--- old/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2018-09-04 14:50:24.431657410 +0000
+++ new/src/hotspot/share/gc/g1/g1CollectedHeap.cpp	2018-09-04 14:50:24.255655449 +0000
@@ -1150,6 +1150,7 @@
   // include the waste in the following calculations.
   const size_t capacity_after_gc = capacity();
   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
+  _last_heap_resize = os::elapsedTime();
 
   // This is enforced in arguments.cpp.
   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
@@ -1423,6 +1424,7 @@
   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
   _g1_policy(new G1Policy(_gc_timer_stw)),
   _collection_set(this, _g1_policy),
+  _last_heap_resize(0.0),
   _dirty_card_queue_set(false),
   _ref_processor_stw(NULL),
   _is_alive_closure_stw(this),
@@ -1906,6 +1908,7 @@
   switch (cause) {
     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
     case GCCause::_g1_humongous_allocation: return true;
+    case GCCause::_g1_idle_compaction:      return true;
     default:                                return is_user_requested_concurrent_full_gc(cause);
   }
 }