8180175: ObjectSynchronizer only needs to iterate in-use monitors
Summary: When using -XX:+MonitorInUseLists, then only iterate in-use monitors.
Reviewed-by: zgu, dholmes, rehn
--- a/hotspot/src/share/vm/runtime/synchronizer.cpp Wed May 17 23:18:19 2017 +0200
+++ b/hotspot/src/share/vm/runtime/synchronizer.cpp Wed May 17 23:36:19 2017 +0200
@@ -964,6 +964,17 @@
void ObjectSynchronizer::oops_do(OopClosure* f) {
+ if (MonitorInUseLists) {
+ // When using thread local monitor lists, 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);
+ } else {
+ global_oops_do(f);
+ }
+}
+
+void ObjectSynchronizer::global_oops_do(OopClosure* f) {
assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
PaddedEnd<ObjectMonitor> * block =
(PaddedEnd<ObjectMonitor> *)OrderAccess::load_ptr_acquire(&gBlockList);
@@ -978,6 +989,26 @@
}
}
+void ObjectSynchronizer::global_used_oops_do(OopClosure* f) {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ list_oops_do(gOmInUseList, 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->omInUseList, f);
+}
+
+void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
+ assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
+ ObjectMonitor* mid;
+ for (mid = list; mid != NULL; mid = mid->FreeNext) {
+ if (mid->object() != NULL) {
+ f->do_oop((oop*)mid->object_addr());
+ }
+ }
+}
+
// -----------------------------------------------------------------------------
// ObjectMonitor Lifecycle
--- a/hotspot/src/share/vm/runtime/synchronizer.hpp Wed May 17 23:18:19 2017 +0200
+++ b/hotspot/src/share/vm/runtime/synchronizer.hpp Wed May 17 23:36:19 2017 +0200
@@ -136,6 +136,8 @@
ObjectMonitor** freeHeadp,
ObjectMonitor** freeTailp);
static void oops_do(OopClosure* f);
+ // Process oops in thread local used monitors
+ static void thread_local_used_oops_do(Thread* thread, OopClosure* f);
// debugging
static void sanity_checks(const bool verbose,
@@ -156,6 +158,14 @@
static ObjectMonitor * volatile gOmInUseList;
// count of entries in gOmInUseList
static int gOmInUseCount;
+
+ // Process oops in all monitors
+ static void global_oops_do(OopClosure* f);
+ // Process oops in all global used monitors (i.e. moribund thread's monitors)
+ static void global_used_oops_do(OopClosure* f);
+ // Process oops in monitors on the given list
+ static void list_oops_do(ObjectMonitor* list, OopClosure* f);
+
};
// ObjectLocker enforced balanced locking and can never thrown an
--- a/hotspot/src/share/vm/runtime/thread.cpp Wed May 17 23:18:19 2017 +0200
+++ b/hotspot/src/share/vm/runtime/thread.cpp Wed May 17 23:36:19 2017 +0200
@@ -792,6 +792,12 @@
// Do oop for ThreadShadow
f->do_oop((oop*)&_pending_exception);
handle_area()->oops_do(f);
+
+ if (MonitorInUseLists) {
+ // When using thread local monitor lists, we scan them here,
+ // and the remaining global monitors in ObjectSynchronizer::oops_do().
+ ObjectSynchronizer::thread_local_used_oops_do(this, f);
+ }
}
void Thread::metadata_handles_do(void f(Metadata*)) {