From 1ef9696c909060ccdae3ade245ca88692b49285b Mon Sep 17 00:00:00 2001 From: Alexey Kuznetsov Date: Tue, 19 Sep 2006 12:52:50 -0700 Subject: [PATCH] [TCP]: Send ACKs each 2nd received segment. It does not affect either mss-sized connections (obviously) or connections controlled by Nagle (because there is only one small segment in flight). The idea is to record the fact that a small segment arrives on a connection, where one small segment has already been received and still not-ACKed. In this case ACK is forced after tcp_recvmsg() drains receive buffer. In other words, it is a "soft" each-2nd-segment ACK, which is enough to preserve ACK clock even when ABC is enabled. Signed-off-by: Alexey Kuznetsov Signed-off-by: David S. Miller --- include/net/inet_connection_sock.h | 3 ++- net/ipv4/tcp.c | 7 +++++-- net/ipv4/tcp_input.c | 2 ++ 3 files changed, 9 insertions(+), 3 deletions(-) diff --git a/include/net/inet_connection_sock.h b/include/net/inet_connection_sock.h index 9bf73fe509..de4e83b6da 100644 --- a/include/net/inet_connection_sock.h +++ b/include/net/inet_connection_sock.h @@ -147,7 +147,8 @@ extern struct sock *inet_csk_clone(struct sock *sk, enum inet_csk_ack_state_t { ICSK_ACK_SCHED = 1, ICSK_ACK_TIMER = 2, - ICSK_ACK_PUSHED = 4 + ICSK_ACK_PUSHED = 4, + ICSK_ACK_PUSHED2 = 8 }; extern void inet_csk_init_xmit_timers(struct sock *sk, diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c index 29e3d606db..66e9a729f6 100644 --- a/net/ipv4/tcp.c +++ b/net/ipv4/tcp.c @@ -955,8 +955,11 @@ void tcp_cleanup_rbuf(struct sock *sk, int copied) * receive buffer and there was a small segment * in queue. */ - (copied > 0 && (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) && - !icsk->icsk_ack.pingpong && !atomic_read(&sk->sk_rmem_alloc))) + (copied > 0 && + ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED2) || + ((icsk->icsk_ack.pending & ICSK_ACK_PUSHED) && + !icsk->icsk_ack.pingpong)) && + !atomic_read(&sk->sk_rmem_alloc))) time_to_ack = 1; } diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 511b738f11..b3def0df14 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -156,6 +156,8 @@ static void tcp_measure_rcv_mss(struct sock *sk, return; } } + if (icsk->icsk_ack.pending & ICSK_ACK_PUSHED) + icsk->icsk_ack.pending |= ICSK_ACK_PUSHED2; icsk->icsk_ack.pending |= ICSK_ACK_PUSHED; } } -- 2.39.5