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[Bugfix][MLA] Change default SM100 MLA prefill backend back to TRT-LLM #38562

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vllm-bot merged 1 commit into from
Mar 30, 2026
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[Bugfix][MLA] Change default SM100 MLA prefill backend back to TRT-LLM #38562

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2 changes: 1 addition & 1 deletion vllm/config/attention.py
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Original file line number Diff line number Diff line change
Expand Up @@ -30,7 +30,7 @@ class AttentionConfig:
use_cudnn_prefill: bool = False
"""Whether to use cudnn prefill."""

use_trtllm_ragged_deepseek_prefill: bool = False
use_trtllm_ragged_deepseek_prefill: bool = True
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@mgoin mgoin Mar 30, 2026

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Where do we control FA4 MLA prefill? I don't see a similar entry for it

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@MatthewBonanni MatthewBonanni Mar 30, 2026

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It falls through to FA4 when trtllm isn't enabled. It's a messy interface, #32623 will clean this up

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@MatthewBonanni MatthewBonanni Mar 30, 2026

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Relevant code block is here:

vllm/vllm/model_executor/layers/attention/mla_attention.py

Line 2130 in dbdd9ae

else: # Use FlashAttention

"""Whether to use TRTLLM ragged deepseek prefill."""

use_trtllm_attention: bool | None = None
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