--- old/src/share/vm/gc/shared/plab.cpp	2017-02-22 13:23:05.933150198 -0500
+++ new/src/share/vm/gc/shared/plab.cpp	2017-02-22 13:23:04.749081999 -0500
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2001, 2016, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2001, 2017, 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
@@ -154,30 +154,33 @@
   assert(is_object_aligned(max_size()) && min_size() <= max_size(),
          "PLAB clipping computation may be incorrect");
 
-  if (_allocated == 0) {
-    assert(_unused == 0,
-           "Inconsistency in PLAB stats: "
-           "_allocated: " SIZE_FORMAT ", "
-           "_wasted: " SIZE_FORMAT ", "
-           "_unused: " SIZE_FORMAT ", "
-           "_undo_wasted: " SIZE_FORMAT,
-           _allocated, _wasted, _unused, _undo_wasted);
+  assert(_allocated != 0 || _unused == 0,
+         "Inconsistency in PLAB stats: "
+         "_allocated: " SIZE_FORMAT ", "
+         "_wasted: " SIZE_FORMAT ", "
+         "_unused: " SIZE_FORMAT ", "
+         "_undo_wasted: " SIZE_FORMAT,
+         _allocated, _wasted, _unused, _undo_wasted);
 
-    _allocated = 1;
-  }
-  double wasted_frac    = (double)_unused / (double)_allocated;
+  size_t plab_sz = compute_desired_plab_sz();
+  // Take historical weighted average
+  _filter.sample(plab_sz);
+  _desired_net_plab_sz = MAX2(min_size(), (size_t)_filter.average());
+
+  log_sizing(plab_sz, _desired_net_plab_sz);
+  // Clear accumulators for next round
+  reset();
+}
+
+size_t PLABStats::compute_desired_plab_sz() {
+  size_t allocated = MAX2(_allocated, size_t(1));
+  double wasted_frac    = (double)_unused / (double)allocated;
   size_t target_refills = (size_t)((wasted_frac * TargetSurvivorRatio) / TargetPLABWastePct);
   if (target_refills == 0) {
     target_refills = 1;
   }
-  size_t used = _allocated - _wasted - _unused;
+  size_t used = allocated - _wasted - _unused;
   // Assumed to have 1 gc worker thread
   size_t recent_plab_sz = used / target_refills;
-  // Take historical weighted average
-  _filter.sample(recent_plab_sz);
-  _desired_net_plab_sz = MAX2(min_size(), (size_t)_filter.average());
-
-  log_sizing(recent_plab_sz, _desired_net_plab_sz);
-
-  reset();
+  return recent_plab_sz;
 }