[LEDE-DEV] [PATCH] ar71xx: Add GRO support to ag71xx

[rosenp at gmail.com]

That's...way better than I expected given how minimal my changes are.

For some context, the ag71xx driver is special in that it does not seem
to do any hardware offloading to the NIC.

As far as I understand this change, GRO takes 1500 MTU packets and
packs then into 64Kb blocks which the kernel then processes.

I would be curious if anyone can do latency comparisons before this
change and after. I do know this driver to have lower latency than
others due to lack of offloads.

I guess all that's left is to add GSO support to the driver. That seems
like a lot more work than a three line change though. ¯\_(ツ)_/¯

On Sun, 2017-09-03 at 23:16 +0200, Christian Lamparter wrote:
> On Sunday, September 3, 2017 11:35:46 AM CEST Rosen Penev wrote:
> > On a TL-WN710N, this patch increases iperf performance from ~92.5
> > to ~93.5 mbps. Keep in mind the WN710N is a 100mbps device. I
> > expect greater numbers from gigabit devices.
> > 
> > Signed-off-by: Rosen Penev <rosenp at gmail.com>
> > ---
> 
> I've done a quick test of the patch on my WD Range Extender.
> (It has a Atheros AR9344 rev 2 SoC @ CPU:560.000MHz, DDR:400.000MHz
> The PHY is a AR8035, which supports 1 GBit/s Links)
> 
> The range extender (DUT) was running iperf3 server in both tests.
> Another desktop PC was acting as the iperf3 client.
> 
> without the patch:
> 
> Connecting to host range-extender, port 5201
> [  4] local 192.168.8.7 port 51518 connected to 192.168.8.204 port
> 5201
> [ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
> [  4]   0.00-1.00   sec  23.5 MBytes   197 Mbits/sec    0    105
> KBytes
> [  4]   1.00-2.00   sec  23.7 MBytes   199 Mbits/sec    0    105
> KBytes
> [  4]   2.00-3.00   sec  23.6 MBytes   198 Mbits/sec    0    105
> KBytes
> [  4]   3.00-4.00   sec  23.0 MBytes   193 Mbits/sec    0    105
> KBytes
> [  4]   4.00-5.00   sec  23.4 MBytes   197 Mbits/sec    0    105
> KBytes
> [  4]   5.00-6.00   sec  23.3 MBytes   195 Mbits/sec    0    105
> KBytes
> [  4]   6.00-7.00   sec  23.4 MBytes   196 Mbits/sec    0    105
> KBytes
> [  4]   7.00-8.00   sec  23.6 MBytes   198 Mbits/sec    0    105
> KBytes
> [  4]   8.00-9.00   sec  23.1 MBytes   194 Mbits/sec    0    105
> KBytes
> [  4]   9.00-10.00  sec  22.1 MBytes   185 Mbits/sec    0    105
> KBytes
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bandwidth       Retr
> [  4]   0.00-10.00  sec   233 MBytes   195
> Mbits/sec    0             sender
> [  4]   0.00-10.00  sec   232 MBytes   195
> Mbits/sec                  receiver
> 
> iperf Done.
> 
> with the patch (gro enabled - this is done by default):
> 
> Connecting to host range-extender, port 5201
> [  4] local 192.168.8.7 port 52004 connected to 192.168.8.204 port
> 5201
> [ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
> [  4]   0.00-1.00   sec  32.7 MBytes   274 Mbits/sec    0    106
> KBytes       
> [  4]   1.00-2.00   sec  32.6 MBytes   274 Mbits/sec    0    106
> KBytes       
> [  4]   2.00-3.00   sec  32.4 MBytes   272 Mbits/sec    0    106
> KBytes       
> [  4]   3.00-4.00   sec  32.3 MBytes   271 Mbits/sec    0    106
> KBytes       
> [  4]   4.00-5.00   sec  32.5 MBytes   273 Mbits/sec    0    106
> KBytes       
> [  4]   5.00-6.00   sec  32.5 MBytes   273 Mbits/sec    0    106
> KBytes       
> [  4]   6.00-7.00   sec  32.6 MBytes   273 Mbits/sec    0    106
> KBytes       
> [  4]   7.00-8.00   sec  32.4 MBytes   272 Mbits/sec    0    106
> KBytes       
> [  4]   8.00-9.00   sec  32.6 MBytes   273 Mbits/sec    0    106
> KBytes       
> [  4]   9.00-10.00  sec  31.4 MBytes   264 Mbits/sec    0    106
> KBytes       
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bandwidth       Retr
> [  4]   0.00-10.00  sec   324 MBytes   272
> Mbits/sec    0             sender
> [  4]   0.00-10.00  sec   324 MBytes   272
> Mbits/sec                  receiver
> 
> iperf Done.
> 
> (range-extender) # ethtool -K eth0 gro off
> 
> Connecting to host range-extender, port 5201
> [  4] local 192.168.8.7 port 52120 connected to 192.168.8.204 port
> 5201
> [ ID] Interval           Transfer     Bandwidth       Retr  Cwnd
> [  4]   0.00-1.00   sec  24.8 MBytes   208 Mbits/sec    0    105
> KBytes       
> [  4]   1.00-2.00   sec  23.6 MBytes   198 Mbits/sec    0    105
> KBytes       
> [  4]   2.00-3.00   sec  24.5 MBytes   206 Mbits/sec    0    105
> KBytes       
> [  4]   3.00-4.00   sec  23.9 MBytes   201 Mbits/sec    0    105
> KBytes       
> [  4]   4.00-5.00   sec  24.6 MBytes   207 Mbits/sec    0    105
> KBytes       
> [  4]   5.00-6.00   sec  24.7 MBytes   207 Mbits/sec    0    105
> KBytes       
> [  4]   6.00-7.00   sec  24.5 MBytes   206 Mbits/sec    0    105
> KBytes       
> [  4]   7.00-8.00   sec  24.0 MBytes   201 Mbits/sec    0    105
> KBytes       
> [  4]   8.00-9.00   sec  24.3 MBytes   204 Mbits/sec    0    105
> KBytes       
> [  4]   9.00-10.00  sec  24.5 MBytes   206 Mbits/sec    0    105
> KBytes       
> - - - - - - - - - - - - - - - - - - - - - - - - -
> [ ID] Interval           Transfer     Bandwidth       Retr
> [  4]   0.00-10.00  sec   244 MBytes   204
> Mbits/sec    0             sender
> [  4]   0.00-10.00  sec   243 MBytes   204
> Mbits/sec                  receiver
> 
> iperf Done.
> 
> So, the throughput went from 195 Mbits/sec to 272 Mbits/sec.
> The gain would be (272 Mbps - 195 Mbps) / 195 Mbps = 0.3949 ~ 40%
> 
> Regards,
> Christian