p) {
+ ObjectMonitor* take = NULL;
+ // Lock the list head to guard against A-B-A race:
+ if ((take = get_list_head_locked(list_p)) == NULL) {
+ return NULL; // None are available.
+ }
+ ObjectMonitor* next = unmarked_next(take);
+ // Switch locked list head to next (which unlocks the list head, but
+ // leaves take locked):
+ Atomic::store(list_p, next);
+ Atomic::dec(count_p);
+ // Unlock take, but leave the next value for any lagging list
+ // walkers. It will get cleaned up when take is prepended to
+ // the in-use list:
+ om_unlock(take);
+ return take;
+}
+
+// Take an ObjectMonitor from the start of the LVars.free_list. Also
+// updates LVars.free_count. Returns NULL if none are available.
+static ObjectMonitor* take_from_start_of_global_free_list() {
+ return take_from_start_of_common(&LVars.free_list, &LVars.free_count);
+}
+
+// Take an ObjectMonitor from the start of a per-thread free-list.
+// Also updates om_free_count. Returns NULL if none are available.
+static ObjectMonitor* take_from_start_of_om_free_list(Thread* self) {
+ return take_from_start_of_common(&self->om_free_list, &self->om_free_count);
+}
+
+
// =====================> Quick functions
// The quick_* forms are special fast-path variants used to improve
// performance. In the simplest case, a "quick_*" implementation could
// simply return false, in which case the caller will perform the necessary
@@ -209,14 +484,22 @@
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 markWord 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(m->object() == obj, "invariant");
Thread* const owner = (Thread *) m->_owner;
// Lock contention and Transactional Lock Elision (TLE) diagnostics
// and observability
@@ -238,14 +521,26 @@
// stack-locking in the object's header, the third check is for
// recursive stack-locking in the displaced header in the BasicLock,
// and last are the inflated Java Monitor (ObjectMonitor) checks.
lock->set_displaced_header(markWord::unused_mark());
- if (owner == NULL && Atomic::replace_if_null(&(m->_owner), self)) {
+ if (owner == NULL && m->try_set_owner_from(self, NULL) == NULL) {
assert(m->_recursions == 0, "invariant");
return true;
}
+
+ if (AsyncDeflateIdleMonitors &&
+ m->try_set_owner_from(self, DEFLATER_MARKER) == DEFLATER_MARKER) {
+ // The deflation protocol finished the first part (setting owner),
+ // but it failed the second part (making ref_count negative) and
+ // bailed. Or the ObjectMonitor was async deflated and reused.
+ // Acquired the monitor.
+ assert(m->_recursions == 0, "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:
@@ -293,11 +588,13 @@
// 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(markWord::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);
}
void ObjectSynchronizer::exit(oop object, BasicLock* lock, TRAPS) {
markWord mark = object->mark();
// We cannot check for Biased Locking if we are racing an inflation.
@@ -342,11 +639,13 @@
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);
}
// -----------------------------------------------------------------------------
// Class Loader support to workaround deadlocks on the class loader lock objects
// Also used by GC
@@ -363,25 +662,26 @@
if (UseBiasedLocking) {
BiasedLocking::revoke(obj, 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, intx recursions, TRAPS) {
if (UseBiasedLocking) {
BiasedLocking::revoke(obj, THREAD);
assert(!obj->mark().has_bias_pattern(), "biases should be revoked by now");
}
- ObjectMonitor* monitor = inflate(THREAD, obj(), inflate_cause_vm_internal);
-
- monitor->reenter(recursions, THREAD);
+ ObjectMonitorHandle omh;
+ inflate(&omh, THREAD, obj(), inflate_cause_vm_internal);
+ omh.om_ptr()->reenter(recursions, THREAD);
}
// -----------------------------------------------------------------------------
// JNI locks on java objects
// NOTE: must use heavy weight monitor to handle jni monitor enter
void ObjectSynchronizer::jni_enter(Handle obj, TRAPS) {
@@ -389,11 +689,13 @@
if (UseBiasedLocking) {
BiasedLocking::revoke(obj, 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) {
@@ -402,11 +704,13 @@
BiasedLocking::revoke(h_obj, 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. We
// intentionally do not use CHECK here because we must exit the
// monitor even if an exception is pending.
if (monitor->check_owner(THREAD)) {
monitor->exit(true, THREAD);
@@ -443,31 +747,36 @@
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::wait_uninterruptibly(Handle obj, jlong millis, TRAPS) {
if (UseBiasedLocking) {
BiasedLocking::revoke(obj, 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(obj, THREAD);
@@ -476,11 +785,13 @@
markWord 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) {
@@ -490,11 +801,13 @@
markWord 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
//
@@ -515,19 +828,19 @@
// As a general policy we use "volatile" to control compiler-based reordering
// and explicit fences (barriers) to control for architectural reordering
// performed by the CPU(s) or platform.
struct SharedGlobals {
- char _pad_prefix[DEFAULT_CACHE_LINE_SIZE];
+ char _pad_prefix[OM_CACHE_LINE_SIZE];
// These are highly shared mostly-read variables.
// To avoid false-sharing they need to be the sole occupants of a cache line.
volatile int stw_random;
volatile int stw_cycle;
- DEFINE_PAD_MINUS_SIZE(1, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int) * 2);
+ DEFINE_PAD_MINUS_SIZE(1, OM_CACHE_LINE_SIZE, sizeof(volatile int) * 2);
// Hot RW variable -- Sequester to avoid false-sharing
volatile int hc_sequence;
- DEFINE_PAD_MINUS_SIZE(2, DEFAULT_CACHE_LINE_SIZE, sizeof(volatile int));
+ DEFINE_PAD_MINUS_SIZE(2, OM_CACHE_LINE_SIZE, sizeof(volatile int));
};
static SharedGlobals GVars;
static int _forceMonitorScavenge = 0; // Scavenge required and pending
@@ -683,10 +996,11 @@
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;
markWord temp, test;
intptr_t hash;
markWord mark = read_stable_mark(obj);
@@ -708,13 +1022,22 @@
// Failed to install the hash. It could be that another thread
// installed the hash just before our attempt or inflation has
// occurred or... so we fall thru to inflate the monitor for
// stability and then install the hash.
} 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, temp.value());
+ // Allow for a lagging install_displaced_markword_in_object() to
+ // have marked the ObjectMonitor's header/dmw field.
+ assert(temp.is_neutral() || (AsyncDeflateIdleMonitors && temp.is_marked()),
+ "invariant: header=" INTPTR_FORMAT, temp.value());
hash = temp.hash();
if (hash != 0) { // if it has a hash, just return it
return hash;
}
// Fall thru so we only have one place that installs the hash in
@@ -737,34 +1060,53 @@
// during an inflate() call so any change to that stack memory
// may not propagate to other threads correctly.
}
// Inflate the monitor to set the hash.
- monitor = inflate(self, obj, inflate_cause_hash_code);
+ ObjectMonitorHandle omh;
+ inflate(&omh, self, obj, inflate_cause_hash_code);
+ monitor = omh.om_ptr();
// Load ObjectMonitor's header/dmw field and see if it has a hash.
mark = monitor->header();
- assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
+ // Allow for a lagging install_displaced_markword_in_object() to
+ // have marked the ObjectMonitor's header/dmw field.
+ assert(mark.is_neutral() || (AsyncDeflateIdleMonitors && mark.is_marked()),
+ "invariant: header=" INTPTR_FORMAT, mark.value());
hash = mark.hash();
if (hash == 0) { // if it does not have a hash
hash = get_next_hash(self, obj); // get a new hash
temp = mark.copy_set_hash(hash); // merge the hash into header
+ if (AsyncDeflateIdleMonitors && temp.is_marked()) {
+ // A lagging install_displaced_markword_in_object() has marked
+ // the ObjectMonitor's header/dmw field. We clear it to avoid
+ // any confusion if we are able to set the hash.
+ temp.set_unmarked();
+ }
assert(temp.is_neutral(), "invariant: header=" INTPTR_FORMAT, temp.value());
uintptr_t v = Atomic::cmpxchg((volatile uintptr_t*)monitor->header_addr(), mark.value(), temp.value());
test = markWord(v);
if (test != mark) {
// The attempt to update the ObjectMonitor's header/dmw field
// did not work. This can happen if another thread managed to
- // merge in the hash just before our cmpxchg().
+ // merge in the hash just before our cmpxchg(). With async
+ // deflation, a lagging install_displaced_markword_in_object()
+ // could have just marked or just unmarked the header/dmw field.
// If we add any new usages of the header/dmw field, this code
// will need to be updated.
+ if (AsyncDeflateIdleMonitors) {
+ // Since async deflation gives us two possible reasons for
+ // the cmwxchg() to fail, it is easier to simply retry.
+ continue;
+ }
hash = test.hash();
assert(test.is_neutral(), "invariant: header=" INTPTR_FORMAT, test.value());
assert(hash != 0, "should only have lost the race to a thread that set a non-zero hash");
}
}
// We finally get the hash.
return hash;
+ }
}
// Deprecated -- use FastHashCode() instead.
intptr_t ObjectSynchronizer::identity_hash_value_for(Handle obj) {
@@ -780,24 +1122,32 @@
}
assert(thread == JavaThread::current(), "Can only be called on current thread");
oop obj = h_obj();
+ while (true) {
markWord mark = read_stable_mark(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
@@ -819,31 +1169,41 @@
"biases should be revoked by now");
}
assert(self == JavaThread::current(), "Can only be called on current thread");
oop obj = h_obj();
+
+ while (true) {
markWord mark = read_stable_mark(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) {
@@ -854,22 +1214,29 @@
}
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;
markWord mark = read_stable_mark(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) {
@@ -881,107 +1248,168 @@
// 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) {
- PaddedObjectMonitor* block = Atomic::load_acquire(&g_block_list);
+ PaddedObjectMonitor* block = Atomic::load(&g_block_list);
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) {
+ ObjectMonitorHandle omh;
+ if (!mid->is_free() && omh.set_om_ptr_if_safe(mid)) {
+ // The ObjectMonitor* is not free and it has been made safe.
+ if (mid->object() == NULL) {
// Only process with closure if the object is set.
+ continue;
+ }
closure->do_monitor(mid);
}
}
- block = (PaddedObjectMonitor*)block->_next_om;
+ // unmarked_next() is not needed with g_block_list (no locking
+ // used with with block linkage _next_om fields).
+ block = (PaddedObjectMonitor*)Atomic::load(&block->_next_om);
}
}
static bool monitors_used_above_threshold() {
- if (g_om_population == 0) {
+ if (Atomic::load(&LVars.population) == 0) {
return false;
}
- int monitors_used = g_om_population - g_om_free_count;
- int monitor_usage = (monitors_used * 100LL) / g_om_population;
+ if (MonitorUsedDeflationThreshold > 0) {
+ int monitors_used = Atomic::load(&LVars.population) - Atomic::load(&LVars.free_count);
+ if (HandshakeAfterDeflateIdleMonitors) {
+ monitors_used -= Atomic::load(&LVars.wait_count);
+ }
+ int monitor_usage = (monitors_used * 100LL) / Atomic::load(&LVars.population);
return monitor_usage > MonitorUsedDeflationThreshold;
+ }
+ return false;
}
-bool ObjectSynchronizer::is_cleanup_needed() {
- if (MonitorUsedDeflationThreshold > 0) {
- if (monitors_used_above_threshold()) {
+// Returns true if MonitorBound is set (> 0) and if the specified
+// cnt is > MonitorBound. Otherwise returns false.
+static bool is_MonitorBound_exceeded(const int cnt) {
+ const int mx = MonitorBound;
+ return mx > 0 && cnt > mx;
+}
+
+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 needs_monitor_scavenge();
+ int monitors_used = Atomic::load(&LVars.population) - Atomic::load(&LVars.free_count);
+ if (HandshakeAfterDeflateIdleMonitors) {
+ monitors_used -= Atomic::load(&LVars.wait_count);
+ }
+ if (is_MonitorBound_exceeded(monitors_used)) {
+ // Not enough ObjectMonitors on the global free list.
+ return true;
+ }
+ return false;
}
bool ObjectSynchronizer::needs_monitor_scavenge() {
if (Atomic::load(&_forceMonitorScavenge) == 1) {
log_info(monitorinflation)("Monitor scavenge needed, triggering safepoint cleanup.");
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 needs_monitor_scavenge();
+ }
+ 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);
}
void ObjectSynchronizer::global_used_oops_do(OopClosure* f) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
- list_oops_do(g_om_in_use_list, f);
+ list_oops_do(Atomic::load(&LVars.in_use_list), Atomic::load(&LVars.in_use_count), f);
}
void ObjectSynchronizer::thread_local_used_oops_do(Thread* thread, OopClosure* f) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
- list_oops_do(thread->om_in_use_list, f);
+ list_oops_do(thread->om_in_use_list, thread->om_in_use_count, f);
}
-void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
+void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, int count, OopClosure* f) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
- ObjectMonitor* mid;
- for (mid = list; mid != NULL; mid = mid->_next_om) {
+ // The oops_do() phase does not overlap with monitor deflation
+ // so no need to update the ObjectMonitor's ref_count for this
+ // ObjectMonitor* use and no need to mark ObjectMonitors for the
+ // list traversal.
+ for (ObjectMonitor* mid = list; mid != NULL; mid = unmarked_next(mid)) {
if (mid->object() != NULL) {
f->do_oop((oop*)mid->object_addr());
}
}
}
// -----------------------------------------------------------------------------
// ObjectMonitor Lifecycle
// -----------------------
-// Inflation unlinks monitors from the global g_free_list and
-// associates them with objects. Deflation -- which occurs at
-// STW-time -- disassociates idle monitors from objects. Such
-// scavenged monitors are returned to the g_free_list.
-//
-// The global list is protected by gListLock. All the critical sections
-// are short and operate in constant-time.
+// Inflation unlinks monitors from LVars.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 LVars.free_list.
//
// ObjectMonitors reside in type-stable memory (TSM) and are immortal.
//
// Lifecycle:
-// -- unassigned and on the global free list
-// -- unassigned and on a thread's private om_free_list
+// -- unassigned and on the LVars.free_list
+// -- unassigned and on a per-thread free list
// -- assigned to an object. The object is inflated and the mark refers
-// to the objectmonitor.
+// to the ObjectMonitor.
// Constraining monitor pool growth via MonitorBound ...
//
// If MonitorBound is not set (<= 0), MonitorBound checks are disabled.
//
+// When safepoint deflation is being used (!AsyncDeflateIdleMonitors):
// The monitor pool is grow-only. We scavenge at STW safepoint-time, but the
// the rate of scavenging is driven primarily by GC. As such, we can find
// an inordinate number of monitors in circulation.
// To avoid that scenario we can artificially induce a STW safepoint
// if the pool appears to be growing past some reasonable bound.
@@ -990,80 +1418,114 @@
// type of limit. Beware that if MonitorBound is set to too low a value
// we could just loop. In addition, if MonitorBound is set to a low value
// we'll incur more safepoints, which are harmful to performance.
// See also: GuaranteedSafepointInterval
//
-// If MonitorBound is set, the boundry applies to
-// (g_om_population - g_om_free_count)
+// When safepoint deflation is being used and MonitorBound is set, the
+// boundry applies to
+// (LVars.population - LVars.free_count)
// i.e., if there are not enough ObjectMonitors on the global free list,
// then a safepoint deflation is induced. Picking a good MonitorBound value
// is non-trivial.
+//
+// When async deflation is being used:
+// The monitor pool is still grow-only. Async deflation is requested
+// by a safepoint's cleanup phase or by the ServiceThread at periodic
+// intervals when is_async_deflation_needed() returns true. In
+// addition to other policies that are checked, if there are not
+// enough ObjectMonitors on the global free list, then
+// is_async_deflation_needed() will return true. The ServiceThread
+// calls deflate_global_idle_monitors_using_JT() and also calls
+// deflate_per_thread_idle_monitors_using_JT() as needed.
static void InduceScavenge(Thread* self, const char * Whence) {
+ assert(!AsyncDeflateIdleMonitors, "is not used by async deflation");
+
// Induce STW safepoint to trim monitors
// Ultimately, this results in a call to deflate_idle_monitors() in the near future.
// More precisely, trigger a cleanup safepoint as the number
// of active monitors passes the specified threshold.
// TODO: assert thread state is reasonable
- if (Atomic::xchg (&_forceMonitorScavenge, 1) == 0) {
+ if (Atomic::xchg(&_forceMonitorScavenge, 1) == 0) {
VMThread::check_for_forced_cleanup();
}
}
-ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
+ObjectMonitor* ObjectSynchronizer::om_alloc(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;
+
stringStream ss;
for (;;) {
ObjectMonitor* m;
// 1: try to allocate from the thread's local om_free_list.
// Threads will attempt to allocate first from their local list, then
- // from the global list, and only after those attempts fail will the thread
- // attempt to instantiate new monitors. Thread-local free lists take
- // heat off the gListLock and improve allocation latency, as well as reducing
- // coherency traffic on the shared global list.
- m = self->om_free_list;
+ // from the global list, and only after those attempts fail will the
+ // thread attempt to instantiate new monitors. Thread-local free lists
+ // improve allocation latency, as well as reducing coherency traffic
+ // on the shared global list.
+ m = take_from_start_of_om_free_list(self);
if (m != NULL) {
- self->om_free_list = m->_next_om;
- self->om_free_count--;
guarantee(m->object() == NULL, "invariant");
- m->_next_om = self->om_in_use_list;
- self->om_in_use_list = m;
- self->om_in_use_count++;
+ m->set_allocation_state(ObjectMonitor::New);
+ prepend_to_om_in_use_list(self, m);
return m;
}
- // 2: try to allocate from the global g_free_list
+ // 2: try to allocate from the global LVars.free_list
// CONSIDER: use muxTry() instead of muxAcquire().
// If the muxTry() fails then drop immediately into case 3.
// If we're using thread-local free lists then try
// to reprovision the caller's free list.
- if (g_free_list != NULL) {
+ if (Atomic::load(&LVars.free_list) != NULL) {
// Reprovision the thread's om_free_list.
// Use bulk transfers to reduce the allocation rate and heat
// on various locks.
- Thread::muxAcquire(&gListLock, "om_alloc(1)");
- for (int i = self->om_free_provision; --i >= 0 && g_free_list != NULL;) {
- g_om_free_count--;
- ObjectMonitor* take = g_free_list;
- g_free_list = take->_next_om;
+ for (int i = self->om_free_provision; --i >= 0;) {
+ ObjectMonitor* take = take_from_start_of_global_free_list();
+ if (take == NULL) {
+ break; // No more are available.
+ }
guarantee(take->object() == NULL, "invariant");
+ if (AsyncDeflateIdleMonitors) {
+ // We allowed 3 field values to linger during async deflation.
+ // We clear header and restore ref_count here, but we leave
+ // owner == DEFLATER_MARKER so the simple C2 ObjectMonitor
+ // enter optimization can no longer race with async deflation
+ // and reuse.
+ take->set_header(markWord::zero());
+ if (take->ref_count() < 0) {
+ // Add back max_jint to restore the ref_count field to its
+ // proper value.
+ Atomic::add(&take->_ref_count, max_jint);
+
+#ifdef ASSERT
+ jint l_ref_count = take->ref_count();
+#endif
+ assert(l_ref_count >= 0, "must not be negative: l_ref_count=%d, ref_count=%d",
+ l_ref_count, take->ref_count());
+ }
+ }
take->Recycle();
+ // Since we're taking from the global free-list, take must be Free.
+ // om_release() also sets the allocation state to Free because it
+ // is called from other code paths.
+ assert(take->is_free(), "invariant");
om_release(self, take, false);
}
- Thread::muxRelease(&gListLock);
- self->om_free_provision += 1 + (self->om_free_provision/2);
+ self->om_free_provision += 1 + (self->om_free_provision / 2);
if (self->om_free_provision > MAXPRIVATE) self->om_free_provision = MAXPRIVATE;
- const int mx = MonitorBound;
- if (mx > 0 && (g_om_population-g_om_free_count) > mx) {
+ if (!AsyncDeflateIdleMonitors &&
+ is_MonitorBound_exceeded(Atomic::load(&LVars.population) - Atomic::load(&LVars.free_count))) {
// Not enough ObjectMonitors on the global free list.
// We can't safely induce a STW safepoint from om_alloc() as our thread
// state may not be appropriate for such activities and callers may hold
// naked oops, so instead we defer the action.
InduceScavenge(self, "om_alloc");
@@ -1080,13 +1542,13 @@
// A better solution would be to use C++ placement-new.
// BEWARE: As it stands currently, we don't run the ctors!
assert(_BLOCKSIZE > 1, "invariant");
size_t neededsize = sizeof(PaddedObjectMonitor) * _BLOCKSIZE;
PaddedObjectMonitor* temp;
- size_t aligned_size = neededsize + (DEFAULT_CACHE_LINE_SIZE - 1);
+ size_t aligned_size = neededsize + (OM_CACHE_LINE_SIZE - 1);
void* real_malloc_addr = NEW_C_HEAP_ARRAY(char, aligned_size, mtInternal);
- temp = (PaddedObjectMonitor*)align_up(real_malloc_addr, DEFAULT_CACHE_LINE_SIZE);
+ temp = (PaddedObjectMonitor*)align_up(real_malloc_addr, OM_CACHE_LINE_SIZE);
(void)memset((void *) temp, 0, neededsize);
// Format the block.
// initialize the linked list, each monitor points to its next
// forming the single linked free list, the very first monitor
@@ -1094,41 +1556,25 @@
// The trick of using the 1st element in the block as g_block_list
// 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]._next_om = (ObjectMonitor *)&temp[i+1];
+ temp[i]._next_om = (ObjectMonitor*)&temp[i + 1];
+ assert(temp[i].is_free(), "invariant");
}
// terminate the last monitor as the end of list
- temp[_BLOCKSIZE - 1]._next_om = NULL;
+ temp[_BLOCKSIZE - 1]._next_om = (ObjectMonitor*)NULL;
// Element [0] is reserved for global list linkage
temp[0].set_object(CHAINMARKER);
// Consider carving out this thread's current request from the
// block in hand. This avoids some lock traffic and redundant
// list activity.
- // Acquire the gListLock to manipulate g_block_list and g_free_list.
- // An Oyama-Taura-Yonezawa scheme might be more efficient.
- Thread::muxAcquire(&gListLock, "om_alloc(2)");
- g_om_population += _BLOCKSIZE-1;
- g_om_free_count += _BLOCKSIZE-1;
-
- // Add the new block to the list of extant blocks (g_block_list).
- // The very first ObjectMonitor in a block is reserved and dedicated.
- // It serves as blocklist "next" linkage.
- temp[0]._next_om = g_block_list;
- // There are lock-free uses of g_block_list so make sure that
- // the previous stores happen before we update g_block_list.
- Atomic::release_store(&g_block_list, temp);
-
- // Add the new string of ObjectMonitors to the global free list
- temp[_BLOCKSIZE - 1]._next_om = g_free_list;
- g_free_list = temp + 1;
- Thread::muxRelease(&gListLock);
+ prepend_block_to_lists(temp);
}
}
// Place "m" on the caller's private per-thread om_free_list.
// In practice there's no need to clamp or limit the number of
@@ -1137,46 +1583,79 @@
// a CAS 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 while we
-// are trying to release them.
+// scavenger -- deflate_monitor_list() or 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) {
guarantee(m->header().value() == 0, "invariant");
guarantee(m->object() == NULL, "invariant");
stringStream ss;
guarantee((m->is_busy() | m->_recursions) == 0, "freeing in-use monitor: "
"%s, recursions=" INTX_FORMAT, m->is_busy_to_string(&ss),
m->_recursions);
+ m->set_allocation_state(ObjectMonitor::Free);
// _next_om is used for both per-thread in-use and free lists so
// we have to remove 'm' from the in-use list first (as needed).
if (from_per_thread_alloc) {
// Need to remove 'm' from om_in_use_list.
+ // We use the more complicated lock-cur_mid_in_use-and-mid-as-we-go
+ // protocol because async deflation can do list deletions in parallel.
ObjectMonitor* cur_mid_in_use = NULL;
+ ObjectMonitor* mid = NULL;
+ ObjectMonitor* next = NULL;
bool extracted = false;
- for (ObjectMonitor* mid = self->om_in_use_list; mid != NULL; cur_mid_in_use = mid, mid = mid->_next_om) {
+
+ if ((mid = get_list_head_locked(&self->om_in_use_list)) == NULL) {
+ fatal("thread=" INTPTR_FORMAT " in-use list must not be empty.", p2i(self));
+ }
+ next = unmarked_next(mid);
+ while (true) {
if (m == mid) {
- // extract from per-thread in-use list
- if (mid == self->om_in_use_list) {
- self->om_in_use_list = mid->_next_om;
- } else if (cur_mid_in_use != NULL) {
- cur_mid_in_use->_next_om = mid->_next_om; // maintain the current thread in-use list
+ // We found 'm' on the per-thread in-use list so try to extract it.
+ if (cur_mid_in_use == NULL) {
+ // mid is the list head and it is locked. Switch the list head
+ // to next which unlocks the list head, but leaves mid locked:
+ Atomic::store(&self->om_in_use_list, next);
+ } else {
+ // mid and cur_mid_in_use are locked. Switch cur_mid_in_use's
+ // next field to next which unlocks cur_mid_in_use, but leaves
+ // mid locked:
+ set_next(cur_mid_in_use, next);
}
extracted = true;
- self->om_in_use_count--;
+ Atomic::dec(&self->om_in_use_count);
+ // Unlock mid, but leave the next value for any lagging list
+ // walkers. It will get cleaned up when mid is prepended to
+ // the thread's free list:
+ om_unlock(mid);
break;
}
+ if (cur_mid_in_use != NULL) {
+ om_unlock(cur_mid_in_use);
+ }
+ // The next cur_mid_in_use keeps mid's locked state so
+ // that it is stable for a possible next field change. It
+ // cannot be deflated while it is locked.
+ cur_mid_in_use = mid;
+ mid = next;
+ if (mid == NULL) {
+ // Reached end of the list and didn't find m so:
+ fatal("must find m=" INTPTR_FORMAT "on om_in_use_list=" INTPTR_FORMAT,
+ p2i(m), p2i(self->om_in_use_list));
+ }
+ // Lock mid so we can possibly extract it:
+ om_lock(mid);
+ next = unmarked_next(mid);
}
- assert(extracted, "Should have extracted from in-use list");
}
- m->_next_om = self->om_free_list;
- self->om_free_list = m;
- self->om_free_count++;
+ prepend_to_om_free_list(self, m);
+ guarantee(m->is_free(), "invariant");
}
// Return ObjectMonitors on a moribund thread's free and in-use
// lists to the appropriate global lists. The ObjectMonitors on the
// per-thread in-use list may still be in use by other threads.
@@ -1187,66 +1666,108 @@
// 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).
+//
+// 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 om_flush() so we have to follow a careful
+// protocol to prevent list corruption.
void ObjectSynchronizer::om_flush(Thread* self) {
+ // This function can race with an async deflater thread. Since
+ // deflation has to process the per-thread in-use list before
+ // prepending the deflated ObjectMonitors to the global free list,
+ // we process the per-thread lists in the same order to prevent
+ // ordering races.
+ int in_use_count = 0;
+ ObjectMonitor* in_use_list = NULL;
+ ObjectMonitor* in_use_tail = NULL;
+
+ // An async deflation thread checks to see if the target thread
+ // is exiting, but if it has made it past that check before we
+ // started exiting, then it is racing to get to the in-use list.
+ if ((in_use_list = get_list_head_locked(&self->om_in_use_list)) != NULL) {
+ // At this point, we have marked the in-use list head so an
+ // async deflation thread cannot come in after us. If an async
+ // deflation thread is ahead of us, then we'll detect that and
+ // wait for it to finish its work.
+ //
+ // The thread is going away, however the ObjectMonitors on the
+ // om_in_use_list may still be in-use by other threads. Link
+ // them to in_use_tail, which will be linked into the global
+ // in-use list (LVars.in_use_list) below.
+ //
+ // Account for the in-use list head before the loop since it is
+ // already marked (by this thread):
+ in_use_tail = in_use_list;
+ in_use_count++;
+ for (ObjectMonitor* cur_om = unmarked_next(in_use_list); cur_om != NULL;) {
+ if (is_locked(cur_om)) {
+ // cur_om is locked so there must be an async deflater
+ // thread ahead of us so we'll give it a chance to finish.
+ while (is_locked(cur_om)) {
+ os::naked_short_sleep(1);
+ }
+ // Refetch the possibly changed next field and try again.
+ cur_om = unmarked_next(in_use_tail);
+ continue;
+ }
+ if (cur_om->is_free()) {
+ // cur_om was deflated and the allocation state was changed
+ // to Free while it was marked. We happened to see it just
+ // after it was unmarked (and added to the free list).
+ // Refetch the possibly changed next field and try again.
+ cur_om = unmarked_next(in_use_tail);
+ continue;
+ }
+ in_use_tail = cur_om;
+ in_use_count++;
+ cur_om = unmarked_next(cur_om);
+ }
+ guarantee(in_use_tail != NULL, "invariant");
+ int l_om_in_use_count = 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);
+ 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);
+ om_unlock(in_use_list);
+ }
+
+ int free_count = 0;
ObjectMonitor* free_list = self->om_free_list;
ObjectMonitor* free_tail = NULL;
- int free_count = 0;
if (free_list != NULL) {
- ObjectMonitor* s;
// The thread is going away. Set 'free_tail' to the last per-thread free
- // monitor which will be linked to g_free_list below under the gListLock.
+ // monitor which will be linked to LVars.free_list below.
stringStream ss;
- for (s = free_list; s != NULL; s = s->_next_om) {
+ for (ObjectMonitor* s = free_list; s != NULL; s = unmarked_next(s)) {
free_count++;
free_tail = s;
guarantee(s->object() == NULL, "invariant");
guarantee(!s->is_busy(), "must be !is_busy: %s", s->is_busy_to_string(&ss));
}
guarantee(free_tail != NULL, "invariant");
- assert(self->om_free_count == free_count, "free-count off");
- self->om_free_list = NULL;
+ int l_om_free_count = 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);
self->om_free_count = 0;
+ Atomic::store(&self->om_free_list, (ObjectMonitor*)NULL);
}
- ObjectMonitor* in_use_list = self->om_in_use_list;
- ObjectMonitor* in_use_tail = NULL;
- int in_use_count = 0;
- if (in_use_list != NULL) {
- // The thread is going away, however the ObjectMonitors on the
- // om_in_use_list may still be in-use by other threads. Link
- // them to in_use_tail, which will be linked into the global
- // in-use list g_om_in_use_list below, under the gListLock.
- ObjectMonitor *cur_om;
- for (cur_om = in_use_list; cur_om != NULL; cur_om = cur_om->_next_om) {
- in_use_tail = cur_om;
- in_use_count++;
- }
- guarantee(in_use_tail != NULL, "invariant");
- assert(self->om_in_use_count == in_use_count, "in-use count off");
- self->om_in_use_list = NULL;
- self->om_in_use_count = 0;
- }
-
- Thread::muxAcquire(&gListLock, "om_flush");
if (free_tail != NULL) {
- free_tail->_next_om = g_free_list;
- g_free_list = free_list;
- g_om_free_count += free_count;
+ prepend_list_to_global_free_list(free_list, free_tail, free_count);
}
if (in_use_tail != NULL) {
- in_use_tail->_next_om = g_om_in_use_list;
- g_om_in_use_list = in_use_list;
- g_om_in_use_count += in_use_count;
+ prepend_list_to_global_in_use_list(in_use_list, in_use_tail, in_use_count);
}
- Thread::muxRelease(&gListLock);
-
LogStreamHandle(Debug, monitorinflation) lsh_debug;
LogStreamHandle(Info, monitorinflation) lsh_info;
LogStream* ls = NULL;
if (log_is_enabled(Debug, monitorinflation)) {
ls = &lsh_debug;
@@ -1271,23 +1792,32 @@
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) {
markWord 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");
+ markWord dmw = monitor->header();
+ assert(dmw.is_neutral(), "sanity check: header=" INTPTR_FORMAT, dmw.value());
+ 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");
@@ -1304,16 +1834,21 @@
// * 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();
markWord dmw = inf->header();
assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
assert(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.
@@ -1345,20 +1880,21 @@
// See the comments in om_alloc().
LogStreamHandle(Trace, monitorinflation) lsh;
if (mark.has_locker()) {
- ObjectMonitor* m = om_alloc(self);
+ ObjectMonitor* m = om_alloc(self, cause);
// 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;
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit; // Consider: maintain by type/class
markWord cmp = object->cas_set_mark(markWord::INFLATING(), mark);
if (cmp != mark) {
+ // om_release() will reset the allocation state from New to Free.
om_release(self, m, true);
continue; // Interference -- just retry
}
// We've successfully installed INFLATING (0) into the mark-word.
@@ -1392,29 +1928,40 @@
// object is in the mark. Furthermore the owner can't complete
// an unlock on the object, either.
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).
- assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
+ ADIM_guarantee(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
// Setup monitor fields to proper values -- prepare the monitor
m->set_header(dmw);
// Optimization: if the mark.locker stack address is associated
// with this thread we could simply set m->_owner = self.
// 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.
- m->set_owner(mark.locker());
+ if (AsyncDeflateIdleMonitors) {
+ m->simply_set_owner_from(mark.locker(), NULL, DEFLATER_MARKER);
+ } else {
+ m->simply_set_owner_from(mark.locker(), NULL);
+ }
m->set_object(object);
// TODO-FIXME: assert BasicLock->dhw != 0.
+ omh_p->set_om_ptr(m);
+
// Must preserve store ordering. The monitor state must
// be stable at the time of publishing the monitor address.
guarantee(object->mark() == markWord::INFLATING(), "invariant");
object->release_set_mark(markWord::encode(m));
+ // Once ObjectMonitor is configured and the object is associated
+ // with the ObjectMonitor, it is safe to allow async deflation:
+ assert(m->is_new(), "freshly allocated monitor must be new");
+ m->set_allocation_state(ObjectMonitor::Old);
+
// Hopefully the performance counters are allocated on distinct cache lines
// to avoid false sharing on MP systems ...
OM_PERFDATA_OP(Inflations, inc());
if (log_is_enabled(Trace, monitorinflation)) {
ResourceMark rm(self);
@@ -1423,11 +1970,12 @@
object->mark().value(), 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
@@ -1437,31 +1985,43 @@
// to inflate and then CAS() again to try to swing _owner from NULL to self.
// An inflateTry() method that we could call from 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, mark.value());
- ObjectMonitor* m = om_alloc(self);
+ ADIM_guarantee(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT,mark.value());
+ ObjectMonitor* m = om_alloc(self, cause);
// prepare m for installation - set monitor to initial state
m->Recycle();
m->set_header(mark);
+ // If we leave _owner == DEFLATER_MARKER here, then the simple C2
+ // ObjectMonitor enter optimization can no longer race with async
+ // deflation and reuse.
m->set_object(object);
m->_Responsible = NULL;
m->_SpinDuration = ObjectMonitor::Knob_SpinLimit; // consider: keep metastats by type/class
+ omh_p->set_om_ptr(m);
+
if (object->cas_set_mark(markWord::encode(m), mark) != mark) {
m->set_header(markWord::zero());
m->set_object(NULL);
m->Recycle();
+ omh_p->set_om_ptr(NULL);
+ // om_release() will reset the allocation state from New to Free.
om_release(self, m, true);
m = NULL;
continue;
// interference - the markword changed - just retry.
// The state-transitions are one-way, so there's no chance of
// live-lock -- "Inflated" is an absorbing state.
}
+ // Once the ObjectMonitor is configured and object is associated
+ // with the ObjectMonitor, it is safe to allow async deflation:
+ assert(m->is_new(), "freshly allocated monitor must be new");
+ m->set_allocation_state(ObjectMonitor::Old);
+
// Hopefully the performance counters are allocated on distinct
// cache lines to avoid false sharing on MP systems ...
OM_PERFDATA_OP(Inflations, inc());
if (log_is_enabled(Trace, monitorinflation)) {
ResourceMark rm(self);
@@ -1470,17 +2030,19 @@
object->mark().value(), 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.
//
+// 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
@@ -1495,10 +2057,44 @@
//
// 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) {
+ 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();
+
+ 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,
@@ -1513,11 +2109,13 @@
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()) {
+ if (mid->is_busy() || mid->ref_count() != 0) {
+ // Easy checks are first - the ObjectMonitor is busy or ObjectMonitor*
+ // is in use 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 ...
@@ -1529,25 +2127,38 @@
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 and we won't race
+ // with the simple C2 ObjectMonitor enter optimization since
+ // we're at a safepoint. DEFLATER_MARKER is the only non-NULL
+ // value we should see here.
+ mid->try_set_owner_from(NULL, DEFLATER_MARKER);
+ }
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.
+ // defined by free_head_p and free_tail_p. No races on this list
+ // so no need for load_acquire() or store_release().
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:
- assert(prevtail->_next_om == NULL, "cleaned up deflated?");
- prevtail->_next_om = mid;
+ // 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.
+ assert(prevtail->_next_om == NULL, "must be NULL: _next_om="
+ INTPTR_FORMAT, p2i(prevtail->_next_om));
+ set_next(prevtail, 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
@@ -1555,13 +2166,157 @@
deflated = true;
}
return deflated;
}
-// 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.
+// 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** 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.
+ 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 (mid->try_set_owner_from(DEFLATER_MARKER, NULL) == NULL) {
+ // 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.
+ mid->try_set_owner_from(NULL, DEFLATER_MARKER);
+ return false;
+ }
+
+ if (Atomic::cmpxchg(&mid->_ref_count, (jint)0, -max_jint) == 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_is_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), obj->mark().value(),
+ 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 free_head_p and free_tail_p. No races on this list
+ // so no need for load_acquire() or store_release().
+ if (*free_head_p == NULL) {
+ // First one on the list.
+ *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:
+ om_lock(prevtail);
+ assert(unmarked_next(prevtail) == NULL, "must be NULL: _next_om="
+ INTPTR_FORMAT, p2i(unmarked_next(prevtail)));
+ set_next(prevtail, mid); // prevtail now points to mid (and is unlocked)
+ }
+ *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.
+
+ // 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(&mid->_ref_count, max_jint);
+
+#ifdef ASSERT
+ jint l_ref_count = mid->ref_count();
+#endif
+ assert(l_ref_count >= 0, "must not be negative: l_ref_count=%d, ref_count=%d",
+ l_ref_count, 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:
+ mid->try_set_owner_from(NULL, 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.
//
// 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
@@ -1569,87 +2324,255 @@
//
// 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* mid;
- ObjectMonitor* next;
ObjectMonitor* cur_mid_in_use = NULL;
+ ObjectMonitor* mid = NULL;
+ ObjectMonitor* next = NULL;
int deflated_count = 0;
- for (mid = *list_p; mid != NULL;) {
+ // We use the simpler lock-mid-as-we-go protocol since there are no
+ // parallel list deletions since we are at a safepoint.
+ if ((mid = get_list_head_locked(list_p)) == NULL) {
+ return 0; // The list is empty so nothing to deflate.
+ }
+ next = unmarked_next(mid);
+
+ while (true) {
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 (mid == *list_p) {
- *list_p = mid->_next_om;
- } else if (cur_mid_in_use != NULL) {
- cur_mid_in_use->_next_om = mid->_next_om; // maintain the current thread in-use list
+ if (cur_mid_in_use == NULL) {
+ // mid is the list head and it is locked. Switch the list head
+ // to next which unlocks the list head, but leaves mid locked:
+ Atomic::store(list_p, next);
+ } else {
+ // mid is locked. Switch cur_mid_in_use's next field to next
+ // which is safe because we have no parallel list deletions,
+ // but we leave mid locked:
+ set_next(cur_mid_in_use, next);
}
- next = mid->_next_om;
- mid->_next_om = NULL; // This mid is current tail in the free_head_p list
- mid = next;
+ // At this point mid is disconnected from the in-use list so
+ // its lock no longer has any effects on the in-use list.
deflated_count++;
+ Atomic::dec(count_p);
+ // mid is current tail in the free_head_p list so NULL terminate it
+ // (which also unlocks it):
+ set_next(mid, NULL);
} else {
+ om_unlock(mid);
+ cur_mid_in_use = mid;
+ }
+ // All the list management is done so move on to the next one:
+ mid = next;
+ if (mid == NULL) {
+ break; // Reached end of the list so nothing more to deflate.
+ }
+ // Lock mid so we can possibly deflate it:
+ om_lock(mid);
+ next = unmarked_next(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.
+// If a safepoint has started, then we save state via saved_mid_in_use_p
+// and return to the caller to honor the safepoint.
+//
+int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** list_p,
+ int* count_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;
+ ObjectMonitor* mid = NULL;
+ ObjectMonitor* next = NULL;
+ ObjectMonitor* next_next = NULL;
+ int deflated_count = 0;
+
+ // We use the more complicated lock-cur_mid_in_use-and-mid-as-we-go
+ // protocol because om_release() can do list deletions in parallel.
+ // We also lock-next-next-as-we-go to prevent an om_flush() that is
+ // behind this thread from passing us.
+ if (*saved_mid_in_use_p == NULL) {
+ // No saved state so start at the beginning.
+ // Lock the list head so we can possibly deflate it:
+ if ((mid = get_list_head_locked(list_p)) == NULL) {
+ return 0; // The list is empty so nothing to deflate.
+ }
+ next = unmarked_next(mid);
+ } else {
+ // We're restarting after a safepoint so restore the necessary state
+ // before we resume.
+ cur_mid_in_use = *saved_mid_in_use_p;
+ // Lock cur_mid_in_use so we can possibly update its
+ // next field to extract a deflated ObjectMonitor.
+ om_lock(cur_mid_in_use);
+ mid = unmarked_next(cur_mid_in_use);
+ if (mid == NULL) {
+ om_unlock(cur_mid_in_use);
+ *saved_mid_in_use_p = NULL;
+ return 0; // The remainder is empty so nothing more to deflate.
+ }
+ // Lock mid so we can possibly deflate it:
+ om_lock(mid);
+ next = unmarked_next(mid);
+ }
+
+ while (true) {
+ // The current mid's next field is marked at this point. If we have
+ // a cur_mid_in_use, then its next field is also marked at this point.
+
+ if (next != NULL) {
+ // We lock next so that an om_flush() thread that is behind us
+ // cannot pass us when we unlock the current mid.
+ om_lock(next);
+ next_next = unmarked_next(next);
+ }
+
+ // 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, 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 and it is locked. Switch the list head
+ // to next which is also locked (if not NULL) and also leave
+ // mid locked:
+ Atomic::store(list_p, next);
+ } else {
+ ObjectMonitor* locked_next = mark_om_ptr(next);
+ // mid and cur_mid_in_use are locked. Switch cur_mid_in_use's
+ // next field to locked_next and also leave mid locked:
+ set_next(cur_mid_in_use, locked_next);
+ }
+ // At this point mid is disconnected from the in-use list so
+ // its lock longer has any effects on in-use list.
+ deflated_count++;
+ Atomic::dec(count_p);
+ // mid is current tail in the free_head_p list so NULL terminate it
+ // (which also unlocks it):
+ set_next(mid, NULL);
+
+ // All the list management is done so move on to the next one:
+ mid = next; // mid keeps non-NULL next's locked next field
+ next = next_next;
+ } 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 om_alloc() (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
+ // om_alloc() is released by om_release() due to losing the race
+ // in inflate().
+
+ // All the list management is done so move on to the next one:
+ if (cur_mid_in_use != NULL) {
+ om_unlock(cur_mid_in_use);
+ }
+ // The next cur_mid_in_use keeps mid's lock state so
+ // that it is stable for a possible next field change. It
+ // cannot be modified by om_release() while it is locked.
cur_mid_in_use = mid;
- mid = mid->_next_om;
+ mid = next; // mid keeps non-NULL next's locked state
+ next = next_next;
+
+ if (SafepointMechanism::should_block(self) &&
+ cur_mid_in_use != Atomic::load(list_p) && 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 before blocking.
+ *saved_mid_in_use_p = cur_mid_in_use;
+ om_unlock(cur_mid_in_use);
+ if (mid != NULL) {
+ om_unlock(mid);
+ }
+ return deflated_count;
+ }
}
+ if (mid == NULL) {
+ if (cur_mid_in_use != NULL) {
+ om_unlock(cur_mid_in_use);
+ }
+ break; // Reached end of the list so nothing more to deflate.
+ }
+
+ // The current mid's next field is locked at this point. If we have
+ // a cur_mid_in_use, then it is also locked at this point.
}
+ // We finished the list without a safepoint starting so there's
+ // no need to save state.
+ *saved_mid_in_use_p = NULL;
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
+ OrderAccess::storestore(); // flush inits for worker threads
}
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* free_head_p = NULL; // Local SLL of scavenged monitors
ObjectMonitor* free_tail_p = NULL;
elapsedTimer timer;
if (log_is_enabled(Info, monitorinflation)) {
timer.start();
}
- // Prevent om_flush from changing mids in Thread dtor's during deflation
- // And in case the vm thread is acquiring a lock during a safepoint
- // See e.g. 6320749
- Thread::muxAcquire(&gListLock, "deflate_idle_monitors");
-
// Note: the thread-local monitors lists get deflated in
// a separate pass. See deflate_thread_local_monitors().
- // For moribund threads, scan g_om_in_use_list
+ // For moribund threads, scan LVars.in_use_list
int deflated_count = 0;
- if (g_om_in_use_list) {
- counters->n_in_circulation += g_om_in_use_count;
- deflated_count = deflate_monitor_list((ObjectMonitor **)&g_om_in_use_list, &free_head_p, &free_tail_p);
- g_om_in_use_count -= deflated_count;
- counters->n_scavenged += deflated_count;
- counters->n_in_use += g_om_in_use_count;
+ if (Atomic::load(&LVars.in_use_list) != NULL) {
+ // Update n_in_circulation before LVars.in_use_count is updated by deflation.
+ Atomic::add(&counters->n_in_circulation, Atomic::load(&LVars.in_use_count));
+
+ deflated_count = deflate_monitor_list(&LVars.in_use_list, &LVars.in_use_count, &free_head_p, &free_tail_p);
+ Atomic::add(&counters->n_in_use, Atomic::load(&LVars.in_use_count));
}
if (free_head_p != NULL) {
// Move the deflated ObjectMonitors back to the global free list.
- guarantee(free_tail_p != NULL && counters->n_scavenged > 0, "invariant");
- assert(free_tail_p->_next_om == NULL, "invariant");
- // constant-time list splice - prepend scavenged segment to g_free_list
- free_tail_p->_next_om = g_free_list;
- g_free_list = free_head_p;
+ // No races on the working free list so no need for load_acquire().
+ guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
+ assert(free_tail_p->_next_om == NULL, "must be NULL: _next_om="
+ INTPTR_FORMAT, p2i(free_tail_p->_next_om));
+ prepend_list_to_global_free_list(free_head_p, free_tail_p, deflated_count);
+ Atomic::add(&counters->n_scavenged, deflated_count);
}
- Thread::muxRelease(&gListLock);
timer.stop();
LogStreamHandle(Debug, monitorinflation) lsh_debug;
LogStreamHandle(Info, monitorinflation) lsh_info;
LogStream* ls = NULL;
@@ -1661,81 +2584,272 @@
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") {}
+
+ void do_thread(Thread* thread) {
+ log_trace(monitorinflation)("HandshakeForDeflation::do_thread: thread="
+ INTPTR_FORMAT, p2i(thread));
+ }
+};
+
+void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
+ assert(AsyncDeflateIdleMonitors, "sanity check");
+
+ // Deflate any global idle monitors.
+ deflate_global_idle_monitors_using_JT();
+
+ int count = 0;
+ for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
+ if (jt->om_in_use_count > 0 && !jt->is_exiting()) {
+ // This JavaThread is using ObjectMonitors so deflate any that
+ // are idle unless this JavaThread is exiting; do not race with
+ // ObjectSynchronizer::om_flush().
+ deflate_per_thread_idle_monitors_using_JT(jt);
+ count++;
+ }
+ }
+ if (count > 0) {
+ log_debug(monitorinflation)("did async deflation of idle monitors for %d thread(s).", count);
+ }
+
+ log_info(monitorinflation)("async global_population=%d, global_in_use_count=%d, "
+ "global_free_count=%d, global_wait_count=%d",
+ Atomic::load(&LVars.population), Atomic::load(&LVars.in_use_count),
+ Atomic::load(&LVars.free_count), Atomic::load(&LVars.wait_count));
+
+ // The ServiceThread's async deflation request has been processed.
+ set_is_async_deflation_requested(false);
+
+ if (HandshakeAfterDeflateIdleMonitors && Atomic::load(&LVars.wait_count) > 0) {
+ // There are deflated ObjectMonitors waiting for a handshake
+ // (or a safepoint) for safety.
+
+ ObjectMonitor* list = Atomic::load(&LVars.wait_list);
+ ADIM_guarantee(list != NULL, "LVars.wait_list must not be NULL");
+ int count = Atomic::load(&LVars.wait_count);
+ Atomic::store(&LVars.wait_count, 0);
+ Atomic::store(&LVars.wait_list, (ObjectMonitor*)NULL);
+
+ // 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.
+ int l_count = 0;
+ ObjectMonitor* tail = NULL;
+ for (ObjectMonitor* n = list; n != NULL; n = unmarked_next(n)) {
+ tail = n;
+ l_count++;
+ }
+ ADIM_guarantee(count == l_count, "count=%d != l_count=%d", count, l_count);
+
+ // Will execute a safepoint if !ThreadLocalHandshakes:
+ HandshakeForDeflation hfd_hc;
+ Handshake::execute(&hfd_hc);
+
+ prepend_list_to_common(list, tail, count, &LVars.free_list, &LVars.free_count);
+
+ log_info(monitorinflation)("moved %d idle monitors from global waiting list to global free list", 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 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);
+}
+
+// Deflate global or per-thread idle ObjectMonitors using a JavaThread.
+//
+void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, JavaThread* target) {
+ JavaThread* self = JavaThread::current();
+
+ int deflated_count = 0;
+ ObjectMonitor* free_head_p = NULL; // Local SLL of scavenged ObjectMonitors
+ ObjectMonitor* free_tail_p = NULL;
+ ObjectMonitor* saved_mid_in_use_p = NULL;
+ elapsedTimer timer;
+
+ if (log_is_enabled(Info, monitorinflation)) {
+ timer.start();
+ }
+
+ if (is_global) {
+ OM_PERFDATA_OP(MonExtant, set_value(Atomic::load(&LVars.in_use_count)));
+ } else {
+ OM_PERFDATA_OP(MonExtant, inc(target->om_in_use_count));
+ }
+
+ do {
+ int local_deflated_count;
+ if (is_global) {
+ local_deflated_count = deflate_monitor_list_using_JT(&LVars.in_use_list, &LVars.in_use_count, &free_head_p, &free_tail_p, &saved_mid_in_use_p);
+ } else {
+ local_deflated_count = deflate_monitor_list_using_JT(&target->om_in_use_list, &target->om_in_use_count, &free_head_p, &free_tail_p, &saved_mid_in_use_p);
+ }
+ deflated_count += local_deflated_count;
+
+ if (free_head_p != NULL) {
+ // Move the deflated ObjectMonitors to the global free list.
+ // No races on the working list so no need for load_acquire().
+ guarantee(free_tail_p != NULL && local_deflated_count > 0, "free_tail_p=" INTPTR_FORMAT ", local_deflated_count=%d", p2i(free_tail_p), local_deflated_count);
+ // Note: The target thread can be doing an om_alloc() that
+ // is trying to prepend an ObjectMonitor on its in-use list
+ // at the same time that we have deflated the current in-use
+ // list head and put it on the local free list. prepend_to_common()
+ // will detect the race and retry which avoids list corruption,
+ // but the next field in free_tail_p can flicker to marked
+ // and then unmarked while prepend_to_common() is sorting it
+ // all out.
+ assert(unmarked_next(free_tail_p) == NULL, "must be NULL: _next_om="
+ INTPTR_FORMAT, p2i(unmarked_next(free_tail_p)));
+
+ if (HandshakeAfterDeflateIdleMonitors) {
+ prepend_list_to_global_wait_list(free_head_p, free_tail_p, local_deflated_count);
+ } else {
+ prepend_list_to_global_free_list(free_head_p, free_tail_p, local_deflated_count);
+ }
+
+ OM_PERFDATA_OP(Deflations, inc(local_deflated_count));
+ }
+
+ if (saved_mid_in_use_p != NULL) {
+ // deflate_monitor_list_using_JT() detected a safepoint starting.
+ 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(target));
+ }
+ assert(SafepointMechanism::should_block(self), "sanity check");
+ ThreadBlockInVM blocker(self);
+ }
+ // Prepare for another loop after the safepoint.
+ free_head_p = NULL;
+ free_tail_p = NULL;
+ if (log_is_enabled(Info, monitorinflation)) {
+ timer.start();
+ }
+ }
+ } while (saved_mid_in_use_p != NULL);
+ 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(target), 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.
log_info(safepoint, cleanup)("deflating per-thread idle monitors, %3.7f secs, monitors=%d", counters->per_thread_times, counters->per_thread_scavenged);
- g_om_free_count += counters->n_scavenged;
+ bool needs_special_deflation = is_special_deflation_requested();
+ if (AsyncDeflateIdleMonitors && !needs_special_deflation) {
+ // Nothing to do when idle ObjectMonitors are deflated using
+ // a JavaThread unless a special deflation has been requested.
+ return;
+ }
if (log_is_enabled(Debug, monitorinflation)) {
// exit_globals()'s call to audit_and_print_stats() is done
- // at the Info level.
+ // 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)) {
- Thread::muxAcquire(&gListLock, "finish_deflate_idle_monitors");
- log_info(monitorinflation)("g_om_population=%d, g_om_in_use_count=%d, "
- "g_om_free_count=%d", g_om_population,
- g_om_in_use_count, g_om_free_count);
- Thread::muxRelease(&gListLock);
+ log_info(monitorinflation)("global_population=%d, global_in_use_count=%d, "
+ "global_free_count=%d, global_wait_count=%d",
+ Atomic::load(&LVars.population), Atomic::load(&LVars.in_use_count),
+ Atomic::load(&LVars.free_count), Atomic::load(&LVars.wait_count));
}
Atomic::store(&_forceMonitorScavenge, 0); // Reset
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++;
+
+ 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 && !is_special_deflation_requested()) {
+ // Nothing to do if a special deflation has NOT been requested.
+ 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();
}
- int deflated_count = deflate_monitor_list(thread->om_in_use_list_addr(), &free_head_p, &free_tail_p);
+ // Update n_in_circulation before om_in_use_count is updated by deflation.
+ Atomic::add(&counters->n_in_circulation, thread->om_in_use_count);
- Thread::muxAcquire(&gListLock, "deflate_thread_local_monitors");
-
- // Adjust counters
- counters->n_in_circulation += thread->om_in_use_count;
- thread->om_in_use_count -= deflated_count;
- counters->n_scavenged += deflated_count;
- counters->n_in_use += thread->om_in_use_count;
- counters->per_thread_scavenged += deflated_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, thread->om_in_use_count);
if (free_head_p != NULL) {
// Move the deflated ObjectMonitors back to the global free list.
+ // No races on the working list so no need for load_acquire().
guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
- assert(free_tail_p->_next_om == NULL, "invariant");
-
- // constant-time list splice - prepend scavenged segment to g_free_list
- free_tail_p->_next_om = g_free_list;
- g_free_list = free_head_p;
+ assert(free_tail_p->_next_om == NULL, "must be NULL: _next_om="
+ INTPTR_FORMAT, p2i(free_tail_p->_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();
// Safepoint logging cares about cumulative per_thread_times and
// we'll capture most of the cost, but not the muxRelease() which
// should be cheap.
counters->per_thread_times += timer.seconds();
- Thread::muxRelease(&gListLock);
-
LogStreamHandle(Debug, monitorinflation) lsh_debug;
LogStreamHandle(Info, monitorinflation) lsh_info;
LogStream* ls = NULL;
if (log_is_enabled(Debug, monitorinflation)) {
ls = &lsh_debug;
@@ -1782,13 +2896,11 @@
void ObjectSynchronizer::release_monitors_owned_by_thread(TRAPS) {
assert(THREAD == JavaThread::current(), "must be current Java thread");
NoSafepointVerifier nsv;
ReleaseJavaMonitorsClosure rjmc(THREAD);
- Thread::muxAcquire(&gListLock, "release_monitors_owned_by_thread");
ObjectSynchronizer::monitors_iterate(&rjmc);
- Thread::muxRelease(&gListLock);
THREAD->clear_pending_exception();
}
const char* ObjectSynchronizer::inflate_cause_name(const InflateCause cause) {
switch (cause) {
@@ -1838,40 +2950,38 @@
} else if (log_is_enabled(Info, monitorinflation)) {
ls = &lsh_info;
}
assert(ls != NULL, "sanity check");
- if (!on_exit) {
- // Not at VM exit so grab the global list lock.
- Thread::muxAcquire(&gListLock, "audit_and_print_stats");
- }
-
// Log counts for the global and per-thread monitor lists:
int chk_om_population = log_monitor_list_counts(ls);
int error_cnt = 0;
ls->print_cr("Checking global lists:");
- // Check g_om_population:
- if (g_om_population == chk_om_population) {
- ls->print_cr("g_om_population=%d equals chk_om_population=%d",
- g_om_population, chk_om_population);
- } else {
- ls->print_cr("ERROR: g_om_population=%d is not equal to "
- "chk_om_population=%d", g_om_population,
- chk_om_population);
- error_cnt++;
+ // Check LVars.population:
+ if (Atomic::load(&LVars.population) == chk_om_population) {
+ ls->print_cr("global_population=%d equals chk_om_population=%d",
+ Atomic::load(&LVars.population), chk_om_population);
+ } else {
+ // With lock free access to the monitor lists, it is possible for
+ // log_monitor_list_counts() to return a value that doesn't match
+ // LVars.population. So far a higher value has been seen in testing
+ // so something is being double counted by log_monitor_list_counts().
+ ls->print_cr("WARNING: global_population=%d is not equal to "
+ "chk_om_population=%d", Atomic::load(&LVars.population), chk_om_population);
}
- // Check g_om_in_use_list and g_om_in_use_count:
+ // Check LVars.in_use_list and LVars.in_use_count:
chk_global_in_use_list_and_count(ls, &error_cnt);
- // Check g_free_list and g_om_free_count:
+ // Check LVars.free_list and LVars.free_count:
chk_global_free_list_and_count(ls, &error_cnt);
- if (!on_exit) {
- Thread::muxRelease(&gListLock);
+ if (HandshakeAfterDeflateIdleMonitors) {
+ // Check LVars.wait_list and LVars.wait_count:
+ chk_global_wait_list_and_count(ls, &error_cnt);
}
ls->print_cr("Checking per-thread lists:");
for (JavaThreadIteratorWithHandle jtiwh; JavaThread *jt = jtiwh.next(); ) {
@@ -1891,11 +3001,11 @@
if ((on_exit && log_is_enabled(Info, monitorinflation)) ||
(!on_exit && log_is_enabled(Trace, monitorinflation))) {
// When exiting this log output is at the Info level. When called
// at a safepoint, this log output is at the Trace level since
// there can be a lot of it.
- log_in_use_monitor_details(ls, on_exit);
+ log_in_use_monitor_details(ls);
}
ls->flush();
guarantee(error_cnt == 0, "ERROR: found monitor list errors: error_cnt=%d", error_cnt);
@@ -1920,17 +3030,18 @@
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),
n->header().value());
- } 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), n->header().value());
- }
*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),
@@ -1942,44 +3053,117 @@
}
*error_cnt_p = *error_cnt_p + 1;
}
}
+// Lock the next ObjectMonitor for traversal. The current ObjectMonitor
+// is unlocked after the next ObjectMonitor is locked. *cur_p and *next_p
+// are updated to their next values in the list traversal. *cur_p is set
+// to NULL when the end of the list is reached.
+static void lock_next_for_traversal(ObjectMonitor** cur_p, ObjectMonitor** next_p) {
+ ObjectMonitor* prev = *cur_p; // Save current for unlocking.
+ if (*next_p == NULL) { // Reached the end of the list.
+ om_unlock(prev); // Unlock previous.
+ *cur_p = NULL; // Tell the caller we are done.
+ return;
+ }
+ om_lock(*next_p); // Lock next.
+ om_unlock(prev); // Unlock previous.
+ *cur_p = *next_p; // Update current.
+ *next_p = unmarked_next(*cur_p); // Update next.
+}
+
// Check the global free list and count; log the results of the checks.
void ObjectSynchronizer::chk_global_free_list_and_count(outputStream * out,
int *error_cnt_p) {
int chk_om_free_count = 0;
- for (ObjectMonitor* n = g_free_list; n != NULL; n = n->_next_om) {
- chk_free_entry(NULL /* jt */, n, out, error_cnt_p);
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&LVars.free_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the global free list head so process the list.
+ while (true) {
+ chk_free_entry(NULL /* jt */, cur, out, error_cnt_p);
chk_om_free_count++;
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
+ }
}
- if (g_om_free_count == chk_om_free_count) {
- out->print_cr("g_om_free_count=%d equals chk_om_free_count=%d",
- g_om_free_count, chk_om_free_count);
+ if (Atomic::load(&LVars.free_count) == chk_om_free_count) {
+ out->print_cr("global_free_count=%d equals chk_om_free_count=%d",
+ Atomic::load(&LVars.free_count), chk_om_free_count);
} else {
- out->print_cr("ERROR: g_om_free_count=%d is not equal to "
- "chk_om_free_count=%d", g_om_free_count,
- chk_om_free_count);
+ // With lock free access to LVars.free_list, it is possible for an
+ // ObjectMonitor to be prepended to LVars.free_list after we started
+ // calculating chk_om_free_count so LVars.free_count may not
+ // match anymore.
+ out->print_cr("WARNING: global_free_count=%d is not equal to "
+ "chk_om_free_count=%d", Atomic::load(&LVars.free_count), chk_om_free_count);
+ }
+}
+
+// Check the global wait list and count; log the results of the checks.
+void ObjectSynchronizer::chk_global_wait_list_and_count(outputStream * out,
+ int *error_cnt_p) {
+ int chk_om_wait_count = 0;
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&LVars.wait_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the global wait list head so process the list.
+ while (true) {
+ // Rules for LVars.wait_list are the same as of LVars.free_list:
+ chk_free_entry(NULL /* jt */, cur, out, error_cnt_p);
+ chk_om_wait_count++;
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
+ }
+ }
+ if (Atomic::load(&LVars.wait_count) == chk_om_wait_count) {
+ out->print_cr("global_wait_count=%d equals chk_om_wait_count=%d",
+ Atomic::load(&LVars.wait_count), chk_om_wait_count);
+ } else {
+ out->print_cr("ERROR: global_wait_count=%d is not equal to "
+ "chk_om_wait_count=%d", Atomic::load(&LVars.wait_count), chk_om_wait_count);
*error_cnt_p = *error_cnt_p + 1;
}
}
// Check the global in-use list and count; log the results of the checks.
void ObjectSynchronizer::chk_global_in_use_list_and_count(outputStream * out,
int *error_cnt_p) {
int chk_om_in_use_count = 0;
- for (ObjectMonitor* n = g_om_in_use_list; n != NULL; n = n->_next_om) {
- chk_in_use_entry(NULL /* jt */, n, out, error_cnt_p);
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&LVars.in_use_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the global in-use list head so process the list.
+ while (true) {
+ chk_in_use_entry(NULL /* jt */, cur, out, error_cnt_p);
chk_om_in_use_count++;
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
}
- if (g_om_in_use_count == chk_om_in_use_count) {
- out->print_cr("g_om_in_use_count=%d equals chk_om_in_use_count=%d", g_om_in_use_count,
- chk_om_in_use_count);
- } else {
- out->print_cr("ERROR: g_om_in_use_count=%d is not equal to chk_om_in_use_count=%d",
- g_om_in_use_count, chk_om_in_use_count);
- *error_cnt_p = *error_cnt_p + 1;
+ }
+ if (Atomic::load(&LVars.in_use_count) == chk_om_in_use_count) {
+ out->print_cr("global_in_use_count=%d equals chk_om_in_use_count=%d",
+ Atomic::load(&LVars.in_use_count), chk_om_in_use_count);
+ } else {
+ // With lock free access to the monitor lists, it is possible for
+ // an exiting JavaThread to put its in-use ObjectMonitors on the
+ // global in-use list after chk_om_in_use_count is calculated above.
+ out->print_cr("WARNING: global_in_use_count=%d is not equal to chk_om_in_use_count=%d",
+ Atomic::load(&LVars.in_use_count), chk_om_in_use_count);
}
}
// Check an in-use monitor entry; log any errors.
void ObjectSynchronizer::chk_in_use_entry(JavaThread* jt, ObjectMonitor* n,
@@ -2043,17 +3227,29 @@
// Check the thread's free list and count; log the results of the checks.
void ObjectSynchronizer::chk_per_thread_free_list_and_count(JavaThread *jt,
outputStream * out,
int *error_cnt_p) {
int chk_om_free_count = 0;
- for (ObjectMonitor* n = jt->om_free_list; n != NULL; n = n->_next_om) {
- chk_free_entry(jt, n, out, error_cnt_p);
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&jt->om_free_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the per-thread free list head so process the list.
+ while (true) {
+ chk_free_entry(jt, cur, out, error_cnt_p);
chk_om_free_count++;
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
+ }
}
if (jt->om_free_count == chk_om_free_count) {
out->print_cr("jt=" INTPTR_FORMAT ": om_free_count=%d equals "
- "chk_om_free_count=%d", p2i(jt), jt->om_free_count, chk_om_free_count);
+ "chk_om_free_count=%d", p2i(jt), jt->om_free_count,
+ chk_om_free_count);
} else {
out->print_cr("ERROR: jt=" INTPTR_FORMAT ": om_free_count=%d is not "
"equal to chk_om_free_count=%d", p2i(jt), jt->om_free_count,
chk_om_free_count);
*error_cnt_p = *error_cnt_p + 1;
@@ -2063,97 +3259,124 @@
// Check the thread's in-use list and count; log the results of the checks.
void ObjectSynchronizer::chk_per_thread_in_use_list_and_count(JavaThread *jt,
outputStream * out,
int *error_cnt_p) {
int chk_om_in_use_count = 0;
- for (ObjectMonitor* n = jt->om_in_use_list; n != NULL; n = n->_next_om) {
- chk_in_use_entry(jt, n, out, error_cnt_p);
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&jt->om_in_use_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the per-thread in-use list head so process the list.
+ while (true) {
+ chk_in_use_entry(jt, cur, out, error_cnt_p);
chk_om_in_use_count++;
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
+ }
}
if (jt->om_in_use_count == chk_om_in_use_count) {
out->print_cr("jt=" INTPTR_FORMAT ": om_in_use_count=%d equals "
- "chk_om_in_use_count=%d", p2i(jt), jt->om_in_use_count,
- chk_om_in_use_count);
+ "chk_om_in_use_count=%d", p2i(jt),
+ jt->om_in_use_count, chk_om_in_use_count);
} else {
out->print_cr("ERROR: jt=" INTPTR_FORMAT ": om_in_use_count=%d is not "
- "equal to chk_om_in_use_count=%d", p2i(jt), jt->om_in_use_count,
- chk_om_in_use_count);
+ "equal to chk_om_in_use_count=%d", p2i(jt),
+ jt->om_in_use_count, chk_om_in_use_count);
*error_cnt_p = *error_cnt_p + 1;
}
}
// Log details about ObjectMonitors on the in-use lists. The 'BHL'
// flags indicate why the entry is in-use, 'object' and 'object type'
// indicate the associated object and its type.
-void ObjectSynchronizer::log_in_use_monitor_details(outputStream * out,
- bool on_exit) {
- if (!on_exit) {
- // Not at VM exit so grab the global list lock.
- Thread::muxAcquire(&gListLock, "log_in_use_monitor_details");
- }
-
+void ObjectSynchronizer::log_in_use_monitor_details(outputStream * out) {
stringStream ss;
- if (g_om_in_use_count > 0) {
+ if (Atomic::load(&LVars.in_use_count) > 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("================== === ================== ==================");
- for (ObjectMonitor* n = g_om_in_use_list; n != NULL; n = n->_next_om) {
- const oop obj = (oop) n->object();
- const markWord mark = n->header();
+ out->print_cr("%18s %s %7s %18s %18s",
+ "monitor", "BHL", "ref_cnt", "object", "object type");
+ out->print_cr("================== === ======= ================== ==================");
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&LVars.in_use_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the global in-use list head so process the list.
+ while (true) {
+ const oop obj = (oop) cur->object();
+ const markWord mark = cur->header();
ResourceMark rm;
- out->print(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());
- if (n->is_busy() != 0) {
- out->print(" (%s)", n->is_busy_to_string(&ss));
+ out->print(INTPTR_FORMAT " %d%d%d %7d " INTPTR_FORMAT " %s",
+ p2i(cur), cur->is_busy() != 0, mark.hash() != 0,
+ cur->owner() != NULL, (int)cur->ref_count(), p2i(obj),
+ obj->klass()->external_name());
+ if (cur->is_busy() != 0) {
+ out->print(" (%s)", cur->is_busy_to_string(&ss));
ss.reset();
}
out->cr();
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
}
}
-
- 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->om_in_use_list; n != NULL; n = n->_next_om) {
- const oop obj = (oop) n->object();
- const markWord mark = n->header();
+ ObjectMonitor* cur = NULL;
+ ObjectMonitor* next = NULL;
+ if ((cur = get_list_head_locked(&jt->om_in_use_list)) != NULL) {
+ next = unmarked_next(cur);
+ // Marked the global in-use list head so process the list.
+ while (true) {
+ const oop obj = (oop) cur->object();
+ const markWord mark = cur->header();
ResourceMark rm;
- out->print(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());
- if (n->is_busy() != 0) {
- out->print(" (%s)", n->is_busy_to_string(&ss));
+ out->print(INTPTR_FORMAT " " INTPTR_FORMAT " %d%d%d %7d "
+ INTPTR_FORMAT " %s", p2i(jt), p2i(cur), cur->is_busy() != 0,
+ mark.hash() != 0, cur->owner() != NULL, (int)cur->ref_count(),
+ p2i(obj), obj->klass()->external_name());
+ if (cur->is_busy() != 0) {
+ out->print(" (%s)", cur->is_busy_to_string(&ss));
ss.reset();
}
out->cr();
+
+ lock_next_for_traversal(&cur, &next);
+ if (cur == NULL) {
+ break;
+ }
+ }
}
}
out->flush();
}
// Log counts for the global and per-thread monitor lists and return
// the population count.
int ObjectSynchronizer::log_monitor_list_counts(outputStream * out) {
int pop_count = 0;
- out->print_cr("%18s %10s %10s %10s",
- "Global Lists:", "InUse", "Free", "Total");
- out->print_cr("================== ========== ========== ==========");
- out->print_cr("%18s %10d %10d %10d", "",
- g_om_in_use_count, g_om_free_count, g_om_population);
- pop_count += g_om_in_use_count + g_om_free_count;
+ out->print_cr("%18s %10s %10s %10s %10s",
+ "Global Lists:", "InUse", "Free", "Wait", "Total");
+ out->print_cr("================== ========== ========== ========== ==========");
+ out->print_cr("%18s %10d %10d %10d %10d", "", Atomic::load(&LVars.in_use_count),
+ Atomic::load(&LVars.free_count), Atomic::load(&LVars.wait_count), Atomic::load(&LVars.population));
+ pop_count += Atomic::load(&LVars.in_use_count) + Atomic::load(&LVars.free_count);
+ if (HandshakeAfterDeflateIdleMonitors) {
+ pop_count += Atomic::load(&LVars.wait_count);
+ }
out->print_cr("%18s %10s %10s %10s",
"Per-Thread Lists:", "InUse", "Free", "Provision");
out->print_cr("================== ========== ========== ==========");
@@ -2170,21 +3393,23 @@
// Check if monitor belongs to the monitor cache
// The list is grow-only so it's *relatively* safe to traverse
// the list of extant blocks without taking a lock.
int ObjectSynchronizer::verify_objmon_isinpool(ObjectMonitor *monitor) {
- PaddedObjectMonitor* block = Atomic::load_acquire(&g_block_list);
+ PaddedObjectMonitor* block = Atomic::load(&g_block_list);
while (block != NULL) {
assert(block->object() == CHAINMARKER, "must be a block header");
if (monitor > &block[0] && monitor < &block[_BLOCKSIZE]) {
address mon = (address)monitor;
address blk = (address)block;
size_t diff = mon - blk;
assert((diff % sizeof(PaddedObjectMonitor)) == 0, "must be aligned");
return 1;
}
- block = (PaddedObjectMonitor*)block->_next_om;
+ // unmarked_next() is not needed with g_block_list (no locking
+ // used with with block linkage _next_om fields).
+ block = (PaddedObjectMonitor*)Atomic::load(&block->_next_om);
}
return 0;
}
#endif
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