/* Run with high priority if the O/S permits (-p at startup) */
} else if (!strcasecmp(v->name, "highpriority")) {
ast_set2_flag(&ast_options, ast_true(v->value), AST_OPT_FLAG_HIGH_PRIORITY);
I assume it sets the nice level to a higher priority. Is that correct? What would be a reason not to set it by default?
That would depend on what else was contending with Asterisk. In general you should either dedicate a real machine to Asterisk or dedicate several real cores, in a virtual environment. However, if there is contention between Asterisk and other applications, for the same cores, someone with an overview of the complete work load, would need to make a policy decision, based on which application needed greater access to the available resources.