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Use CUDA driver APIs to avoid scheduling too large blocks #690

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5 changes: 3 additions & 2 deletions makefile
Original file line number Diff line number Diff line change
Expand Up @@ -172,8 +172,9 @@ update-examples/%: examples/%.dx build
$(dex) script --allow-errors $< > $<.tmp
mv $<.tmp $<

run-gpu-tests: export DEX_ALLOC_CONTRACTIONS=0
run-gpu-tests: tests/gpu-tests.dx build
gpu-tests: run-gpu-tests/gpu-tests

run-gpu-tests/%: tests/%.dx build
misc/check-quine $< $(dex) --backend llvm-cuda script --allow-errors

update-gpu-tests: export DEX_ALLOW_CONTRACTIONS=0
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16 changes: 11 additions & 5 deletions src/lib/dexrt.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -234,17 +234,23 @@ void dex_cuMemcpyHtoD(int64_t bytes, char* device_ptr, char* host_ptr) {
CHECK(cuMemcpyHtoD, reinterpret_cast<CUdeviceptr>(device_ptr), host_ptr, bytes);
}

void dex_queryParallelismCUDA(const char* kernel_func, int64_t iters,
void dex_queryParallelismCUDA(char* kernel_func, int64_t iters,
int32_t* numWorkgroups, int32_t* workgroupSize) {
if (iters == 0) {
*numWorkgroups = 0;
*workgroupSize = 0;
return;
}
// TODO: Use the occupancy calculator, or at least use a fixed number of blocks?
const int64_t fixedWgSize = 1024;
*workgroupSize = fixedWgSize;
*numWorkgroups = std::min((iters + fixedWgSize - 1) / fixedWgSize, fixedWgSize);
int min_grid_size_for_max_occupancy;
int block_size_32;
CUfunction kernel = reinterpret_cast<CUfunction>(kernel_func);
CHECK(cuOccupancyMaxPotentialBlockSize,
&min_grid_size_for_max_occupancy,
&block_size_32,
kernel, nullptr, 0, 0);
int64_t block_size = block_size_32;
*workgroupSize = block_size;
*numWorkgroups = (iters + block_size - 1) / block_size;
}

void dex_loadKernelCUDA(const char* kernel_text, char** module_storage, char** kernel_storage) {
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