1/*
2 * tc_cbq.c		CBQ maintanance routines.
3 *
4 *		This program is free software; you can redistribute it and/or
5 *		modify it under the terms of the GNU General Public License
6 *		as published by the Free Software Foundation; either version
7 *		2 of the License, or (at your option) any later version.
8 *
9 * Authors:	Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
10 *
11 */
12
13#include <stdio.h>
14#include <stdlib.h>
15#include <unistd.h>
16#include <syslog.h>
17#include <fcntl.h>
18#include <math.h>
19#include <sys/socket.h>
20#include <netinet/in.h>
21#include <arpa/inet.h>
22#include <string.h>
23
24#include "tc_core.h"
25#include "tc_cbq.h"
26
27unsigned tc_cbq_calc_maxidle(unsigned bndw, unsigned rate, unsigned avpkt,
28			     int ewma_log, unsigned maxburst)
29{
30	double maxidle;
31	double g = 1.0 - 1.0/(1<<ewma_log);
32	double xmt = (double)avpkt/bndw;
33
34	maxidle = xmt*(1-g);
35	if (bndw != rate && maxburst) {
36		double vxmt = (double)avpkt/rate - xmt;
37		vxmt *= (pow(g, -(double)maxburst) - 1);
38		if (vxmt > maxidle)
39			maxidle = vxmt;
40	}
41	return tc_core_time2tick(maxidle*(1<<ewma_log)*TIME_UNITS_PER_SEC);
42}
43
44unsigned tc_cbq_calc_offtime(unsigned bndw, unsigned rate, unsigned avpkt,
45			     int ewma_log, unsigned minburst)
46{
47	double g = 1.0 - 1.0/(1<<ewma_log);
48	double offtime = (double)avpkt/rate - (double)avpkt/bndw;
49
50	if (minburst == 0)
51		return 0;
52	if (minburst == 1)
53		offtime *= pow(g, -(double)minburst) - 1;
54	else
55		offtime *= 1 + (pow(g, -(double)(minburst-1)) - 1)/(1-g);
56	return tc_core_time2tick(offtime*TIME_UNITS_PER_SEC);
57}
58