fix flashmla bug (#5272)

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

@@ -68,9 +68,6 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
         self.num_q_heads = (
             model_runner.model_config.num_attention_heads // get_attention_tp_size()
         )
-        self.num_kv_heads = model_runner.model_config.get_num_kv_heads(
-            get_attention_tp_size()
-        )
         self.req_to_token = model_runner.req_to_token_pool.req_to_token
         self.num_local_heads = (
             model_runner.model_config.num_attention_heads // get_attention_tp_size()
@@ -111,8 +108,8 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
                 )
                 mla_metadata, num_splits = get_mla_metadata(
                     forward_batch.seq_lens.to(torch.int32),
-                    Q_LEN * self.num_q_heads // self.num_kv_heads,
-                    self.num_kv_heads,
+                    Q_LEN * self.num_q_heads,
+                    1,
                 )
                 self.forward_metadata = FlashMLADecodeMetadata(
                     mla_metadata,
@@ -141,8 +138,8 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
 
         self.cuda_graph_mla_metadata, self.cuda_graph_num_splits = get_mla_metadata(
             torch.ones(max_bs, dtype=torch.int32, device=cuda_graph_kv_indices.device),
-            Q_LEN * self.num_q_heads // self.num_kv_heads,
-            self.num_kv_heads,
+            Q_LEN * self.num_q_heads,
+            1,
         )
         self.cuda_graph_kv_indices = cuda_graph_kv_indices
 
@@ -171,8 +168,8 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
                 )
                 mla_metadata, num_splits = get_mla_metadata(
                     seq_lens.to(torch.int32),
-                    Q_LEN * self.num_q_heads // self.num_kv_heads,
-                    self.num_kv_heads,
+                    Q_LEN * self.num_q_heads,
+                    1,
                 )
                 self.cuda_graph_mla_metadata.copy_(mla_metadata)
                 self.cuda_graph_num_splits[: bs + 1].copy_(num_splits)
@@ -221,8 +218,8 @@ class FlashMLABackend(FlashInferMLAAttnBackend):
             )
             mla_metadata, num_splits = get_mla_metadata(
                 seq_lens.to(torch.int32),
-                Q_LEN * self.num_q_heads // self.num_kv_heads,
-                self.num_kv_heads,
+                Q_LEN * self.num_q_heads,
+                1,
             )
             self.cuda_graph_mla_metadata.copy_(mla_metadata)
             self.cuda_graph_num_splits[: bs + 1].copy_(num_splits)