Check for open() syscalls
~> grep open strace.out
open("/var/www/wp1/wp-load.php", O_RDONLY) = 27
open("/var/www/wp1/wp-config.php", O_RDONLY) = 27
open("/var/www/wp1/wp-settings.php", O_RDONLY) = 27
open("/var/www/wp1/wp-includes/pomo/translations.php", O_RDONLY) = 27
open("/var/www/wp1/wp-includes/pomo/entry.php", O_RDONLY) = 27
open("/var/www/wp1/wp-includes/pomo/streams.php", O_RDONLY) = 27
open("/var/www/wp1/wp-includes/wp-db.php", O_RDONLY) = 27
open("/var/www/wp1/wp-includes/cache.php", O_RDONLY) = 28
open("/var/www/wp1/wp-includes/l10n.php", O_RDONLY) = 28
open("/var/www/wp1/wp-includes/default-widgets.php", O_RDONLY) = 28
open("/var/www/wp1/wp-includes/locale.php", O_RDONLY) = 28
open("/var/www/wp1/wp-includes/template-loader.php", O_RDONLY) = 28
open("/var/www/wp1/wp-content/themes/twentyeleven/header.php", O_RDONLY) = 28
open("/var/www/wp1/wp-content/themes/twentyeleven/style.css", O_RDONLY) = 28
open("/var/www/wp1/wp-content/themes/twentyeleven/footer.php", O_RDONLY) = 28
open("/var/www/wp1/wp-content/themes/twentyeleven/sidebar-footer.php", O_RDONLY) = 28
Conditional config include in wp-load.php
<?php
if ( file_exists( ABSPATH . 'wp-config.php') ) {

        /** The config file resides in ABSPATH */
        require_once( ABSPATH . 'wp-config.php' );

} elseif ( file_exists( dirname(ABSPATH) . '/wp-config.php' ) && ! file_exists( dirname(ABSPATH) . '/wp-settings.php' ) ) {

        /** The config file resides one level above ABSPATH but is not part of another install */
        require_once( dirname(ABSPATH) . '/wp-config.php' );

} else {

        // A config file doesn't exist

        // Set a path for the link to the installer
        if ( strpos($_SERVER['PHP_SELF'], 'wp-admin') !== false )
                $path = 'setup-config.php';
        else
                $path = 'wp-admin/setup-config.php';

        define( 'WPINC', 'wp-includes' );
        define( 'WP_CONTENT_DIR', ABSPATH . 'wp-content' );
        require_once( ABSPATH . WPINC . '/load.php' );
        require_once( ABSPATH . WPINC . '/version.php' );

        wp_load_translations_early();
        wp_check_php_mysql_versions();

        // Die with an error message
        $die  = __( "There doesn't seem to be a <code>wp-config.php</code> file. I need this before we can get started." ) . '</p>';
        $die .= '<p>' . __( "Need more help? <a href='http://codex.wordpress.org/Editing_wp-config.php'>We got it</a>." ) . '</p>';
        $die .= '<p>' . __( "You can create a <code>wp-config.php</code> file through a web interface, but this doesn't work for all server setups. The safest way is to manually create the file." ) . '</p>';
        $die .= '<p><a href="' . $path . '" class="button">' . __( "Create a Configuration File" ) . '</a>';

        wp_die( $die, __( 'WordPress &rsaquo; Error' ) );
}
Replace with
<?php
include './wp-config.php';
Get rid of require_once of wp-settings.php in wp-config.php
<?php
#require_once(ABSPATH . 'wp-settings.php');
require './wp-settings.php';
Get rid of require_once calls in wp-settings.php
<?php
#require_once( ABSPATH . WPINC . '/l10n.php' )
require './wp-includes/l10n.php';
...
require_once( ABSPATH . WPINC . '/locale.php' );
require './wp-includes/locale.php';
Conditional did-header check in wp-blog-header.php
<?php
#if ( !isset($wp_did_header) ) {
#  $wp_did_header = true;
#  require_once( dirname(__FILE__) . '/wp-load.php' );
#  wp();
#  require_once( ABSPATH . WPINC . '/template-loader.php' );
#}
require './wp-load.php';
wp();
require './wp-includes/template-loader.php';
?>
require_wp_db() call in wp-includes/load.php
<?php
function require_wp_db() {
        global $wpdb;

        require_once( ABSPATH . WPINC . '/wp-db.php' );
        if ( file_exists( WP_CONTENT_DIR . '/db.php' ) )
                require_once( WP_CONTENT_DIR . '/db.php' );

        if ( isset( $wpdb ) )
                return;

        $wpdb = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );
}
Don't call require_wp_db() from wp-settings.php
<?php
#require_wp_db();
require './wp-includes/wp-db.php';
$wpdb = new wpdb( DB_USER, DB_PASSWORD, DB_NAME, DB_HOST );
Hardcode built-in wp cache in wp-settings.php
<?php
require './wp-includes/cache.php';
$_wp_using_ext_object_cache = false;
wp_cache_init();
wp_cache_add_global_groups( array( 'users', 'userlogins', 'usermeta', 'user_meta', 'site-transient', 'site-options', 'site-lookup', 'blog-lookup', 'blog-details', 'rss', 'global-posts' ) );
wp_cache_add_non_persistent_groups( array( 'comment', 'counts', 'plugins' ) );
#wp_start_object_cache();
PHP 5.3 has a __DIR__ constant - use in wp-load.php
<?php
#define( 'ABSPATH', dirname(__FILE__) . '/' );
define( 'ABSPATH', __DIR__ . '/' );
Check again
~> grep open strace2.out
open("/var/www/wp2/wp-includes/pomo/translations.php", O_RDONLY) = 27
open("/var/www/wp2/wp-includes/pomo/entry.php", O_RDONLY) = 27
open("/var/www/wp2/wp-includes/pomo/streams.php", O_RDONLY) = 27
open("/var/www/wp2/wp-includes/default-widgets.php", O_RDONLY) = 28
open("/var/www/wp2/wp-content/themes/twentyeleven/header.php", O_RDONLY) = 28
open("/var/www/wp2/wp-content/themes/twentyeleven/style.css", O_RDONLY) = 28
open("/var/www/wp2/wp-content/themes/twentyeleven/footer.php", O_RDONLY) = 28
open("/var/www/wp2/wp-content/themes/twentyeleven/sidebar-footer.php", O_RDONLY) = 28
We just have translations, plugin widgets and themes left here now. We could hardcode these as well, but then we start to lose the main characteristics of Wordpress.