ceph/src/common/DecayCounter.cc

   1 // -*- mode:C++; tab-width:8; c-basic-offset:2; indent-tabs-mode:t -*-
   2 // vim: ts=8 sw=2 smarttab
   3 /*
   4  * Ceph - scalable distributed file system
   5  *
   6  * Copyright (C) 2004-2006 Sage Weil <sage@newdream.net>
   7  *
   8  * This is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU Lesser General Public
  10  * License version 2.1, as published by the Free Software
  11  * Foundation.  See file COPYING.
  12  *
  13  */
  14
  15 #include "DecayCounter.h"
  16 #include "Formatter.h"
  17
  18 void DecayCounter::encode(bufferlist& bl) const
  19 {
  20   ENCODE_START(4, 4, bl);
  21   ::encode(val, bl);
  22   ::encode(delta, bl);
  23   ::encode(vel, bl);
  24   ENCODE_FINISH(bl);
  25 }
  26
  27 void DecayCounter::decode(const utime_t &t, bufferlist::iterator &p)
  28 {
  29   DECODE_START_LEGACY_COMPAT_LEN(4, 4, 4, p);
  30   if (struct_v < 2) {
  31     double half_life;
  32     ::decode(half_life, p);
  33   }
  34   if (struct_v < 3) {
  35     double k;
  36     ::decode(k, p);
  37   }
  38   ::decode(val, p);
  39   ::decode(delta, p);
  40   ::decode(vel, p);
  41   DECODE_FINISH(p);
  42 }
  43
  44 void DecayCounter::dump(Formatter *f) const
  45 {
  46   f->dump_float("value", val);
  47   f->dump_float("delta", delta);
  48   f->dump_float("velocity", vel);
  49 }
  50
  51 void DecayCounter::generate_test_instances(list<DecayCounter*>& ls)
  52 {
  53   utime_t fake_time;
  54   DecayCounter *counter = new DecayCounter(fake_time);
  55   counter->val = 3.0;
  56   counter->delta = 2.0;
  57   counter->vel = 1.0;
  58   ls.push_back(counter);
  59   counter = new DecayCounter(fake_time);
  60   ls.push_back(counter);
  61 }
  62
  63 void DecayCounter::decay(utime_t now, const DecayRate &rate)
  64 {
  65   if (now >= last_decay) {
  66     double el = (double)(now - last_decay);
  67     if (el >= 1.0) {
  68       // calculate new value
  69       double newval = (val+delta) * exp(el * rate.k);
  70       if (newval < .01)
  71         newval = 0.0;
  72
  73       // calculate velocity approx
  74       vel += (newval - val) * el;
  75       vel *= exp(el * rate.k);
  76
  77       val = newval;
  78       delta = 0;
  79       last_decay = now;
  80     }
  81   } else {
  82       last_decay = now;
  83   }
  84 }