--- old/src/share/vm/gc_implementation/shared/plab.cpp	2015-04-20 17:36:21.100942281 +0300
+++ new/src/share/vm/gc_implementation/shared/plab.cpp	2015-04-20 17:36:21.024941103 +0300
@@ -24,6 +24,7 @@
 
 #include "precompiled.hpp"
 #include "gc_implementation/shared/plab.hpp"
+#include "gc_interface/collectedHeap.hpp"
 #include "memory/threadLocalAllocBuffer.hpp"
 #include "oops/arrayOop.hpp"
 #include "oops/oop.inline.hpp"
@@ -86,6 +87,28 @@
   return result;
 }
 
+void PLAB::add_undo_waste(HeapWord* obj, size_t word_sz) {
+  CollectedHeap::fill_with_object(obj, word_sz);
+  _undo_wasted += word_sz;
+}
+
+void PLAB::undo_last_allocation(HeapWord* obj, size_t word_sz) {
+  assert(pointer_delta(_top, _bottom) >= word_sz, "Bad undo");
+  assert(pointer_delta(_top, obj) == word_sz, "Bad undo");
+  _top = obj;
+}
+
+void PLAB::undo_allocation(HeapWord* obj, size_t word_sz) {
+  // Is the alloc in the current alloc buffer?
+  if (contains(obj)) {
+    assert(contains(obj + word_sz - 1),
+      "should contain whole object");
+    undo_last_allocation(obj, word_sz);
+  } else {
+    add_undo_waste(obj, word_sz);
+  }
+}
+
 // Compute desired plab size and latch result for later
 // use. This should be called once at the end of parallel
 // scavenge; it clears the sensor accumulators.
@@ -100,8 +123,8 @@
            err_msg("Inconsistency in PLAB stats: "
                    "_allocated: "SIZE_FORMAT", "
                    "_wasted: "SIZE_FORMAT", "
-                   "_unused: "SIZE_FORMAT", ",
-                   "_undo_wasted: "SIZE_FORMAT, 
+                   "_unused: "SIZE_FORMAT", "
+                   "_undo_wasted: "SIZE_FORMAT,
                    _allocated, _wasted, _unused, _undo_wasted));
 
     _allocated = 1;