Add a hint when MaxVUs is more than the total number of iterations

Combined with mentions in the readme, docs and CLI help this should be enough to prevent confusion, so we can close #663

cmd/options.go

@@ -48,7 +48,7 @@ func optionFlagSet() *pflag.FlagSet {
 	flags.Int64P("vus", "u", 1, "number of virtual users")
 	flags.Int64P("max", "m", 0, "max available virtual users")
 	flags.DurationP("duration", "d", 0, "test duration limit")
-	flags.Int64P("iterations", "i", 0, "script iteration limit")
+	flags.Int64P("iterations", "i", 0, "script total iteration limit (among all VUs)")
 	flags.StringSliceP("stage", "s", nil, "add a `stage`, as `[duration]:[target]`")
 	flags.BoolP("paused", "p", false, "start the test in a paused state")
 	flags.Int64("max-redirects", 10, "follow at most n redirects")

cmd/run.go

@@ -147,6 +147,13 @@ a commandline interface for interacting with it.`,
 			conf.Iterations = null.IntFrom(1)
 		}
 
+		if conf.Iterations.Valid && conf.Iterations.Int64 < conf.VUsMax.Int64 {
+			log.Warnf(
+				"All iterations (%d in this test run) are shared between all VUs, so some of the %d VUs will not execute even a single iteration!",
+				conf.Iterations.Int64, conf.VUsMax.Int64,
+			)
+		}
+
 		// If duration is explicitly set to 0, it means run forever.
 		if conf.Duration.Valid && conf.Duration.Duration == 0 {
 			conf.Duration = types.NullDuration{}