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the difference between the measured throughput in RC to EP case and EP to EP case through a PCIe switch.And between EDMA3 transfer sync A and sync AB.

FADIL Said
Prodigy 80 points

I tried a memory write transaction type DSP-to-DSP (C6678) RC to  EP and EP to EP using a PCIe switch and I compare the throughput measured in both cases I find that measured in the RC to EP case is better than that measured in the EP to EP case .

The following figure show the obtained throughputs :

In memory write transaction type ,RC to EP  I used EDMA3 transfer sync A  and sync AB. I  find that

EDMA3 transfer sync A  is better than EDMA3 transfer sync AB for data size less than 4 kbytes ,the thing that seem not normal .

The following figure show the obtained throughputs :

Please if it exist an explanation .

 

  • 0
    TI__Mastermind 28085 points

    Hi,

    Welcome to the TI E2E forum. I hope you will find many good answers here and in the TI.com documents and in the TI Wiki Pages (for processor issues). Be sure to search those for helpful information and to browse for the questions others may have asked on similar topics (e2e.ti.com).

    To optimize EDMA/PCIe transfer, please note that the EDAM data burst size (DBS) could be different in different EDMA TC (transfer controller), which will affect the payload size of each PCIe packet generated by EDMA. Please take a look at the data manual for EDMA DBS configuration. And section "2.3 EDMA Considerations" in PCIe use case application note discussed about the EDMA for PCIe usage. Hope it could help.

    Also refer the below similar thread:

    ADC12DJ5200RFEVM: Revision B and C Board - Data converters forum - Data converters - TI E2E support ...

    e2e.ti.com
    Part Number: ADC12DJ5200RFEVM Hi Team, seeking from some clarification. We want to know the difference between Rev B & Rev C configuration\driver differences

    Thanks,

  • 0 in reply to Ganapathi Dhandapani95
    Prodigy 80 points

    Ganapathi,

    Thanks very much for your helpful and guidelines. I made the transactions in the same conditions; same TC and  same  DBS (128) , the only difference is between the synchronization type (sync A or sync AB) .and I put data  in MCSRAM for the tow devices .

    Tanks,

    Fadil

  • 0 in reply to FADIL Said
    TI__Mastermind 28085 points

    Hi,

    AB-sync transfer will be faster than a A-sync transfer with large payload size. The reason is that, in AB-sync, ACNT*BCNT bytes of data are transferred in one shot upon DMA trigger. But in the case of A-sync, only ACNT bytes of data is transferred. So if you have to transfer ACNT*BCNT bytes of data in A-sync mode, you would have to call the DMA trigger function BCNT number of times, would consumes more time.

    I would suggest to go through the below attached slides on EDMA3 first. Intro_to_ EDMA.pdf

    Refer Chapter "2.2 Types of EDMA3 Transfers" in the EDAM3 User's Guide, It will helpful  to learn about the complete functionality of the Keystone EDMA engine.

    Thanks,

  • 0 in reply to Ganapathi Dhandapani95
    Prodigy 80 points
    HI,
    Thanks very much for the explanation that you submit ,but my problem is to find an explanation for the data sizes less than 4 Kbytes in where the A sync is efficient than AB sync .
    Thanks,
    Fadil.
  • 0 in reply to FADIL Said
    TI__Mastermind 28085 points
    Hi,

    AB-Sync can be used if the amount of data you are trying to transfer is more than max ACNT value, it will give the better throughput. Else(Payload is less than ACNT value), A-sync would do fine for your transfer.

    Thanks,
  • 0 in reply to Ganapathi Dhandapani95
    Prodigy 80 points

    HI,
    Thanks very much for your helpful.Please what you mean by max ACNT:128 bytes or 65536 bytes.

    Thanks,

    Fadil.

  • 0 in reply to FADIL Said
    TI__Mastermind 28085 points
    Hi,

    Maximum ACNT size is 65536 bytes. But the EDMA max burst size is 128 bytes.

    I will check with EDMA experts and get back to you.

    Thanks,
  • 0 in reply to Ganapathi Dhandapani95
    Prodigy 80 points

    HI,

    Thanks very much for your helpful.I will wait your response.

    Thanks,

    Fadil.

  • 0 in reply to FADIL Said
    TI__Mastermind 35645 points

    Hi,

    The EDMA max burst size can be 128 or 64 bytes and it depends on the EDMA3TC attempts to issue the largest possible read/write command size as limited by the DBS value or the ACNT/BCNT value of the transfer request (TR).

    Kindly refer the c6678 device datasheet as below, Table 7-34 for the DBS (default burst size) values for EDMA3 TC configuration (for CC0, CC1 & CC2)

    http://www.ti.com/lit/ds/symlink/tms320c6678.pdf

    Thanks & regards,

    Sivaraj K

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