| Message ID | 20201207114625.9079-1-abuehaze@amazon.com |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [net] tcp: fix receive buffer autotuning to trigger for any valid advertised MSS | expand |
On Mon, 7 Dec 2020 11:46:25 +0000 Hazem Mohamed Abuelfotoh wrote: > Previously receiver buffer auto-tuning starts after receiving > one advertised window amount of data.After the initial > receiver buffer was raised by > commit a337531b942b ("tcp: up initial rmem to 128KB > and SYN rwin to around 64KB"),the receiver buffer may > take too long for TCP autotuning to start raising > the receiver buffer size. > commit 041a14d26715 ("tcp: start receiver buffer autotuning sooner") > tried to decrease the threshold at which TCP auto-tuning starts > but it's doesn't work well in some environments > where the receiver has large MTU (9001) especially with high RTT > connections as in these environments rcvq_space.space will be the same > as rcv_wnd so TCP autotuning will never start because > sender can't send more than rcv_wnd size in one round trip. > To address this issue this patch is decreasing the initial > rcvq_space.space so TCP autotuning kicks in whenever the sender is > able to send more than 5360 bytes in one round trip regardless the > receiver's configured MTU. > > Fixes: a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB") > Fixes: 041a14d26715 ("tcp: start receiver buffer autotuning sooner") > > Signed-off-by: Hazem Mohamed Abuelfotoh <abuehaze@amazon.com> If the discussion concludes in favor of this patch please un-indent this commit message, remove the empty line after the fixes tag, and repost.
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c index 389d1b340248..f0ffac9e937b 100644 --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -504,13 +504,14 @@ static void tcp_grow_window(struct sock *sk, const struct sk_buff *skb) static void tcp_init_buffer_space(struct sock *sk) { int tcp_app_win = sock_net(sk)->ipv4.sysctl_tcp_app_win; + struct inet_connection_sock *icsk = inet_csk(sk); struct tcp_sock *tp = tcp_sk(sk); int maxwin; if (!(sk->sk_userlocks & SOCK_SNDBUF_LOCK)) tcp_sndbuf_expand(sk); - tp->rcvq_space.space = min_t(u32, tp->rcv_wnd, TCP_INIT_CWND * tp->advmss); + tp->rcvq_space.space = min_t(u32, tp->rcv_wnd, TCP_INIT_CWND * icsk->icsk_ack.rcv_mss); tcp_mstamp_refresh(tp); tp->rcvq_space.time = tp->tcp_mstamp; tp->rcvq_space.seq = tp->copied_seq;
Previously receiver buffer auto-tuning starts after receiving one advertised window amount of data.After the initial receiver buffer was raised by commit a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB"),the receiver buffer may take too long for TCP autotuning to start raising the receiver buffer size. commit 041a14d26715 ("tcp: start receiver buffer autotuning sooner") tried to decrease the threshold at which TCP auto-tuning starts but it's doesn't work well in some environments where the receiver has large MTU (9001) especially with high RTT connections as in these environments rcvq_space.space will be the same as rcv_wnd so TCP autotuning will never start because sender can't send more than rcv_wnd size in one round trip. To address this issue this patch is decreasing the initial rcvq_space.space so TCP autotuning kicks in whenever the sender is able to send more than 5360 bytes in one round trip regardless the receiver's configured MTU. Fixes: a337531b942b ("tcp: up initial rmem to 128KB and SYN rwin to around 64KB") Fixes: 041a14d26715 ("tcp: start receiver buffer autotuning sooner") Signed-off-by: Hazem Mohamed Abuelfotoh <abuehaze@amazon.com> --- net/ipv4/tcp_input.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)