Replace time.time() to time.perf_counter() for benchmarking. (#6178)

Signed-off-by: Lifu Huang <lifu.hlf@gmail.com>

benchmark/multi_chain_reasoning/bench_sglang.py

@@ -90,7 +90,7 @@ def main(args):
     backend = select_sglang_backend(args)
 
     # Run requests
-    tic = time.time()
+    tic = time.perf_counter()
     states = multi_chain_gsm8k.run_batch(
         arguments,
         temperature=0,
@@ -98,7 +98,7 @@ def main(args):
         num_threads=args.parallel,
         progress_bar=True,
     )
-    latency = time.time() - tic
+    latency = time.perf_counter() - tic
 
     preds = []
     for i in range(len(states)):