[Bugfix] Fix max_num_batched_tokens for MLA (vllm-project#13620)

Signed-off-by: mgoin <mgoin64@gmail.com>

Author: mgoin

vllm/config.py

@@ -51,6 +51,9 @@
 
 logger = init_logger(__name__)
 
+# This value is chosen to have a balance between ITL and TTFT. Note it is
+# not optimized for throughput.
+_DEFAULT_MAX_NUM_BATCHED_TOKENS = 2048
 _POOLING_MODEL_MAX_NUM_BATCHED_TOKENS = 32768
 _MULTIMODAL_MODEL_MAX_NUM_BATCHED_TOKENS = 5120
 
@@ -1526,15 +1529,17 @@ def __post_init__(self) -> None:
                     # for now. Have max_num_batched_tokens set to max_model_len
                     # so we don't reject sequences on account of a short
                     # max_num_batched_tokens.
-                    self.max_num_batched_tokens = max(self.max_model_len, 2048)
+                    self.max_num_batched_tokens = max(
+                        self.max_model_len, _DEFAULT_MAX_NUM_BATCHED_TOKENS)
                 else:
-                    # This value is chosen to have a balance between ITL
-                    # and TTFT. Note it is not optimized for throughput.
-                    self.max_num_batched_tokens = 2048
+                    self.max_num_batched_tokens = (
+                        _DEFAULT_MAX_NUM_BATCHED_TOKENS)
             else:
-                # If max_model_len is too short, use 2048 as the default value
+                # If max_model_len is too short, use
+                # _DEFAULT_MAX_NUM_BATCHED_TOKENS as the default value
                 # for higher throughput.
-                self.max_num_batched_tokens = max(self.max_model_len, 2048)
+                self.max_num_batched_tokens = max(
+                    self.max_model_len, _DEFAULT_MAX_NUM_BATCHED_TOKENS)
 
             if self.runner_type == "pooling":
                 # Choose specific value for higher throughput
@@ -3333,6 +3338,9 @@ def __post_init__(self):
                         "caching to be disabled.")
             self.scheduler_config.enable_chunked_prefill = False
             self.scheduler_config.chunked_prefill_enabled = False
+            self.scheduler_config.max_num_batched_tokens = max(
+                self.scheduler_config.max_model_len,
+                _DEFAULT_MAX_NUM_BATCHED_TOKENS)
 
             if self.cache_config is not None:
                 self.cache_config.enable_prefix_caching = False