[ROCm] Resolve the indexer fp8 cache dtype once at import - #8
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current_platform.fp8_dtype() cannot change after import, but the sparse MLA indexer ops call it on every invocation - once per DSA layer per forward. vllm-project#46172 added the module-level FP8_DTYPE constant but left the call sites untouched. Route every use in rocm_aiter_mla_sparse.py through FP8_DTYPE and drop the per-call locals, so exactly one lookup survives, at import. The fused QK prologue's two call sites are not touched here: vllm#51315 moves that impl and its fake into _aiter_ops.py, where they already read that file's FP8_DTYPE constant. Signed-off-by: Sriram Kumar <sriramkumar.kishorekumar@amd.com>
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Summary
current_platform.fp8_dtype()cannot change after import, butvllm/v1/attention/ops/rocm_aiter_mla_sparse.pycalled it on every functioninvocation — once per DSA layer per forward pass, including inside the fused
QK prologue custom op.
vllm#46172 introduced a module-level
FP8_DTYPEconstant but only wired it upin two places and left five call sites behind. This PR routes every use through
the constant and removes the per-call locals, so exactly one
fp8_dtype()lookup survives, at import time.
Tests
No behavior change. Existing
test_rocm_aiter_mla_decode.pycovers the callpaths.