diff options
Diffstat (limited to 'net')
| -rw-r--r-- | net/ipv4/Kconfig | 15 | ||||
| -rw-r--r-- | net/ipv4/Makefile | 1 | ||||
| -rw-r--r-- | net/ipv4/tcp_westwood.c | 259 |
3 files changed, 275 insertions, 0 deletions
diff --git a/net/ipv4/Kconfig b/net/ipv4/Kconfig index 712ebacacb6..adbe855d931 100644 --- a/net/ipv4/Kconfig +++ b/net/ipv4/Kconfig @@ -452,6 +452,21 @@ config TCP_CONG_BIC increase provides TCP friendliness. See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/ +config TCP_CONG_WESTWOOD + tristate "TCP Westwood+" + depends on INET + default m + ---help--- + TCP Westwood+ is a sender-side only modification of the TCP Reno + protocol stack that optimizes the performance of TCP congestion + control. It is based on end-to-end bandwidth estimation to set + congestion window and slow start threshold after a congestion + episode. Using this estimation, TCP Westwood+ adaptively sets a + slow start threshold and a congestion window which takes into + account the bandwidth used at the time congestion is experienced. + TCP Westwood+ significantly increases fairness wrt TCP Reno in + wired networks and throughput over wireless links. + endmenu source "net/ipv4/ipvs/Kconfig" diff --git a/net/ipv4/Makefile b/net/ipv4/Makefile index 1d1cac5ac06..dedfbe62a10 100644 --- a/net/ipv4/Makefile +++ b/net/ipv4/Makefile @@ -32,6 +32,7 @@ obj-$(CONFIG_IP_VS) += ipvs/ obj-$(CONFIG_IP_TCPDIAG) += tcp_diag.o obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o +obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \ xfrm4_output.o diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c new file mode 100644 index 00000000000..ef827242c94 --- /dev/null +++ b/net/ipv4/tcp_westwood.c @@ -0,0 +1,259 @@ +/* + * TCP Westwood+ + * + * Angelo Dell'Aera: TCP Westwood+ support + */ + +#include <linux/config.h> +#include <linux/mm.h> +#include <linux/module.h> +#include <linux/skbuff.h> +#include <linux/tcp_diag.h> +#include <net/tcp.h> + +/* TCP Westwood structure */ +struct westwood { + u32 bw_ns_est; /* first bandwidth estimation..not too smoothed 8) */ + u32 bw_est; /* bandwidth estimate */ + u32 rtt_win_sx; /* here starts a new evaluation... */ + u32 bk; + u32 snd_una; /* used for evaluating the number of acked bytes */ + u32 cumul_ack; + u32 accounted; + u32 rtt; + u32 rtt_min; /* minimum observed RTT */ +}; + + +/* TCP Westwood functions and constants */ +#define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */ +#define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */ + +/* + * @tcp_westwood_create + * This function initializes fields used in TCP Westwood+, + * it is called after the initial SYN, so the sequence numbers + * are correct but new passive connections we have no + * information about RTTmin at this time so we simply set it to + * TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative + * since in this way we're sure it will be updated in a consistent + * way as soon as possible. It will reasonably happen within the first + * RTT period of the connection lifetime. + */ +static void tcp_westwood_init(struct tcp_sock *tp) +{ + struct westwood *w = tcp_ca(tp); + + w->bk = 0; + w->bw_ns_est = 0; + w->bw_est = 0; + w->accounted = 0; + w->cumul_ack = 0; + w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT; + w->rtt_win_sx = tcp_time_stamp; + w->snd_una = tp->snd_una; +} + +/* + * @westwood_do_filter + * Low-pass filter. Implemented using constant coefficients. + */ +static inline u32 westwood_do_filter(u32 a, u32 b) +{ + return (((7 * a) + b) >> 3); +} + +static inline 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); +} + +/* + * @westwood_pkts_acked + * Called after processing group of packets. + * but all westwood needs is the last sample of srtt. + */ +static void tcp_westwood_pkts_acked(struct tcp_sock *tp, u32 cnt) +{ + struct westwood *w = tcp_ca(tp); + if (cnt > 0) + w->rtt = tp->srtt >> 3; +} + +/* + * @westwood_update_window + * It updates RTT evaluation window if it is the right moment to do + * it. If so it calls filter for evaluating bandwidth. + */ +static void westwood_update_window(struct tcp_sock *tp) +{ + struct westwood *w = tcp_ca(tp); + s32 delta = tcp_time_stamp - w->rtt_win_sx; + + /* + * See if a RTT-window has passed. + * Be careful since if RTT is less than + * 50ms we don't filter but we continue 'building the sample'. + * This minimum limit was chosen since an estimation on small + * time intervals is better to avoid... + * Obviously on a LAN we reasonably will always have + * right_bound = left_bound + WESTWOOD_RTT_MIN + */ + if (w->rtt && delta > max_t(u32, w->rtt, TCP_WESTWOOD_RTT_MIN)) { + westwood_filter(w, delta); + + w->bk = 0; + w->rtt_win_sx = tcp_time_stamp; + } +} + +/* + * @westwood_fast_bw + * It is called when we are in fast path. In particular it is called when + * header prediction is successful. In such case in fact update is + * straight forward and doesn't need any particular care. + */ +static inline void westwood_fast_bw(struct tcp_sock *tp) +{ + struct westwood *w = tcp_ca(tp); + + westwood_update_window(tp); + + w->bk += tp->snd_una - w->snd_una; + w->snd_una = tp->snd_una; + w->rtt_min = min(w->rtt, w->rtt_min); +} + +/* + * @westwood_acked_count + * This function evaluates cumul_ack for evaluating bk in case of + * delayed or partial acks. + */ +static inline u32 westwood_acked_count(struct tcp_sock *tp) +{ + struct westwood *w = tcp_ca(tp); + + w->cumul_ack = tp->snd_una - w->snd_una; + + /* If cumul_ack is 0 this is a dupack since it's not moving + * tp->snd_una. + */ + if (!w->cumul_ack) { + w->accounted += tp->mss_cache; + w->cumul_ack = tp->mss_cache; + } + + if (w->cumul_ack > tp->mss_cache) { + /* Partial or delayed ack */ + if (w->accounted >= w->cumul_ack) { + w->accounted -= w->cumul_ack; + w->cumul_ack = tp->mss_cache; + } else { + w->cumul_ack -= w->accounted; + w->accounted = 0; + } + } + + w->snd_una = tp->snd_una; + + return w->cumul_ack; +} + +static inline u32 westwood_bw_rttmin(const struct tcp_sock *tp) +{ + struct westwood *w = tcp_ca(tp); + return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2); +} + +/* + * TCP Westwood + * Here limit is evaluated as Bw estimation*RTTmin (for obtaining it + * in packets we use mss_cache). Rttmin is guaranteed to be >= 2 + * so avoids ever returning 0. + */ +static u32 tcp_westwood_cwnd_min(struct tcp_sock *tp) +{ + return westwood_bw_rttmin(tp); +} + +static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event) +{ + struct westwood *w = tcp_ca(tp); + + switch(event) { + case CA_EVENT_FAST_ACK: + westwood_fast_bw(tp); + break; + + case CA_EVENT_COMPLETE_CWR: + tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(tp); + break; + + case CA_EVENT_FRTO: + tp->snd_ssthresh = westwood_bw_rttmin(tp); + break; + + case CA_EVENT_SLOW_ACK: + westwood_update_window(tp); + w->bk += westwood_acked_count(tp); + w->rtt_min = min(w->rtt, w->rtt_min); + break; + + default: + /* don't care */ + break; + } +} + + +/* Extract info for Tcp socket info provided via netlink. */ +static void tcp_westwood_info(struct tcp_sock *tp, u32 ext, + struct sk_buff *skb) +{ + const struct westwood *ca = tcp_ca(tp); + if (ext & (1<<(TCPDIAG_VEGASINFO-1))) { + struct rtattr *rta; + struct tcpvegas_info *info; + + rta = __RTA_PUT(skb, TCPDIAG_VEGASINFO, sizeof(*info)); + info = RTA_DATA(rta); + info->tcpv_enabled = 1; + info->tcpv_rttcnt = 0; + info->tcpv_rtt = jiffies_to_usecs(ca->rtt); + info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min); + rtattr_failure: ; + } +} + + +static struct tcp_congestion_ops tcp_westwood = { + .init = tcp_westwood_init, + .ssthresh = tcp_reno_ssthresh, + .cong_avoid = tcp_reno_cong_avoid, + .min_cwnd = tcp_westwood_cwnd_min, + .cwnd_event = tcp_westwood_event, + .get_info = tcp_westwood_info, + .pkts_acked = tcp_westwood_pkts_acked, + + .owner = THIS_MODULE, + .name = "westwood" +}; + +static int __init tcp_westwood_register(void) +{ + BUG_ON(sizeof(struct westwood) > TCP_CA_PRIV_SIZE); + return tcp_register_congestion_control(&tcp_westwood); +} + +static void __exit tcp_westwood_unregister(void) +{ + tcp_unregister_congestion_control(&tcp_westwood); +} + +module_init(tcp_westwood_register); +module_exit(tcp_westwood_unregister); + +MODULE_AUTHOR("Stephen Hemminger, Angelo Dell'Aera"); +MODULE_LICENSE("GPL"); +MODULE_DESCRIPTION("TCP Westwood+"); |