Disable Transparent Huge Pages.

See examples online from various system vendors recommending turning THP off:
http://blog.couchbase.com/often-overlooked-linux-os-tweaks
https://my.vertica.com/docs/7.1.x/HTML/Content/Authoring/InstallationGuide/BeforeYouInstall/transparenthugepages.htm
http://www.cloudera.com/content/cloudera-content/cloudera-docs/CDH4/4.2.2/CDH4-Installation-Guide/cdh4ig_topic_11_6.html


Information on THP: 
http://www.slideshare.net/raghusiddarth/transparent-hugepages-in-rhel-6

dstat/perf trace when the problem happens:
https://gist.github.com/rxin/eac982fe23396d5efddf