Subject: Re: r8169 regression: UDP packets dropped intermittantly
To: Jonathan Woithe <jwoithe@atrad.com.au>, netdev@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
References: <20171218054951.GJ17747@marvin.atrad.com.au>
From: =?UTF-8?Q?Holger_Hoffst=c3=a4tte?= <holger@applied-asynchrony.com>
Organization: Applied Asynchrony, Inc.
Message-ID: <c47cfb79-afb9-e39b-4861-7c534c55bb70@applied-asynchrony.com>
Date: Mon, 18 Dec 2017 14:38:53 +0100
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On 12/18/17 06:49, Jonathan Woithe wrote:
> Resend to netdev.  LKML CCed in case anyone in the wider kernel community
> can suggest a way forward.  Please CC responses if replying only to LKML.
> 
> It seems that this 4+ year old regression in the r8169 driver (documented in
> this thread on netdev beginning on 9 March 2013) will never be fixed,
> despite the identification of the commit which broke it.  Cards using this
> driver will therefore remain unusable for certain workloads utilising UDP.
(snip)

Hi,

Since I've seen your postings several times now with no comment or resolution
I've decided to try your reproducer on my own systems. In short, I cannot
reproduce any packet loss, despite having 2 (cheap) 1Gb switches between the
two machines. Both are running 4.14.7.

Both NICs are onboard PCIe and identify as:
04:00.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL8111/8168/8411 PCI Express Gigabit Ethernet Controller (rev 06)

$ethtool -i eth0
driver: r8169
version: 2.3LK-NAPI
firmware-version: rtl8168e-3_0.0.4 03/27/12
..

Both machines are from 2012, so quite dated already. Nevertheless your
reproducer runs forever and all I see is 6 bytes request, 14 bytes response,
with no drops. Not one. I tried in both directions - no difference.

I realize this doesn't actually solve your immediate problem, but it is
nevertheless an indicator that whatever you have been observing is caused
by something else.

regards,
Holger