[Performance] Cache loaded custom logitsprocs to avoid overheads (#28462)

Signed-off-by: Isotr0py <mozf@mail2.sysu.edu.cn>

vllm/v1/sample/logits_processor/__init__.py

@@ -5,7 +5,7 @@ import inspect
 import itertools
 from abc import abstractmethod
 from collections.abc import Sequence
-from functools import partial
+from functools import lru_cache, partial
 from typing import TYPE_CHECKING
 
 import torch
@@ -216,11 +216,17 @@ def build_logitsprocs(
     )
 
 
+cached_load_custom_logitsprocs = lru_cache(_load_custom_logitsprocs)
+
+
 def validate_logits_processors_parameters(
     logits_processors: Sequence[str | type[LogitsProcessor]] | None,
     sampling_params: SamplingParams,
 ):
-    for logits_procs in _load_custom_logitsprocs(logits_processors):
+    logits_processors = (
+        tuple(logits_processors) if logits_processors is not None else None
+    )
+    for logits_procs in cached_load_custom_logitsprocs(logits_processors):
         logits_procs.validate_params(sampling_params)