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Date:   Mon, 16 Oct 2023 11:10:48 +0200
From:   Simon Horman <horms@kernel.org>
To:     Haiyang Zhang <haiyangz@microsoft.com>
Cc:     linux-hyperv@vger.kernel.org, netdev@vger.kernel.org,
        kys@microsoft.com, davem@davemloft.net, edumazet@google.com,
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        dsahern@kernel.org, ncardwell@google.com, ycheng@google.com,
        kuniyu@amazon.com, morleyd@google.com, mfreemon@cloudflare.com,
        mubashirq@google.com, linux-doc@vger.kernel.org, weiwan@google.com,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH net-next,v3] tcp: Set pingpong threshold via sysctl
Message-ID: <20231016091048.GG1501712@kernel.org>
References: <1697056244-21888-1-git-send-email-haiyangz@microsoft.com>
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On Wed, Oct 11, 2023 at 01:30:44PM -0700, Haiyang Zhang 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@microsoft.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.

Thanks,

this looks clean to me. It seems to address the review of v2.
And keeps the knob as syctl as discussed in v2.

Reviewed-by: Simon Horman <horms@kernel.org>