topic Re: UDP Ethernet bandwidth vs global memory bandwidth usage in i.MX Processors

UDP Ethernet bandwidth vs global memory bandwidth usage

ericb — Mon, 16 Sep 2013 14:40:32 GMT

Dear all,

The bandwidth of the Ethernet seems to be limited by the global memory bandwidth usage!

Known issue:

The Ethernet bandwidth is limited to 470 Mb/s with the Imx6q.

My project description:

With the 3 first cores, I do a video process which uses memory and neon instructions.

With the last core, I send data through the UDP Ethernet.

Problem description:

More the video process uses the global memory (200 to 600 MB/s), more the Ethernet bandwidth decreases (430 to 150 Mb/s).

Note: the same video process with small part of memory (in this case, data should be in cache), doesn't decrease the Ethernet bandwidth (always 416 Mb/s) (the same cpu usage, but low global memory usage).

Configuration:

BoundaryDevices Nitrogen6X

Memory 1GBytes of 64-bit wide DDR3 @ 532MHz

Ubuntu L3.0.35_4.0.0_UBUNTU_RFS / LTIB 4.0.0 / or LTIB 4.1.0

I have written a simple test (code attached):

- 3 cores copy memory: 10 MB of data, by block of 64 kB. The memory bandwidth is measured and limited to a desired value for the test.

- 1 core sends udp packets (1472 bytes) : after 10s, the Ethernet bandwidth is calculated

1 thread memory bandwidth (MB/s)	Threads count	Total memory bandwidth (MB/s)	Measured Ethernet bandwidth (Mb/s)	Cpu usage (%)
0	3	0	438	5
1	3	3	434	7
5	3	15	429	10
10	3	30	424	11
20	3	60	417	12
50	3	150	400	20
100	3	300	379	35
150	3	450	365	46
200	3	600	341	62
250	3	750	279	73
300	3	900	210	84
400	3	1200	151	94
max	3	max	149	98

Result:

The bandwidth of the Ethernet depends of the global memory bandwidth usage.

- No memory usage: Ethernet bandwidth 438 Mb/s

- Max memory usage: Ethernet bandwidth 149 Mb/s

For my project, I really need the max of Ethernet bandwidth. I have spent many to time to adjust socket options, threads priority, the BSP versions,…, without improvement.

Is there any idea to help me go on?

Thank you very much.

Original Attachment has been moved to: TestUdp.tar.gz

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

ericb — Tue, 01 Oct 2013 09:29:38 GMT

Is someone can confirm this Ethernet problem with the imx6 ?

It will help me to know if I do something wrong or if the problem is hardware/software.

In advance thank you.

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

YixingKong — Fri, 21 Feb 2014 07:44:13 GMT

Ericb

We are sorry for getting back to you so late. Are you still stuck with the issue? If you have somehow to resolved the

issue, can we close the discussion? If you still need help, please feel free to reply with an update to this discussion.

Thanks,
Yixing

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

YixingKong — Wed, 26 Feb 2014 09:16:59 GMT

Ericb

We have not got your response yet and will close the discussion in 3 days. If you still need help, please feel free to reply with an update to this discussion.

Thanks,

Yixing

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

YixingKong — Mon, 03 Mar 2014 08:58:50 GMT

Ericb

This discussion is closed since no activity. If you still need help, please feel free to reply with an update to this discussion, or create another discussion.

Thanks,

Yixing

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

justinfarrellya — Mon, 10 Aug 2015 14:08:08 GMT

Yixing - did a solution to this problem become discovered? We are having the same issue. We have a memory to memory copy that is then ported to the Ethernet causing a slowdown in the overall bandwidth exactly as in the case described here. We need to get a fix for this.....

Re: UDP Ethernet bandwidth vs global memory bandwidth usage

BiyongSUN — Mon, 10 Aug 2015 21:41:34 GMT

Please check the Chip Errata. It is long time ago, file the errata in document.

ERR004512 ENET: 1 Gb Ethernet MAC (ENET) system limitation