[Perf] Cache vllm.env.__getattr__ result to avoid recomputation (#26146)

Signed-off-by: Jialin Ouyang <Jialin.Ouyang@gmail.com>

vllm/v1/executor/multiproc_executor.py

@@ -33,6 +33,7 @@ from vllm.distributed.parallel_state import (
     get_pp_group,
     get_tp_group,
 )
+from vllm.envs import enable_envs_cache
 from vllm.logger import init_logger
 from vllm.utils import (
     _maybe_force_spawn,
@@ -455,6 +456,10 @@ class WorkerProc:
         # Load model
         self.worker.load_model()
 
+        # Enable environment variable cache (e.g. assume no more
+        # environment variable overrides after this point)
+        enable_envs_cache()
+
     @staticmethod
     def make_worker_process(
         vllm_config: VllmConfig,