Move --shm-name from MPServerConfig to L1MemoryManagerConfig

[Copilot]

--shm-name was parsed into MPServerConfig.shm_name but never propagated to L1MemoryManagerConfig.shm_name before StorageManager was created. Result: the allocator created the SHM segment under the default pid-based name while _compute_shm_pool_info returned the user-specified name — worker got FileNotFoundError.

Changes

• lmcache/v1/multiprocess/config.py: Remove shm_name field from MPServerConfig, remove --shm-name from add_mp_server_args, remove shm_name=args.shm_name from parse_args_to_mp_server_config.

• lmcache/v1/distributed/config.py: Add --shm-name to add_storage_manager_args (L1 Memory Manager group). In parse_args_to_config, pass it directly into L1MemoryManagerConfig:

  shm_name = getattr(args, "shm_name", None)
  memory_config = L1MemoryManagerConfig(
      size_in_bytes=int(args.l1_size_gb * (1 << 30)),
      use_lazy=args.l1_use_lazy,
      init_size_in_bytes=int(args.l1_init_size_gb * (1 << 30)),
      align_bytes=args.l1_align_bytes,
      **({"shm_name": shm_name} if shm_name is not None else {}),
  )

  The conditional unpacking is intentional: L1MemoryManagerConfig.shm_name uses a default_factory for the pid-based name; passing None would suppress it. Empty string "" explicitly disables SHM; a name uses that segment.

The CLI invocation is unchanged — --shm-name moves transparently from the MP Server arg group to the L1 Memory Manager arg group.

Original prompt

Move --shm-name from MPServerConfig / add_mp_server_args to L1MemoryManagerConfig / add_storage_manager_args so that the allocator directly uses the user-specified SHM name.

Current problem

--shm-name is parsed into MPServerConfig.shm_name but never written into L1MemoryManagerConfig.shm_name before the StorageManager is created. The allocator creates a segment with the default pid-based name (lmcache_l1_pool_{pid}) while _compute_shm_pool_info returns the user-specified name → worker gets FileNotFoundError.

Required changes

1. lmcache/v1/multiprocess/config.py: Remove --shm-name from add_mp_server_args and remove shm_name field from MPServerConfig. Remove shm_name=args.shm_name from parse_args_to_mp_server_config.

2. lmcache/v1/distributed/config.py:

   • Add --shm-name argument to add_storage_manager_args in the "L1 Memory Manager" group:

     memory_group.add_argument(
         "--shm-name",
         type=str,
         default=None,
         help="POSIX shared-memory segment name for L1 pool. "
         "Default (not specified): auto-allocate pid-based name. "
         'Set to "" to disable SHM. '
         "Set to a name to use that specific SHM segment.",
     )

   • In parse_args_to_config, pass shm_name into L1MemoryManagerConfig when provided:

     shm_name = getattr(args, "shm_name", None)
     memory_config = L1MemoryManagerConfig(
         size_in_bytes=int(args.l1_size_gb * (1 << 30)),
         use_lazy=args.l1_use_lazy,
         init_size_in_bytes=int(args.l1_init_size_gb * (1 << 30)),
         align_bytes=args.l1_align_bytes,
         **({"shm_name": shm_name} if shm_name is not None else {}),
     )

3. lmcache/v1/multiprocess/modules/non_gpu_transfer.py: Remove the _shm_name_override logic from NonGPUTransferModule.__init__ and the override branch in _compute_shm_pool_info. Revert __init__ signature to just (self, ctx: MPCacheEngineContext) (no mp_config parameter). Remove the MPServerConfig import.

4. lmcache/v1/multiprocess/server.py:

   • Revert NonGPUTransferModule(ctx, mp_config) back to NonGPUTransferModule(ctx).
   • Remove the if mp_config.shm_name is not None: override block if present.

5. Update tests in tests/v1/multiprocess/test_non_cuda_data_transfer.py: Remove or update tests that reference MPServerConfig(shm_name=...) in NonGPUTransferModule construction. The tests for _compute_shm_pool_info should now just set storage_manager_config.l1_manager_config.memory_config.shm_name directly.

Branch

Base branch: ww21_PR_shm

The following is the prior conversation context from the user's chat exploration (may be truncated):

User: 怎么又改server，能不在这层改吗

Assistant: 改在 parse_args_to_config 那层，让 --shm-name 直接写进 L1MemoryManagerConfig.shm_name。

看 config.py 第 294-299 行，parse_args_to_config 构造 L1MemoryManagerConfig 时没传 shm_name。但 --shm-name 是在 mp_server_args 里定义的，不在 storage_manager_args 里。

最干净的改法：把 shm_name 加到 add_storage_manager_args 里，parse_args_to_config 直接传进去。

但如果你不想改 storage_manager 的 arg 定义（因为它是通用的），那就改 MPServerConfig 的调用方 —— 在 parse_args_to_mp_server_config 之后、创建 context 之前。不管怎样都得在 server.py 或 http_server.py 的入口处做。

或者，改 MPCacheEngineContext.__init__，让它接收 shm_name_override 参数：

class MPCacheEngineContext:
    def __init__(
        self,
        storage_manager_config: StorageManagerConfig,
        chunk_size: int = 256,
        hash_algorithm: str = "blake3",
        shm_name_override: str | None = None,
    ) -> None:
        self._chunk_size = chunk_size
        self._storage_manager_config = storage_manager_config

        # Apply shm_name override before creating StorageManager
        if shm_name_override is not None:
            storage_manager_config.l1_manager_config.memory_config.shm_name = (
                shm_name_override
            )

        self._storage_manager = StorageManager(storage_manager_config)
        self._token_hasher = TokenHasher(
            chunk_size=chunk_size, hash_algorithm=hash_algorithm
        )
        self._session_manager = SessionManager(self._token_hasher)
        self._event_bus = get_event_bus()
        self._layout_desc_registry = LayoutDescRegistry()

然后 server.py 只改传参：

    ctx = MPCacheEngineContext(
        storage_manager_config=storage_manager_config,
        chunk_size=mp_config.chunk_size,
        hash_algorithm=mp_config.hash_algorithm,
        shm_name_override=mp_config.shm_name,
    )

这样 server.py 只多传一个参数，逻辑全在 engine_context.py 里。你觉得行吗？

User: @hlin99/LMCache/pull/308 这个PR不是已经做了吗

Assistant: 你说得对，PR #308 确实改了 _compute_shm_pool_info 让它返回 override 的名字。

但问题是这只改了"告诉 worker 用什么名字"，没改"allocator 实际用什么名字创建 segment"。

PR #308 的改法：

• _compute_shm_pool_info 返回 lmcache_l1_pool_hlin ✅
• 但 StorageManager 创建时 config 里的 shm_name 还是默...

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