# This is a BitKeeper generated diff -Nru style patch.
#
# ChangeSet
#   2004/09/30 20:09:28-07:00 davem@nuts.davemloft.net 
#   [TCP]: Add tcp_tso_win_divisor sysctl.
#   
#   This allows control over what percentage of
#   the congestion window can be consumed by a
#   single TSO frame.
#   
#   The setting of this parameter is a choice
#   between burstiness and building larger TSO
#   frames.
#   
#   Signed-off-by: David S. Miller <davem@davemloft.net>
# 
# net/ipv4/tcp_output.c
#   2004/09/30 20:07:20-07:00 davem@nuts.davemloft.net +19 -7
#   [TCP]: Add tcp_tso_win_divisor sysctl.
# 
# net/ipv4/sysctl_net_ipv4.c
#   2004/09/30 20:07:20-07:00 davem@nuts.davemloft.net +8 -0
#   [TCP]: Add tcp_tso_win_divisor sysctl.
# 
# include/net/tcp.h
#   2004/09/30 20:07:20-07:00 davem@nuts.davemloft.net +1 -0
#   [TCP]: Add tcp_tso_win_divisor sysctl.
# 
# include/linux/sysctl.h
#   2004/09/30 20:07:20-07:00 davem@nuts.davemloft.net +1 -0
#   [TCP]: Add tcp_tso_win_divisor sysctl.
# 
diff -Nru a/include/linux/sysctl.h b/include/linux/sysctl.h
--- a/include/linux/sysctl.h	2004-09-30 21:03:00 -07:00
+++ b/include/linux/sysctl.h	2004-09-30 21:03:00 -07:00
@@ -341,6 +341,7 @@
 	NET_TCP_BIC_LOW_WINDOW=104,
 	NET_TCP_DEFAULT_WIN_SCALE=105,
 	NET_TCP_MODERATE_RCVBUF=106,
+	NET_TCP_TSO_WIN_DIVISOR=107,
 };
 
 enum {
diff -Nru a/include/net/tcp.h b/include/net/tcp.h
--- a/include/net/tcp.h	2004-09-30 21:03:00 -07:00
+++ b/include/net/tcp.h	2004-09-30 21:03:00 -07:00
@@ -609,6 +609,7 @@
 extern int sysctl_tcp_bic_fast_convergence;
 extern int sysctl_tcp_bic_low_window;
 extern int sysctl_tcp_moderate_rcvbuf;
+extern int sysctl_tcp_tso_win_divisor;
 
 extern atomic_t tcp_memory_allocated;
 extern atomic_t tcp_sockets_allocated;
diff -Nru a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
--- a/net/ipv4/sysctl_net_ipv4.c	2004-09-30 21:03:01 -07:00
+++ b/net/ipv4/sysctl_net_ipv4.c	2004-09-30 21:03:01 -07:00
@@ -674,6 +674,14 @@
 		.mode		= 0644,
 		.proc_handler	= &proc_dointvec,
 	},
+	{
+		.ctl_name	= NET_TCP_TSO_WIN_DIVISOR,
+		.procname	= "tcp_tso_win_divisor",
+		.data		= &sysctl_tcp_tso_win_divisor,
+		.maxlen		= sizeof(int),
+		.mode		= 0644,
+		.proc_handler	= &proc_dointvec,
+	},
 	{ .ctl_name = 0 }
 };
 
diff -Nru a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
--- a/net/ipv4/tcp_output.c	2004-09-30 21:03:00 -07:00
+++ b/net/ipv4/tcp_output.c	2004-09-30 21:03:01 -07:00
@@ -45,6 +45,12 @@
 /* People can turn this off for buggy TCP's found in printers etc. */
 int sysctl_tcp_retrans_collapse = 1;
 
+/* This limits the percentage of the congestion window which we
+ * will allow a single TSO frame to consume.  Building TSO frames
+ * which are too large can cause TCP streams to be bursty.
+ */
+int sysctl_tcp_tso_win_divisor = 8;
+
 static __inline__
 void update_send_head(struct sock *sk, struct tcp_opt *tp, struct sk_buff *skb)
 {
@@ -658,7 +664,7 @@
 {
 	struct tcp_opt *tp = tcp_sk(sk);
 	struct dst_entry *dst = __sk_dst_get(sk);
-	int do_large, mss_now;
+	unsigned int do_large, mss_now;
 
 	mss_now = tp->mss_cache_std;
 	if (dst) {
@@ -673,7 +679,7 @@
 		    !tp->urg_mode);
 
 	if (do_large) {
-		int large_mss, factor;
+		unsigned int large_mss, factor, limit;
 
 		large_mss = 65535 - tp->af_specific->net_header_len -
 			tp->ext_header_len - tp->ext2_header_len -
@@ -683,13 +689,19 @@
 			large_mss = max((tp->max_window>>1),
 					68U - tp->tcp_header_len);
 
+		factor = large_mss / mss_now;
+
 		/* Always keep large mss multiple of real mss, but
-		 * do not exceed 1/4 of the congestion window so we
-		 * can keep the ACK clock ticking.
+		 * do not exceed 1/tso_win_divisor of the congestion window
+		 * so we can keep the ACK clock ticking and minimize
+		 * bursting.
 		 */
-		factor = large_mss / mss_now;
-		if (factor > (tp->snd_cwnd >> 2))
-			factor = max(1, tp->snd_cwnd >> 2);
+		limit = tp->snd_cwnd;
+		if (sysctl_tcp_tso_win_divisor)
+			limit /= sysctl_tcp_tso_win_divisor;
+		limit = max(1U, limit);
+		if (factor > limit)
+			factor = limit;
 
 		tp->mss_cache = mss_now * factor;