benchmarking request between index.php and other controllers

Hi
in Ci3 can I place:

PHP Code:

$this->benchmark->mark('code_start'); 


in the "index.php" page, so I start my benchmark the moment the request gets in. Then at the target controller (in the function of interest) i will place the rest:

PHP Code:

$this->benchmark->mark('code_end');
  
echo $this->benchmark->elapsed_time('code_start', 'code_end'); 


Will that be accurate, do I need to load, pre-load? any ideas on this?

Thx guys.