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Cubic changes: 

* correct W(t) calculation
 * check wmax limits
 * change W_max in slow and fast retransmit
 * correct rtt approximation
Reno:
 * move comment I forgot behind after fast_retransmit() split
This commit is contained in:
kefren 2013-11-18 11:48:34 +00:00
parent 7bc55a445e
commit be55f323ec
1 changed files with 58 additions and 39 deletions
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97
sys/netinet/tcp_congctl.c
View File

@ -1,4 +1,4 @@
/* $NetBSD: tcp_congctl.c,v 1.18 2013/11/12 09:02:05 kefren Exp $ */
/* $NetBSD: tcp_congctl.c,v 1.19 2013/11/18 11:48:34 kefren Exp $ */
/*-
* Copyright (c) 1997, 1998, 1999, 2001, 2005, 2006 The NetBSD Foundation, Inc.
@ -135,7 +135,7 @@
*/
#include <sys/cdefs.h>
__KERNEL_RCSID(0, "$NetBSD: tcp_congctl.c,v 1.18 2013/11/12 09:02:05 kefren Exp $");
__KERNEL_RCSID(0, "$NetBSD: tcp_congctl.c,v 1.19 2013/11/18 11:48:34 kefren Exp $");
#include "opt_inet.h"
#include "opt_tcp_debug.h"
@ -469,12 +469,6 @@ static int
tcp_reno_do_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
{
/*
* We know we're losing at the current
* window size so do congestion avoidance
* (set ssthresh to half the current window
* and pull our congestion window back to
* the new ssthresh).
*
* Dup acks mean that packets have left the
* network (they're now cached at the receiver)
* so bump cwnd by the amount in the receiver
@ -506,7 +500,7 @@ tcp_reno_do_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
tp->snd_cwnd = tp->snd_ssthresh + tp->t_segsz * tp->t_dupacks;
if (SEQ_GT(onxt, tp->snd_nxt))
tp->snd_nxt = onxt;
return 0;
}
@ -514,6 +508,14 @@ static int
tcp_reno_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
{
/*
* We know we're losing at the current
* window size so do congestion avoidance
* (set ssthresh to half the current window
* and pull our congestion window back to
* the new ssthresh).
*/
tcp_reno_congestion_exp(tp);
return tcp_reno_do_fast_retransmit(tp, th);
}
@ -800,7 +802,7 @@ const struct tcp_congctl tcp_newreno_ctl = {
static void tcp_cubic_update_ctime(struct tcpcb *tp);
static uint32_t tcp_cubic_diff_ctime(struct tcpcb *);
static uint32_t tcp_cubic_cbrt(uint32_t);
static uint32_t tcp_cubic_getW(struct tcpcb *);
static ulong tcp_cubic_getW(struct tcpcb *, uint32_t, uint32_t);
/* Cubic TIME functions - XXX I don't like using timevals and microuptime */
/*
@ -862,25 +864,30 @@ tcp_cubic_cbrt(uint32_t v)
return (uint32_t)x;
}
/* Draft Rhee Section 3.1 - get W(t) */
static uint32_t
tcp_cubic_getW(struct tcpcb *tp)
/* Draft Rhee Section 3.1 - get W(t+rtt) - Eq. 1 */
static ulong
tcp_cubic_getW(struct tcpcb *tp, uint32_t ms_elapsed, uint32_t rtt)
{
uint32_t ms_elapsed = tcp_cubic_diff_ctime(tp);
uint32_t K, CtK;
uint32_t K;
long tK3;
K = tcp_cubic_cbrt(tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB *
/* Section 3.1 Eq. 2 */
K = tcp_cubic_cbrt(tp->snd_cubic_wmax / CUBIC_BETAB *
CUBIC_CB / CUBIC_CA);
/* C*(t-K) */
CtK = CUBIC_CA * (ms_elapsed - K) / CUBIC_CB;
/* (t-K)^3 - not clear why is the measure unit mattering */
tK3 = (long)(ms_elapsed + rtt) - (long)K;
tK3 = tK3 * tK3 * tK3;
return CtK * CtK * CtK + tp->snd_cubic_wmax;
return CUBIC_CA * tK3 / CUBIC_CB + tp->snd_cubic_wmax;
}
static void
tcp_cubic_congestion_exp(struct tcpcb *tp)
{
/*
* Congestion - Set WMax and shrink cwnd
*/
tcp_cubic_update_ctime(tp);
/* Section 3.6 - Fast Convergence */
@ -892,6 +899,10 @@ tcp_cubic_congestion_exp(struct tcpcb *tp)
tp->snd_cubic_wmax_last = tp->snd_cubic_wmax;
tp->snd_cubic_wmax = tp->snd_cwnd;
}
tp->snd_cubic_wmax = max(tp->t_segsz, tp->snd_cubic_wmax);
/* Shrink CWND */
tcp_common_congestion_exp(tp, CUBIC_BETAA, CUBIC_BETAB);
}
@ -906,15 +917,12 @@ tcp_cubic_fast_retransmit(struct tcpcb *tp, const struct tcphdr *th)
}
/*
* do CUBIC if not in fast recovery
* mark WMax
*/
if (tp->t_partialacks < 0) {
/* Adjust W_max, W_max_last, cwnd and ssthresh */
tcp_cubic_congestion_exp(tp);
/* Reno and NewReno FR */
return tcp_reno_do_fast_retransmit(tp, th);
} else
return tcp_reno_fast_retransmit(tp, th);
tcp_cubic_congestion_exp(tp);
/* Do fast retransmit */
return tcp_reno_do_fast_retransmit(tp, th);
}
static void
@ -923,20 +931,24 @@ tcp_cubic_newack(struct tcpcb *tp, const struct tcphdr *th)
uint32_t ms_elapsed, rtt;
u_long w_tcp;
/* Congestion avoidance and not in fast recovery */
if (tp->snd_cwnd > tp->snd_ssthresh && tp->t_partialacks < 0) {
/* Congestion avoidance and not in fast recovery and usable rtt */
if (tp->snd_cwnd > tp->snd_ssthresh && tp->t_partialacks < 0 &&
/*
* t_srtt is 1/32 units of slow ticks
* converting it in ms would be equal to
* (t_srtt >> 5) * 1000 / PR_SLOWHZ ~= (t_srtt << 5) / PR_SLOWHZ
*/
(rtt = (tp->t_srtt << 5) / PR_SLOWHZ) > 0) {
ms_elapsed = tcp_cubic_diff_ctime(tp);
rtt = max(hztoms(1), hztoms((tp->t_srtt >> TCP_RTT_SHIFT)));
/* Compute W_tcp(t) - XXX should use BETA defines */
w_tcp = tp->snd_cubic_wmax * 4 / 5 +
/* Compute W_tcp(t) */
w_tcp = tp->snd_cubic_wmax * CUBIC_BETAA / CUBIC_BETAB +
ms_elapsed / rtt / 3;
if (tp->snd_cwnd > w_tcp) {
/* Not in TCP mode */
tp->snd_cwnd += (tcp_cubic_getW(tp) - tp->snd_cwnd) /
tp->snd_cwnd;
/* Not in TCP friendly mode */
tp->snd_cwnd += (tcp_cubic_getW(tp, ms_elapsed, rtt) -
tp->snd_cwnd) / tp->snd_cwnd;
} else {
/* friendly TCP mode */
tp->snd_cwnd = w_tcp;
@ -955,10 +967,17 @@ static void
tcp_cubic_slow_retransmit(struct tcpcb *tp)
{
/* Reset */
tp->snd_cubic_wmax = tp->snd_cubic_wmax_last = tp->snd_cubic_ctime = 0;
/* Timeout - Mark new congestion */
tcp_cubic_congestion_exp(tp);
tcp_reno_slow_retransmit(tp);
/* Loss Window MUST be one segment. */
tp->snd_cwnd = tp->t_segsz;
tp->t_partialacks = -1;
tp->t_dupacks = 0;
tp->t_bytes_acked = 0;
if (TCP_ECN_ALLOWED(tp))
tp->t_flags |= TF_ECN_SND_CWR;
}
const struct tcp_congctl tcp_cubic_ctl = {