Drupal APC Steps Ubuntu 12.04 LTS Apache 2 mod_php

apc_drupal

Pre-req:
apt-get install libpcre3-dev 

pecl install apc

drush dl apc

edit /etc/php5/apache2/php.ini add:

extension=apc.so

sudo service apache2 restart

edit settings.php add:

/**
 * Add APC Caching.
 */
$conf['cache_backends'][] = 'sites/all/modules/apc/drupal_apc_cache.inc';
$conf['cache_class_cache'] = 'DrupalAPCCache';
$conf['cache_class_cache_bootstrap'] = 'DrupalAPCCache';

cp cp /usr/share/php/apc.php to webdir to check

use devel module with query logging turned on to check query times.