I'm trying to configure memcache module and failed to load dmemcache.inc
Modifications to settings.php are required. Read the docs on how to configure it. Here is an example configuration I use with two memcached servers:

$conf['memcache_key_prefix'] = __FILE__;
$conf['cache_backends'][] = 'sites/all/modules/contrib/memcache/memcache.inc';
$conf['cache_default_class'] = 'MemCacheDrupal';
$conf['lock_inc'] = 'sites/all/modules/contrib/memcache/memcache-lock.inc';
$conf['memcache_stampede_protection'] = TRUE;
$conf['cache_class_cache_form'] = 'DrupalDatabaseCache';
$conf['page_cache_without_database'] = TRUE;
$conf['page_cache_invoke_hooks'] = FALSE;
$conf['memcache_servers'] = ['172.16.12.51:11211' =&gt; 'default', '172.16.12.52:11211' =&gt; 'default'];