PHP's APC extension includes two configuration settings for enabling lazy loading of functions and classes; apc.lazy_functions
and apc.lazy_classes
.
My websites use APC with noticable performance benefits. They've also had the lazy loading settings enabled and disabled at various times, with no obviously noticable difference.
On the internet there isn't much on the subject other than mere discussion, but no metrics.
Has anybody actually measured the performance impact of using APC lazy loading or are there people who have noticed significant differences using these settings? When is it advantageous to enable lazy loading? When should it be avoided at all cost?