如何避免来自 mongodb 的父页面/碎片整理警告？

我收到了 Mongodb 关于 THP 的警告

2015-03-06T21:01:15.526-0800 I CONTROL  [initandlisten] ** WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'.
2015-03-06T21:01:15.526-0800 I CONTROL  [initandlisten] **        We suggest setting it to 'never'

但我成功手动关闭了 THP

frederick@UbuntuVirtual:~$ cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
frederick@UbuntuVirtual:~$ cat /sys/kernel/mm/transparent_hugepage/defrag
always madvise [never]

我通过在 /etc/default/grub中将 transparent_hugepage=never添加到 GRUB_CMDLINE_LINUX_DEFAULT并添加

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

到 /etc/rc.local

我到底怎样才能避免这种警告呢？

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小开

  1. Open /etc/default/grub

    sudo vi /etc/default/grub

  2. Update
    GRUB_CMDLINE_LINUX_DEFAULT="" to GRUB_CMDLINE_LINUX_DEFAULT="transparent_hugepage=never"

  3. Save file
    :wq (in vi)

  4. Run update-grub

    sudo update-grub

  5. Reboot machine

Update: If you are using a virtual hosting provider, this will work IFF grub boot is supported. DigitalOcean DOES NOT support grub boot.

小开
最佳答案

Official MongoDB documentation gives several solutions for this issue. You can also try this solution, which worked for me:

Note: Try official documentation directives if MongoDB version is greater than 3.0

  1. Open /etc/init.d/mongod file.
    (if no such file you might check /etc/init.d/mongod, /etc/init/mongod.conf files - credit: the below comments)

  2. Add the lines below immediately after chown $DAEMONUSER /var/run/mongodb.pid and before end script.

  3. Restart mongod (service mongod restart).

Here are the lines to add to /etc/init.d/mongod:

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

That's it!

小开

MongoDB have updated their recommendation to use an init.d script now: http://docs.mongodb.org/master/tutorial/transparent-huge-pages/

小开

Verified that the defrag is examined without regard to the enabled:

$ cat /sys/kernel/mm/transparent_hugepage/enabled
always madvise [never]
$ cat /sys/kernel/mm/transparent_hugepage/defrag
[always] madvise never
$ service mongod start
... (in log) WARNING: /sys/kernel/mm/transparent_hugepage/defrag is 'always'
$ echo 'never' > /sys/kernel/mm/transparent_hugepage/defrag
$ cat /sys/kernel/mm/transparent_hugepage/defrag
always madvise [never]
$ service mongod stop
$ service mongod start
... (no warning in log)

Therefore, the fix to this bug is to first look at transparent_hugepage/enabled, and if it is never, don't bother looking at the irrelevant transparent_hugepage/defrag setting.

Source.

小开

For Ubuntu 14.04 using upstart:

Since we are deploying machines with Ansible I don't like modifying rc files or GRUB configs.

I tried using sysfsutils / sysfs.conf but ran into timing issues when starting the services on fast (or slow machines). It looked like sometimes mongod was started before sysfsutils. Sometimes it worked, sometimes it did not.

Since mongod is an upstart process I found that the cleanest solution was to add the file /etc/init/mongod_vm_settings.conf with the following content:

# Ubuntu upstart file at /etc/init/mongod_vm_settings.conf
#
#   This file will set the correct kernel VM settings for MongoDB
#   This file is maintained in Ansible


start on (starting mongod)
script
echo "never" > /sys/kernel/mm/transparent_hugepage/enabled
echo "never" > /sys/kernel/mm/transparent_hugepage/defrag
end script

This will run the script just before mongod will be started. Restart mongod (sudo service mongod restart) and done.

小开

Ubuntu 16.04 using systemd:

systemctl edit mongod

Paste the following:

[Service]
PermissionsStartOnly=true
ExecStartPre=/bin/sh -c "echo never > /sys/kernel/mm/transparent_hugepage/enabled"
ExecStartPre=/bin/sh -c "echo never > /sys/kernel/mm/transparent_hugepage/defrag"

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