Super tiny rename total_train_time to step_time for clarity (#629)

Author: fzyzcjy

slime/backends/megatron_utils/data.py

@@ -452,7 +452,7 @@ def log_perf_data(rollout_id: int, args: Namespace) -> None:
         if "perf/train_wait_time" in log_dict and "perf/train_time" in log_dict:
             total_time = log_dict["perf/train_wait_time"] + log_dict["perf/train_time"]
             if total_time > 0:
-                log_dict["perf/total_train_time"] = total_time
+                log_dict["perf/step_time"] = total_time
                 log_dict["perf/wait_time_ratio"] = log_dict["perf/train_wait_time"] / total_time
 
         print(f"perf {rollout_id}: {log_dict}")