DTRACEOPT_SWITCHRATE
dtrace_optval_t interval = dtp->dt_options[DTRACEOPT_SWITCHRATE];
{ "switchrate", dt_opt_rate, DTRACEOPT_SWITCHRATE },
{ DTRACEOPT_SWITCHRATE, offsetof(dtrace_hdl_t, dt_lastswitch) },
opt[DTRACEOPT_SWITCHRATE] = dtrace_switchrate_default;