i.MX8M Mini PCIe performance

[Yanjun_Luo]

Hi ,

Have anybody tried the i.MX8M Mini's PCIe performance? I installed a RTL8125 which is a 2.5G Ethernet card and tried with WiFi, I can get 1.8G at both send and receiver on TCP test. I fixed on one CPU core, I found if I don't fixed to one CPU core, the performance is lower.

CPU: I.MX8M Mini
NIC: RTL8125 / 2.5G Ethernet
OS: Linux 5.10.52
Iperf3: 3.12
Test command: iperf3 -c SERVER_IP -A 3 -w 32M

I bind the test to core 3, if I remove this parameter, the performance will be 1.7xG, a little lower. I use top to check the CPU usage, it shows about 20%.

Does this the performance I can get? Where is the limitation? Since I only use one CPU core, it's not the CPU for sure.

Does anybody tried with any device can exceed this? 

BTW, I tried with Intel's i225V, but somehow it can't be recognized by CPU at all, I mean lspci shows nothing.

 Thanks in advanced.

[Yanjun_Luo]

Hi @Dhruvit, thanks for your reply. The i.MX8M Mini is GEN 2.0 while RTL8125B is GEN 2.1. I used the mini PCIe connector for RTL8125B NIC. RTL8125B connects to a 2.5G port of the switch while my Linux PC server connects to 10G port of the same switch. Linux PC running a iperf3 server, the test command is iperf3 -c SERVER_IP -A 3 -w 32M

Regards,

Yanjun Luo.

[Dhruvit]

Hi @Yanjun_Luo,

I hope you are doing well

Thanks for your patience. We are working on your query.

The performance of PCI is based on the number of lanes. How many PCI lanes you are using? One can try increasing the number of lanes to get better throughput.

Thanks & Regards
Dhruvit Vasavada

[Yanjun_Luo]

Hi @Dhruvit ,

As we know, imx8m mini only supports one lane, I can't use more. Also I still don't know what is the bottleneck of the PCIe.  imx8m mini has 4 CPUs, I bind the test to one CPU I got 1.8G, I think it should get 2.2G ~ 2.3G, where is the restriction?

Regards,

Yanjun Luo.

[Dhruvit]

Hi @Yanjun_Luo ,

I hope you are doing well.

To know about the performance of PCI in IMX8M mini, one can refer to the test result of the below community thread. This is the throughput supported by IMX8M Mini. 

And about the lower throughput, it depends on the availability of the bus, the channel(medium) for the data transfer, or the delay produced by the end device.

Based on this thread, it seems that the issue is not from the PCI.

https://community.nxp.com/t5/i-MX-Processors/PCIe-Bandwidth/m-p/1063269#M156271

Thanks & Regards,

Dhruvit Vasavada.

[Yanjun_Luo]

Thanks for your help, it's useful information. 

[Dhruvit]

Hi @Yanjun_Luo,

Can I mark this case as close now?

Thanks & Regards,
Dhruvit Vasavada

[Yanjun_Luo]

Yes, thanks again.

[Dhruvit]

Hi @Yanjun_Luo 

Any updates from your side?

Thanks & Regards

Dhruvit Vasavada

[Dhruvit]

Hi @Yanjun_Luo 

I hope you are doing well

Can you elaborate on the environment of the test?

i.e The GEN of PCI from both the side(root complex and endpoint) 

Also mention how you are connecting the devices to perform the test?

Please share the steps of the test you are performing for debugging purposes.

Thanks & Regards

Dhruvit Vasavada