--- old/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	2018-04-03 14:10:08.771032207 +0200
+++ new/src/hotspot/share/gc/g1/g1ConcurrentMark.cpp	2018-04-03 14:10:08.515024408 +0200
@@ -1025,15 +1025,22 @@
 
   void distribute_marked_bytes(HeapRegion* hr, size_t marked_words) {
     uint const region_idx = hr->hrm_index();
-    assert(hr->is_starts_humongous(), "Should not have marked bytes " SIZE_FORMAT " in non-starts humongous region %u (%s)", marked_words, region_idx, hr->get_type_str());
+    assert(hr->is_starts_humongous(),
+           "Should not have marked bytes " SIZE_FORMAT " in non-starts humongous region %u (%s)",
+           marked_words, region_idx, hr->get_type_str());
     uint num_regions_in_humongous = (uint)G1CollectedHeap::humongous_obj_size_in_regions(marked_words);
 
     for (uint i = region_idx; i < (region_idx + num_regions_in_humongous); i++) {
       HeapRegion* const r = _g1h->region_at(i);
       size_t const words_to_add = MIN2(HeapRegion::GrainWords, marked_words);
+      assert(words_to_add > 0, "Out of space to distribute before end of humongous object in region %u (starts %u)", i, region_idx);
+
       r->add_to_marked_bytes(words_to_add * HeapWordSize);
       marked_words -= words_to_add;
     }
+    assert(marked_words == 0,
+           SIZE_FORMAT " words left after distributing space across %u regions",
+           marked_words, num_regions_in_humongous);
   }
 
   void update_marked_bytes(HeapRegion* hr) {
@@ -1042,20 +1049,23 @@
     // The marking attributes the object's size completely to the humongous starts
     // region. We need to distribute this value across the entire set of regions a
     // humongous object spans.
-    if (!hr->is_humongous()) {
-      hr->add_to_marked_bytes(marked_words * HeapWordSize);
-      log_trace(gc)("Added " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
-    } else {
+    if (hr->is_humongous()) {
       if (marked_words > 0) {
-        log_trace(gc)("Distributing " SIZE_FORMAT " words to humongous start region %u (%s), word size %d (%f)", 
-                      marked_words, region_idx, hr->get_type_str(),
-                      oop(hr->bottom())->size(), (double)oop(hr->bottom())->size() / HeapRegion::GrainWords);
+        log_trace(gc, marking)("Adding " SIZE_FORMAT " words to humongous start region %u (%s), word size %d (%f)", 
+                               marked_words, region_idx, hr->get_type_str(),
+                               oop(hr->bottom())->size(), (double)oop(hr->bottom())->size() / HeapRegion::GrainWords);
         distribute_marked_bytes(hr, marked_words);
       } else {
-        log_trace(gc)("NOT Added " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
+        assert(marked_words == 0,
+               "Asked to add " SIZE_FORMAT " words to add to continues humongous region %u (%s)",
+               marked_words, region_idx, hr->get_type_str());
       }
+    } else {
+      log_trace(gc, marking)("Adding " SIZE_FORMAT " words to region %u (%s)", marked_words, region_idx, hr->get_type_str());
+      hr->add_to_marked_bytes(marked_words * HeapWordSize);
     }
   }
+
 public:
   G1UpdateRemSetTrackingBeforeRebuild(G1CollectedHeap* g1h, G1ConcurrentMark* cm) :
     _g1h(g1h), _cm(cm), _cl("Post-Marking"), _num_regions_selected_for_rebuild(0) { }
@@ -1680,15 +1690,13 @@
 void G1ConcurrentMark::report_object_count(bool mark_completed) {
   // Depending on the completion of the marking liveness needs to be determined
   // using either the next or prev bitmap.
-  G1ObjectCountIsAliveClosure is_alive_prev(_g1h);
-  G1CMIsAliveClosure is_alive_next(_g1h);
-  BoolObjectClosure* is_alive;
   if (mark_completed) {
-    is_alive = &is_alive_prev;
+    G1ObjectCountIsAliveClosure is_alive(_g1h);
+    _gc_tracer_cm->report_object_count_after_gc(&is_alive);
   } else {
-    is_alive = &is_alive_next;
+    G1CMIsAliveClosure is_alive(_g1h);
+    _gc_tracer_cm->report_object_count_after_gc(&is_alive);
   }
-  _gc_tracer_cm->report_object_count_after_gc(is_alive);
 }