[LMCache] Pass TP size in lookup for MLA multi-reader locking (#36129)

Signed-off-by: baoloongmao <baoloongmao@tencent.com>
Co-authored-by: Yihua Cheng <yihua98@uchicago.edu>

vllm/distributed/kv_transfer/kv_connector/v1/lmcache_integration/multi_process_adapter.py

@@ -114,6 +114,7 @@ class LMCacheMPSchedulerAdapter:
         world_size: int,
         kv_rank: int,
         vllm_block_size: int,
+        tp_size: int = 1,
     ):
         """
         Args:
@@ -124,6 +125,8 @@ class LMCacheMPSchedulerAdapter:
             world_size: The world size used for LMCache keys
             kv_rank: The kv rank used for LMCache keys
             vllm_block_size: The block size used in vLLM
+            tp_size: Tensor-parallel size for MLA
+                multi-reader locking (default 1).
         """
         self.mq_client = MessageQueueClient(server_url, context)
 
@@ -133,6 +136,7 @@ class LMCacheMPSchedulerAdapter:
         self.model_name = model_name
         self.world_size = world_size
         self.worker_id = kv_rank
+        self.tp_size = tp_size
 
         # Read chunk size from lmcache
         self.chunk_size = get_lmcache_chunk_size(self.mq_client)
@@ -281,6 +285,7 @@ class LMCacheMPSchedulerAdapter:
             start=start,
             end=end,
             request_id=request_id,
+            tp_size=self.tp_size,
         )
 
     def _create_hash_key(
@@ -293,6 +298,7 @@ class LMCacheMPSchedulerAdapter:
             worker_id=None,
             chunk_hash=chunk_hash,
             request_id=request_id,
+            tp_size=self.tp_size,
         )
 
 

vllm/distributed/kv_transfer/kv_connector/v1/lmcache_mp_connector.py

 # SPDX-License-Identifier: Apache-2.0
 # SPDX-FileCopyrightText: Copyright contributors to the vLLM project
 import enum
+import inspect
 from collections.abc import Iterable
 from dataclasses import dataclass, field
 from typing import TYPE_CHECKING, Any, Literal
@@ -52,6 +53,12 @@ if TYPE_CHECKING:
 logger = lmcache_init_logger(__name__)
 
 
+def _adapter_accepts_tp_size() -> bool:
+    """Check if the imported adapter accepts tp_size."""
+    sig = inspect.signature(LMCacheMPSchedulerAdapter.__init__)
+    return "tp_size" in sig.parameters
+
+
 # Helper functions
 def reformat_block_ids(block_ids: tuple[list[int], ...] | None) -> list[int]:
     if block_ids is None:
@@ -101,6 +108,14 @@ def create_scheduler_adapter(
         vllm_config.parallel_config.rank,
         vllm_config,
     )
+    tp_size = vllm_config.parallel_config.tensor_parallel_size
+
+    # Pass tp_size only when the adapter accepts it so that
+    # a newer vllm can still work with an older LMCache.
+    kwargs: dict[str, Any] = {}
+    if _adapter_accepts_tp_size():
+        kwargs["tp_size"] = tp_size
+
     return LMCacheMPSchedulerAdapter(
         server_url,
         zmq_context,
@@ -108,6 +123,7 @@ def create_scheduler_adapter(
         world_size,
         kv_rank,
         vllm_config.cache_config.block_size,
+        **kwargs,
     )