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Fix Flashinfer Allreduce+Norm enable disable calculation based on fi_allreduce_fusion_max_token_num #21325

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Merged
merged 3 commits into from
Jul 22, 2025
+13 −6
Merged

Fix Flashinfer Allreduce+Norm enable disable calculation based on fi_allreduce_fusion_max_token_num #21325

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3fb686f
fix flashifner enable disable calculation
xinli-sw Jul 21, 2025
bf3fa63
address copilot feedback
xinli-sw Jul 21, 2025
8195e6c
address review feedback when world size is uncommon
xinli-sw Jul 21, 2025
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19 changes: 13 additions & 6 deletions vllm/compilation/collective_fusion.py
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Original file line number Diff line number Diff line change
Expand Up @@ -159,6 +159,9 @@ def __call__(self, graph: fx.Graph):
6: MiB // 2, # 512KB
8: MiB // 2, # 512KB
}
# opt for a more conservative default value
# when world size is not in _FI_MAX_SIZES
_DEFAULT_FI_MAX_SIZE = MiB // 2

def call_trtllm_fused_allreduce_norm(
allreduce_in: torch.Tensor,
Expand All @@ -173,12 +176,16 @@ def call_trtllm_fused_allreduce_norm(
max_token_num: int,
norm_out: Optional[torch.Tensor] = None,
) -> None:
use_flashinfer = allreduce_in.shape[0] * allreduce_in.shape[
1] * allreduce_in.element_size() <= min(
_FI_MAX_SIZES[world_size],
max_token_num * allreduce_in.shape[0] *
allreduce_in.element_size(),
)

num_tokens, hidden_size = allreduce_in.shape
element_size = allreduce_in.element_size()
current_tensor_size = num_tokens * hidden_size * element_size
max_fusion_size = max_token_num * hidden_size * element_size
use_flashinfer = current_tensor_size <= min(
_FI_MAX_SIZES.get(world_size, _DEFAULT_FI_MAX_SIZE),
max_fusion_size,
)

if use_flashinfer:
assert (_FI_WORKSPACE_TENSOR is not None
), "Flashinfer must be enabled when using flashinfer"
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