8298191: Enhance object reclamation process

Reviewed-by: phh
Backport-of: 780327d1de4fee3e77c3e48018908bf0c3fcd55a

hotspot/src/share/vm/gc_implementation/g1/dirtyCardQueue.hpp

@@ -161,7 +161,6 @@ class DirtyCardQueueSet: public PtrQueueSet {
 
   // If any threads have partial logs, add them to the global list of logs.
   void concatenate_logs();
-  void clear_n_completed_buffers() { _n_completed_buffers = 0;}
 
   jint processed_buffers_mut() {
     return _processed_buffers_mut;

hotspot/src/share/vm/gc_implementation/g1/g1CollectedHeap.cpp

@@ -2287,7 +2287,6 @@ void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
     n_completed_buffers++;
   }
   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
-  dcqs.clear_n_completed_buffers();
   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
 }
 

hotspot/src/share/vm/gc_implementation/g1/g1RemSet.cpp

@@ -377,9 +377,8 @@ void G1RemSet::cleanup_after_oops_into_collection_set_do() {
   // Free any completed buffers in the DirtyCardQueueSet used to hold cards
   // which contain references that point into the collection.
   _g1->into_cset_dirty_card_queue_set().clear();
-  assert(_g1->into_cset_dirty_card_queue_set().completed_buffers_num() == 0,
+  assert(!_g1->into_cset_dirty_card_queue_set().completed_buffers_exist_dirty(),
          "all buffers should be freed");
-  _g1->into_cset_dirty_card_queue_set().clear_n_completed_buffers();
 }
 
 class ScrubRSClosure: public HeapRegionClosure {

hotspot/src/share/vm/gc_implementation/g1/ptrQueue.hpp

@@ -279,7 +279,7 @@ class PtrQueueSet VALUE_OBJ_CLASS_SPEC {
   bool process_or_enqueue_complete_buffer(void** buf);
 
   bool completed_buffers_exist_dirty() {
-    return _n_completed_buffers > 0;
+    return _n_completed_buffers > 0 || _completed_buffers_head != NULL;
   }
 
   bool process_completed_buffers() { return _process_completed; }