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476daa7278
[IPROUTE]: Use tc_calc_xmittime() where appropriate
Replace expressions of the form "tc_core_usec2tick(1000000 * size/rate)"
by tc_calc_xmittime().
The CBQ case deserves an extra comment: when called with bnwd=rate,
tc_cbq_calc_maxidle() behaves identical to tc_calc_xmittime():
unsigned tc_cbq_calc_maxidle(...)
{
double g = 1.0 - 1.0/(1<<ewma_log);
double xmt = (double)avpkt/bndw;
maxidle = xmt*(1-g);
if (bndw != rate && maxburst) {
...
}
return tc_core_usec2tick(maxidle*(1<<ewma_log)*1000000);
}
which comes down to:
maxidle = xmt * (1 - g)
= xmt * (1 - (1.0 - 1.0/(1 << ewma_log))
= xmt * (1.0/(1 << ewma_log))
so:
maxidle * (1 << ewma_log) * 1000000
= xmt * (1.0/(1 << ewma_log)) * (1 << ewma_log) * 1000000
= xmt * 1000000
= avpkt/bndw * 1000000
Which means tc_core_usec2tick(maxidle*(1<<ewma_log)*1000000) is identical
to tc_calc_xmittime(bndw, avpkt). Use it directly since its a lot easier
to understand its limits.
Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Stephen Hemminger <shemminger@linux-foundation.org>
98 lines
1.8 KiB
C
98 lines
1.8 KiB
C
/*
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* tc_red.c RED maintanance routines.
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Authors: Alexey Kuznetsov, <kuznet@ms2.inr.ac.ru>
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*
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <syslog.h>
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#include <fcntl.h>
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#include <math.h>
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#include <sys/socket.h>
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#include <netinet/in.h>
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#include <arpa/inet.h>
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#include <string.h>
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#include "tc_core.h"
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#include "tc_red.h"
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/*
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Plog = log(prob/(qmax - qmin))
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*/
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int tc_red_eval_P(unsigned qmin, unsigned qmax, double prob)
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{
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int i = qmax - qmin;
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if (i <= 0)
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return -1;
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prob /= i;
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for (i=0; i<32; i++) {
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if (prob > 1.0)
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break;
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prob *= 2;
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}
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if (i>=32)
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return -1;
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return i;
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}
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/*
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burst + 1 - qmin/avpkt < (1-(1-W)^burst)/W
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*/
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int tc_red_eval_ewma(unsigned qmin, unsigned burst, unsigned avpkt)
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{
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int wlog = 1;
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double W = 0.5;
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double a = (double)burst + 1 - (double)qmin/avpkt;
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if (a < 1.0)
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return -1;
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for (wlog=1; wlog<32; wlog++, W /= 2) {
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if (a <= (1 - pow(1-W, burst))/W)
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return wlog;
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}
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return -1;
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}
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/*
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Stab[t>>Scell_log] = -log(1-W) * t/xmit_time
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*/
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int tc_red_eval_idle_damping(int Wlog, unsigned avpkt, unsigned bps, __u8 *sbuf)
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{
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double xmit_time = tc_calc_xmittime(bps, avpkt);
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double lW = -log(1.0 - 1.0/(1<<Wlog))/xmit_time;
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double maxtime = 31/lW;
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int clog;
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int i;
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double tmp;
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tmp = maxtime;
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for (clog=0; clog<32; clog++) {
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if (maxtime/(1<<clog) < 512)
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break;
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}
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if (clog >= 32)
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return -1;
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sbuf[0] = 0;
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for (i=1; i<255; i++) {
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sbuf[i] = (i<<clog)*lW;
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if (sbuf[i] > 31)
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sbuf[i] = 31;
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}
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sbuf[255] = 31;
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return clog;
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}
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