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Date:      Tue, 22 Oct 2024 20:00:53 +0000
From:      bugzilla-noreply@freebsd.org
To:        net@FreeBSD.org
Subject:   [Bug 280386] if_bridge throws output errors under load
Message-ID:  <bug-280386-7501-AI48rmcdEq@https.bugs.freebsd.org/bugzilla/>
In-Reply-To: <bug-280386-7501@https.bugs.freebsd.org/bugzilla/>
References:  <bug-280386-7501@https.bugs.freebsd.org/bugzilla/>

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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D280386

Cheng Cui <cc@FreeBSD.org> changed:

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                 CC|                            |cc@FreeBSD.org

--- Comment #25 from Cheng Cui <cc@FreeBSD.org> ---
(In reply to Kevin Bowling from comment #22)
(In reply to pascal.guitierrez from comment #23)

I had a similar experience last year when I was debugging a ENOBUFS error
returned to TCP on using bce NICs. But I am not sure if you can find a simi=
lar
solution.

<snap from 2023>
Turns out the root cause is the default NIC send queue length is too small.=
 The
enobufs error came from the _IF_QFULL check in ifq.h.

However, tuning "sysctl net.link.ifqmaxlen" directly does not work. There i=
s a
per NIC interface setup in the driver to setup device tx/rx queues. I have =
to
increase the tx queue "ifq_maxlen" from the device sysctl "hw.bce.tx_pages".
After tuning that, I can achieve a stable 1Gbps x 100ms delay BDP.
</snap from 2023>

Talking about review D4295, it reminds me of `Linux has some work like TCP
small queue at the sender side.`

Talking about workaround, you may also test the following two patches I
prepared in stable/14 branch as a workaround of improving TCP performance in
congestion control.

https://reviews.freebsd.org/D47218     << apply this patch firstly
https://reviews.freebsd.org/D47213     << apply this patch secondly

--=20
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