netdev - Re: [PATCH] tcp: disable tcp_autocorking for socket when TCP

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Message-Id: 
 <170246402592.27343.16161766477481368647.git-patchwork-notify@kernel.org>
Date: Wed, 13 Dec 2023 10:40:25 +0000
From: patchwork-bot+netdevbpf@...nel.org
To: Salvatore Dipietro <dipiets@...zon.com>
Cc: edumazet@...gle.com, davem@...emloft.net, dsahern@...nel.org,
 kuba@...nel.org, pabeni@...hat.com, netdev@...r.kernel.org,
 blakgeof@...zon.com, alisaidi@...zon.com, benh@...zon.com,
 dipietro.salvatore@...il.com
Subject: Re: [PATCH] tcp: disable tcp_autocorking for socket when TCP_NODELAY flag
 is set

Hello:

This patch was applied to netdev/net.git (main)
by David S. Miller <davem@...emloft.net>:

On Fri, 8 Dec 2023 10:20:49 -0800 you wrote:
> Based on the tcp man page, if TCP_NODELAY is set, it disables Nagle's algorithm
> and packets are sent as soon as possible. However in the `tcp_push` function
> where autocorking is evaluated the `nonagle` value set by TCP_NODELAY is not
> considered which can trigger unexpected corking of packets and induce delays.
> 
> For example, if two packets are generated as part of a server's reply, if the
> first one is not transmitted on the wire quickly enough, the second packet can
> trigger the autocorking in `tcp_push` and be delayed instead of sent as soon as
> possible. It will either wait for additional packets to be coalesced or an ACK
> from the client before transmitting the corked packet. This can interact badly
> if the receiver has tcp delayed acks enabled, introducing 40ms extra delay in
> completion times. It is not always possible to control who has delayed acks
> set, but it is possible to adjust when and how autocorking is triggered.
> Patch prevents autocorking if the TCP_NODELAY flag is set on the socket.
> 
> [...]

Here is the summary with links:
  - tcp: disable tcp_autocorking for socket when TCP_NODELAY flag is set
    https://git.kernel.org/netdev/net/c/f3f32a356c0d

You are awesome, thank you!
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