[TCP]: Appropriate Byte Count support
This is an updated version of the RFC3465 ABC patch originally
for Linux 2.6.11-rc4 by Yee-Ting Li. ABC is a way of counting
bytes ack'd rather than packets when updating congestion control.
The orignal ABC described in the RFC applied to a Reno style
algorithm. For advanced congestion control there is little
change after leaving slow start.
Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 54c39988..44ba4a2 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -218,6 +218,7 @@
extern int sysctl_tcp_nometrics_save;
extern int sysctl_tcp_moderate_rcvbuf;
extern int sysctl_tcp_tso_win_divisor;
+extern int sysctl_tcp_abc;
extern atomic_t tcp_memory_allocated;
extern atomic_t tcp_sockets_allocated;
@@ -770,6 +771,23 @@
*/
static inline void tcp_slow_start(struct tcp_sock *tp)
{
+ if (sysctl_tcp_abc) {
+ /* RFC3465: Slow Start
+ * TCP sender SHOULD increase cwnd by the number of
+ * previously unacknowledged bytes ACKed by each incoming
+ * acknowledgment, provided the increase is not more than L
+ */
+ if (tp->bytes_acked < tp->mss_cache)
+ return;
+
+ /* We MAY increase by 2 if discovered delayed ack */
+ if (sysctl_tcp_abc > 1 && tp->bytes_acked > 2*tp->mss_cache) {
+ if (tp->snd_cwnd < tp->snd_cwnd_clamp)
+ tp->snd_cwnd++;
+ }
+ }
+ tp->bytes_acked = 0;
+
if (tp->snd_cwnd < tp->snd_cwnd_clamp)
tp->snd_cwnd++;
}
@@ -804,6 +822,7 @@
struct tcp_sock *tp = tcp_sk(sk);
tp->prior_ssthresh = 0;
+ tp->bytes_acked = 0;
if (inet_csk(sk)->icsk_ca_state < TCP_CA_CWR) {
__tcp_enter_cwr(sk);
tcp_set_ca_state(sk, TCP_CA_CWR);