diff --git a/src/share/vm/classfile/javaClasses.cpp b/src/share/vm/classfile/javaClasses.cpp
index cc0db7a173bda483535b41ad4e3db2928d96ac72..a5cef1683b30e146092e70d3c1e467009fb4a2ee 100644
--- a/src/share/vm/classfile/javaClasses.cpp
+++ b/src/share/vm/classfile/javaClasses.cpp
@@ -1124,8 +1124,7 @@ class BacktraceBuilder: public StackObj {
     if (_dirty && _methods != NULL) {
       BarrierSet* bs = Universe::heap()->barrier_set();
       assert(bs->has_write_ref_array_opt(), "Barrier set must have ref array opt");
-      bs->write_ref_array(MemRegion((HeapWord*)_methods->base(),
-                                    _methods->array_size()));
+      bs->write_ref_array((HeapWord*)_methods->base(), _methods->length());
       _dirty = false;
     }
   }
diff --git a/src/share/vm/includeDB_core b/src/share/vm/includeDB_core
index e96a5e9be1a4f1b59cda2da86fe458d1884ba5af..a8bc76aad0b63e338deda266e4138eb6ff3950d9 100644
--- a/src/share/vm/includeDB_core
+++ b/src/share/vm/includeDB_core
@@ -289,7 +289,7 @@ attachListener.hpp                      allocation.hpp
 attachListener.hpp                      debug.hpp
 attachListener.hpp                      ostream.hpp
 
-barrierSet.cpp				barrierSet.hpp
+barrierSet.cpp				barrierSet.inline.hpp
 barrierSet.cpp			        collectedHeap.hpp
 barrierSet.cpp				universe.hpp
 
diff --git a/src/share/vm/memory/barrierSet.cpp b/src/share/vm/memory/barrierSet.cpp
index 07ff7a0fc21ccaa8cb73b23b9ab83b26b3a3807d..8cd80b7c437c63db9b511dde95acd887cde54ece 100644
--- a/src/share/vm/memory/barrierSet.cpp
+++ b/src/share/vm/memory/barrierSet.cpp
@@ -41,11 +41,6 @@ void BarrierSet::static_write_ref_array_pre(HeapWord* start, size_t count) {
 
 // count is number of array elements being written
 void BarrierSet::static_write_ref_array_post(HeapWord* start, size_t count) {
-  assert(count <= (size_t)max_intx, "count too large");
-  HeapWord* end = start + objArrayOopDesc::array_size((int)count);
-#if 0
-  warning("Post:\t" INTPTR_FORMAT "[" SIZE_FORMAT "] : [" INTPTR_FORMAT","INTPTR_FORMAT")\t",
-                   start,            count,              start,          end);
-#endif
-  Universe::heap()->barrier_set()->write_ref_array_work(MemRegion(start, end));
+  // simply delegate to instance method
+  Universe::heap()->barrier_set()->write_ref_array(start, count);
 }
diff --git a/src/share/vm/memory/barrierSet.hpp b/src/share/vm/memory/barrierSet.hpp
index 0fc6a0061400567bffefe8bbc8ff765a415c04c1..c624f2506e290f1644697c054a7cbdb21e3c05fe 100644
--- a/src/share/vm/memory/barrierSet.hpp
+++ b/src/share/vm/memory/barrierSet.hpp
@@ -121,17 +121,20 @@ public:
   virtual void read_ref_array(MemRegion mr) = 0;
   virtual void read_prim_array(MemRegion mr) = 0;
 
+  // Below length is the # array elements being written
   virtual void write_ref_array_pre(      oop* dst, int length) {}
   virtual void write_ref_array_pre(narrowOop* dst, int length) {}
+  // Below MemRegion mr is expected to be HeapWord-aligned
   inline void write_ref_array(MemRegion mr);
+  // Below count is the # array elements being written, starting
+  // at the address "start", which may not necessarily be HeapWord-aligned
+  inline void write_ref_array(HeapWord* start, size_t count);
 
-  // Static versions, suitable for calling from generated code.
+  // Static versions, suitable for calling from generated code;
+  // count is # array elements being written, starting with "start",
+  // which may not necessarily be HeapWord-aligned.
   static void static_write_ref_array_pre(HeapWord* start, size_t count);
   static void static_write_ref_array_post(HeapWord* start, size_t count);
-  // Narrow oop versions of the above; count is # of array elements being written,
-  // starting with "start", which is HeapWord-aligned.
-  static void static_write_ref_array_pre_narrow(HeapWord* start, size_t count);
-  static void static_write_ref_array_post_narrow(HeapWord* start, size_t count);
 
 protected:
   virtual void write_ref_array_work(MemRegion mr) = 0;
diff --git a/src/share/vm/memory/barrierSet.inline.hpp b/src/share/vm/memory/barrierSet.inline.hpp
index edcb551bdcdf0f1eb64ab1b4e042d775e79d9d9a..ddc398348caa9f4e322bef4fb5c25f082706e233 100644
--- a/src/share/vm/memory/barrierSet.inline.hpp
+++ b/src/share/vm/memory/barrierSet.inline.hpp
@@ -43,6 +43,8 @@ void BarrierSet::write_ref_field(void* field, oop new_val) {
 }
 
 void BarrierSet::write_ref_array(MemRegion mr) {
+  assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start() , "Unaligned start");
+  assert((HeapWord*)align_size_up  ((uintptr_t)mr.end(),   HeapWordSize) == mr.end(),    "Unaligned end"  );
   if (kind() == CardTableModRef) {
     ((CardTableModRefBS*)this)->inline_write_ref_array(mr);
   } else {
@@ -50,6 +52,34 @@ void BarrierSet::write_ref_array(MemRegion mr) {
   }
 }
 
+// count is number of array elements being written
+void BarrierSet::write_ref_array(HeapWord* start, size_t count) {
+  assert(count <= (size_t)max_intx, "count too large");
+  HeapWord* end = (HeapWord*)((char*)start + (count*heapOopSize));
+  // In the case of compressed oops, start and end may potentially be misaligned;
+  // so we need to conservatively align the first downward (this is not
+  // strictly necessary for current uses, but a case of good hygiene and,
+  // if you will, aesthetics) and the second upward (this is essential for
+  // current uses) to a HeapWord boundary, so we mark all cards overlapping
+  // this write. In the event that this evolves in the future to calling a
+  // logging barrier of narrow oop granularity, like the pre-barrier for G1
+  // (mentioned here merely by way of example), we will need to change this
+  // interface, much like the pre-barrier one above, so it is "exactly precise"
+  // (if i may be allowed the adverbial redundancy for emphasis) and does not
+  // include narrow oop slots not included in the original write interval.
+  HeapWord* aligned_start = (HeapWord*)align_size_down((uintptr_t)start, HeapWordSize);
+  HeapWord* aligned_end   = (HeapWord*)align_size_up  ((uintptr_t)end,   HeapWordSize);
+  // If compressed oops were not being used, these should already be aligned
+  assert(UseCompressedOops || (aligned_start == start && aligned_end == end),
+         "Expected heap word alignment of start and end");
+#if 0
+  warning("Post:\t" INTPTR_FORMAT "[" SIZE_FORMAT "] : [" INTPTR_FORMAT","INTPTR_FORMAT")\t",
+                   start,            count,              aligned_start,   aligned_end);
+#endif
+  write_ref_array_work(MemRegion(aligned_start, aligned_end));
+}
+
+
 void BarrierSet::write_region(MemRegion mr) {
   if (kind() == CardTableModRef) {
     ((CardTableModRefBS*)this)->inline_write_region(mr);
diff --git a/src/share/vm/memory/cardTableModRefBS.cpp b/src/share/vm/memory/cardTableModRefBS.cpp
index c036a355514dab46bf7a0ff88745cd2b71f5a520..2deb7da83f0fc3c0b7042a502f9d7e5969b791c7 100644
--- a/src/share/vm/memory/cardTableModRefBS.cpp
+++ b/src/share/vm/memory/cardTableModRefBS.cpp
@@ -511,6 +511,8 @@ void CardTableModRefBS::mod_oop_in_space_iterate(Space* sp,
 }
 
 void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
+  assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
+  assert((HeapWord*)align_size_up  ((uintptr_t)mr.end(),   HeapWordSize) == mr.end(),   "Unaligned end"  );
   jbyte* cur  = byte_for(mr.start());
   jbyte* last = byte_after(mr.last());
   while (cur < last) {
@@ -520,6 +522,8 @@ void CardTableModRefBS::dirty_MemRegion(MemRegion mr) {
 }
 
 void CardTableModRefBS::invalidate(MemRegion mr, bool whole_heap) {
+  assert((HeapWord*)align_size_down((uintptr_t)mr.start(), HeapWordSize) == mr.start(), "Unaligned start");
+  assert((HeapWord*)align_size_up  ((uintptr_t)mr.end(),   HeapWordSize) == mr.end(),   "Unaligned end"  );
   for (int i = 0; i < _cur_covered_regions; i++) {
     MemRegion mri = mr.intersection(_covered[i]);
     if (!mri.is_empty()) dirty_MemRegion(mri);
diff --git a/src/share/vm/oops/objArrayKlass.cpp b/src/share/vm/oops/objArrayKlass.cpp
index 212126490cdd5868dd8597ed7471b77e9c1ef384..68556a5a0cf28670621e5966b2101fa2a3edcd13 100644
--- a/src/share/vm/oops/objArrayKlass.cpp
+++ b/src/share/vm/oops/objArrayKlass.cpp
@@ -127,16 +127,14 @@ template <class T> void objArrayKlass::do_copy(arrayOop s, T* src,
           // pointer delta is scaled to number of elements (length field in
           // objArrayOop) which we assume is 32 bit.
           assert(pd == (size_t)(int)pd, "length field overflow");
-          const size_t done_word_len = objArrayOopDesc::array_size((int)pd);
-          bs->write_ref_array(MemRegion((HeapWord*)dst, done_word_len));
+          bs->write_ref_array((HeapWord*)dst, pd);
           THROW(vmSymbols::java_lang_ArrayStoreException());
           return;
         }
       }
     }
   }
-  const size_t word_len = objArrayOopDesc::array_size(length);
-  bs->write_ref_array(MemRegion((HeapWord*)dst, word_len));
+  bs->write_ref_array((HeapWord*)dst, length);
 }
 
 void objArrayKlass::copy_array(arrayOop s, int src_pos, arrayOop d,
diff --git a/src/share/vm/oops/objArrayOop.hpp b/src/share/vm/oops/objArrayOop.hpp
index 626f398a6be11e1f2a98d66378e54a4491ac1d44..a00eb7c1a9bb7535c67512e92d75c43ee4dce178 100644
--- a/src/share/vm/oops/objArrayOop.hpp
+++ b/src/share/vm/oops/objArrayOop.hpp
@@ -37,6 +37,32 @@ class objArrayOopDesc : public arrayOopDesc {
     return &((T*)base())[index];
   }
 
+private:
+  // Give size of objArrayOop in HeapWords minus the header
+  static int array_size(int length) {
+    const int OopsPerHeapWord = HeapWordSize/heapOopSize;
+    assert(OopsPerHeapWord >= 1 && (HeapWordSize % heapOopSize == 0),
+           "Else the following (new) computation would be in error");
+#ifdef ASSERT
+    // The old code is left in for sanity-checking; it'll
+    // go away pretty soon. XXX
+    // Without UseCompressedOops, this is simply:
+    // oop->length() * HeapWordsPerOop;
+    // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
+    // The oop elements are aligned up to wordSize
+    const int HeapWordsPerOop = heapOopSize/HeapWordSize;
+    int old_res;
+    if (HeapWordsPerOop > 0) {
+      old_res = length * HeapWordsPerOop;
+    } else {
+      old_res = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
+    }
+#endif  // ASSERT
+    int res = (length + OopsPerHeapWord - 1)/OopsPerHeapWord;
+    assert(res == old_res, "Inconsistency between old and new.");
+    return res;
+  }
+
  public:
   // Returns the offset of the first element.
   static int base_offset_in_bytes() {
@@ -67,29 +93,12 @@ class objArrayOopDesc : public arrayOopDesc {
   // Sizing
   static int header_size()    { return arrayOopDesc::header_size(T_OBJECT); }
   int object_size()           { return object_size(length()); }
-  int array_size()            { return array_size(length()); }
 
   static int object_size(int length) {
     // This returns the object size in HeapWords.
     return align_object_size(header_size() + array_size(length));
   }
 
-  // Give size of objArrayOop in HeapWords minus the header
-  static int array_size(int length) {
-    // Without UseCompressedOops, this is simply:
-    // oop->length() * HeapWordsPerOop;
-    // With narrowOops, HeapWordsPerOop is 1/2 or equal 0 as an integer.
-    // The oop elements are aligned up to wordSize
-    const int HeapWordsPerOop = heapOopSize/HeapWordSize;
-    if (HeapWordsPerOop > 0) {
-      return length * HeapWordsPerOop;
-    } else {
-      const int OopsPerHeapWord = HeapWordSize/heapOopSize;
-      int word_len = align_size_up(length, OopsPerHeapWord)/OopsPerHeapWord;
-      return word_len;
-    }
-  }
-
   // special iterators for index ranges, returns size of object
 #define ObjArrayOop_OOP_ITERATE_DECL(OopClosureType, nv_suffix)     \
   int oop_iterate_range(OopClosureType* blk, int start, int end);