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diff --git a/src/ceph/src/common/DecayCounter.cc b/src/ceph/src/common/DecayCounter.cc
new file mode 100644
index 0000000..67a129c
--- /dev/null
+++ b/src/ceph/src/common/DecayCounter.cc
@@ -0,0 +1,82 @@
+// -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
+// vim: ts=8 sw=2 smarttab
+/*
+ * Ceph - scalable distributed file system
+ *
+ * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
+ *
+ * This is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License version 2.1, as published by the Free Software
+ * Foundation.  See file COPYING.
+ *
+ */
+
+#include "DecayCounter.h"
+#include "Formatter.h"
+
+void DecayCounter::encode(bufferlist& bl) const
+{
+  ENCODE_START(4, 4, bl);
+  ::encode(val, bl);
+  ::encode(delta, bl);
+  ::encode(vel, bl);
+  ENCODE_FINISH(bl);
+}
+
+void DecayCounter::decode(const utime_t &t, bufferlist::iterator &p)
+{
+  DECODE_START_LEGACY_COMPAT_LEN(4, 4, 4, p);
+  if (struct_v < 2) {
+    double half_life;
+    ::decode(half_life, p);
+  }
+  if (struct_v < 3) {
+    double k;
+    ::decode(k, p);
+  }
+  ::decode(val, p);
+  ::decode(delta, p);
+  ::decode(vel, p);
+  DECODE_FINISH(p);
+}
+
+void DecayCounter::dump(Formatter *f) const
+{
+  f->dump_float("value", val);
+  f->dump_float("delta", delta);
+  f->dump_float("velocity", vel);
+}
+
+void DecayCounter::generate_test_instances(list<DecayCounter*>& ls)
+{
+  utime_t fake_time;
+  DecayCounter *counter = new DecayCounter(fake_time);
+  counter->val = 3.0;
+  counter->delta = 2.0;
+  counter->vel = 1.0;
+  ls.push_back(counter);
+  counter = new DecayCounter(fake_time);
+  ls.push_back(counter);
+}
+
+void DecayCounter::decay(utime_t now, const DecayRate &rate)
+{
+  utime_t el = now;
+  el -= last_decay;
+
+  if (el.sec() >= 1) {
+    // calculate new value
+    double newval = (val+delta) * exp((double)el * rate.k);
+    if (newval < .01)
+      newval = 0.0;
+
+    // calculate velocity approx
+    vel += (newval - val) * (double)el;
+    vel *= exp((double)el * rate.k);
+
+    val = newval;
+    delta = 0;
+    last_decay = now;
+  }
+}