#1265: replay: clarify usage in tool

tools/workload_replay/simulate_replay.cc

@@ -51,14 +51,18 @@ int main(int argc, char** argv) {
 
   vtAbortIf(
     argc != 3,
-    "Must have two arguments: <initial phase> <phases to run>"
+    "Must have two app-specific arguments: <initial phase> <phases to run>\n"
+    "The json workload files needs to be specified using\n"
+    "--vt_lb_stats_file_in and --vt_lb_stats_dir_in"
   );
 
   // initial phase to simulate
   PhaseType initial_phase = atoi(argv[1]);
   // number of phases to simulate
   PhaseType phases_to_run = atoi(argv[2]);
 
+  // the workloads used will be those specified with the command-line arguments
+  // --vt_lb_stats_file_in and --vt_lb_stats_dir_in
   vt::vrt::collection::balance::replayWorkloads(
     initial_phase, phases_to_run
   );