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/*
* Event rate calculation functions.
*
* Copyright 2000-2010 Willy Tarreau <w@1wt.eu>
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public License
* as published by the Free Software Foundation; either version
* 2 of the License, or (at your option) any later version.
*
*/
#include <common/config.h>
#include <common/standard.h>
#include <common/time.h>
#include <common/tools.h>
#include <proto/freq_ctr.h>
/* Read a frequency counter taking history into account for missing time in
* current period. Current second is sub-divided in 1000 chunks of one ms,
* and the missing ones are read proportionally from previous value. The
* return value has the same precision as one input data sample, so low rates
* will be inaccurate still appropriate for max checking. One trick we use for
* low values is to specially handle the case where the rate is between 0 and 1
* in order to avoid flapping while waiting for the next event.
*
* For immediate limit checking, it's recommended to use freq_ctr_remain() and
* next_event_delay() instead which do not have the flapping correction, so
* that even frequencies as low as one event/period are properly handled.
*/
unsigned int read_freq_ctr(struct freq_ctr *ctr)
{
unsigned int curr, past;
unsigned int age;
age = now.tv_sec - ctr->curr_sec;
if (unlikely(age > 1))
return 0;
curr = 0;
past = ctr->curr_ctr;
if (likely(!age)) {
curr = past;
past = ctr->prev_ctr;
}
if (past <= 1 && !curr)
return past; /* very low rate, avoid flapping */
return curr + mul32hi(past, ms_left_scaled);
}
/* returns the number of remaining events that can occur on this freq counter
* while respecting <freq> and taking into account that <pend> events are
* already known to be pending. Returns 0 if limit was reached.
*/
unsigned int freq_ctr_remain(struct freq_ctr *ctr, unsigned int freq, unsigned int pend)
{
unsigned int curr, past;
unsigned int age;
curr = 0;
age = now.tv_sec - ctr->curr_sec;
if (likely(age <= 1)) {
past = ctr->curr_ctr;
if (likely(!age)) {
curr = past;
past = ctr->prev_ctr;
}
curr += mul32hi(past, ms_left_scaled);
}
curr += pend;
if (curr >= freq)
return 0;
return freq - curr;
}
/* return the expected wait time in ms before the next event may occur,
* respecting frequency <freq>, and assuming there may already be some pending
* events. It returns zero if we can proceed immediately, otherwise the wait
* time, which will be rounded down 1ms for better accuracy, with a minimum
* of one ms.
*/
unsigned int next_event_delay(struct freq_ctr *ctr, unsigned int freq, unsigned int pend)
{
unsigned int curr, past;
unsigned int wait, age;
past = 0;
curr = 0;
age = now.tv_sec - ctr->curr_sec;
if (likely(age <= 1)) {
past = ctr->curr_ctr;
if (likely(!age)) {
curr = past;
past = ctr->prev_ctr;
}
curr += mul32hi(past, ms_left_scaled);
}
curr += pend;
if (curr < freq)
return 0;
wait = 999 / curr;
return MAX(wait, 1);
}
/* Reads a frequency counter taking history into account for missing time in
* current period. The period has to be passed in number of ticks and must
* match the one used to feed the counter. The counter value is reported for
* current date (now_ms). The return value has the same precision as one input
* data sample, so low rates over the period will be inaccurate but still
* appropriate for max checking. One trick we use for low values is to specially
* handle the case where the rate is between 0 and 1 in order to avoid flapping
* while waiting for the next event.
*
* For immediate limit checking, it's recommended to use freq_ctr_period_remain()
* instead which does not have the flapping correction, so that even frequencies
* as low as one event/period are properly handled.
*
* For measures over a 1-second period, it's better to use the implicit functions
* above.
*/
unsigned int read_freq_ctr_period(struct freq_ctr_period *ctr, unsigned int period)
{
unsigned int curr, past;
unsigned int remain;
curr = ctr->curr_ctr;
past = ctr->prev_ctr;
remain = ctr->curr_tick + period - now_ms;
if (unlikely((int)remain < 0)) {
/* We're past the first period, check if we can still report a
* part of last period or if we're too far away.
*/
remain += period;
if ((int)remain < 0)
return 0;
past = curr;
curr = 0;
}
if (past <= 1 && !curr)
return past; /* very low rate, avoid flapping */
curr += div64_32((unsigned long long)past * remain, period);
return curr;
}
/* Returns the number of remaining events that can occur on this freq counter
* while respecting <freq> events per period, and taking into account that
* <pend> events are already known to be pending. Returns 0 if limit was reached.
*/
unsigned int freq_ctr_remain_period(struct freq_ctr_period *ctr, unsigned int period,
unsigned int freq, unsigned int pend)
{
unsigned int curr, past;
unsigned int remain;
curr = ctr->curr_ctr;
past = ctr->prev_ctr;
remain = ctr->curr_tick + period - now_ms;
if (likely((int)remain < 0)) {
/* We're past the first period, check if we can still report a
* part of last period or if we're too far away.
*/
past = curr;
curr = 0;
remain += period;
if ((int)remain < 0)
past = 0;
}
if (likely(past))
curr += div64_32((unsigned long long)past * remain, period);
curr += pend;
freq -= curr;
if ((int)freq < 0)
freq = 0;
return freq;
}
/*
* Local variables:
* c-indent-level: 8
* c-basic-offset: 8
* End:
*/