linux-kernel - Re: [PATCH net-next,v3] tcp: Set pingpong threshold via sysctl

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Date:   Mon, 16 Oct 2023 12:17:37 -0400
From:   Neal Cardwell <ncardwell@...gle.com>
To:     Haiyang Zhang <haiyangz@...rosoft.com>
Cc:     linux-hyperv@...r.kernel.org, netdev@...r.kernel.org,
        kys@...rosoft.com, davem@...emloft.net, edumazet@...gle.com,
        kuba@...nel.org, pabeni@...hat.com, corbet@....net,
        dsahern@...nel.org, ycheng@...gle.com, kuniyu@...zon.com,
        morleyd@...gle.com, mfreemon@...udflare.com, mubashirq@...gle.com,
        linux-doc@...r.kernel.org, weiwan@...gle.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH net-next,v3] tcp: Set pingpong threshold via sysctl

On Wed, Oct 11, 2023 at 4:31 PM Haiyang Zhang <haiyangz@...rosoft.com> wrote:
>
> TCP pingpong threshold is 1 by default. But some applications, like SQL DB
> may prefer a higher pingpong threshold to activate delayed acks in quick
> ack mode for better performance.
>
> The pingpong threshold and related code were changed to 3 in the year
> 2019 in:
>   commit 4a41f453bedf ("tcp: change pingpong threshold to 3")
> And reverted to 1 in the year 2022 in:
>   commit 4d8f24eeedc5 ("Revert "tcp: change pingpong threshold to 3"")
>
> There is no single value that fits all applications.
> Add net.ipv4.tcp_pingpong_thresh sysctl tunable, so it can be tuned for
> optimal performance based on the application needs.
>
> Signed-off-by: Haiyang Zhang <haiyangz@...rosoft.com>
> ---
> v3: Updated doc as suggested by Neal Cardwell.
>     Updated variable location in struct netns_ipv4 as suggested by Kuniyuki
>     Iwashima.
>
> v2: Make it per-namesapce setting, and other updates suggested by Neal Cardwell,
> and Kuniyuki Iwashima.
> ---
>  Documentation/networking/ip-sysctl.rst | 13 +++++++++++++
>  include/net/inet_connection_sock.h     | 16 ++++++++++++----
>  include/net/netns/ipv4.h               |  2 ++
>  net/ipv4/sysctl_net_ipv4.c             |  8 ++++++++
>  net/ipv4/tcp_ipv4.c                    |  2 ++
>  net/ipv4/tcp_output.c                  |  4 ++--
>  6 files changed, 39 insertions(+), 6 deletions(-)

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

Thanks!

neal