Host Memory Copy Buffer

This is simple host memory example to describe how host-only memory can be copied to device-only memory and vice-versa.

KEY CONCEPTS: host memory

KEYWORDS: XCL_MEM_EXT_HOST_ONLY, CL_MEM_HOST_NO_ACCESS, enqueueCopyBuffer

This example illustrates how host only memory can be copied to device only memory and vice-versa using EnqueueCopyBuffer API.

Host only buffer is created using XCL_MEM_EXT_HOST_ONLY flag whereas device only buffer is created using CL_MEM_HOST_NO_ACCESS flag. The following data transfers take place in the example -

  1. Copy the HOST_ONLY input buffer buffer_in_host into DEVICE_ONLY input buffer buffer_in_dev using M2M.

OCL_CHECK(err,
          err = q.enqueueCopyBuffer(buffer_in_host_a, buffer_in_dev_a, 0, 0,
                                    size_in_bytes, 0, nullptr)); // transfer
OCL_CHECK(err,
          err = q.enqueueCopyBuffer(buffer_in_host_b, buffer_in_dev_b, 0, 0,
                                    size_in_bytes, 0, nullptr)); // transfer

  1. Enqueue kernel to do computations on DEVICE_ONLY input buffer buffer_in_dev and put output in DEVICE_ONLY output buffer buffer_out_dev.

q.enqueueTask(krnl);

  1. Copy the DEVICE_ONLY output buffer buffer_out_dev into HOST_ONLY output buffer buffer_out_host using M2M.

OCL_CHECK(err,
          err = q.enqueueCopyBuffer(buffer_out_dev, buffer_out_host, 0, 0,
                                    size_in_bytes, 0, nullptr)); // transfer

EXCLUDED PLATFORMS:

  • Alveo U25 SmartNIC

  • Alveo U30

  • Alveo U50c

  • Alveo U50lv

  • Alveo U50 gen3x4

  • Alveo U55

  • Alveo U250

  • All Embedded Zynq Platforms, i.e zc702, zcu102 etc

  • All Versal Platforms, i.e vck190 etc

  • All Platforms with 2019 Version

  • All Platforms with 2018 Version

  • Samsung U.2 SmartSSD

DESIGN FILES

Application code is located in the src directory. Accelerator binary files will be compiled to the xclbin directory. The xclbin directory is required by the Makefile and its contents will be filled during compilation. A listing of all the files in this example is shown below

src/host.cpp
src/krnl_vadd.cpp

Access these files in the github repo by clicking here.

COMMAND LINE ARGUMENTS

Once the environment has been configured, the application can be executed by

./host_memory_copy_buffer.exe <krnl_vadd XCLBIN>