netdev - Re: [PATCH net-next] tcp: remove mss check in tcp_select_initial

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Date:   Thu, 26 Apr 2018 17:05:45 +0000
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Wei Wang <weiwan@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>,
        Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Soheil Hassas Yeganeh <soheil@...gle.com>
Subject: Re: [PATCH net-next] tcp: remove mss check in tcp_select_initial_window()

On Thu, Apr 26, 2018 at 12:58 PM Wei Wang <weiwan@...gle.com> wrote:

> From: Wei Wang <weiwan@...gle.com>

> In tcp_select_initial_window(), we only set rcv_wnd to
> tcp_default_init_rwnd() if current mss > (1 << wscale). Otherwise,
> rcv_wnd is kept at the full receive space of the socket which is a
> value way larger than tcp_default_init_rwnd().
> With larger initial rcv_wnd value, receive buffer autotuning logic
> takes longer to kick in and increase the receive buffer.

> In a TCP throughput test where receiver has rmem[2] set to 125MB
> (wscale is 11), we see the connection gets recvbuf limited at the
> beginning of the connection and gets less throughput overall.

> Signed-off-by: Wei Wang <weiwan@...gle.com>
> Acked-by: Eric Dumazet <edumazet@...gle.com>
> Acked-by: Soheil Hassas Yeganeh <soheil@...gle.com>
> Acked-by: Yuchung Cheng <ycheng@...gle.com>
> ---

Acked-by: Neal Cardwell <ncardwell@...gle.com>

Thanks, Wei!

neal