I cleaned these up and put them in a git tree. Luco if you want to be the
maintainer of this, then the correct way is to send a patch to the MAINTAINER
file.
---
The following changes since commit bd6673d239e7041bc3f81f8d6d0242b7bf6dd62f:
Andreas Schwab:
[CONNECTOR]: Fix warning in cn_queue.c
are found in the git repository at:
git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/tcp-2.6.18.git#tcp
Luca De Cicco:
TCP Westwood: comment fixes
TCP Westwood: bandwidth filter startup
TCP Westwood: reset RTT min after FRTO
Stephen Hemminger:
TCP Westwood: fix first sample
net/ipv4/tcp_westwood.c | 62 ++-
1 files changed, 55 insertions(+), 7 deletions(-)
diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c
index 62a96b7..4247da1 100644
--- a/net/ipv4/tcp_westwood.c
+++ b/net/ipv4/tcp_westwood.c
@@ -1,7 +1,24 @@
/*
- * TCP Westwood+
+ * TCP Westwood+: end-to-end bandwidth estimation for TCP
*
- * Angelo Dell'Aera: TCP Westwood+ support
+ * Angelo Dell'Aera: author of the first version of TCP Westwood+ in
Linux 2.4
+ *
+ * Support at http://c3lab.poliba.it/index.php/Westwood
+ * Main references in literature:
+ *
+ * - Mascolo S, Casetti, M. Gerla et al.
+ * TCP Westwood: bandwidth estimation for TCP Proc. ACM Mobicom 2001
+ *
+ * - A. Grieco, s. Mascolo
+ * Performance evaluation of New Reno, Vegas, Westwood+ TCP ACM Computer
+ * Comm. Review, 2004
+ *
+ * - A. Dell'Aera, L. Grieco, S. Mascolo.
+ * Linux 2.4 Implementation of Westwood+ TCP with Rate-Halving :
+ *A Performance Evaluation Over the Internet (ICC 2004), Paris, June 2004
+ *
+ * Westwood+ employs end-to-end bandwidth measurement to set cwnd and
+ * ssthresh after packet loss. The probing phase is as the original Reno.
*/
#include linux/config.h
@@ -23,6 +40,7 @@ struct westwood {
u32rtt;
u32rtt_min; /* minimum observed RTT */
u8 first_ack;/* flag which infers that this is the first
ack */
+ u8 reset_rtt_min;/* Reset RTT min to next RTT sample*/
};
@@ -50,6 +68,7 @@ static void tcp_westwood_init(struct soc
w-bw_est = 0;
w-accounted = 0;
w-cumul_ack = 0;
+ w-reset_rtt_min = 1;
w-rtt_min = w-rtt = TCP_WESTWOOD_INIT_RTT;
w-rtt_win_sx = tcp_time_stamp;
w-snd_una = tcp_sk(sk)-snd_una;
@@ -65,10 +84,16 @@ static inline u32 westwood_do_filter(u32
return (((7 * a) + b) 3);
}
-static inline void westwood_filter(struct westwood *w, u32 delta)
+static void westwood_filter(struct westwood *w, u32 delta)
{
- w-bw_ns_est = westwood_do_filter(w-bw_ns_est, w-bk / delta);
- w-bw_est = westwood_do_filter(w-bw_est, w-bw_ns_est);
+ /* If the filter is empty fill it with the first sample of bandwidth */
+ if (w-bw_ns_est == 0 w-bw_est == 0) {
+ w-bw_ns_est = w-bk / delta;
+ w-bw_est = w-bw_ns_est;
+ } else {
+ w-bw_ns_est = westwood_do_filter(w-bw_ns_est, w-bk / delta);
+ w-bw_est = westwood_do_filter(w-bw_est, w-bw_ns_est);
+ }
}
/*
@@ -93,7 +118,7 @@ static void westwood_update_window(struc
struct westwood *w = inet_csk_ca(sk);
s32 delta = tcp_time_stamp - w-rtt_win_sx;
- /* Initialise w-snd_una with the first acked sequence number in order
+ /* Initialize w-snd_una with the first acked sequence number in order
* to fix mismatch between tp-snd_una and w-snd_una for the first
* bandwidth sample
*/
@@ -119,6 +144,16 @@ static void westwood_update_window(struc
}
}
+static inline void update_rtt_min(struct westwood *w)
+{
+ if (w-reset_rtt_min) {
+ w-rtt_min = w-rtt;
+ w-reset_rtt_min = 0;
+ } else
+ w-rtt_min = min(w-rtt, w-rtt_min);
+}
+
+
/*
* @westwood_fast_bw
* It is called when we are in fast path. In particular it is called when
@@ -134,7 +169,7 @@ static inline void westwood_fast_bw(stru
w-bk += tp-snd_una - w-snd_una;
w-snd_una = tp-snd_una;
- w-rtt_min = min(w-rtt, w-rtt_min);
+ update_rtt_min(w);
}
/*
@@ -191,7 +226,7 @@ static void tcp_westwood_event(struct so
{
struct tcp_sock *tp = tcp_sk(sk);
struct westwood *w = inet_csk_ca(sk);
-
+
switch(event) {
case CA_EVENT_FAST_ACK:
westwood_fast_bw(sk);
@@ -203,12 +238,14 @@ static void tcp_westwood_event(struct so
case CA_EVENT_FRTO:
tp-snd_ssthresh = tcp_westwood_bw_rttmin(sk);
+ /* Update RTT_min when next ack arrives */
+ w-reset_rtt_min = 1;
break;
case CA_EVENT_SLOW_ACK:
westwood_update_window(sk);
w-bk += westwood_acked_count(sk);
- w-rtt_min = min(w-rtt, w-rtt_min);
+
