8270842: G1: Only young regions need to redirty outside references in remset.

Reviewed-by: tschatzl

Author: Hamlin Li

src/hotspot/share/gc/g1/g1EvacFailure.cpp

@@ -80,6 +80,7 @@ class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
   G1CollectedHeap* _g1h;
   G1ConcurrentMark* _cm;
   HeapRegion* _hr;
+  const bool _is_young;
   size_t _marked_bytes;
   UpdateLogBuffersDeferred* _log_buffer_cl;
   bool _during_concurrent_start;
@@ -94,6 +95,7 @@ class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
     _g1h(G1CollectedHeap::heap()),
     _cm(_g1h->concurrent_mark()),
     _hr(hr),
+    _is_young(hr->is_young()),
     _marked_bytes(0),
     _log_buffer_cl(log_buffer_cl),
     _during_concurrent_start(during_concurrent_start),
@@ -140,19 +142,14 @@ class RemoveSelfForwardPtrObjClosure: public ObjectClosure {
       _marked_bytes += (obj_size * HeapWordSize);
       PreservedMarks::init_forwarded_mark(obj);
 
-      // While we were processing RSet buffers during the collection,
-      // we actually didn't scan any cards on the collection set,
-      // since we didn't want to update remembered sets with entries
-      // that point into the collection set, given that live objects
-      // from the collection set are about to move and such entries
-      // will be stale very soon.
-      // This change also dealt with a reliability issue which
-      // involved scanning a card in the collection set and coming
-      // across an array that was being chunked and looking malformed.
-      // The problem is that, if evacuation fails, we might have
-      // remembered set entries missing given that we skipped cards on
-      // the collection set. So, we'll recreate such entries now.
-      obj->oop_iterate(_log_buffer_cl);
+      // During evacuation failure we do not record inter-region
+      // references referencing regions that need a remembered set
+      // update originating from young regions (including eden) that
+      // failed evacuation. Make up for that omission now by rescanning
+      // these failed objects.
+      if (_is_young) {
+        obj->oop_iterate(_log_buffer_cl);
+      }
 
       HeapWord* obj_end = obj_addr + obj_size;
       _last_forwarded_object_end = obj_end;