Linux/AM5708: PRU-Ethenet has latency, how to solve it

TianShen

Intellectual 510 points

Part Number: AM5708
Other Parts Discussed in Thread: AM5728

Tool/software: Linux

Hi:

Software version: ti-processor-sdk-linux-am57xx-evm-04.03.00.05, hardware version: AM5708-ES2.0, custom board,

Windows is directly connected to AM5708 PRU-Ethenet (eth2、 eth3) and "ping" is used to detect delays.

root@am57xx-evm:~# ping 192.168.100.23
PING 192.168.100.23 (192.168.100.23): 56 data bytes
64 bytes from 192.168.100.23: seq=0 ttl=128 time=5.327 ms
64 bytes from 192.168.100.23: seq=1 ttl=128 time=1.628 ms
64 bytes from 192.168.100.23: seq=2 ttl=128 time=5.026 ms
64 bytes from 192.168.100.23: seq=3 ttl=128 time=4.944 ms
64 bytes from 192.168.100.23: seq=4 ttl=128 time=3.307 ms
64 bytes from 192.168.100.23: seq=5 ttl=128 time=4.726 ms
64 bytes from 192.168.100.23: seq=6 ttl=128 time=4.639 ms
64 bytes from 192.168.100.23: seq=7 ttl=128 time=4.482 ms
64 bytes from 192.168.100.23: seq=8 ttl=128 time=1.950 ms
64 bytes from 192.168.100.23: seq=9 ttl=128 time=4.260 ms
64 bytes from 192.168.100.23: seq=10 ttl=128 time=3.368 ms
64 bytes from 192.168.100.23: seq=11 ttl=128 time=4.054 ms
64 bytes from 192.168.100.23: seq=12 ttl=128 time=3.944 ms
64 bytes from 192.168.100.23: seq=13 ttl=128 time=2.403 ms
64 bytes from 192.168.100.23: seq=14 ttl=128 time=3.726 ms

What can I do to reduce Pru ethernel latency？

Thanks

over 5 years ago

0 Schuyler Patton over 5 years ago

TI__Mastermind 34765 points

Hi,

At the moment I do not see how to improve the ping latency. What latency do you require? Can you describe the traffic you are passing on the link?

Best Regards,
Schuyler

0 TianShen over 5 years ago in reply to Schuyler Patton

Intellectual 510 points

Hi,

The board and PC are connected directly by a network cable. The delay of board-card 100 Mbp network is relatively large, and the normal waiting time is 1 ms.

Thanks

0 TianShen over 5 years ago in reply to Schuyler Patton

Intellectual 510 points

Hi，

I'm waiting for your reply.

Thanks

0 Schuyler Patton over 5 years ago in reply to TianShen

TI__Mastermind 34765 points

Hi,

I am able to replicate the times you are experiencing but I am not able to reduce the ping latency at the moment. I see your point that 1mS is the typical response time, this is the case on the CPSW interface. These two MAC interfaces are implemented differently in the hardware which will account for part of the latency difference. The PRU is uses firmware to move packets and the CPSW is more of a high throughput interface. Is this latency time critical to your application?

Best Regards,
Schuyler

0 TianShen over 5 years ago in reply to Schuyler Patton

Intellectual 510 points

Hi,

Network latency is critical to my application.

I use the 100M network port (PRU) on the AM5728 without network delay. Why is there a 100 Mbps network (PRU) delay on the AM5708?

AM5728 Software version: ti-processor-sdk-linux-am57xx-evm-04.03.00.05, hardware version: AM5728-ES2.0, custom board,

Thanks

0 Schuyler Patton over 5 years ago in reply to TianShen

TI__Mastermind 34765 points

Hi,

I tried the RT version of the 5.02 Linux SDK and I see a consistent response time of less than 1mS. Typically less that 500mS on my particular setup. Would you be able to switch the latest RT version of the kernel from TI or of the one that you are using and see what the ping response time is?

Best Regards,
Schuyler

0 Schuyler Patton over 5 years ago in reply to Schuyler Patton

TI__Mastermind 34765 points

Hi,

Since I have not heard back I am assuming that you were able to move past the issue or the suggestion of using the RT kernel also enabled you to move past the issue. I am marking the thread as resolved, if that is not the case please respond or open a new thread based on this thread.

Best Regards,
Schuyler

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Linux/AM5708: PRU-Ethenet has latency, how to solve it