[Log] Warning Once for Cutlass MLA

[yewentao256]

Purpose

Warning Once for Cutlass MLA

To avoid

(EngineCore_2 pid=2626618) WARNING 08-18 16:51:26 [cutlass_mla.py:126] Forcing num_kv_splits to 1
(EngineCore_2 pid=2626618) WARNING 08-18 16:51:26 [cutlass_mla.py:126] Forcing num_kv_splits to 1
(EngineCore_2 pid=2626618) WARNING 08-18 16:51:26 [cutlass_mla.py:126] Forcing num_kv_splits to 1
(EngineCore_2 pid=2626618) WARNING 08-18 16:51:26 [cutlass_mla.py:126] Forcing num_kv_splits to 1

[github-actions]

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[gemini-code-assist]

Code Review

This pull request aims to reduce log spam from Cutlass MLA by replacing logger.warning with logger.warning_once. While the intention is correct, the implementation of warning_once in vllm/logger.py is flawed. It uses functools.lru_cache on a function that takes a logging.Logger object as an argument. Since Logger objects are not hashable, this will lead to a TypeError at runtime, causing a crash. This critical issue needs to be fixed in vllm/logger.py for this change to work correctly.