[Qwen3-next] Add PD disaggregation support for mamba with extra_buffer (#15180)

Signed-off-by: Shangming Cai <csmthu@gmail.com>
Co-authored-by: ybyang <10629930+whybeyoung@users.noreply.github.com>

python/sglang/srt/disaggregation/decode.py

@@ -144,6 +144,7 @@ class HybridMambaDecodeReqToTokenPool(HybridReqToTokenPool):
         enable_memory_saver: bool,
         cache_params: "Mamba2CacheParams",
         speculative_num_draft_tokens: int,
+        enable_mamba_extra_buffer: bool,
         pre_alloc_size: int,
     ):
         DecodeReqToTokenPool.__init__(
@@ -154,10 +155,11 @@ class HybridMambaDecodeReqToTokenPool(HybridReqToTokenPool):
             enable_memory_saver=enable_memory_saver,
             pre_alloc_size=pre_alloc_size,
         )
-        self.enable_memory_saver = enable_memory_saver
-        self.enable_mamba_extra_buffer = (
-            False  # TODO: add PD support for mamba cache extra_buffer
+        self.mamba_ping_pong_track_buffer_size = (
+            2 if speculative_num_draft_tokens is None else 1
         )
+        self.enable_mamba_extra_buffer = enable_mamba_extra_buffer
+        self.enable_memory_saver = enable_memory_saver
         self._init_mamba_pool(
             size=size + pre_alloc_size,
             mamba_spec_state_size=size + pre_alloc_size,

python/sglang/srt/model_executor/model_runner.py

@@ -1797,6 +1797,7 @@ class ModelRunner:
                         enable_memory_saver=self.server_args.enable_memory_saver,
                         cache_params=config.mamba2_cache_params,
                         speculative_num_draft_tokens=self.server_args.speculative_num_draft_tokens,
+                        enable_mamba_extra_buffer=self.server_args.enable_mamba_extra_buffer(),
                         pre_alloc_size=pre_alloc_size,
                     )
                 else:

python/sglang/srt/server_args.py

@@ -1382,9 +1382,6 @@ class ServerArgs:
                 assert (
                     is_cuda()
                 ), "Mamba extra_buffer is only supported on CUDA devices with FLA backend"
-                assert (
-                    self.disaggregation_mode == "null"
-                ), "Mamba extra_buffer is not compatible with disaggregation mode yet."
                 if self.speculative_num_draft_tokens is not None:
                     assert (
                         self.mamba_track_interval >= self.speculative_num_draft_tokens