From 7354c8c389d18719dd71cc810da70b0921d66694 Mon Sep 17 00:00:00 2001 From: Florian Westphal Date: Fri, 26 Sep 2014 22:37:34 +0200 Subject: [PATCH] net: tcp: split ack slow/fast events from cwnd_event The congestion control ops "cwnd_event" currently supports CA_EVENT_FAST_ACK and CA_EVENT_SLOW_ACK events (among others). Both FAST and SLOW_ACK are only used by Westwood congestion control algorithm. This removes both flags from cwnd_event and adds a new in_ack_event callback for this. The goal is to be able to provide more detailed information about ACKs, such as whether ECE flag was set, or whether the ACK resulted in a window update. It is required for DataCenter TCP (DCTCP) congestion control algorithm as it makes a different choice depending on ECE being set or not. Joint work with Daniel Borkmann and Glenn Judd. Signed-off-by: Florian Westphal Signed-off-by: Daniel Borkmann Signed-off-by: Glenn Judd Acked-by: Stephen Hemminger Signed-off-by: David S. Miller --- include/net/tcp.h | 8 ++++++-- net/ipv4/tcp_input.c | 12 ++++++++++-- net/ipv4/tcp_westwood.c | 28 ++++++++++++++++------------ 3 files changed, 32 insertions(+), 16 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index a12f145cfbc3..7ec6a28305c0 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -763,8 +763,10 @@ enum tcp_ca_event { CA_EVENT_CWND_RESTART, /* congestion window restart */ CA_EVENT_COMPLETE_CWR, /* end of congestion recovery */ CA_EVENT_LOSS, /* loss timeout */ - CA_EVENT_FAST_ACK, /* in sequence ack */ - CA_EVENT_SLOW_ACK, /* other ack */ +}; + +enum tcp_ca_ack_event_flags { + CA_ACK_SLOWPATH = (1 << 0), }; /* @@ -796,6 +798,8 @@ struct tcp_congestion_ops { void (*set_state)(struct sock *sk, u8 new_state); /* call when cwnd event occurs (optional) */ void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev); + /* call when ack arrives (optional) */ + void (*in_ack_event)(struct sock *sk, u32 flags); /* new value of cwnd after loss (optional) */ u32 (*undo_cwnd)(struct sock *sk); /* hook for packet ack accounting (optional) */ diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index fb0fe97e1c54..8a38774cc66e 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3362,6 +3362,14 @@ static void tcp_process_tlp_ack(struct sock *sk, u32 ack, int flag) } } +static inline void tcp_in_ack_event(struct sock *sk, u32 flags) +{ + const struct inet_connection_sock *icsk = inet_csk(sk); + + if (icsk->icsk_ca_ops->in_ack_event) + icsk->icsk_ca_ops->in_ack_event(sk, flags); +} + /* This routine deals with incoming acks, but not outgoing ones. */ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) { @@ -3421,7 +3429,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) tp->snd_una = ack; flag |= FLAG_WIN_UPDATE; - tcp_ca_event(sk, CA_EVENT_FAST_ACK); + tcp_in_ack_event(sk, 0); NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPHPACKS); } else { @@ -3439,7 +3447,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag) if (TCP_ECN_rcv_ecn_echo(tp, tcp_hdr(skb))) flag |= FLAG_ECE; - tcp_ca_event(sk, CA_EVENT_SLOW_ACK); + tcp_in_ack_event(sk, CA_ACK_SLOWPATH); } /* We passed data and got it acked, remove any soft error diff --git a/net/ipv4/tcp_westwood.c b/net/ipv4/tcp_westwood.c index 81911a92356c..bb63fba47d47 100644 --- a/net/ipv4/tcp_westwood.c +++ b/net/ipv4/tcp_westwood.c @@ -220,32 +220,35 @@ static u32 tcp_westwood_bw_rttmin(const struct sock *sk) return max_t(u32, (w->bw_est * w->rtt_min) / tp->mss_cache, 2); } +static void tcp_westwood_ack(struct sock *sk, u32 ack_flags) +{ + if (ack_flags & CA_ACK_SLOWPATH) { + struct westwood *w = inet_csk_ca(sk); + + westwood_update_window(sk); + w->bk += westwood_acked_count(sk); + + update_rtt_min(w); + return; + } + + westwood_fast_bw(sk); +} + static void tcp_westwood_event(struct sock *sk, enum tcp_ca_event event) { 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); - break; - case CA_EVENT_COMPLETE_CWR: tp->snd_cwnd = tp->snd_ssthresh = tcp_westwood_bw_rttmin(sk); break; - case CA_EVENT_LOSS: 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); - update_rtt_min(w); - break; - default: /* don't care */ break; @@ -274,6 +277,7 @@ static struct tcp_congestion_ops tcp_westwood __read_mostly = { .ssthresh = tcp_reno_ssthresh, .cong_avoid = tcp_reno_cong_avoid, .cwnd_event = tcp_westwood_event, + .in_ack_event = tcp_westwood_ack, .get_info = tcp_westwood_info, .pkts_acked = tcp_westwood_pkts_acked,