netdev - Re: [PATCH net] r8169: disable TSO on a single version of RTL8168c to fix performance

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Message-ID: <6947347d-376e-ec13-a62c-5a67ed66c5aa@gmail.com>
Date:   Wed, 20 Nov 2019 07:49:16 +0100
From:   Heiner Kallweit <hkallweit1@...il.com>
To:     David Miller <davem@...emloft.net>, vinschen@...hat.com
Cc:     netdev@...r.kernel.org, nic_swsd@...ltek.com
Subject: Re: [PATCH net] r8169: disable TSO on a single version of RTL8168c to
 fix performance

On 20.11.2019 01:42, David Miller wrote:
> From: Corinna Vinschen <vinschen@...hat.com>
> Date: Tue, 19 Nov 2019 10:09:39 +0100
> 
>> During performance testing, I found that one of my r8169 NICs suffered
>> a major performance loss, a 8168c model.
>>
>> Running netperf's TCP_STREAM test didn't return the expected
>> throughput of > 900 Mb/s, but rather only about 22 Mb/s.  Strange
>> enough, running the TCP_MAERTS and UDP_STREAM tests all returned with
>> throughput > 900 Mb/s, as did TCP_STREAM with the other r8169 NICs I can
>> test (either one of 8169s, 8168e, 8168f).
>>
>> Bisecting turned up commit 93681cd7d94f83903cb3f0f95433d10c28a7e9a5,
>> "r8169: enable HW csum and TSO" as the culprit.
>>
>> I added my 8168c version, RTL_GIGA_MAC_VER_22, to the code
>> special-casing the 8168evl as per the patch below.  This fixed the
>> performance problem for me.
>>
>> Fixes: 93681cd7d94f ("r8169: enable HW csum and TSO")
>> Signed-off-by: Corinna Vinschen <vinschen@...hat.com>
> 
> Applied, but it would be really nice to know why this is happening
> instead of just turning it off completely.
> 
For RTL8168e-vl Realtek confirmed a HW issue, for this RTL8168c version
supposedly it's the same as other chip versions are working fine with TSO.