}
 
 static void print_metric_headers_std(struct perf_stat_config *config,
-                                    const char *prefix, bool no_indent)
+                                    bool no_indent)
 {
-       if (prefix)
-               fprintf(config->output, "%s", prefix);
+       fputc(' ', config->output);
 
        if (!no_indent) {
                int len = aggr_header_lens[config->aggr_mode];
 }
 
 static void print_metric_headers_csv(struct perf_stat_config *config,
-                                    const char *prefix,
                                     bool no_indent __maybe_unused)
 {
-       if (prefix)
-               fprintf(config->output, "%s", prefix);
        if (config->interval)
                fputs("time,", config->output);
        if (!config->iostat_run)
 }
 
 static void print_metric_headers_json(struct perf_stat_config *config,
-                                     const char *prefix __maybe_unused,
                                      bool no_indent __maybe_unused)
 {
        if (config->interval)
 }
 
 static void print_metric_headers(struct perf_stat_config *config,
-                                struct evlist *evlist,
-                                const char *prefix, bool no_indent)
+                                struct evlist *evlist, bool no_indent)
 {
        struct evsel *counter;
        struct outstate os = {
        };
 
        if (config->json_output)
-               print_metric_headers_json(config, prefix, no_indent);
+               print_metric_headers_json(config, no_indent);
        else if (config->csv_output)
-               print_metric_headers_csv(config, prefix, no_indent);
+               print_metric_headers_csv(config, no_indent);
        else
-               print_metric_headers_std(config, prefix, no_indent);
+               print_metric_headers_std(config, no_indent);
 
        if (config->iostat_run)
                iostat_print_header_prefix(config);
        }
 
        if (config->metric_only)
-               print_metric_headers(config, evlist, " ", true);
+               print_metric_headers(config, evlist, true);
        else
                fprintf(output, " %*s %*s events\n",
                        COUNTS_LEN, "counts", config->unit_width, "unit");
        fprintf(output, ":\n\n");
 
        if (config->metric_only)
-               print_metric_headers(config, evlist, " ", false);
+               print_metric_headers(config, evlist, false);
 }
 
 static void print_header_csv(struct perf_stat_config *config,
                             const char **argv __maybe_unused)
 {
        if (config->metric_only)
-               print_metric_headers(config, evlist, " ", true);
+               print_metric_headers(config, evlist, true);
 }
 static void print_header_json(struct perf_stat_config *config,
                              struct target *_target __maybe_unused,
                              const char **argv __maybe_unused)
 {
        if (config->metric_only)
-               print_metric_headers(config, evlist, " ", true);
+               print_metric_headers(config, evlist, true);
 }
 
 static void print_header(struct perf_stat_config *config,