Burst Read/Write (OpenCL Kernel)

This is simple example of using AXI4-master interface for burst read and write

KEY CONCEPTS: burst access

KEYWORDS: compiler.interfaceRdBurstLen, compiler.interfaceWrBurstLen

The usual reason for having a burst mode capability, or using burst mode, is to increase data throughput. This example demonstrates how multiple items can be read from global memory to kernel’s local memory in a single burst. This is done to achieve low memory access latency and also for efficient use of bandwidth provided by the AXI interface. Similarly, computation results are stored in a buffer and are written to global memory in a burst.

__attribute__((xcl_pipeline_loop(1)))
__attribute__((xcl_loop_tripcount(c_size, c_size)))
        read_buf: for (int j = 0; j < chunk_size; j++) {
            burstbuffer[j] = a[i+j]

The for loops used have the following requirements to implement burst read/write:

  • Pipeline the loop : Loop pipeline must have II(Initiation interval) = 1 specfied by the pipeline pragma inside the loop.

  • Aligned memory : Memory addresses for read/write should be contiguous.

EXCLUDED PLATFORMS:

  • All NoDMA Platforms, i.e u50 nodma etc

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/vadd.cl

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

./cl_burst_rw <vadd XCLBIN>