WARNING: /sys/kernel/mm/transparent_hugepage/enabled is ‘always’.

After I install MongoDB 3.2.3 in Centos 7, I received this error when I start mongo in shell.

[code lang=”shell”]
[[email protected] ~]# mongo
MongoDB shell version: 3.2.3
connecting to: test
Server has startup warnings:
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten]
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/enabled is ‘always’.
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten] ** We suggest setting it to ‘never’
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten]
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is ‘always’.
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten] ** We suggest setting it to ‘never’
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten]
2016-02-29T14:11:49.308-0500 I CONTROL [initandlisten] ** WARNING: soft rlimits too low. rlimits set to 4096 processes, 64000 files. Number of processes should be at least 32000 : 0.5 times number of files.
[/code]

Solution

Create the init.d script.
Create the following file at /etc/init.d/disable-transparent-hugepages:

[code lang=”shell”]
#!/bin/sh
### BEGIN INIT INFO
# Provides: disable-transparent-hugepages
# Required-Start: $local_fs
# Required-Stop:
# X-Start-Before: mongod mongodb-mms-automation-agent
# Default-Start: 2 3 4 5
# Default-Stop: 0 1 6
# Short-Description: Disable Linux transparent huge pages
# Description: Disable Linux transparent huge pages, to improve
# database performance.
### END INIT INFO

case $1 in
start)
if [ -d /sys/kernel/mm/transparent_hugepage ]; then
thp_path=/sys/kernel/mm/transparent_hugepage
elif [ -d /sys/kernel/mm/redhat_transparent_hugepage ]; then
thp_path=/sys/kernel/mm/redhat_transparent_hugepage
else
return 0
fi

echo ‘never’ > ${thp_path}/enabled
echo ‘never’ > ${thp_path}/defrag

unset thp_path
;;
esac
[/code]

Make it executable.
Run the following command to ensure that the init script can be used:

[code lang=”shell”]
sudo chmod 755 /etc/init.d/disable-transparent-hugepages
[/code]

[code lang=”shell”]
sudo chkconfig –add disable-transparent-hugepages
[/code]

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