Steps to install memcache in drupal

1. Install the memcached binaries on your server. See How to install Memcache on Debian Etch[ http://www.lullabot.com/articles/how_install_memcache_debian_etch ] or How to install Memcache on OSX [ http://www.lullabot.com/articles/setup-memcached-mamp-sandbox-environmen... ]
2. Install the PECL memcache extension for PHP.
3. In settings.php add ini_set('memcache.hash_strategy','consistent');
4. Put your site into offline mode.
5. Download and install the memcache module [ http://drupal.org/project/memcache ]
6. If you have previously been running the memcache module, run update.php.
7. Apply the DRUPAL-5-cache-serialize.patch that comes with memcache module [memcache/patches]
I applied DRUPAL-5-3-cache-serialize.patch hence I am using drupal 5.3
8. Start at least one instance of memcache on the server.
[ex ./memcached -d -m 2048 -l 10.0.0.40 -p 11211 ]
Here 11211 is an instance of memcache, 10.0.0.40 is the IP of the server, 2048 is the allocated memory.
9. Add following in the settings.php
$conf = array(
  'cache_inc' => './sites/all/modules/memcache/memcache.inc',
  'memcache_servers' => array(
    'localhost:11211' => 'default',
  ),
  'memcache_bins' =>array(
    'cache' => 'default',
    'cache_views' => 'default',
    'cache_page' => 'default',
    'cache_path' => 'default',
    'cache_filter' => 'default',
    'cache_menu' => 'default',
  ),
);
10. Change memcache_stampede_semaphore time from 15 seconds to 600 in dmemcache.inc lineno:86
if ($result->expire && $result->expire <= time() && $mc->add($full_key .'_semaphore', '', FALSE, variable_get('memcache_stampede_semaphore', 600))) {
located in modules/memcache to get clear result of memcache.
Every 600 seconds cache from memcache will be cleared. If this is not set we will not see any performance benefit. Refer links… http://drupal.org/files/issues/stampede.patch . http://drupal.org/node/295738 .
11. First time after install, truncate all cache tables that are memcached.
12. Bring your site back online.
13. To check the memcache status login as admin and check memcahce logs at /admin/logs/memcache