From ed6e7268b930e0a9a65d895d368eac79a438d992 Mon Sep 17 00:00:00 2001 From: Neal Cardwell Date: Mon, 19 Sep 2016 23:39:17 -0400 Subject: [PATCH] tcp: allow congestion control module to request TSO skb segment count Add the tso_segs_goal() function in tcp_congestion_ops to allow the congestion control module to specify the number of segments that should be in a TSO skb sent by tcp_write_xmit() and tcp_xmit_retransmit_queue(). The congestion control module can either request a particular number of segments in TSO skb that we transmit, or return 0 if it doesn't care. This allows the upcoming BBR congestion control module to select small TSO skb sizes if the module detects that the bottleneck bandwidth is very low, or that the connection is policed to a low rate. Signed-off-by: Van Jacobson Signed-off-by: Neal Cardwell Signed-off-by: Yuchung Cheng Signed-off-by: Nandita Dukkipati Signed-off-by: Eric Dumazet Signed-off-by: Soheil Hassas Yeganeh Signed-off-by: David S. Miller --- include/net/tcp.h | 2 ++ net/ipv4/tcp_output.c | 15 +++++++++++++-- 2 files changed, 15 insertions(+), 2 deletions(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index a69ed7f0030c..f8f581fd05f5 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -913,6 +913,8 @@ struct tcp_congestion_ops { u32 (*undo_cwnd)(struct sock *sk); /* hook for packet ack accounting (optional) */ void (*pkts_acked)(struct sock *sk, const struct ack_sample *sample); + /* suggest number of segments for each skb to transmit (optional) */ + u32 (*tso_segs_goal)(struct sock *sk); /* get info for inet_diag (optional) */ size_t (*get_info)(struct sock *sk, u32 ext, int *attr, union tcp_cc_info *info); diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index e02c8ebf3ed4..01379567a732 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -1566,6 +1566,17 @@ static u32 tcp_tso_autosize(const struct sock *sk, unsigned int mss_now) return min_t(u32, segs, sk->sk_gso_max_segs); } +/* Return the number of segments we want in the skb we are transmitting. + * See if congestion control module wants to decide; otherwise, autosize. + */ +static u32 tcp_tso_segs(struct sock *sk, unsigned int mss_now) +{ + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; + u32 tso_segs = ca_ops->tso_segs_goal ? ca_ops->tso_segs_goal(sk) : 0; + + return tso_segs ? : tcp_tso_autosize(sk, mss_now); +} + /* Returns the portion of skb which can be sent right away */ static unsigned int tcp_mss_split_point(const struct sock *sk, const struct sk_buff *skb, @@ -2061,7 +2072,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle, } } - max_segs = tcp_tso_autosize(sk, mss_now); + max_segs = tcp_tso_segs(sk, mss_now); while ((skb = tcp_send_head(sk))) { unsigned int limit; @@ -2778,7 +2789,7 @@ void tcp_xmit_retransmit_queue(struct sock *sk) last_lost = tp->snd_una; } - max_segs = tcp_tso_autosize(sk, tcp_current_mss(sk)); + max_segs = tcp_tso_segs(sk, tcp_current_mss(sk)); tcp_for_write_queue_from(skb, sk) { __u8 sacked; int segs; -- 2.20.1