mongodb 运行时禁用 Transparent Huge Pages

Transparent Huge Pages 简称 THP，本来是linux为提高系统性能而做的努力，结果反而成了性能的隐患。mongodb的官方文档明确说明要禁止 linux 的 THP。

检查

#cat /sys/kernel/mm/transparent_hugepage/enabled

#cat /sys/kernel/mm/transparent_hugepage/defrag

均应该输出如下

always madvise [never]

临时设置

生产环境发现这个问题后，需要先临时设置，然后再永久设置

#echo 'never' > /sys/kernel/mm/transparent_hugepage/enabled

#echo 'never' > /sys/kernel/mm/transparent_hugepage/defrag

永久设置

第一种方法

# vi /etc/rc.local

echo 'never' > /sys/kernel/mm/transparent_hugepage/enabled

echo 'never' > /sys/kernel/mm/transparent_hugepage/defrag

第二种方法

# vi /etc/init.d/disable-transparent-hugepages:

#!/bin/bash

### 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

    re='^[0-1]+$'

    if [[ $(cat ${thp_path}/khugepaged/defrag) =~ $re ]]

    then

      # RHEL 7

      echo 0  > ${thp_path}/khugepaged/defrag

    else

      # RHEL 6

      echo 'no' > ${thp_path}/khugepaged/defrag

    fi

    unset re

    unset thp_path

    ;;

esac

chmod 755 /etc/init.d/disable-transparent-hugepages

chkconfig --add disable-transparent-hugepages

参考:

https://docs.mongodb.com/manual/tutorial/transparent-huge-pages/

https://docs.mongodb.com/v3.2/tutorial/transparent-huge-pages/index.html