netdev - Re: [PATCH net 2/2] tcp: fix delayed ACKs for MSS boundary condition

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Message-ID: <CAMaK5_jxXu+no76U9ucUSdzN_qeNUFT2-n8GYoy=B3Yh9+ChmQ@mail.gmail.com>
Date: Mon, 2 Oct 2023 13:33:54 +0800
From: Xin Guo <guoxin0309@...il.com>
To: Neal Cardwell <ncardwell@...gle.com>
Cc: Neal Cardwell <ncardwell.sw@...il.com>, David Miller <davem@...emloft.net>, 
	Jakub Kicinski <kuba@...nel.org>, Eric Dumazet <edumazet@...gle.com>, Netdev <netdev@...r.kernel.org>, 
	Yuchung Cheng <ycheng@...gle.com>
Subject: Re: [PATCH net 2/2] tcp: fix delayed ACKs for MSS boundary condition

Thanks,
the commit message in the v2 is so good.

Regards
Guo Xin

Neal Cardwell <ncardwell@...gle.com> 于2023年10月1日周日 23:19写道：
>
> On Thu, Sep 28, 2023 at 11:56 AM Xin Guo <guoxin0309@...il.com> wrote:
> >
> > Neal,
> > thanks for your explanation,
> > 1)when I read the patch, i cannot understood "if an app reads  >1*MSS data",
> > because in my view that "the app reads" mean that the copied data
> > length from sk_receive_queue to user-space buffer
> > in function tcp_recvmsg_locked(as example) when an app reads data from a socket,
> > but for "tp->rcv_nxt - tp->rcv_wup > icsk->icsk_ack.rcv_mss ||"
> > "tp->rcv_nxt - tp->rcv_wup" means that the received data length from
> > last ack in the kernel for the sk,
> > and not always the length of copied data to user-space buffer.
> >
> > 2) when we received two small packets(<1*MSS) in the kernel for the
> > sk, the total length of the two packets may  > 1*MSS.
>
> Thanks for clarifying. Those are good points; the commit message could
> and should be more precise when describing the existing logic in
> tcp_cleanup_rbuf(). I have posted a v2 series with a more precise
> commit message:
>   https://patchwork.kernel.org/project/netdevbpf/patch/20231001151239.1866845-2-ncardwell.sw@gmail.com/
>
> best regards,
> neal