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Date: Sat, 20 Sep 2014 23:29:20 +0200
From: Florian Westphal <fw@...len.de>
To: davem@...emloft.net
Cc: hagen@...u.net, lars@...app.com, eric.dumazet@...il.com,
fontana@...rpeleven.org, hannes@...essinduktion.org,
glenn.judd@...ganstanley.com, dborkman@...hat.com,
netdev@...r.kernel.org, Florian Westphal <fw@...len.de>
Subject: [PATCH net-next v2 3/5] 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 <fw@...len.de>
Signed-off-by: Daniel Borkmann <dborkman@...hat.com>
Signed-off-by: Glenn Judd <glenn.judd@...ganstanley.com>
---
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 82d012e..e71884a 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -744,8 +744,10 @@ 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),
};
/*
@@ -777,6 +779,8 @@ 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 0af12a4..14dc3ee 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3361,6 +3361,14 @@ 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)
{
@@ -3420,7 +3428,7 @@ 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 {
@@ -3438,7 +3446,7 @@ 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 81911a9..bb63fba 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,
--
1.7.11.7
--
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