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authorkefren <kefren@NetBSD.org>2013-11-18 11:48:34 +0000
committerkefren <kefren@NetBSD.org>2013-11-18 11:48:34 +0000
commit339be3e11bebd60ccaf37da71cbdb0c2640d8ee2 (patch)
tree3761e66b4a373a0940c23426261af23fc903586f /sys
parentaf40279509c362f8e77e7c564b4a311dceca062e (diff)
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
Diffstat (limited to 'sys')
-rw-r--r--sys/netinet/tcp_congctl.c97
1 files changed, 58 insertions, 39 deletions
diff --git a/sys/netinet/tcp_congctl.c b/sys/netinet/tcp_congctl.c
index 82921f875f7..6f1aa464910 100644
--- a/sys/netinet/tcp_congctl.c
+++ b/sys/netinet/tcp_congctl.c
@@ -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 = {