Remove unnecessary metadata_expand.max_seq_len_k operations in fa3 to… (#7140)

python/sglang/srt/layers/attention/flashattention_backend.py

@@ -394,7 +394,6 @@ class FlashAttentionBackend(AttentionBackend):
                         dtype=torch.int32,
                     )
                     metadata_expand.max_seq_len_q = 1
-                    metadata_expand.max_seq_len_k = self.speculative_step_id + 1
                     metadata_expand.cu_seqlens_q = torch.arange(
                         0,
                         metadata_expand.cache_seqlens_int32.numel() + 1,
@@ -550,9 +549,6 @@ class FlashAttentionBackend(AttentionBackend):
                     ),
                     (1, 0),
                 )
-                metadata_expand.max_seq_len_k = (
-                    metadata_expand.cache_seqlens_int32.max().item()
-                )
                 self.forward_metadata_spec_decode_expand = metadata_expand
         elif forward_batch.forward_mode.is_extend_or_draft_extend_or_mixed():
             metadata.cache_seqlens_int32 = seqlens_in_batch.to(torch.int32)
@@ -1421,9 +1417,6 @@ class FlashAttentionBackend(AttentionBackend):
                         ]
                     )
                     metadata_expand.max_seq_len_q = 1
-                    metadata_expand.max_seq_len_k = (
-                        self.speculative_step_id + 1
-                    )  # , do this in replay
                     metadata_expand.cu_seqlens_q = (
                         self.draft_decode_metadata_topk_expand["cu_seqlens_q"][
                             : bs * self.topk + 1
@@ -1766,9 +1759,6 @@ class FlashAttentionBackend(AttentionBackend):
                         dtype=torch.int32,
                     )
                 )
-                metadata_expand.max_seq_len_k = (
-                    metadata_expand.cache_seqlens_int32.max().item()
-                )
         elif forward_mode.is_draft_extend():
             metadata = self.draft_extend_metadata[bs]
             metadata.cache_seqlens_int32.copy_(seq_lens)