--- old/src/share/vm/gc/shared/cardTableModRefBS.hpp	2016-03-29 11:56:35.286007330 -0700
+++ new/src/share/vm/gc/shared/cardTableModRefBS.hpp	2016-03-29 11:56:35.154007334 -0700
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000, 2015, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2000, 2016, 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
@@ -89,14 +89,6 @@
   MemRegion _guard_region;
 
  protected:
-  // Initialization utilities; covered_words is the size of the covered region
-  // in, um, words.
-  inline size_t cards_required(size_t covered_words) {
-    // Add one for a guard card, used to detect errors.
-    const size_t words = align_size_up(covered_words, card_size_in_words);
-    return words / card_size_in_words + 1;
-  }
-
   inline size_t compute_byte_map_size();
 
   // Finds and return the index of the region, if any, to which the given
@@ -172,6 +164,14 @@
 
   bool has_write_ref_pre_barrier() { return false; }
 
+  // Initialization utilities; covered_words is the size of the covered region
+  // in, um, words.
+  inline size_t cards_required(size_t covered_words) {
+    // Add one for a guard card, used to detect errors.
+    const size_t words = align_size_up(covered_words, card_size_in_words);
+    return words / card_size_in_words + 1;
+  }
+
 protected:
 
   CardTableModRefBS(MemRegion whole_heap, const BarrierSet::FakeRtti& fake_rtti);
--- old/src/share/vm/runtime/commandLineFlagConstraintsGC.cpp	2016-03-29 11:56:35.802007312 -0700
+++ new/src/share/vm/runtime/commandLineFlagConstraintsGC.cpp	2016-03-29 11:56:35.658007317 -0700
@@ -386,21 +386,21 @@
 #if INCLUDE_ALL_GCS
   if (UseConcMarkSweepGC) {
     // ParGCCardsPerStrideChunk shoule be compared with card table size.
-    // As CardTableModRefBS::_last_valid_index is 'protected', calculate it in a same way.
     size_t heap_size = Universe::heap()->reserved_region().word_size();
-    size_t card_table_size = align_size_up(heap_size, CardTableModRefBS::card_size_in_words);
-    card_table_size /= (CardTableModRefBS::card_size_in_words + 1);
-    card_table_size -= 1;
+    CardTableModRefBS* bs = (CardTableModRefBS*)GenCollectedHeap::heap()->rem_set()->bs();
+    size_t card_table_size = bs->cards_required(heap_size) - 1; // Valid card table size
 
     if ((size_t)value > card_table_size) {
       CommandLineError::print(verbose,
-                              "ParGCCardsPerStrideChunk (" INTX_FORMAT ") must be "
-                              "less than or equal to card table size (" SIZE_FORMAT ")\n",
+                              "ParGCCardsPerStrideChunk (" INTX_FORMAT ") is too large for the heap size and "
+                              "must be less than or equal to card table size (" SIZE_FORMAT ")\n",
                               value, card_table_size);
       return Flag::VIOLATES_CONSTRAINT;
     }
 
-    // If n_strides which is used with ParGCCardsPerStrideChunk is really large, we would face an overflow.
+    // ParGCCardsPerStrideChunk is used with n_strides(ParallelGCThreads*ParGCStridesPerThread)
+    // from CardTableModRefBSForCTRS::process_stride(). However, ParGCStridesPerThread is already checked
+    // not to make an overflow with ParallelGCThreads from its constraint function.
     uintx n_strides = ParallelGCThreads * ParGCStridesPerThread;
     uintx ergo_max = max_uintx / n_strides;
     if ((uintx)value > ergo_max) {