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

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Message-Id: <20180427.140550.112235314130624063.davem@davemloft.net>
Date:   Fri, 27 Apr 2018 14:05:50 -0400 (EDT)
From:   David Miller <davem@...emloft.net>
To:     weiwan@...gle.com
Cc:     netdev@...r.kernel.org, ycheng@...gle.com, edumazet@...gle.com,
        soheil@...gle.com
Subject: Re: [PATCH net-next] tcp: remove mss check in
 tcp_select_initial_window()

From: Wei Wang <weiwan@...gle.com>
Date: Thu, 26 Apr 2018 09:58:10 -0700

> 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>

Very nice commit message.

Applied.