The first time clSetKernelArg is called for a
given kernel object, XRT identifies the group of symmetrical CUs for subsequent
executions of the kernel. When clEnqueueTask is called
for that kernel, any of the symmetrical CUs in that group can be used to process the
task.
If all CUs for a given kernel are symmetrical, a single kernel object is
sufficient to access any of the CUs. However, if there are
asymmetrical CUs, the host application will need to create a
unique kernel object for each group of asymmetrical CUs. In this
case, the call to clEnqueueTask must specify the kernel
object to use for the task, and any matching CU for that kernel
can be used by XRT.
Creating Kernel Objects for Specific Compute Units
For creating kernels associated with
specific compute units, the clCreateKernel command supports
specifying the CUs at the time the kernel object is
created by the host program. The syntax of this
command is shown below:
// Create kernel object only for a specific compute unit
cl_kernel kernelA = clCreateKernel(program,"<kernel_name>:{compute_unit_name}",&err);
// Create a kernel object for two specific compute units
cl_kernel kernelB = clCreateKernel(program, "<kernel_name>:{CU1,CU2}", &err);
connectivity.nk option
in a config file used by the v++ command during
linking. Therefore, whatever is specified in the
host program, to create or enqueue kernel objects,
must match the options specified by the config file
used during linking.In this case, the Xilinx Runtime identifies the kernel handles (kernelA, kernelB) for specific CUs, or group
of CUs, when the kernel is created. This lets you control which kernel configuration, or
specific CU instance is used, when using clEnqueueTask
from within the host program. This can be useful in the case of asymmetrical CUs, or to
perform load and priority management of CUs.