Poor IPv6 TCP performance in 4.3-rc3

Poor IPv6 TCP performance in 4.3-rc3

[Russell King - ARM Linux]

Hi,

I'm seeing really poor IPv6 performance compared to IPv4.  I've
checked using two different ARM platforms - an iMX6 platform using
the FEC driver, and an Armada 38x using mvneta.

The following was captured using iperf between the target system
and my laptop.  The problem only occurs one-way.  The 4.3-rc3
platform is running iperf in server mode, the laptop is in client
mode.

Armada 38x:
ipv6: [  4]  0.0-23.9 sec   170 KBytes  58.3 Kbits/sec
ipv4: [  4]  0.0-10.0 sec  1.09 GBytes   936 Mbits/sec

iMX6Q:
ipv6: [  4]  0.0-11.1 sec   640 KBytes   474 Kbits/sec
ipv4: [  4]  0.0-10.0 sec   655 MBytes   549 Mbits/sec

iMX6D with 4.2:
ipv6: [  4]  0.0-10.0 sec   685 MBytes   574 Mbits/sec
ipv4: [  4]  0.0-10.0 sec   696 MBytes   583 Mbits/sec

It looks like there's an IPv6 regression between 4.2 and 4.3-rc3.

Turning GRO off on Armada 38x gives:
ipv6: [  4]  0.0-10.0 sec  1.08 GBytes   923 Mbits/sec
ipv4: [  5]  0.0-10.0 sec  1.09 GBytes   936 Mbits/sec

I haven't started to debug yet, but I thought I'd post a heads-up in
case it's a known problem.  I'll try to get some packet logs on
Thursday, and I'll try to bisect.

-- 
FTTC broadband for 0.8mile line: currently at 9.6Mbps down 400kbps up
according to speedtest.net.

Re: Poor IPv6 TCP performance in 4.3-rc3

[Fabio Estevam]

Hi Russell,

On Tue, Sep 29, 2015 at 8:32 PM, Russell King - ARM Linux
<linux@arm.linux.org.uk> wrote:
> Hi,
>
> I'm seeing really poor IPv6 performance compared to IPv4.  I've
> checked using two different ARM platforms - an iMX6 platform using
> the FEC driver, and an Armada 38x using mvneta.

Does this patch help?
https://patchwork.ozlabs.org/patch/523632/

It was suggested in the following thread:
https://lkml.org/lkml/2015/9/29/258

and it seems to have fixed the performance issue.

Regards,

Fabio Estevam