netdev - Re: Re: [EXT] Re: tcp: socket stuck with zero receive window after SACK

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Message-ID: <CAAHxn99QAYkxcAS5nKdaR93taCPykzxLXOXEJfDh7a1k0y9sug@mail.gmail.com>
Date: Tue, 3 Jun 2025 09:26:50 +0200
From: Simon Campion <simon.campion@...pl.com>
To: Neal Cardwell <ncardwell@...gle.com>
Cc: netdev@...r.kernel.org, Eric Dumazet <edumazet@...gle.com>, 
	Yuchung Cheng <ycheng@...gle.com>, Kevin Yang <yyd@...gle.com>, Jon Maloy <jmaloy@...hat.com>
Subject: Re: Re: [EXT] Re: tcp: socket stuck with zero receive window after SACK

> I agree it will take a while to gather more confidence that the issue
> is gone for your workload with net.ipv4.tcp_shrink_window=0.

To confirm, it's been over a week since we set
net.ipv4.tcp_shrink_window=0, and so far we haven't seen an issue with
TCP connections being stuck with a zero window and an empty recv-q.
So, it looks like the problem is either entirely gone or occurs much
less frequently with net.ipv4.tcp_shrink_window=0.

We also attempted to reproduce the issue with a program that sends
data over a TCP connection but leaves out the first N bytes.
Unfortunately, we haven't been able to reproduce the issue so far,
even with net.ipv4.tcp_shrink_window=1 and with a system under memory
pressure.

Simon