Drupal 8 performance: enabling the classloader cache
Drupal 8 is using some of the PHP language features that make PHP a "more or less decent" programming language and one of them is Autoloading. But because autoloading in PHP leaves the real autoloading job to userland code this can easily have very nasty performance implications.
If you want to use Autoloading now in Drupal 7 check out the extremely useful XAutoload module.
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