On Fri, Dec 4, 2020 at 7:08 PM Hazem Mohamed Abuelfotoh
<abuehaze@xxxxxxxxxx> 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) configured
> specially within environments where RTT is high.
> To address this issue this patch is relying on RCV_MSS
> so auto-tuning can start early regardless
> the receiver 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@xxxxxxxxxx>
> ---
> net/ipv4/tcp_input.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> 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);
So are you claiming icsk->icsk_ack.rcv_mss is related to MTU 9000 ?
RCV_MSS is not known until we receive actual packets... The initial
value is somthing like 536 if I am not mistaken.
I think your patch does not match the changelog.
> tcp_mstamp_refresh(tp);
> tp->rcvq_space.time = tp->tcp_mstamp;
> tp->rcvq_space.seq = tp->copied_seq;
> --
> 2.16.6
>
>
>
>
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