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README > Dependent kernel launch

Dependent kernel launches

The Hopper architecture supports a new feature through which two kernels in the same stream can overlap their execution, named Programmatic Dependent Launch (PDL). This allows kernels with conflict in global memory to programmatically and safely overlap portions of their execution. Primary kernel can signal it is about to finish execution, and the next kernel can optionally wait on the previous kernel to finish flushing its memory.

For more information, we refer you to the PDL section in the CUDA Programming Guide.

Using dependent launch in CUTLASS

When building CUTLASS, you can use the CUTLASS_ENABLE_GDC_FOR_SM90 macro to enable PDL-related instructions in Hopper kernels:

cmake . -DCUTLASS_ENABLE_GDC_FOR_SM90=1

Note that this only adds PDL-related instructions to the kernels, but to actually allow a dependent launch, you must also run your GEMM kernel with PDL:

gemm.run(
  /* stream = */ stream,
  /* cuda_adapter = */ nullptr,
  /* launch_with_pdl = */ true
);_