src/share/vm/gc/shared/plab.cpp

@@ -1,7 +1,7 @@
 /*
- * 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
  * under the terms of the GNU General Public License version 2 only, as
  * published by the Free Software Foundation.

@@ -152,32 +152,37 @@
   }
 
   assert(is_object_aligned(max_size()) && min_size() <= max_size(),
          "PLAB clipping computation may be incorrect");
 
-  if (_allocated == 0) {
-    assert(_unused == 0,
+  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);
 
+  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() {
+  if (_allocated == 0) {
     _allocated = 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;
   // 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;
 }