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// -*- 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.
*
*/
#ifndef CEPH_DECAYCOUNTER_H
#define CEPH_DECAYCOUNTER_H
#include "include/utime.h"
#include <math.h>
/**
*
* TODO: normalize value based on some fucntion of half_life,
* so that it can be interpreted as an approximation of a
* moving average of N seconds. currently, changing half-life
* skews the scale of the value, even at steady state.
*
*/
class DecayRate {
double k; // k = ln(.5)/half_life
friend class DecayCounter;
public:
DecayRate() : k(0) {}
DecayRate(const DecayRate &dr) : k(dr.k) {}
// cppcheck-suppress noExplicitConstructor
DecayRate(double hl) { set_halflife(hl); }
void set_halflife(double hl) {
k = ::log(.5) / hl;
}
};
class DecayCounter {
public:
double val; // value
double delta; // delta since last decay
double vel; // recent velocity
utime_t last_decay; // time of last decay
DecayRate rate;
void encode(bufferlist& bl) const;
void decode(const utime_t &t, bufferlist::iterator& p);
void dump(Formatter *f) const;
static void generate_test_instances(list<DecayCounter*>& ls);
explicit DecayCounter(const utime_t &now)
: val(0), delta(0), vel(0), last_decay(now)
{
}
explicit DecayCounter(const utime_t &now, const DecayRate &rate)
: val(0), delta(0), vel(0), last_decay(now), rate(rate)
{
}
// these two functions are for the use of our dencoder testing infrastructure
DecayCounter() : val(0), delta(0), vel(0), last_decay() {}
void decode(bufferlist::iterator& p) {
utime_t fake_time;
decode(fake_time, p);
}
/**
* reading
*/
double get(utime_t now, const DecayRate& rate) {
decay(now, rate);
return val+delta;
}
double get(utime_t now) {
decay(now, rate);
return val+delta;
}
double get_last() {
return val;
}
double get_last_vel() {
return vel;
}
utime_t get_last_decay() {
return last_decay;
}
/**
* adjusting
*/
double hit(utime_t now, const DecayRate& rate, double v = 1.0) {
decay(now, rate);
delta += v;
return val+delta;
}
double hit(utime_t now, double v = 1.0) {
decay(now, rate);
delta += v;
return val+delta;
}
void adjust(double a) {
val += a;
}
void adjust(utime_t now, const DecayRate& rate, double a) {
decay(now, rate);
val += a;
}
void scale(double f) {
val *= f;
delta *= f;
vel *= f;
}
/**
* decay etc.
*/
void reset(utime_t now) {
last_decay = now;
val = delta = 0;
}
void decay(utime_t now, const DecayRate &rate);
};
inline void encode(const DecayCounter &c, bufferlist &bl) { c.encode(bl); }
inline void decode(DecayCounter &c, const utime_t &t, bufferlist::iterator &p) {
c.decode(t, p);
}
// for dencoder
inline void decode(DecayCounter &c, bufferlist::iterator &p) {
utime_t t;
c.decode(t, p);
}
#endif
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