usdt::tide:startroute 
{ 
    @start[arg2] = nsecs;
}
usdt::tide:endroute 
/@start[arg2]/ 
{ 
    $duration_us = (nsecs - @start[arg2]) / 1000;        
    @us[str(arg0), str(arg1)] = hist($duration_us);
    delete(@start[arg2]);
}