[benchmarks]allow skip ready check for bench serve (#25420)

Signed-off-by: Lu Fang <fanglu@fb.com>
Signed-off-by: Lucia Fang <116399278+luccafong@users.noreply.github.com>
Co-authored-by: Lucia (Lu) Fang <fanglu@meta.com>

vllm/benchmarks/serve.py

@@ -531,6 +531,7 @@ async def benchmark(
         extra_body=extra_body,
     )
 
+    if ready_check_timeout_sec > 0:
         test_output = await wait_for_endpoint(
             request_func,
             test_input,
@@ -539,10 +540,13 @@ async def benchmark(
         )
         if not test_output.success:
             raise ValueError(
-            "Initial test run failed - Please make sure benchmark arguments "
-            f"are correctly specified. Error: {test_output.error}")
+                "Initial test run failed - Please make sure benchmark "
+                "arguments are correctly specified. "
+                f"Error: {test_output.error}")
         else:
             print("Initial test run completed. Starting main benchmark run...")
+    else:
+        print("Skipping endpoint ready check.")
 
     if lora_modules:
         # For each input request, choose a LoRA module at random.
@@ -1151,7 +1155,8 @@ def add_cli_args(parser: argparse.ArgumentParser):
         type=int,
         default=600,
         help="Maximum time to wait for the endpoint to become ready "
-        "in seconds (default: 600 seconds / 10 minutes).",
+        "in seconds (default: 600 seconds / 10 minutes). If set to 0, "
+        "the ready check will be skipped."
     )