在 CentOS 7 上禁用 Transparent Huge Pages（THP）

因為資料庫的工作負載通常在THP上表現不佳，所以應該禁用THP，確保MongoDB能獲得最佳的效能。

建立init.d script
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

讓script可執行

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

 設置成作業系統啟動時能自動執行

sudo chkconfig --add disable-transparent-hugepages

使用tuned及ktune

建立新的profile

sudo mkdir /etc/tuned/no-thp

編輯tuned.conf

vi /etc/tuned/no-thp/tuned.conf

  [main]
  include=virtual-guest

  [vm]
  transparent_hugepages=never

啟動新的profile

sudo tuned-adm profile no-thp

測試變更後結果

重新開機後執行下列指令

cat /sys/kernel/mm/transparent_hugepage/enabled
cat /sys/kernel/mm/transparent_hugepage/defrag

執行後的結果應該顯示為

always madvise [never]