Transparent Huge Pages

You should read the compatibility of your application with THP.(transparent huge pages)

How do you find its status

cat /sys/kernel/mm/redhat_transparent_hugepage/enabled  
grep -i --color huge /proc/meminfo

sudo sysctl -a | grep hugepage

at present you will see cat /sys/kernel/mm/transparent_hugepage/enabled telling it is enabled [always]. Other commands are other ways to see the usage.

How do you modify it?

1. Edit /etc/rc.local or better yet /etc/sysctl.conf . WRT rc.local add

if test -f /sys/kernel/mm/transparent_hugepage/enabled; then
echo never > /sys/kernel/mm/transparent_hugepage/enabled
fi
if test -f /sys/kernel/mm/transparent_hugepage/defrag; then
echo never > /sys/kernel/mm/transparent_hugepage/defrag
fi

2. Add “transparent_hugepage=never” to the kernel boot line in the “/etc/grub.conf” file.

Oracle – does not like THP.

Mongo – does not like THP and prefers 4k pages.

Cassandra – There was a thread on twitter and the google group wrt THP. Looks like suggestion is to disable it.

Hadoop does not like THP.

Splunk does not like THP.

MySql does not like THP.

Postgres does not like THP.

What does it do – here are the details.