Document xhprof and mysql usage

[dergachev]

For the third time, I've forgotten how to get xhprof up and running. Here's how to do it:

• xhprof recipe is already included
  • see /usr/share/php5-xhprof/
  • see https://github.com/msonnabaum/chef-xhprof/blob/master/recipes/default.rb
• ensure devel module is enabled, then go to "http://localhost:8080/admin/config/development/devel"
• ensure the following are set in the XHProf section:
  • "Enable profiling..." checkbox is checked
  • /usr/share/php5-xhprof as the "xhprof directory" variable,
  • /xhprof_html as the "xhprof url" variable,
• then actually get the drupal vhost to support xhprof:
  • sudo ln -s /usr/share/php5-xhprof/xhprof_html/ xhprof_html

After that, drupal will inject the correct link at the bottom of every web page. Disable that checkbox to get rid of it.

Adding the "-d" (debug) flag to any drush command will produce an xhprof link, eg drush cc all -d

[dergachev]

On a somewhat related note, my xhprof shows that DB cache is killing performance. So to get memcache going, we follow the instructions for installing memcached.module (http://drupal.org/node/1131468)

• Confirm that by default the memcached daemon is installed and launched by the included memcache recipe:
  • ps aux | grep memcached => /usr/bin/memcached -v -m 64 -p 11211 -u nobody -l 0.0.0.0
• Confirm that php includes memcache support: php -i | grep memcache => "memcache support => enabled

# sudo is required until the permissions issue is resolved
sudo drush dl memcache
sudo drush en -y memache memcache_admin
sudo vim sites/default/settings.php 

sudo tee -a sites/default/settings.php << 'EOF' 
$conf['cache_backends'][] = 'sites/all/modules/memcache/memcache.inc';
$conf['cache_default_class'] = 'MemCacheDrupal';
$conf['memcache_key_prefix'] = 'drupal_k2j4k32j'; #something unique and random
EOF

This did the trick!