netdev - Re: MT7530 bug, forward broadcast and unknown frames to the correct CPU port

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Date: Wed, 10 May 2023 17:02:58 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: Arınç ÜNAL <arinc.unal@...nc9.com>
Cc: Daniel Golle <daniel@...rotopia.org>, DENG Qingfang <dqfext@...il.com>,
	Greg Ungerer <gerg@...nel.org>,
	Richard van Schagen <richard@...terhints.com>,
	Richard van Schagen <vschagen@...com>,
	Frank Wunderlich <frank-w@...lic-files.de>, mithat.guner@...ont.com,
	erkin.bozoglu@...ont.com, bartel.eerdekens@...stell8.be,
	netdev <netdev@...r.kernel.org>
Subject: Re: MT7530 bug, forward broadcast and unknown frames to the correct
 CPU port

On Wed, May 10, 2023 at 10:59:36AM +0200, Arınç ÜNAL wrote:
> > You seem to be rather talking about MT7530 while I think preferring port 6
> > would benefit MT7531BE the most.
> > 
> > Can you test the actual speed with SGMII on MT7531? Route between two ports and
> > do a bidirectional iperf3 speed test.
> > 
> > SGMII should at least provide you with 2 Gbps bandwidth in total in a
> > router-on-a-stick scenario which is the current situation until the changing
> > DSA conduit support is added.
> > 
> > If we were to use port 5, download and upload speed would be capped at 500
> > Mbps. With SGMII you should get 1000 Mbps on each.
> 
> I tested this on Daniel's Banana Pi BPI-R3 which has got an MT7531AE switch.
> I can confirm I get more than 500 Mbps for RX and TX on a bidirectional
> speed test.
> 
> [SUM][RX-S]   0.00-18.00  sec  1.50 GBytes   715 Mbits/sec    receiver
> 
> [SUM][TX-S]   0.00-18.00  sec  1.55 GBytes   742 Mbits/sec  6996     sender
> 
> The test was run between two computers on different networks, 192.168.1.0/24
> and 192.168.2.0/24, both computers had static routes to reach each other. I
> tried iperf3 as the server and client on both computers with similar
> results.
> 
> This concludes preferring port 6 is practically beneficial for MT7531BE.

One thing you seem to not realize is that "1 Gbit/sec full duplex" means
that there is 1Gbps of bandwidth in the TX direction and 1 Gbps of
bandwidth of throughput in the RX direction. So, I don't see how your
test proves anything, since a single SGMII full duplex link to the CPU
should be able to absorb your 715 RX + 742 TX traffic just fine.