[TCP]: Add TCP Westwood congestion control module.
This is the existing 2.6.12 Westwood code moved from tcp_input to the new congestion framework. A lot of the inline functions have been eliminated to try and make it clearer. Signed-off-by: Stephen Hemminger <shemminger@osdl.org> Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Stephen Hemminger
David S. Miller
Родитель
83803034f4
Коммит
8727076289
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@ -452,6 +452,21 @@ config TCP_CONG_BIC
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increase provides TCP friendliness.
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See http://www.csc.ncsu.edu/faculty/rhee/export/bitcp/
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config TCP_CONG_WESTWOOD
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tristate "TCP Westwood+"
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depends on INET
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default m
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---help---
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TCP Westwood+ is a sender-side only modification of the TCP Reno
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protocol stack that optimizes the performance of TCP congestion
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control. It is based on end-to-end bandwidth estimation to set
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congestion window and slow start threshold after a congestion
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episode. Using this estimation, TCP Westwood+ adaptively sets a
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slow start threshold and a congestion window which takes into
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account the bandwidth used at the time congestion is experienced.
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TCP Westwood+ significantly increases fairness wrt TCP Reno in
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wired networks and throughput over wireless links.
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endmenu
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source "net/ipv4/ipvs/Kconfig"
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@ -32,6 +32,7 @@ obj-$(CONFIG_IP_VS) += ipvs/
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obj-$(CONFIG_IP_TCPDIAG) += tcp_diag.o
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obj-$(CONFIG_IP_ROUTE_MULTIPATH_CACHED) += multipath.o
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obj-$(CONFIG_TCP_CONG_BIC) += tcp_bic.o
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obj-$(CONFIG_TCP_CONG_WESTWOOD) += tcp_westwood.o
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obj-$(CONFIG_XFRM) += xfrm4_policy.o xfrm4_state.o xfrm4_input.o \
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xfrm4_output.o
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@ -0,0 +1,259 @@
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/*
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* TCP Westwood+
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*
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* Angelo Dell'Aera: TCP Westwood+ support
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*/
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#include <linux/config.h>
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#include <linux/mm.h>
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#include <linux/module.h>
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#include <linux/skbuff.h>
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#include <linux/tcp_diag.h>
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#include <net/tcp.h>
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/* TCP Westwood structure */
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struct westwood {
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u32 bw_ns_est; /* first bandwidth estimation..not too smoothed 8) */
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u32 bw_est; /* bandwidth estimate */
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u32 rtt_win_sx; /* here starts a new evaluation... */
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u32 bk;
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u32 snd_una; /* used for evaluating the number of acked bytes */
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u32 cumul_ack;
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u32 accounted;
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u32 rtt;
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u32 rtt_min; /* minimum observed RTT */
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};
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/* TCP Westwood functions and constants */
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#define TCP_WESTWOOD_RTT_MIN (HZ/20) /* 50ms */
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#define TCP_WESTWOOD_INIT_RTT (20*HZ) /* maybe too conservative?! */
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/*
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* @tcp_westwood_create
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* This function initializes fields used in TCP Westwood+,
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* it is called after the initial SYN, so the sequence numbers
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* are correct but new passive connections we have no
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* information about RTTmin at this time so we simply set it to
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* TCP_WESTWOOD_INIT_RTT. This value was chosen to be too conservative
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* since in this way we're sure it will be updated in a consistent
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* way as soon as possible. It will reasonably happen within the first
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* RTT period of the connection lifetime.
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*/
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static void tcp_westwood_init(struct tcp_sock *tp)
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{
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struct westwood *w = tcp_ca(tp);
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w->bk = 0;
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w->bw_ns_est = 0;
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w->bw_est = 0;
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w->accounted = 0;
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w->cumul_ack = 0;
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w->rtt_min = w->rtt = TCP_WESTWOOD_INIT_RTT;
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w->rtt_win_sx = tcp_time_stamp;
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w->snd_una = tp->snd_una;
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}
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/*
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* @westwood_do_filter
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* Low-pass filter. Implemented using constant coefficients.
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*/
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static inline u32 westwood_do_filter(u32 a, u32 b)
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{
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return (((7 * a) + b) >> 3);
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}
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static inline void westwood_filter(struct westwood *w, u32 delta)
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{
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w->bw_ns_est = westwood_do_filter(w->bw_ns_est, w->bk / delta);
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w->bw_est = westwood_do_filter(w->bw_est, w->bw_ns_est);
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}
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/*
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* @westwood_pkts_acked
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* Called after processing group of packets.
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* but all westwood needs is the last sample of srtt.
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*/
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static void tcp_westwood_pkts_acked(struct tcp_sock *tp, u32 cnt)
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{
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struct westwood *w = tcp_ca(tp);
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if (cnt > 0)
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w->rtt = tp->srtt >> 3;
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}
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/*
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* @westwood_update_window
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* It updates RTT evaluation window if it is the right moment to do
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* it. If so it calls filter for evaluating bandwidth.
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*/
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static void westwood_update_window(struct tcp_sock *tp)
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{
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struct westwood *w = tcp_ca(tp);
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s32 delta = tcp_time_stamp - w->rtt_win_sx;
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/*
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* See if a RTT-window has passed.
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* Be careful since if RTT is less than
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* 50ms we don't filter but we continue 'building the sample'.
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* This minimum limit was chosen since an estimation on small
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* time intervals is better to avoid...
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* Obviously on a LAN we reasonably will always have
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* right_bound = left_bound + WESTWOOD_RTT_MIN
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*/
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if (w->rtt && delta > max_t(u32, w->rtt, TCP_WESTWOOD_RTT_MIN)) {
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westwood_filter(w, delta);
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w->bk = 0;
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w->rtt_win_sx = tcp_time_stamp;
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}
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}
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/*
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* @westwood_fast_bw
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* It is called when we are in fast path. In particular it is called when
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* header prediction is successful. In such case in fact update is
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* straight forward and doesn't need any particular care.
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*/
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static inline void westwood_fast_bw(struct tcp_sock *tp)
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{
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struct westwood *w = tcp_ca(tp);
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westwood_update_window(tp);
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w->bk += tp->snd_una - w->snd_una;
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w->snd_una = tp->snd_una;
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w->rtt_min = min(w->rtt, w->rtt_min);
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}
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/*
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* @westwood_acked_count
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* This function evaluates cumul_ack for evaluating bk in case of
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* delayed or partial acks.
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*/
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static inline u32 westwood_acked_count(struct tcp_sock *tp)
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{
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struct westwood *w = tcp_ca(tp);
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w->cumul_ack = tp->snd_una - w->snd_una;
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/* If cumul_ack is 0 this is a dupack since it's not moving
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* tp->snd_una.
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*/
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if (!w->cumul_ack) {
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w->accounted += tp->mss_cache;
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w->cumul_ack = tp->mss_cache;
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}
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if (w->cumul_ack > tp->mss_cache) {
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/* Partial or delayed ack */
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if (w->accounted >= w->cumul_ack) {
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w->accounted -= w->cumul_ack;
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w->cumul_ack = tp->mss_cache;
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} else {
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w->cumul_ack -= w->accounted;
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w->accounted = 0;
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}
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}
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w->snd_una = tp->snd_una;
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return w->cumul_ack;
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}
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static inline u32 westwood_bw_rttmin(const struct tcp_sock *tp)
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{
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struct westwood *w = tcp_ca(tp);
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return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2);
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}
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/*
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* TCP Westwood
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* Here limit is evaluated as Bw estimation*RTTmin (for obtaining it
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* in packets we use mss_cache). Rttmin is guaranteed to be >= 2
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* so avoids ever returning 0.
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*/
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static u32 tcp_westwood_cwnd_min(struct tcp_sock *tp)
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{
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return westwood_bw_rttmin(tp);
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}
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static void tcp_westwood_event(struct tcp_sock *tp, enum tcp_ca_event event)
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{
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struct westwood *w = tcp_ca(tp);
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switch(event) {
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case CA_EVENT_FAST_ACK:
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westwood_fast_bw(tp);
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break;
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case CA_EVENT_COMPLETE_CWR:
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tp->snd_cwnd = tp->snd_ssthresh = westwood_bw_rttmin(tp);
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break;
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case CA_EVENT_FRTO:
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tp->snd_ssthresh = westwood_bw_rttmin(tp);
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break;
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case CA_EVENT_SLOW_ACK:
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westwood_update_window(tp);
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w->bk += westwood_acked_count(tp);
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w->rtt_min = min(w->rtt, w->rtt_min);
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break;
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default:
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/* don't care */
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break;
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}
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}
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/* Extract info for Tcp socket info provided via netlink. */
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static void tcp_westwood_info(struct tcp_sock *tp, u32 ext,
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struct sk_buff *skb)
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{
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const struct westwood *ca = tcp_ca(tp);
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if (ext & (1<<(TCPDIAG_VEGASINFO-1))) {
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struct rtattr *rta;
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struct tcpvegas_info *info;
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rta = __RTA_PUT(skb, TCPDIAG_VEGASINFO, sizeof(*info));
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info = RTA_DATA(rta);
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info->tcpv_enabled = 1;
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info->tcpv_rttcnt = 0;
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info->tcpv_rtt = jiffies_to_usecs(ca->rtt);
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info->tcpv_minrtt = jiffies_to_usecs(ca->rtt_min);
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rtattr_failure: ;
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}
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}
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static struct tcp_congestion_ops tcp_westwood = {
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.init = tcp_westwood_init,
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.ssthresh = tcp_reno_ssthresh,
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.cong_avoid = tcp_reno_cong_avoid,
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.min_cwnd = tcp_westwood_cwnd_min,
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.cwnd_event = tcp_westwood_event,
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.get_info = tcp_westwood_info,
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.pkts_acked = tcp_westwood_pkts_acked,
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.owner = THIS_MODULE,
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.name = "westwood"
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};
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static int __init tcp_westwood_register(void)
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{
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BUG_ON(sizeof(struct westwood) > TCP_CA_PRIV_SIZE);
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return tcp_register_congestion_control(&tcp_westwood);
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}
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static void __exit tcp_westwood_unregister(void)
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{
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tcp_unregister_congestion_control(&tcp_westwood);
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}
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module_init(tcp_westwood_register);
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module_exit(tcp_westwood_unregister);
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MODULE_AUTHOR("Stephen Hemminger, Angelo Dell'Aera");
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MODULE_LICENSE("GPL");
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MODULE_DESCRIPTION("TCP Westwood+");
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