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Ethernet throughput getting reduced when DDR caching is disabled

ti_user
Expert 1265 points

Hi,

My project contains two TI DSP C6674 processors, which are enabled with Ethernet and SRIO communication. Ethernet and SRIO both are working.

Each DSP has DDR3 of size 2GB, where 1GB is used for SRIO communication. During SRIO interface bringup, I came to know that to work with SRIO, SRIO memory region should be cache disabled, so for that reason i disabled cache for SRIO memory.

Ethernet throughput got effected with this change i.e., :

Disabled cache of 2GB DDR3, Ethernet throughput : 80Mbps

Disabled cache of 1GB DDR3, Ethernet throughput : 150Mbps

Enabled cache of DDR3, Ethernet throughput : 300Mbps

My Hardware Ethernet supports a data speed of 1Gbps

I would like to know is this the same expected as per DSP Processor design or do I need to modify my application?

and also, Does TI/anyone has any practical Ethernet throughput observation for above cases?

Awaiting for your response

Thanks

  • 0
    TI__Guru** 116100 points
    Hi,
    What exact example code did you use and how did you disable it (which way)?
    Have you tried to disable cache when you work with ethernet example code alone (not merging SRIO code) ?
    Yes, we could get less throughput when you disable cache functionality.


    Each DSP has DDR3 of size 2GB, where 1GB is used for SRIO communication. During SRIO interface bringup, I came to know that to work with SRIO, SRIO memory region should be cache disabled, so for that reason i disabled cache for SRIO memory.

    If "cache disable" is required, during SRIO bringup, then you can disable cache and then after SRIo brought up, you can enable cache right ?
    Have you tried this ?
  • 0 in reply to Titusrathinaraj Stalin
    Expert 1265 points

    Hi,

    I developed my code based on HelloWorld example code.

    I disabled cache using cfg file : Cache.setMarMeta(0xC0000000, 0x40000000, 0);

    Yes, I had tried disabling cache in example project and Throughput effected half the rate. With cache enabling : 303Mbps, with cache disabling : 162Mbps.

    Titusrathinaraj Stalin said:
    If "cache disable" is required, during SRIO bringup, then you can disable cache and then after SRIo brought up, you can enable cache right ?
    Have you tried this ?

    Yes, I tried this but there is no change in results (100Mbps), and few times throughput plunged (70-80Mbps) than the average value (100Mbps).

    Thanks