netdev - Re: Question about TCP delayed-ack and PUSH flag behavior

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Message-ID: <CAPpvP8JZL0zUg13kbMnkz=he93p87SBj+8K3ubRA=JheKT1p0Q@mail.gmail.com>
Date: Fri, 14 Feb 2025 12:58:21 -0500
From: 제임스 <jaymaacton@...il.com>
To: Willy Tarreau <w@....eu>
Cc: netdev@...r.kernel.org
Subject: Re: Question about TCP delayed-ack and PUSH flag behavior

2025년 2월 14일 (금) 오후 12:12, Willy Tarreau <w@....eu>님이 작성:
>
> On Fri, Feb 14, 2025 at 12:03:17PM -0500, ??? wrote:
> > Hi netdev,
> >
> > When tcp stack receives a segment with PUSH flag set, does the stack
> > immediately send out for the corresponding ACK with ignoring delay-ack
> > timer?
> > Or regardless of the PUSH flag, delay-ack is always enforced?
>
> It depends, it's possible for the application to force a delayed ack
> by setting TCP_QUICKACK to zero. This is convenient for web servers
> that know they respond quickly and can merge this ack with the
> response to save one packet.

Thanks but my question is about the kernel's default behavior.
It sounds like there is no interaction between PUSH and delayed-ack,
and it should be handled by application scope.
Can someone confirm my understanding?

JY