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Device resident GPU block buffer instead of UVM as hit likely UVM

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bug. Code worked on CUDA 11.4 but fails on later drivers (certainly 530.30.02, but need to
find the perlmutter driver version).
This commit is contained in:
Peter Boyle 2023-03-22 19:07:32 -04:00
parent c6621806ca
commit d0bb033ea2
1 changed files with 19 additions and 4 deletions
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23
Grid/lattice/Lattice_reduction_gpu.h
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@ -211,13 +211,28 @@ inline typename vobj::scalar_objectD sumD_gpu_small(const vobj *lat, Integer osi
assert(ok);
Integer smemSize = numThreads * sizeof(sobj);
Vector<sobj> buffer(numBlocks);
// UVM seems to be buggy under later CUDA drivers
// This fails on A100 and driver 5.30.02 / CUDA 12.1
// Fails with multiple NVCC versions back to 11.4,
// which worked with earlier drivers.
// Not sure which driver had first fail and this bears checking
// Is awkward as must install multiple driver versions
#undef UVM_BLOCK_BUFFER
#ifndef UVM_BLOCK_BUFFER
commVector<sobj> buffer(numBlocks);
sobj *buffer_v = &buffer[0];
sobj result;
reduceKernel<<< numBlocks, numThreads, smemSize >>>(lat, buffer_v, size);
accelerator_barrier();
auto result = buffer_v[0];
acceleratorCopyFromDevice(buffer_v,&result,sizeof(result));
#else
Vector<sobj> buffer(numBlocks);
sobj *buffer_v = &buffer[0];
sobj result;
reduceKernel<<< numBlocks, numThreads, smemSize >>>(lat, buffer_v, size);
accelerator_barrier();
result = *buffer_v;
#endif
return result;
}