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

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Date:   Tue, 19 Nov 2019 10:12:26 +0100
From:   Corinna Vinschen <vinschen@...hat.com>
To:     Heiner Kallweit <hkallweit1@...il.com>
Cc:     netdev@...r.kernel.org, nic_swsd@...ltek.com,
        David Miller <davem@...emloft.net>
Subject: Re: [PATCH net-next] r8169: disable TSO on a single version of
 RTL8168c to fix performance

On Nov 18 20:33, Heiner Kallweit wrote:
> On 18.11.2019 10:55, Corinna Vinschen wrote:
> > 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>
> 
> Thanks for reporting and the fix. Just two small nits:
> - fix should be annotated "net", not "net-next"
> - comment blocks in net subsystem don't have /* on a separate line

See my v2 patch.

> Apart from that:
> Reviewed-by: Heiner Kallweit <hkallweit1@...il.com>
> 
> Out of curiosity: Did you test also with iperf3? If yes,
> do you see the same issue?

I didn't test with iperf3 originally, but I did so now.  The results are
the same.  941 Mbits/sec vs. 23.3 Mbits/sec.


Thanks,
Corinna