--- a/hotspot/src/share/vm/utilities/globalDefinitions.hpp	Tue Dec 30 12:59:20 2014 -0500
+++ b/hotspot/src/share/vm/utilities/globalDefinitions.hpp	Mon Jan 05 12:07:37 2015 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 1997, 2014, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 1997, 2015, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -124,9 +124,6 @@
 extern int BytesPerHeapOop;
 extern int BitsPerHeapOop;
 
-// Oop encoding heap max
-extern uint64_t OopEncodingHeapMax;
-
 const int BitsPerJavaInteger = 32;
 const int BitsPerJavaLong    = 64;
 const int BitsPerSize_t      = size_tSize * BitsPerByte;
@@ -195,7 +192,6 @@
   return (byte_size + (HeapWordSize-1)) >> LogHeapWordSize;
 }
 
-
 const size_t K                  = 1024;
 const size_t M                  = K*K;
 const size_t G                  = M*K;
@@ -397,8 +393,17 @@
 const int KlassAlignmentInBytes    = 1 << LogKlassAlignmentInBytes;
 const int KlassAlignment           = KlassAlignmentInBytes / HeapWordSize;
 
-// Klass encoding metaspace max size
-const uint64_t KlassEncodingMetaspaceMax = (uint64_t(max_juint) + 1) << LogKlassAlignmentInBytes;
+// Maximal size of heap where unscaled compression can be used. Also upper bound
+// for heap placement: 4GB.
+const  uint64_t UnscaledOopHeapMax = (uint64_t(max_juint) + 1);
+// Maximal size of heap where compressed oops can be used. Also upper bound for heap
+// placement for zero based compression algorithm: UnscaledOopHeapMax << LogMinObjAlignmentInBytes.
+extern uint64_t OopEncodingHeapMax;
+
+// Maximal size of compressed class space. Above this limit compression is not possible.
+// Also upper bound for placement of zero based class space. (Class space is further limited
+// to be < 3G, see arguments.cpp.)
+const  uint64_t KlassEncodingMetaspaceMax = (uint64_t(max_juint) + 1) << LogKlassAlignmentInBytes;
 
 // Machine dependent stuff