Groupwise GEMM Full Kernel Tuning #4521
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Summary:
This diff introduces extensive kernel tuning and heuristics for Cutlass version of DeepGemm. With these heuristics, performance of the cutlass kernel is generally as good or better than DeepGemm for an equivalent workload and numerics are identical. This makes cutlass kernels in FBGEMM quite a bit easier to use than DeepGEMM as they are AOT compiled and do not require runtime tuning or JIT. We also expect substantially better performance for memory bound workloads like decode.
The key tricks we used to get this performance were limiting tile swizzling for compute bound shapes, which reduces register pressure and dramatically improves performance and doing an implicit input transpose for memory bound shapes that allows more efficient WGMMA tiling.
Benchmarking across a wide range of shapes shows the general performance benefits of these kernels in memory bound domains and their competitiveness with deepgemm in compute bound domains.
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Differential Revision: D78537466