8246476: remove AsyncDeflateIdleMonitors option and the safepoint based deflation mechanism

Reviewed-by: dholmes, pchilanomate, coleenp

src/hotspot/share/runtime/globals.hpp

@@ -688,9 +688,6 @@ const size_t minimumSymbolTableSize = 1024;
                "Disable the use of stack guard pages if the JVM is loaded " \
                "on the primordial process thread")                          \
                                                                             \
-  diagnostic(bool, AsyncDeflateIdleMonitors, true,                          \
-          "Deflate idle monitors using the ServiceThread.")                 \
-                                                                            \
   /* notice: the max range value here is max_jint, not max_intx  */         \
   /* because of overflow issue                                   */         \
   diagnostic(intx, AsyncDeflationInterval, 250,                             \

src/hotspot/share/runtime/init.cpp

@@ -170,10 +170,8 @@ void exit_globals() {
     if (log_is_enabled(Info, monitorinflation)) {
       // The ObjectMonitor subsystem uses perf counters so
       // do this before perfMemory_exit().
-      // These other two audit_and_print_stats() calls are done at the
+      // This other audit_and_print_stats() call is done at the
       // Debug level at a safepoint:
-      // - for safepoint based deflation auditing:
-      //   ObjectSynchronizer::finish_deflate_idle_monitors()
       // - for async deflation auditing:
       //   ObjectSynchronizer::do_safepoint_work()
       ObjectSynchronizer::audit_and_print_stats(true /* on_exit */);

src/hotspot/share/runtime/objectMonitor.cpp

@@ -290,8 +290,6 @@ bool ObjectMonitor::enter(TRAPS) {
   JavaThread * jt = (JavaThread *) Self;
   assert(!SafepointSynchronize::is_at_safepoint(), "invariant");
   assert(jt->thread_state() != _thread_blocked, "invariant");
-  assert(AsyncDeflateIdleMonitors || this->object() != NULL, "invariant");
-  assert(AsyncDeflateIdleMonitors || contentions() >= 0, "must not be negative: contentions=%d", contentions());
 
   // Keep track of contention for JVM/TI and M&M queries.
   add_to_contentions(1);
@@ -455,12 +453,12 @@ void ObjectMonitor::install_displaced_markword_in_object(const oop obj) {
     // deflation so we're done here.
     return;
   }
-  ADIM_guarantee(l_object == obj, "object=" INTPTR_FORMAT " must equal obj="
+  assert(l_object == obj, "object=" INTPTR_FORMAT " must equal obj="
          INTPTR_FORMAT, p2i(l_object), p2i(obj));
 
   markWord dmw = header();
   // The dmw has to be neutral (not NULL, not locked and not marked).
-  ADIM_guarantee(dmw.is_neutral(), "must be neutral: dmw=" INTPTR_FORMAT, dmw.value());
+  assert(dmw.is_neutral(), "must be neutral: dmw=" INTPTR_FORMAT, dmw.value());
 
   // Install displaced mark word if the object's header still points
   // to this ObjectMonitor. More than one racing caller to this function
@@ -487,10 +485,6 @@ void ObjectMonitor::install_displaced_markword_in_object(const oop obj) {
 // used for diagnostic output.
 const char* ObjectMonitor::is_busy_to_string(stringStream* ss) {
   ss->print("is_busy: waiters=%d, ", _waiters);
-  if (!AsyncDeflateIdleMonitors) {
-    ss->print("contentions=%d, ", contentions());
-    ss->print("owner=" INTPTR_FORMAT, p2i(_owner));
-  } else {
   if (contentions() > 0) {
     ss->print("contentions=%d, ", contentions());
   } else {
@@ -503,7 +497,6 @@ const char* ObjectMonitor::is_busy_to_string(stringStream* ss) {
     // ignores DEFLATER_MARKER values.
     ss->print("owner=" INTPTR_FORMAT, NULL);
   }
-  }
   ss->print(", cxq=" INTPTR_FORMAT ", EntryList=" INTPTR_FORMAT, p2i(_cxq),
             p2i(_EntryList));
   return ss->base();
@@ -524,8 +517,7 @@ void ObjectMonitor::EnterI(TRAPS) {
     return;
   }
 
-  if (AsyncDeflateIdleMonitors &&
+  if (try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
-      try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
     // Cancelled the in-progress async deflation by changing owner from
     // DEFLATER_MARKER to Self. As part of the contended enter protocol,
     // contentions was incremented to a positive value before EnterI()
@@ -659,8 +651,7 @@ void ObjectMonitor::EnterI(TRAPS) {
 
     if (TryLock(Self) > 0) break;
 
-    if (AsyncDeflateIdleMonitors &&
+    if (try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
-        try_set_owner_from(DEFLATER_MARKER, Self) == DEFLATER_MARKER) {
       // Cancelled the in-progress async deflation by changing owner from
       // DEFLATER_MARKER to Self. As part of the contended enter protocol,
       // contentions was incremented to a positive value before EnterI()
@@ -1007,8 +998,8 @@ void ObjectMonitor::exit(bool not_suspended, TRAPS) {
                     " is exiting an ObjectMonitor it does not own.", p2i(THREAD));
       lsh.print_cr("The imbalance is possibly caused by JNI locking.");
       print_debug_style_on(&lsh);
-#endif
       assert(false, "Non-balanced monitor enter/exit!");
+#endif
       return;
     }
   }

src/hotspot/share/runtime/objectMonitor.hpp

@@ -175,7 +175,7 @@ class ObjectMonitor {
   jint  _contentions;               // Number of active contentions in enter(). It is used by is_busy()
                                     // along with other fields to determine if an ObjectMonitor can be
                                     // deflated. It is also used by the async deflation protocol. See
-                                    // ObjectSynchronizer::deflate_monitor() and deflate_monitor_using_JT().
+                                    // ObjectSynchronizer::deflate_monitor_using_JT().
  protected:
   ObjectWaiter* volatile _WaitSet;  // LL of threads wait()ing on the monitor
   volatile jint  _waiters;          // number of waiting threads
@@ -243,16 +243,12 @@ class ObjectMonitor {
   intptr_t is_busy() const {
     // TODO-FIXME: assert _owner == null implies _recursions = 0
     intptr_t ret_code = _waiters | intptr_t(_cxq) | intptr_t(_EntryList);
-    if (!AsyncDeflateIdleMonitors) {
-      ret_code |= contentions() | intptr_t(_owner);
-    } else {
     if (contentions() > 0) {
       ret_code |= contentions();
     }
     if (_owner != DEFLATER_MARKER) {
       ret_code |= intptr_t(_owner);
     }
-    }
     return ret_code;
   }
   const char* is_busy_to_string(stringStream* ss);
@@ -315,9 +311,9 @@ class ObjectMonitor {
     // _recursions == 0 _WaitSet == NULL
 #ifdef ASSERT
     stringStream ss;
-#endif
     assert((is_busy() | _recursions) == 0, "freeing in-use monitor: %s, "
            "recursions=" INTX_FORMAT, is_busy_to_string(&ss), _recursions);
+#endif
     _succ          = NULL;
     _EntryList     = NULL;
     _cxq           = NULL;
@@ -374,15 +370,4 @@ class ObjectMonitor {
   void      install_displaced_markword_in_object(const oop obj);
 };
 
-// Macro to use guarantee() for more strict AsyncDeflateIdleMonitors
-// checks and assert() otherwise.
-#define ADIM_guarantee(p, ...)       \
-  do {                               \
-    if (AsyncDeflateIdleMonitors) {  \
-      guarantee(p, __VA_ARGS__);     \
-    } else {                         \
-      assert(p, __VA_ARGS__);        \
-    }                                \
-  } while (0)
-
 #endif // SHARE_RUNTIME_OBJECTMONITOR_HPP

src/hotspot/share/runtime/objectMonitor.inline.hpp

@@ -67,7 +67,7 @@ inline bool ObjectMonitor::owner_is_DEFLATER_MARKER() {
 
 // Returns true if 'this' is being async deflated and false otherwise.
 inline bool ObjectMonitor::is_being_async_deflated() {
-  return AsyncDeflateIdleMonitors && contentions() < 0;
+  return contentions() < 0;
 }
 
 inline void ObjectMonitor::clear() {
@@ -80,7 +80,6 @@ inline void ObjectMonitor::clear() {
 }
 
 inline void ObjectMonitor::clear_common() {
-  if (AsyncDeflateIdleMonitors) {
   // Async deflation protocol uses the header, owner and contentions
   // fields. While the ObjectMonitor being deflated is on the global
   // free list, we leave those three fields alone; contentions < 0
@@ -90,7 +89,6 @@ inline void ObjectMonitor::clear_common() {
   guarantee(_owner == NULL || _owner == DEFLATER_MARKER,
             "must be NULL or DEFLATER_MARKER: owner=" INTPTR_FORMAT,
             p2i(_owner));
-  }
   assert(contentions() <= 0, "must not be positive: contentions=%d", contentions());
   assert(_waiters == 0, "must be 0: waiters=%d", _waiters);
   assert(_recursions == 0, "must be 0: recursions=" INTX_FORMAT, _recursions);
@@ -124,9 +122,11 @@ inline void ObjectMonitor::add_to_contentions(jint value) {
 
 // Clear _owner field; current value must match old_value.
 inline void ObjectMonitor::release_clear_owner(void* old_value) {
+#ifdef ASSERT
   void* prev = Atomic::load(&_owner);
-  ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
+  assert(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
          ", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
+#endif
   Atomic::release_store(&_owner, (void*)NULL);
   log_trace(monitorinflation, owner)("release_clear_owner(): mid="
                                      INTPTR_FORMAT ", old_value=" INTPTR_FORMAT,
@@ -136,9 +136,11 @@ inline void ObjectMonitor::release_clear_owner(void* old_value) {
 // Simply set _owner field to new_value; current value must match old_value.
 // (Simple means no memory sync needed.)
 inline void ObjectMonitor::set_owner_from(void* old_value, void* new_value) {
+#ifdef ASSERT
   void* prev = Atomic::load(&_owner);
-  ADIM_guarantee(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
+  assert(prev == old_value, "unexpected prev owner=" INTPTR_FORMAT
          ", expected=" INTPTR_FORMAT, p2i(prev), p2i(old_value));
+#endif
   Atomic::store(&_owner, new_value);
   log_trace(monitorinflation, owner)("set_owner_from(): mid="
                                      INTPTR_FORMAT ", old_value=" INTPTR_FORMAT
@@ -150,7 +152,7 @@ inline void ObjectMonitor::set_owner_from(void* old_value, void* new_value) {
 // (Simple means no memory sync needed.)
 inline void ObjectMonitor::set_owner_from(void* old_value1, void* old_value2, void* new_value) {
   void* prev = Atomic::load(&_owner);
-  ADIM_guarantee(prev == old_value1 || prev == old_value2,
+  assert(prev == old_value1 || prev == old_value2,
          "unexpected prev owner=" INTPTR_FORMAT ", expected1="
          INTPTR_FORMAT " or expected2=" INTPTR_FORMAT, p2i(prev),
          p2i(old_value1), p2i(old_value2));
@@ -165,9 +167,11 @@ inline void ObjectMonitor::set_owner_from(void* old_value1, void* old_value2, vo
 
 // Simply set _owner field to self; current value must match basic_lock_p.
 inline void ObjectMonitor::set_owner_from_BasicLock(void* basic_lock_p, Thread* self) {
+#ifdef ASSERT
   void* prev = Atomic::load(&_owner);
-  ADIM_guarantee(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
+  assert(prev == basic_lock_p, "unexpected prev owner=" INTPTR_FORMAT
          ", expected=" INTPTR_FORMAT, p2i(prev), p2i(basic_lock_p));
+#endif
   // Non-null owner field to non-null owner field is safe without
   // cmpxchg() as long as all readers can tolerate either flavor.
   Atomic::store(&_owner, self);

src/hotspot/share/runtime/safepoint.cpp

@@ -490,9 +490,6 @@ void SafepointSynchronize::end() {
 }
 
 bool SafepointSynchronize::is_cleanup_needed() {
-  // Need a cleanup safepoint if there are too many monitors in use
-  // and the monitor deflation needs to be done at a safepoint.
-  if (ObjectSynchronizer::is_safepoint_deflation_needed()) return true;
   // Need a safepoint if some inline cache buffers is non-empty
   if (!InlineCacheBuffer::is_empty()) return true;
   if (StringTable::needs_rehashing()) return true;
@@ -500,51 +497,24 @@ bool SafepointSynchronize::is_cleanup_needed() {
   return false;
 }
 
-class ParallelSPCleanupThreadClosure : public ThreadClosure {
-private:
-  DeflateMonitorCounters* _counters;
-
-public:
-  ParallelSPCleanupThreadClosure(DeflateMonitorCounters* counters) :
-    _counters(counters) {}
-
-  void do_thread(Thread* thread) {
-    // deflate_thread_local_monitors() handles or requests deflation of
-    // this thread's idle monitors. If !AsyncDeflateIdleMonitors or if
-    // there is a special cleanup request, deflation is handled now.
-    // Otherwise, async deflation is requested via a flag.
-    ObjectSynchronizer::deflate_thread_local_monitors(thread, _counters);
-  }
-};
-
 class ParallelSPCleanupTask : public AbstractGangTask {
 private:
   SubTasksDone _subtasks;
-  ParallelSPCleanupThreadClosure _cleanup_threads_cl;
   uint _num_workers;
-  DeflateMonitorCounters* _counters;
 public:
-  ParallelSPCleanupTask(uint num_workers, DeflateMonitorCounters* counters) :
+  ParallelSPCleanupTask(uint num_workers) :
     AbstractGangTask("Parallel Safepoint Cleanup"),
     _subtasks(SafepointSynchronize::SAFEPOINT_CLEANUP_NUM_TASKS),
-    _cleanup_threads_cl(ParallelSPCleanupThreadClosure(counters)),
+    _num_workers(num_workers) {}
-    _num_workers(num_workers),
-    _counters(counters) {}
 
   void work(uint worker_id) {
     uint64_t safepoint_id = SafepointSynchronize::safepoint_id();
-    // All threads deflate monitors and mark nmethods (if necessary).
-    Threads::possibly_parallel_threads_do(true, &_cleanup_threads_cl);
 
     if (_subtasks.try_claim_task(SafepointSynchronize::SAFEPOINT_CLEANUP_DEFLATE_MONITORS)) {
-      const char* name = "deflating global idle monitors";
+      const char* name = "deflating idle monitors";
       EventSafepointCleanupTask event;
       TraceTime timer(name, TRACETIME_LOG(Info, safepoint, cleanup));
-      // AsyncDeflateIdleMonitors only uses DeflateMonitorCounters
+      ObjectSynchronizer::do_safepoint_work();
-      // when a special cleanup has been requested.
-      // Note: This logging output will include global idle monitor
-      // elapsed times, but not global idle monitor deflation count.
-      ObjectSynchronizer::do_safepoint_work(_counters);
 
       post_safepoint_cleanup_task_event(event, safepoint_id, name);
     }
@@ -615,23 +585,17 @@ void SafepointSynchronize::do_cleanup_tasks() {
 
   TraceTime timer("safepoint cleanup tasks", TRACETIME_LOG(Info, safepoint, cleanup));
 
-  // Prepare for monitor deflation.
-  DeflateMonitorCounters deflate_counters;
-  ObjectSynchronizer::prepare_deflate_idle_monitors(&deflate_counters);
-
   CollectedHeap* heap = Universe::heap();
   assert(heap != NULL, "heap not initialized yet?");
   WorkGang* cleanup_workers = heap->get_safepoint_workers();
   if (cleanup_workers != NULL) {
     // Parallel cleanup using GC provided thread pool.
     uint num_cleanup_workers = cleanup_workers->active_workers();
-    ParallelSPCleanupTask cleanup(num_cleanup_workers, &deflate_counters);
+    ParallelSPCleanupTask cleanup(num_cleanup_workers);
-    StrongRootsScope srs(num_cleanup_workers);
     cleanup_workers->run_task(&cleanup);
   } else {
     // Serial cleanup using VMThread.
-    ParallelSPCleanupTask cleanup(1, &deflate_counters);
+    ParallelSPCleanupTask cleanup(1);
-    StrongRootsScope srs(1);
     cleanup.work(0);
   }
 
@@ -644,9 +608,6 @@ void SafepointSynchronize::do_cleanup_tasks() {
     ClassLoaderDataGraph::walk_metadata_and_clean_metaspaces();
   }
 
-  // Finish monitor deflation.
-  ObjectSynchronizer::finish_deflate_idle_monitors(&deflate_counters);
-
   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
 }
 

src/hotspot/share/runtime/serviceThread.cpp

@@ -142,10 +142,9 @@ void ServiceThread::service_thread_entry(JavaThread* jt, TRAPS) {
               (deflate_idle_monitors = ObjectSynchronizer::is_async_deflation_needed())
              ) == 0) {
         // Wait until notified that there is some work to do.
-        // If AsyncDeflateIdleMonitors, then we wait for
+        // We wait for GuaranteedSafepointInterval so that
-        // GuaranteedSafepointInterval so that is_async_deflation_needed()
+        // is_async_deflation_needed() is checked at the same interval.
-        // is checked at the same interval.
+        ml.wait(GuaranteedSafepointInterval);
-        ml.wait(AsyncDeflateIdleMonitors ? GuaranteedSafepointInterval : 0);
       }
 
       if (has_jvmti_events) {

src/hotspot/share/runtime/synchronizer.cpp

@@ -491,16 +491,12 @@ bool ObjectSynchronizer::quick_enter(oop obj, Thread* self,
 
   if (mark.has_monitor()) {
     ObjectMonitor* const m = mark.monitor();
-    if (AsyncDeflateIdleMonitors) {
     // An async deflation can race us before we manage to make the
     // ObjectMonitor busy by setting the owner below. If we detect
     // that race we just bail out to the slow-path here.
     if (m->object() == NULL) {
       return false;
     }
-    } else {
-      assert(m->object() == obj, "invariant");
-    }
     Thread* const owner = (Thread *) m->_owner;
 
     // Lock contention and Transactional Lock Elision (TLE) diagnostics
@@ -986,9 +982,8 @@ static inline intptr_t get_next_hash(Thread* self, oop obj) {
 intptr_t ObjectSynchronizer::FastHashCode(Thread* self, oop obj) {
   if (UseBiasedLocking) {
     // NOTE: many places throughout the JVM do not expect a safepoint
-    // to be taken here, in particular most operations on perm gen
+    // to be taken here. However, we only ever bias Java instances and all
-    // objects. However, we only ever bias Java instances and all of
+    // of the call sites of identity_hash that might revoke biases have
-    // the call sites of identity_hash that might revoke biases have
     // been checked to make sure they can handle a safepoint. The
     // added check of the bias pattern is to avoid useless calls to
     // thread-local storage.
@@ -1193,8 +1188,6 @@ ObjectSynchronizer::LockOwnership ObjectSynchronizer::query_lock_ownership
   }
 
   // CASE: inflated. Mark (tagged pointer) points to an ObjectMonitor.
-  // The Object:ObjectMonitor relationship is stable as long as we're
-  // not at a safepoint and AsyncDeflateIdleMonitors is false.
   if (mark.has_monitor()) {
     // The first stage of async deflation does not affect any field
     // used by this comparison so the ObjectMonitor* is usable here.
@@ -1294,9 +1287,6 @@ static bool monitors_used_above_threshold() {
 }
 
 bool ObjectSynchronizer::is_async_deflation_needed() {
-  if (!AsyncDeflateIdleMonitors) {
-    return false;
-  }
   if (is_async_deflation_requested()) {
     // Async deflation request.
     return true;
@@ -1313,16 +1303,10 @@ bool ObjectSynchronizer::is_async_deflation_needed() {
   return false;
 }
 
-bool ObjectSynchronizer::is_safepoint_deflation_needed() {
-  return !AsyncDeflateIdleMonitors &&
-         monitors_used_above_threshold();  // Too many monitors in use.
-}
-
 bool ObjectSynchronizer::request_deflate_idle_monitors() {
   bool is_JavaThread = Thread::current()->is_Java_thread();
   bool ret_code = false;
 
-  if (AsyncDeflateIdleMonitors) {
   jlong last_time = last_async_deflation_time_ns();
   set_is_async_deflation_requested(true);
   {
@@ -1347,15 +1331,6 @@ bool ObjectSynchronizer::request_deflate_idle_monitors() {
   if (!ret_code) {
     log_info(monitorinflation)("Async Deflation DID NOT happen after %d checks.", N_CHECKS);
   }
-  } else {
-    // Only need to force this safepoint if we are not using async
-    // deflation. The VMThread won't call this function before the
-    // final safepoint if we are not using async deflation so we
-    // don't have to reason about the VMThread executing a VM-op here.
-    VM_ForceSafepoint force_safepoint_op;
-    VMThread::execute(&force_safepoint_op);
-    ret_code = true;
-  }
 
   return ret_code;
 }
@@ -1396,9 +1371,9 @@ void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
 // ObjectMonitor Lifecycle
 // -----------------------
 // Inflation unlinks monitors from om_list_globals._free_list or a per-thread
-// free list and associates them with objects. Deflation -- which occurs at
+// free list and associates them with objects. Async deflation disassociates
-// STW-time or asynchronously -- disassociates idle monitors from objects.
+// idle monitors from objects. Such scavenged monitors are returned to the
-// Such scavenged monitors are returned to the om_list_globals._free_list.
+// om_list_globals._free_list.
 //
 // ObjectMonitors reside in type-stable memory (TSM) and are immortal.
 //
@@ -1411,7 +1386,7 @@ void ObjectSynchronizer::list_oops_do(ObjectMonitor* list, OopClosure* f) {
 ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
   // 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
+  // number of ObjectMonitors in circulation as well as the
   // scavenge costs.  As usual, we lean toward time in space-time
   // tradeoffs.
   const int MAXPRIVATE = 1024;
@@ -1447,7 +1422,6 @@ ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
           break;  // No more are available.
         }
         guarantee(take->object() == NULL, "invariant");
-        if (AsyncDeflateIdleMonitors) {
         // We allowed 3 field values to linger during async deflation.
         // Clear or restore them as appropriate.
         take->set_header(markWord::zero());
@@ -1460,10 +1434,9 @@ ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
 
 #ifdef ASSERT
           jint l_contentions = take->contentions();
-#endif
           assert(l_contentions >= 0, "must not be negative: l_contentions=%d, contentions=%d",
                  l_contentions, take->contentions());
-          }
+#endif
         }
         take->Recycle();
         // Since we're taking from the global free-list, take must be Free.
@@ -1529,8 +1502,8 @@ ObjectMonitor* ObjectSynchronizer::om_alloc(Thread* self) {
 //
 // 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() or deflate_monitor_list_using_JT()
+// scavenger -- deflate_monitor_list_using_JT() -- from reclaiming them
-// -- from reclaiming them while we are trying to release them.
+// while we are trying to release them.
 
 void ObjectSynchronizer::om_release(Thread* self, ObjectMonitor* m,
                                     bool from_per_thread_alloc) {
@@ -1639,15 +1612,13 @@ void ObjectSynchronizer::om_release(Thread* self, ObjectMonitor* m,
 //
 // We currently call om_flush() from Threads::remove() before the
 // thread has been excised from the thread list and is no longer a
-// mutator. This means that om_flush() cannot run concurrently with
+// mutator. In particular, this ensures that the thread's in-use
-// a safepoint and interleave with deflate_idle_monitors(). In
+// monitors are scanned by a GC safepoint, either via Thread::oops_do()
-// particular, this ensures that the thread's in-use monitors are
+// (before om_flush() is called) or via ObjectSynchronizer::oops_do()
-// scanned by a GC safepoint, either via Thread::oops_do() (before
+// (after om_flush() is called).
-// om_flush() is called) or via ObjectSynchronizer::oops_do() (after
-// om_flush() is called).
 //
-// With AsyncDeflateIdleMonitors, deflate_global_idle_monitors_using_JT()
+// deflate_global_idle_monitors_using_JT() and
-// and deflate_per_thread_idle_monitors_using_JT() (in another thread) can
+// 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.
 
@@ -1701,9 +1672,11 @@ void ObjectSynchronizer::om_flush(Thread* self) {
       cur_om = unmarked_next(cur_om);
     }
     guarantee(in_use_tail != NULL, "invariant");
+#ifdef ASSERT
     int l_om_in_use_count = Atomic::load(&self->om_in_use_count);
-    ADIM_guarantee(l_om_in_use_count == in_use_count, "in-use counts don't match: "
+    assert(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);
+#endif
     Atomic::store(&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);
@@ -1744,9 +1717,11 @@ void ObjectSynchronizer::om_flush(Thread* self) {
       }
     }
     guarantee(free_tail != NULL, "invariant");
+#ifdef ASSERT
     int l_om_free_count = Atomic::load(&self->om_free_count);
-    ADIM_guarantee(l_om_free_count == free_count, "free counts don't match: "
+    assert(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);
+#endif
     Atomic::store(&self->om_free_count, 0);
     Atomic::store(&self->om_free_list, (ObjectMonitor*)NULL);
     om_unlock(free_list);
@@ -1825,7 +1800,6 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
       ObjectMonitor* inf = mark.monitor();
       markWord dmw = inf->header();
       assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
-      assert(AsyncDeflateIdleMonitors || inf->object() == object, "invariant");
       assert(ObjectSynchronizer::verify_objmon_isinpool(inf), "monitor is invalid");
       return inf;
     }
@@ -1911,7 +1885,7 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
       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).
-      ADIM_guarantee(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
+      assert(dmw.is_neutral(), "invariant: header=" INTPTR_FORMAT, dmw.value());
 
       // Setup monitor fields to proper values -- prepare the monitor
       m->set_header(dmw);
@@ -1921,11 +1895,7 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
       // 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.
-      if (AsyncDeflateIdleMonitors) {
       m->set_owner_from(NULL, DEFLATER_MARKER, mark.locker());
-      } else {
-        m->set_owner_from(NULL, mark.locker());
-      }
       m->set_object(object);
       // TODO-FIXME: assert BasicLock->dhw != 0.
 
@@ -1965,15 +1935,13 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
 
     // Catch if the object's header is not neutral (not locked and
     // not marked is what we care about here).
-    ADIM_guarantee(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
+    assert(mark.is_neutral(), "invariant: header=" INTPTR_FORMAT, mark.value());
     ObjectMonitor* m = om_alloc(self);
     // prepare m for installation - set monitor to initial state
     m->Recycle();
     m->set_header(mark);
-    if (AsyncDeflateIdleMonitors) {
     // DEFLATER_MARKER is the only non-NULL value we should see here.
     m->try_set_owner_from(DEFLATER_MARKER, NULL);
-    }
     m->set_object(object);
     m->_Responsible  = NULL;
     m->_SpinDuration = ObjectMonitor::Knob_SpinLimit;       // consider: keep metastats by type/class
@@ -2013,45 +1981,11 @@ ObjectMonitor* ObjectSynchronizer::inflate(Thread* self, oop object,
 }
 
 
-// We maintain a list of in-use monitors for each thread.
+// An async deflation request is registered with the ServiceThread
-//
+// and it is notified.
-// For safepoint based deflation:
+void ObjectSynchronizer::do_safepoint_work() {
-// 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
-// are stopped, but before any objects have moved. Collectively they traverse
-// the population of in-use monitors, deflating where possible. The scavenged
-// monitors are returned to the global monitor free list.
-//
-// Beware that we scavenge at *every* stop-the-world point. Having a large
-// number of monitors in-use could negatively impact performance. We also want
-// to minimize the total # of monitors in circulation, as they incur a small
-// footprint penalty.
-//
-// 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) {
-    // Use the older mechanism for the global in-use list.
-    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);
@@ -2061,85 +1995,10 @@ void ObjectSynchronizer::do_safepoint_work(DeflateMonitorCounters* counters) {
   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,
-                                         ObjectMonitor** free_tail_p) {
-  bool deflated;
-  // Normal case ... The monitor is associated with obj.
-  const markWord mark = obj->mark();
-  guarantee(mark == markWord::encode(mid), "should match: mark="
-            INTPTR_FORMAT ", encoded mid=" INTPTR_FORMAT, mark.value(),
-            markWord::encode(mid).value());
-  // Make sure that mark.monitor() and markWord::encode() agree:
-  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()) {
-    // Easy checks are first - the ObjectMonitor is busy 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 ...
-    if (log_is_enabled(Trace, monitorinflation)) {
-      ResourceMark rm;
-      log_trace(monitorinflation)("deflate_monitor: "
-                                  "object=" INTPTR_FORMAT ", mark="
-                                  INTPTR_FORMAT ", type='%s'", p2i(obj),
-                                  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.
-      // DEFLATER_MARKER is the only non-NULL value we should see here.
-      mid->try_set_owner_from(DEFLATER_MARKER, NULL);
-    }
-    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.
-    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:
-      // 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.
-#ifdef ASSERT
-      ObjectMonitor* l_next_om = prevtail->next_om();
-#endif
-      assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
-      prevtail->set_next_om(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
-    // cleaned up by the caller who has the complete context.
-    deflated = true;
-  }
-  return deflated;
-}
-
 // Deflate the specified ObjectMonitor if not in-use using a JavaThread.
 // Returns true if it was deflated and false otherwise.
 //
@@ -2156,7 +2015,6 @@ bool ObjectSynchronizer::deflate_monitor(ObjectMonitor* mid, oop obj,
 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.
@@ -2245,8 +2103,8 @@ bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
     // prevtail should have been cleaned up by the caller:
 #ifdef ASSERT
     ObjectMonitor* l_next_om = unmarked_next(prevtail);
-#endif
     assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
+#endif
     om_lock(prevtail);
     prevtail->set_next_om(mid);  // prevtail now points to mid (and is unlocked)
   }
@@ -2262,56 +2120,6 @@ bool ObjectSynchronizer::deflate_monitor_using_JT(ObjectMonitor* mid,
   return true;  // Success, ObjectMonitor has been deflated.
 }
 
-// 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
-// process the same monitor lists concurrently.
-//
-// 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* cur_mid_in_use = NULL;
-  ObjectMonitor* mid = NULL;
-  ObjectMonitor* next = NULL;
-  int deflated_count = 0;
-
-  // This list walk executes at a safepoint and does not race with any
-  // other list walkers.
-
-  for (mid = Atomic::load(list_p); mid != NULL; mid = next) {
-    next = unmarked_next(mid);
-    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 (cur_mid_in_use == NULL) {
-        // mid is the list head so switch the list head to next:
-        Atomic::store(list_p, next);
-      } else {
-        // Switch cur_mid_in_use's next field to next:
-        cur_mid_in_use->set_next_om(next);
-      }
-      // At this point mid is disconnected from the in-use list.
-      deflated_count++;
-      Atomic::dec(count_p);
-      // mid is current tail in the free_head_p list so NULL terminate it:
-      mid->set_next_om(NULL);
-    } else {
-      cur_mid_in_use = 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.
@@ -2323,7 +2131,6 @@ int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** list_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;
@@ -2453,75 +2260,6 @@ int ObjectSynchronizer::deflate_monitor_list_using_JT(ObjectMonitor** list_p,
   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
-}
-
-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.
-    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();
-  }
-
-  // Note: the thread-local monitors lists get deflated in
-  // a separate pass. See deflate_thread_local_monitors().
-
-  // For moribund threads, scan om_list_globals._in_use_list
-  int deflated_count = 0;
-  if (Atomic::load(&om_list_globals._in_use_list) != NULL) {
-    // Update n_in_circulation before om_list_globals._in_use_count is
-    // updated by deflation.
-    Atomic::add(&counters->n_in_circulation,
-                Atomic::load(&om_list_globals._in_use_count));
-
-    deflated_count = deflate_monitor_list(&om_list_globals._in_use_list,
-                                          &om_list_globals._in_use_count,
-                                          &free_head_p, &free_tail_p);
-    Atomic::add(&counters->n_in_use, Atomic::load(&om_list_globals._in_use_count));
-  }
-
-  if (free_head_p != NULL) {
-    // Move the deflated ObjectMonitors back to the global free list.
-    guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
-#ifdef ASSERT
-    ObjectMonitor* l_next_om = free_tail_p->next_om();
-#endif
-    assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
-    prepend_list_to_global_free_list(free_head_p, free_tail_p, deflated_count);
-    Atomic::add(&counters->n_scavenged, deflated_count);
-  }
-  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) {
-    ls->print_cr("deflating global idle monitors, %3.7f secs, %d monitors", timer.seconds(), deflated_count);
-  }
-}
-
 class HandshakeForDeflation : public HandshakeClosure {
  public:
   HandshakeForDeflation() : HandshakeClosure("HandshakeForDeflation") {}
@@ -2533,8 +2271,6 @@ class HandshakeForDeflation : public HandshakeClosure {
 };
 
 void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
-  assert(AsyncDeflateIdleMonitors, "sanity check");
-
   // Deflate any global idle monitors.
   deflate_global_idle_monitors_using_JT();
 
@@ -2568,7 +2304,7 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
     // (or a safepoint) for safety.
 
     ObjectMonitor* list = Atomic::load(&om_list_globals._wait_list);
-    ADIM_guarantee(list != NULL, "om_list_globals._wait_list must not be NULL");
+    assert(list != NULL, "om_list_globals._wait_list must not be NULL");
     int count = Atomic::load(&om_list_globals._wait_count);
     Atomic::store(&om_list_globals._wait_count, 0);
     Atomic::store(&om_list_globals._wait_list, (ObjectMonitor*)NULL);
@@ -2576,13 +2312,17 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
     // 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.
+#ifdef ASSERT
     int l_count = 0;
+#endif
     ObjectMonitor* tail = NULL;
     for (ObjectMonitor* n = list; n != NULL; n = unmarked_next(n)) {
       tail = n;
+#ifdef ASSERT
       l_count++;
+#endif
     }
-    ADIM_guarantee(count == l_count, "count=%d != l_count=%d", count, l_count);
+    assert(count == l_count, "count=%d != l_count=%d", count, l_count);
 
     // Will execute a safepoint if !ThreadLocalHandshakes:
     HandshakeForDeflation hfd_hc;
@@ -2598,7 +2338,6 @@ void ObjectSynchronizer::deflate_idle_monitors_using_JT() {
 // 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();
 
@@ -2608,7 +2347,6 @@ void ObjectSynchronizer::deflate_global_idle_monitors_using_JT() {
 // 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);
@@ -2664,8 +2402,8 @@ void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, J
       // all out.
 #ifdef ASSERT
       ObjectMonitor* l_next_om = unmarked_next(free_tail_p);
-#endif
       assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_next_om));
+#endif
 
       prepend_list_to_global_wait_list(free_head_p, free_tail_p, local_deflated_count);
 
@@ -2711,94 +2449,6 @@ void ObjectSynchronizer::deflate_common_idle_monitors_using_JT(bool is_global, J
   }
 }
 
-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);
-
-  if (AsyncDeflateIdleMonitors) {
-    // Nothing to do when idle ObjectMonitors are deflated using
-    // a JavaThread.
-    return;
-  }
-
-  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 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)) {
-    log_info(monitorinflation)("global_population=%d, global_in_use_count=%d, "
-                               "global_free_count=%d, global_wait_count=%d",
-                               Atomic::load(&om_list_globals._population),
-                               Atomic::load(&om_list_globals._in_use_count),
-                               Atomic::load(&om_list_globals._free_count),
-                               Atomic::load(&om_list_globals._wait_count));
-  }
-
-  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++;
-}
-
-void ObjectSynchronizer::deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters) {
-  assert(SafepointSynchronize::is_at_safepoint(), "must be at safepoint");
-
-  if (AsyncDeflateIdleMonitors) {
-    // Nothing to do when per-thread idle ObjectMonitors are deflated
-    // using a JavaThread.
-    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();
-  }
-
-  // Update n_in_circulation before om_in_use_count is updated by deflation.
-  Atomic::add(&counters->n_in_circulation, Atomic::load(&thread->om_in_use_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, Atomic::load(&thread->om_in_use_count));
-
-  if (free_head_p != NULL) {
-    // Move the deflated ObjectMonitors back to the global free list.
-    guarantee(free_tail_p != NULL && deflated_count > 0, "invariant");
-#ifdef ASSERT
-    ObjectMonitor* l_next_om = free_tail_p->next_om();
-#endif
-    assert(l_next_om == NULL, "must be NULL: _next_om=" INTPTR_FORMAT, p2i(l_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();
-  counters->per_thread_times += timer.seconds();
-
-  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) {
-    ls->print_cr("jt=" INTPTR_FORMAT ": deflating per-thread idle monitors, %3.7f secs, %d monitors", p2i(thread), timer.seconds(), deflated_count);
-  }
-}
-
 // Monitor cleanup on JavaThread::exit
 
 // Iterate through monitor cache and attempt to release thread's monitors
@@ -2824,7 +2474,7 @@ class ReleaseJavaMonitorsClosure: public MonitorClosure {
 // A simple optimization is to add a per-thread flag that indicates a thread
 // called jni_monitorenter() during its lifetime.
 //
-// Instead of No_Savepoint_Verifier it might be cheaper to
+// Instead of NoSafepointVerifier it might be cheaper to
 // use an idiom of the form:
 //   auto int tmp = SafepointSynchronize::_safepoint_counter ;
 //   <code that must not run at safepoint>
@@ -2883,8 +2533,6 @@ u_char* ObjectSynchronizer::get_gvars_stw_random_addr() {
 // aid; pass 'true' for the 'on_exit' parameter to have in-use monitor
 // details logged at the Info level and 'false' for the 'on_exit'
 // parameter to have in-use monitor details logged at the Trace level.
-// deflate_monitor_list() no longer uses spin-locking so be careful
-// when adding audit_and_print_stats() calls at a safepoint.
 //
 void ObjectSynchronizer::audit_and_print_stats(bool on_exit) {
   assert(on_exit || SafepointSynchronize::is_at_safepoint(), "invariant");
@@ -2983,11 +2631,6 @@ void ObjectSynchronizer::chk_free_entry(JavaThread* jt, ObjectMonitor* n,
                     "field: _header=" INTPTR_FORMAT, p2i(jt), p2i(n),
                     n->header().value());
       *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) {

src/hotspot/share/runtime/synchronizer.hpp

@@ -42,14 +42,6 @@ class ThreadsList;
 
 typedef PaddedEnd<ObjectMonitor, OM_CACHE_LINE_SIZE> PaddedObjectMonitor;
 
-struct DeflateMonitorCounters {
-  volatile int n_in_use;              // currently associated with objects
-  volatile int n_in_circulation;      // extant
-  volatile int n_scavenged;           // reclaimed (global and per-thread)
-  volatile int per_thread_scavenged;  // per-thread scavenge total
-           double per_thread_times;   // per-thread scavenge times
-};
-
 class ObjectSynchronizer : AllStatic {
   friend class VMStructs;
  public:
@@ -131,20 +123,11 @@ class ObjectSynchronizer : AllStatic {
   // GC: we current use aggressive monitor deflation policy
   // Basically we deflate all monitors that are not busy.
   // An adaptive profile-based deflation policy could be used if needed
-  static void deflate_idle_monitors(DeflateMonitorCounters* counters);
   static void deflate_idle_monitors_using_JT();
   static void deflate_global_idle_monitors_using_JT();
   static void deflate_per_thread_idle_monitors_using_JT(JavaThread* target);
   static void deflate_common_idle_monitors_using_JT(bool is_global, JavaThread* target);
-  static void deflate_thread_local_monitors(Thread* thread, DeflateMonitorCounters* counters);
-  static void prepare_deflate_idle_monitors(DeflateMonitorCounters* counters);
-  static void finish_deflate_idle_monitors(DeflateMonitorCounters* counters);
 
-  // For a given monitor list: global or per-thread, deflate idle monitors
-  static int deflate_monitor_list(ObjectMonitor** list_p,
-                                  int* count_p,
-                                  ObjectMonitor** free_head_p,
-                                  ObjectMonitor** free_tail_p);
   // For a given in-use monitor list: global or per-thread, deflate idle
   // monitors using a JavaThread.
   static int deflate_monitor_list_using_JT(ObjectMonitor** list_p,
@@ -152,14 +135,10 @@ class ObjectSynchronizer : AllStatic {
                                            ObjectMonitor** free_head_p,
                                            ObjectMonitor** free_tail_p,
                                            ObjectMonitor** saved_mid_in_use_p);
-  static bool deflate_monitor(ObjectMonitor* mid, oop obj,
-                              ObjectMonitor** free_head_p,
-                              ObjectMonitor** free_tail_p);
   static bool deflate_monitor_using_JT(ObjectMonitor* mid,
                                        ObjectMonitor** free_head_p,
                                        ObjectMonitor** free_tail_p);
   static bool is_async_deflation_needed();
-  static bool is_safepoint_deflation_needed();
   static bool is_async_deflation_requested() { return _is_async_deflation_requested; }
   static jlong last_async_deflation_time_ns() { return _last_async_deflation_time_ns; }
   static bool request_deflate_idle_monitors();  // for whitebox test support and VM exit logging
@@ -191,7 +170,7 @@ class ObjectSynchronizer : AllStatic {
   static int  log_monitor_list_counts(outputStream * out);
   static int  verify_objmon_isinpool(ObjectMonitor *addr) PRODUCT_RETURN0;
 
-  static void do_safepoint_work(DeflateMonitorCounters* counters);
+  static void do_safepoint_work();
 
  private:
   friend class SynchronizerTest;

src/hotspot/share/runtime/vmOperations.cpp

@@ -431,10 +431,10 @@ int VM_Exit::wait_for_threads_in_native_to_block() {
 }
 
 bool VM_Exit::doit_prologue() {
-  if (AsyncDeflateIdleMonitors && log_is_enabled(Info, monitorinflation)) {
+  if (log_is_enabled(Info, monitorinflation)) {
-    // AsyncDeflateIdleMonitors does a special deflation in order
+    // Do a deflation in order to reduce the in-use monitor population
-    // to reduce the in-use monitor population that is reported by
+    // that is reported by ObjectSynchronizer::log_in_use_monitor_details()
-    // ObjectSynchronizer::log_in_use_monitor_details() at VM exit.
+    // at VM exit.
     ObjectSynchronizer::request_deflate_idle_monitors();
   }
   return true;

src/hotspot/share/runtime/vmThread.cpp

@@ -260,10 +260,10 @@ void VMThread::run() {
     assert(should_terminate(), "termination flag must be set");
   }
 
-  if (AsyncDeflateIdleMonitors && log_is_enabled(Info, monitorinflation)) {
+  if (log_is_enabled(Info, monitorinflation)) {
-    // AsyncDeflateIdleMonitors does a special deflation in order
+    // Do a deflation in order to reduce the in-use monitor population
-    // to reduce the in-use monitor population that is reported by
+    // that is reported by ObjectSynchronizer::log_in_use_monitor_details()
-    // ObjectSynchronizer::log_in_use_monitor_details() at VM exit.
+    // at VM exit.
     ObjectSynchronizer::request_deflate_idle_monitors();
   }
 

src/hotspot/share/services/threadService.cpp

@@ -222,13 +222,11 @@ Handle ThreadService::get_current_contended_monitor(JavaThread* thread) {
   if (wait_obj != NULL) {
     // thread is doing an Object.wait() call
     obj = (oop) wait_obj->object();
-    assert(AsyncDeflateIdleMonitors || obj != NULL, "Object.wait() should have an object");
   } else {
     ObjectMonitor *enter_obj = thread->current_pending_monitor();
     if (enter_obj != NULL) {
       // thread is trying to enter() an ObjectMonitor.
       obj = (oop) enter_obj->object();
-      assert(AsyncDeflateIdleMonitors || obj != NULL, "ObjectMonitor should have an associated object!");
     }
   }
 

test/hotspot/gtest/oops/test_markWord.cpp

@@ -138,19 +138,5 @@ TEST_VM(markWord, printing) {
     assert_test_pattern(h_obj, "monitor");
     done.wait_with_safepoint_check(THREAD);  // wait till the thread is done.
   }
-
-  if (!AsyncDeflateIdleMonitors) {
-    // With AsyncDeflateIdleMonitors, the collect() call below
-    // does not guarantee monitor deflation.
-    // Make the object older. Not all GCs use this field.
-    Universe::heap()->collect(GCCause::_java_lang_system_gc);
-    if (UseParallelGC) {
-      assert_test_pattern(h_obj, "is_neutral no_hash age 1");
-    }
-
-    // Hash the object then print it.
-    intx hash = h_obj->identity_hash();
-    assert_test_pattern(h_obj, "is_neutral hash=0x");
-  }
 }
 #endif // PRODUCT

test/hotspot/jtreg/runtime/logging/SafepointCleanupTest.java

@@ -29,23 +29,17 @@
  * @modules java.base/jdk.internal.misc
  *          java.management
  * @run driver SafepointCleanupTest
- * @run driver SafepointCleanupTest -XX:+AsyncDeflateIdleMonitors
  */
 
 import jdk.test.lib.process.OutputAnalyzer;
 import jdk.test.lib.process.ProcessTools;
 
 public class SafepointCleanupTest {
-    static final String ASYNC_DISABLE_OPTION = "-XX:-AsyncDeflateIdleMonitors";
-    static final String ASYNC_ENABLE_OPTION = "-XX:+AsyncDeflateIdleMonitors";
-    static final String UNLOCK_DIAG_OPTION = "-XX:+UnlockDiagnosticVMOptions";
-
     static void analyzeOutputOn(ProcessBuilder pb) throws Exception {
         OutputAnalyzer output = new OutputAnalyzer(pb.start());
         output.shouldContain("[safepoint,cleanup]");
         output.shouldContain("safepoint cleanup tasks");
-        output.shouldContain("deflating global idle monitors");
+        output.shouldContain("deflating idle monitors");
-        output.shouldContain("deflating per-thread idle monitors");
         output.shouldContain("updating inline caches");
         output.shouldContain("compilation policy safepoint handler");
         output.shouldHaveExitValue(0);
@@ -58,40 +52,19 @@ public class SafepointCleanupTest {
     }
 
     public static void main(String[] args) throws Exception {
-        String async_option;
-        if (args.length == 0) {
-            // By default test deflating idle monitors at a safepoint.
-            async_option = ASYNC_DISABLE_OPTION;
-        } else {
-            async_option = args[0];
-        }
-        if (!async_option.equals(ASYNC_DISABLE_OPTION) &&
-            !async_option.equals(ASYNC_ENABLE_OPTION)) {
-            throw new RuntimeException("Unknown async_option value: '"
-                                       + async_option + "'");
-        }
-
         ProcessBuilder pb = ProcessTools.createJavaProcessBuilder("-Xlog:safepoint+cleanup=info",
-                                                                  UNLOCK_DIAG_OPTION,
-                                                                  async_option,
                                                                   InnerClass.class.getName());
         analyzeOutputOn(pb);
 
         pb = ProcessTools.createJavaProcessBuilder("-XX:+TraceSafepointCleanupTime",
-                                                   UNLOCK_DIAG_OPTION,
-                                                   async_option,
                                                    InnerClass.class.getName());
         analyzeOutputOn(pb);
 
         pb = ProcessTools.createJavaProcessBuilder("-Xlog:safepoint+cleanup=off",
-                                                   UNLOCK_DIAG_OPTION,
-                                                   async_option,
                                                    InnerClass.class.getName());
         analyzeOutputOff(pb);
 
         pb = ProcessTools.createJavaProcessBuilder("-XX:-TraceSafepointCleanupTime",
-                                                   UNLOCK_DIAG_OPTION,
-                                                   async_option,
                                                    InnerClass.class.getName());
         analyzeOutputOff(pb);
     }