[SpecV2-Mamba]: Refactor additional_ratio calculation when init mamba pool (#19660)

python/sglang/srt/model_executor/model_runner_kv_cache_mixin.py

@@ -342,10 +342,11 @@ class ModelRunnerKVCacheMixin:
 
         additional_ratio = 0
         if self.server_args.enable_mamba_extra_buffer():
-            if not self.spec_algorithm.is_none():
-                additional_ratio = MAMBA_CACHE_V2_ADDITIONAL_RATIO_NO_OVERLAP
-            else:
+            # ping-pong buffer size is 2 when overlap schedule is on, 1 otherwise.
+            if not self.server_args.disable_overlap_schedule:
                 additional_ratio = MAMBA_CACHE_V2_ADDITIONAL_RATIO_OVERLAP
+            else:
+                additional_ratio = MAMBA_CACHE_V2_ADDITIONAL_RATIO_NO_OVERLAP
 
         return MAMBA_CACHE_SIZE_MAX_RUNNING_REQUESTS_RATIO + additional_ratio