Date: Wed, 17 Jul 2002 22:44:39 -0700 (PDT) From: Matthew Dillon <dillon@apollo.backplane.com> To: Mike Silbersack <silby@silby.com> Cc: cvs-committers@FreeBSD.ORG, <cvs-all@FreeBSD.ORG> Subject: Re: cvs commit: src/sys/netinet tcp_timer.h Message-ID: <200207180544.g6I5idxA016066@apollo.backplane.com> References: <20020718001924.J83856-100000@patrocles.silby.com>
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Here's the proposed patch.
-Matt0
Index: tcp_subr.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/tcp_subr.c,v
retrieving revision 1.136
diff -u -r1.136 tcp_subr.c
--- tcp_subr.c 11 Jul 2002 23:18:43 -0000 1.136
+++ tcp_subr.c 18 Jul 2002 05:34:57 -0000
@@ -196,6 +196,8 @@
tcp_keepintvl = TCPTV_KEEPINTVL;
tcp_maxpersistidle = TCPTV_KEEP_IDLE;
tcp_msl = TCPTV_MSL;
+ tcp_rexmit_min = TCPTV_MIN;
+ tcp_rexmit_slop = TCPTV_CPU_VAR;
INP_INFO_LOCK_INIT(&tcbinfo, "tcp");
LIST_INIT(&tcb);
@@ -542,7 +544,7 @@
*/
tp->t_srtt = TCPTV_SRTTBASE;
tp->t_rttvar = ((TCPTV_RTOBASE - TCPTV_SRTTBASE) << TCP_RTTVAR_SHIFT) / 4;
- tp->t_rttmin = TCPTV_MIN;
+ tp->t_rttmin = tcp_rexmit_min;
tp->t_rxtcur = TCPTV_RTOBASE;
tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT;
tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT;
Index: tcp_timer.c
===================================================================
RCS file: /home/ncvs/src/sys/netinet/tcp_timer.c,v
retrieving revision 1.51
diff -u -r1.51 tcp_timer.c
--- tcp_timer.c 10 Jun 2002 20:05:38 -0000 1.51
+++ tcp_timer.c 18 Jul 2002 05:34:57 -0000
@@ -109,6 +109,14 @@
SYSCTL_PROC(_net_inet_tcp, OID_AUTO, msl, CTLTYPE_INT|CTLFLAG_RW,
&tcp_msl, 0, sysctl_msec_to_ticks, "I", "Maximum segment lifetime");
+int tcp_rexmit_min;
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_min, CTLTYPE_INT|CTLFLAG_RW,
+ &tcp_rexmit_min, 0, sysctl_msec_to_ticks, "I", "Minimum Retransmission Timeout");
+
+int tcp_rexmit_slop;
+SYSCTL_PROC(_net_inet_tcp, OID_AUTO, rexmit_slop, CTLTYPE_INT|CTLFLAG_RW,
+ &tcp_rexmit_slop, 0, sysctl_msec_to_ticks, "I", "Retransmission Timer Slop");
+
static int always_keepalive = 1;
SYSCTL_INT(_net_inet_tcp, OID_AUTO, always_keepalive, CTLFLAG_RW,
&always_keepalive , 0, "Assume SO_KEEPALIVE on all TCP connections");
Index: tcp_timer.h
===================================================================
RCS file: /home/ncvs/src/sys/netinet/tcp_timer.h,v
retrieving revision 1.20
diff -u -r1.20 tcp_timer.h
--- tcp_timer.h 17 Jul 2002 23:32:03 -0000 1.20
+++ tcp_timer.h 18 Jul 2002 05:34:57 -0000
@@ -92,11 +92,18 @@
/*
* Minimum retransmit timer is 3 ticks, for algorithmic stability.
- * The maximum is 64 seconds. The prior minimum of 1*hz (1 second) badly
- * breaks throughput on any networks faster then a modem that has minor
- * (e.g. 1%) packet loss.
+ * TCPT_RANGESET() will add another TCPTV_CPU_VAR to deal with
+ * the expected worst-case processing variances by the kernels
+ * representing the end points. Such variances do not always show
+ * up in the srtt because the timestamp is often calculated at
+ * the interface rather then at the TCP layer. This value is
+ * typically 50ms.
+ *
+ * The prior minimum of 1*hz (1 second) badly breaks throughput on any
+ * networks faster then a modem that has minor (e.g. 1%) packet loss.
*/
#define TCPTV_MIN ( 3 ) /* minimum allowable value */
+#define TCPTV_CPU_VAR ( hz/20 ) /* cpu variance allowed (50ms) */
#define TCPTV_REXMTMAX ( 64*hz) /* max allowable REXMT value */
#define TCPTV_TWTRUNC 8 /* RTO factor to truncate TW */
@@ -116,7 +123,7 @@
* Force a time value to be in a certain range.
*/
#define TCPT_RANGESET(tv, value, tvmin, tvmax) do { \
- (tv) = (value); \
+ (tv) = (value) + tcp_rexmit_slop; \
if ((u_long)(tv) < (u_long)(tvmin)) \
(tv) = (tvmin); \
else if ((u_long)(tv) > (u_long)(tvmax)) \
@@ -130,6 +137,8 @@
extern int tcp_maxidle; /* time to drop after starting probes */
extern int tcp_delacktime; /* time before sending a delayed ACK */
extern int tcp_maxpersistidle;
+extern int tcp_rexmit_min;
+extern int tcp_rexmit_slop;
extern int tcp_msl;
extern int tcp_ttl; /* time to live for TCP segs */
extern int tcp_backoff[];
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