tc/tc_cbq.c

   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
  27 unsigned 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_usec2tick(maxidle*(1<<ewma_log)*TIME_UNITS_PER_SEC);
  42 }
  43
  44 unsigned 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_usec2tick(offtime*TIME_UNITS_PER_SEC);
  57 }