From mboxrd@z Thu Jan 1 00:00:00 1970 From: Neal Cardwell Subject: [PATCH v3 net-next 13/16] tcp: allow congestion control to expand send buffer differently Date: Sun, 18 Sep 2016 18:03:50 -0400 Message-ID: <1474236233-28511-14-git-send-email-ncardwell@google.com> References: <1474236233-28511-1-git-send-email-ncardwell@google.com> Cc: netdev@vger.kernel.org, Yuchung Cheng , Van Jacobson , Neal Cardwell , Nandita Dukkipati , Eric Dumazet , Soheil Hassas Yeganeh To: David Miller Return-path: Received: from mail-qt0-f173.google.com ([209.85.216.173]:32983 "EHLO mail-qt0-f173.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932119AbcIRWEX (ORCPT ); Sun, 18 Sep 2016 18:04:23 -0400 Received: by mail-qt0-f173.google.com with SMTP id 11so64695463qtc.0 for ; Sun, 18 Sep 2016 15:04:22 -0700 (PDT) In-Reply-To: <1474236233-28511-1-git-send-email-ncardwell@google.com> Sender: netdev-owner@vger.kernel.org List-ID: From: Yuchung Cheng Currently the TCP send buffer expands to twice cwnd, in order to allow limited transmits in the CA_Recovery state. This assumes that cwnd does not increase in the CA_Recovery. For some congestion control algorithms, like the upcoming BBR module, if the losses in recovery do not indicate congestion then we may continue to raise cwnd multiplicatively in recovery. In such cases the current multiplier will falsely limit the sending rate, much as if it were limited by the application. This commit adds an optional congestion control callback to use a different multiplier to expand the TCP send buffer. For congestion control modules that do not specificy this callback, TCP continues to use the previous default of 2. 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 --- include/net/tcp.h | 2 ++ net/ipv4/tcp_input.c | 4 +++- 2 files changed, 5 insertions(+), 1 deletion(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 3492041..1aa9628 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -917,6 +917,8 @@ struct tcp_congestion_ops { 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); + /* returns the multiplier used in tcp_sndbuf_expand (optional) */ + u32 (*sndbuf_expand)(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_input.c b/net/ipv4/tcp_input.c index 17de77d..5af0bf3 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -289,6 +289,7 @@ static bool tcp_ecn_rcv_ecn_echo(const struct tcp_sock *tp, const struct tcphdr static void tcp_sndbuf_expand(struct sock *sk) { const struct tcp_sock *tp = tcp_sk(sk); + const struct tcp_congestion_ops *ca_ops = inet_csk(sk)->icsk_ca_ops; int sndmem, per_mss; u32 nr_segs; @@ -309,7 +310,8 @@ static void tcp_sndbuf_expand(struct sock *sk) * Cubic needs 1.7 factor, rounded to 2 to include * extra cushion (application might react slowly to POLLOUT) */ - sndmem = 2 * nr_segs * per_mss; + sndmem = ca_ops->sndbuf_expand ? ca_ops->sndbuf_expand(sk) : 2; + sndmem *= nr_segs * per_mss; if (sk->sk_sndbuf < sndmem) sk->sk_sndbuf = min(sndmem, sysctl_tcp_wmem[2]); -- 2.8.0.rc3.226.g39d4020