Bringing back up this old topic:
http://marc.theaimsgroup.com/?l=linux-netdev&m=114564962420171&w=2
I've decided to add this tunable to the net-2.6.18 tree, patch below.
The more I think about it, allowing it to be turned off is
reasonable, but it will be left on by default.
diff-tree 1cd14da556199b2827a92f1eaa9d3e8411c2b68d (from
2fa95182e211572e998c7d1f906aa74fb119b025)
Author: David S. Miller <[EMAIL PROTECTED]>
Date: Tue Jun 13 22:33:04 2006 -0700
[TCP]: Add tcp_slow_start_after_idle sysctl.
A lot of people have asked for a way to disable tcp_cwnd_restart(),
and it seems reasonable to add a sysctl to do that.
Signed-off-by: David S. Miller <[EMAIL PROTECTED]>
diff --git a/Documentation/networking/ip-sysctl.txt
b/Documentation/networking/ip-sysctl.txt
index f12007b..d46338a 100644
--- a/Documentation/networking/ip-sysctl.txt
+++ b/Documentation/networking/ip-sysctl.txt
@@ -362,6 +362,13 @@ tcp_workaround_signed_windows - BOOLEAN
not receive a window scaling option from them.
Default: 0
+tcp_slow_start_after_idle - BOOLEAN
+ If set, provide RFC2861 behavior and time out the congestion
+ window after an idle period. An idle period is defined at
+ the current RTO. If unset, the congestion window will not
+ be timed out after an idle period.
+ Default: 1
+
IP Variables:
ip_local_port_range - 2 INTEGERS
diff --git a/include/linux/sysctl.h b/include/linux/sysctl.h
index 98338ed..cee944d 100644
--- a/include/linux/sysctl.h
+++ b/include/linux/sysctl.h
@@ -405,6 +405,7 @@ enum
NET_TCP_BASE_MSS=114,
NET_IPV4_TCP_WORKAROUND_SIGNED_WINDOWS=115,
NET_TCP_DMA_COPYBREAK=116,
+ NET_TCP_SLOW_START_AFTER_IDLE=117,
};
enum {
diff --git a/include/net/tcp.h b/include/net/tcp.h
index de88c54..bfc71f9 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -227,6 +227,7 @@ extern int sysctl_tcp_abc;
extern int sysctl_tcp_mtu_probing;
extern int sysctl_tcp_base_mss;
extern int sysctl_tcp_workaround_signed_windows;
+extern int sysctl_tcp_slow_start_after_idle;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index e7fb665..ce4cd5f 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -690,6 +690,14 @@ ctl_table ipv4_table[] = {
.proc_handler = &proc_dointvec
},
#endif
+ {
+ .ctl_name = NET_TCP_SLOW_START_AFTER_IDLE,
+ .procname = "tcp_slow_start_after_idle",
+ .data = &sysctl_tcp_slow_start_after_idle,
+ .maxlen = sizeof(int),
+ .mode = 0644,
+ .proc_handler = &proc_dointvec
+ },
{ .ctl_name = 0 }
};
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 743016b..be6d929 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -59,6 +59,9 @@ int sysctl_tcp_tso_win_divisor = 3;
int sysctl_tcp_mtu_probing = 0;
int sysctl_tcp_base_mss = 512;
+/* By default, RFC2861 behavior. */
+int sysctl_tcp_slow_start_after_idle = 1;
+
static void update_send_head(struct sock *sk, struct tcp_sock *tp,
struct sk_buff *skb)
{
@@ -138,7 +141,8 @@ static void tcp_event_data_sent(struct t
struct inet_connection_sock *icsk = inet_csk(sk);
const u32 now = tcp_time_stamp;
- if (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto)
+ if (sysctl_tcp_slow_start_after_idle &&
+ (!tp->packets_out && (s32)(now - tp->lsndtime) > icsk->icsk_rto))
tcp_cwnd_restart(sk, __sk_dst_get(sk));
tp->lsndtime = now;
-
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