Getting a better handle on APC Cache Bins / code for settings.php I've got APC up and running on my VPS and have installed the APC module on my Drupal 7 site. I followed the documentation here and added this code to my settings.php file:

$conf['cache_backends'] = array('sites/all/modules/apc/drupal_apc_cache.inc');
$conf['cache_default_class'] = 'DrupalAPCCache';
//$conf['apc_show_debug'] = TRUE;  // Remove the slashes to use debug mode.


However, on my site's status page under APC, it says:

APC has been running for 3 min 54 sec. Currently caching 0 entries (0 bytes).


To me the "0 entries" indicated that there was no cache being created / used. I did some digging around and it looks like there might be additional code I need to add but cannot find documentation anywhere. 

I found this snippet but not really sure if I need it or what part it I am supposed to use and what it does, I could not find any documentation for this. I suspect this is what makes the cache work.  

'page_cache_without_database' =&gt; TRUE,
        'page_cache_invoke_hooks'     =&gt; FALSE,
        'page_cache_maximum_age'      =&gt; 3600,
        'cache_lifetime'              =&gt; 0,
        /* my note -- noticed "cacherouter" in the path below 
         so I am guessing this needs to be adapeted to the path for APC?? */
        'session_inc'      =&gt; './sites/all/modules/cacherouter/session.inc',
            'cache_default_class'               =&gt; 'DrupalAPCCache',
            'cache_class_cache'                 =&gt; 'DrupalAPCCache',
            'cache_class_cache_block'           =&gt; 'DrupalAPCCache',
            'cache_class_cache_bootstrap'       =&gt; 'DrupalAPCCache',
            'cache_class_cache_content'         =&gt; 'DrupalAPCCache',
            'cache_class_cache_filter'          =&gt; 'DrupalAPCCache',
            'cache_class_cache_form'            =&gt; 'DrupalAPCCache',
            'cache_class_cache_menu'            =&gt; 'DrupalAPCCache',
            'cache_class_cache_page'            =&gt; 'DrupalAPCCache',
            'cache_class_cache_pathdst'         =&gt; 'DrupalAPCCache',
            'cache_class_cache_pathsrc'         =&gt; 'DrupalAPCCache',
            'cache_class_cache_session'         =&gt; 'DrupalAPCCache',
            'cache_class_cache_session_user'    =&gt; 'DrupalAPCCache',
            'cache_class_cache_update'          =&gt; 'DrupalAPCCache',
            'cache_class_cache_users'           =&gt; 'DrupalAPCCache',
            'cache_class_cache_views'           =&gt; 'DrupalAPCCache',
            'cache_class_cache_views_data'      =&gt; 'DrupalAPCCache',
      );


Any help on this matter would be appreciated. 

The information about the APC extension returned from phpinfo() are the following ones.
"APC has been running for 3 min 54 sec. Currently caching 0 entries (0
  bytes)."


This message suggests that your APC is running for each php request separately ultimately not caching anything at all.

I had a similar issue and it required to set up PHP once again but in a different mode.

APC works fine for multiple processes with apache/2 + php 5.3.x + php-fpm + fcgi in FPM/FastCGI mode.

PHP 5.3.x is configured with following options --enable-force-cgi-redirect --enable-fastcgi --enable-fpm

In APC section of my php info I can see:

APC Support = enabled
Serialization Support = php
MMAP File Mask = /tmp/apc.something  | where something is a random 6-character string

Please check your phpinfo 

In PHP Configure Command you should have:
'--enable-fastcgi'
and
'--enable-fpm'

In Server API :
 FPM/FastCGI

Check if you have cgi-fcgi section and if you can find 
php-fpm set to "active"

NOTE: There might be another solution if you use php 5.2.x or older.