DMA Samples

NVIDIA DOCA DMA Sample Guide

This document provides DMA sample implementation on top of NVIDIA® BlueField® DPU.

DOCA Direct Memory Access (DMA) library provides an API for copying data between buffers using hardware acceleration, supporting both local and remote memory regions.

The library provides an API for executing DMA operations on DOCA buffers. These buffers can reside in local memory (i.e., within the DPU) or remote memory (i.e., on the host). Using DOCA DMA you can easily execute complex memory copy operations in an optimized, hardware-accelerated way:

  • The dma_local_copy sample copies content between two local buffers on the DPU.
  • The dma_copy_dpu/dma_copy_host copies user-defined text from the host to the DPU.
    Note:

    DMA Copy Host must be run before DMA Copy DPU.

For more information about the DOCA DMA library, refer to NVIDIA DOCA DMA Programing Guide.

The library requires a minimum DPU firmware version of 24.33.0100.

  1. Refer to the following documents:
  2. To build a given sample:
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    cd /opt/mellanox/doca/samples/doca_dma/<sample_name> meson build ninja -C build

    Note:

    The binary doca_<sample_name> will be created under ./build/.

  3. Sample (e.g., dma_copy_host) usage:
    Sample Argument Description
    DMA Local Copy -p, --pci DOCA DMA device PCIe address
    -t, --text Text to DMA copy from one local buffer to another
    DMA Copy Host -p, --pci DOCA DMA device PCIe address
    -t, --text Text to DMA copy from the host to the DPU
    -d, --descriptor-path Path on which the exported descriptor file is saved
    -b, --buffer-path Path on which the buffer information file is saved
    DMA Copy DPU -p, --pci DOCA DMA device PCIe address
    -d, --descriptor-path Path from which the exported descriptor file is read
    -b, --buffer-path Path from which the buffer information file is read

  4. For additional information per sample, use the -h option:
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    ./build/doca_<sample_name> -h


DMA Local Copy

This sample illustrates how to locally copy memory with DMA from one buffer to another on the DPU. This sample should be run on the DPU. The sample logic includes:

  1. Locating DOCA device.
  2. Initializing needed DOCA core structures.
  3. Populating DOCA memory map with two relevant buffers.
  4. Allocating element in DOCA buffer inventory for each buffer.
  5. Initializing DOCA DMA job object.
  6. Submitting DMA job into work queue.
  7. Retrieving DMA job from the queue once it is done.
  8. Checking job result.
  9. Destroying all DMA and DOCA core structures.

Reference:

  • /opt/mellanox/doca/samples/doca_dma/dma_local_copy/dma_local_copy_sample.c
  • /opt/mellanox/doca/samples/doca_dma/dma_local_copy/dma_local_copy_main.c
  • /opt/mellanox/doca/samples/doca_dma/dma_local_copy/dma_local_copy_main.c

5.2. DMA Copy DPU

Note:

This sample should run only after DMA Copy Host is run and the required configuration files (descriptor and buffer) have been copied to the DPU.

This sample illustrates how to copy memory (which contains user-defined text) with DMA from the x86 host into the DPU. This sample should be run on the DPU.
The sample logic includes:

  1. Locating DOCA device.
  2. Initializing needed DOCA core structures.
  3. Reading configuration files and saving their content into local buffers.
  4. Allocating the local destination buffer in which the host text will be saved.
  5. Populating DOCA memory map with destination buffer.
  6. Creating the remote memory map with the export descriptor file.
  7. Creating memory map to the remote buffer.
  8. Allocating element in DOCA buffer inventory for each buffer.
  9. Initializing DOCA DMA job object.
  10. Submitting DMA job into work queue.
  11. Retrieving DMA job from the queue once it is done.
  12. Checking DMA job result.
  13. If the DMA job ends successfully, printing the text that has been copied to log.
  14. Printing to log that the host-side sample can be closed.
  15. Destroying all DMA and DOCA core structures.

Reference:

  • /opt/mellanox/doca/samples/doca_dma/dma_copy_dpu/dma_copy_dpu_sample.c
  • /opt/mellanox/doca/samples/doca_dma/dma_copy_dpu/dma_copy_dpu_main.c
  • /opt/mellanox/doca/samples/doca_dma/dma_copy_dpu/meson.build

5.3. DMA Copy Host

Note:

This sample should be run first. It is user responsibility to transfer the two configuration files (descriptor and buffer) to the DPU and provide their path to the DMA Copy DPU sample.

This sample illustrates how to allow memory copy with DMA from the x86 host into the DPU. This sample should be run on the host.
The sample logic includes:

  1. Locating DOCA device.
  2. Initializing needed DOCA core structures.
  3. Populating DOCA memory map with source buffer.
  4. Exporting memory map.
  5. Saving export descriptor and local DMA buffer information into files. These files should be transferred to the DPU before running the DPU sample.
  6. Waiting until DPU DMA sample has finished.
  7. Destroying all DMA and DOCA core structures.

Reference:

  • /opt/mellanox/doca/samples/doca_dma/dma_copy_host/dma_copy_host_sample.c
  • /opt/mellanox/doca/samples/doca_dma/dma_copy_host/dma_copy_host_main.c
  • /opt/mellanox/doca/samples/doca_dma/dma_copy_host/meson.build

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