This plugin dumps the colorized filenames and memory consumptions or file sizes after the normal WordPress HTML output, after the closing html tag. This generates invalid HTML but gives you an overview of loaded plugins and the current theme.
What’s running lists all files parsed and executed by the PHP engine. It can be used for plugin or theme refactoring.
Provide a part of its path in wp-config.php:
define( 'WHATS_RUNNING_HIGHLIGHT', 'wp-content/plugins/my-plugin' );
You can watch WP core bug #28364 to get more information about WordPress entry points.
You can find some documentaion here what makes a WordPress plugin efficient: https://github.com/szepeviktor/WPHW
Development of this plugin goes on on GitHub.