如何以编程方式确定持久 kernel 的正确启动参数？

Question

What is the correct way to programmatically determine the launch parameters of a persistent kernel? All examples I have found use hard coded values.

Is the following correct?

cudaDeviceProp props;

cudaGetDeviceProperties(&props, 0);

int blockCount = props.maxBlocksPerMultiProcessor * props.multiProcessorCount;
int blockThreadCount = props.maxThreadsPerMultiProcessor / props.maxBlocksPerMultiProcessor;

//  Gives <<<1312, 96>>> on a RTX 3090
PersistentKernel<<<blockCount, blockThreadCount>>>(...);

Answer 1

Is the following correct?

No.

Use cudaOccupancyMaxPotentialBlockSize . That will give you both the grid size and block size for the current device which maximizes the occupancy of a given kernel with the minimum number of blocks. That is the optimal launch parameters for a given persistent kernel.

Note that the returned block and grid dimensions are scalars. You are free to reshape them into multidimensional dim3 block and/or grid dimensions which preserve the total number of threads per block and blocks which are returned by the API.