Posts Tagged ‘cpu fan’

How to disable ACPI on productive Linux servers to decrease kernel panics and increase CPU fan lifespan

Tuesday, May 15th, 2012

Linux TUX ACPI logo / Tux Hates ACPI logohttp://www.pc-freak.net/images/linux_tux_acpi_logo-tux-hates-acpi.png

Why would anyone disable ACPI support on a server machine??
Well  ACPI support kernel loaded code is just another piece of code constantly being present in the memory,  that makes the probability for a fatal memory mess up leading to  a fatal bug resulting in system crash (kernel panic) more likely.

Many computers ship with buggy or out of specifications ACPI firmware which can cause a severe oddities on a brand new bought piece of comp equipment.

One such oddity related to ACPI motherboard support problems is if you notice your machine randomly powering off or failing to boot with a brand new Linux installed on it.

Another reason to switch off ACPI code will would to be prevent the CPU FAN rotation from being kernel controlled.

If the kernel controls the CPU fan on  high CPU heat up it will instruct the fan to rotate quickly and on low system loads it will bring back the fan to loose speed.
 This frequent switch of FAN from high speed to low speed  increases the probability for a short fan damage due to frequent changes of fan speed. Such a fan damage leads often to  system outage due to fan failure to rotate properly.

Therefore in my view it is better ACPI support is switched off completely on  servers. On some servers ACPI is useful as it can be used to track CPU temperature with embedded motherboard sensors with lm_sensors or any piece of hardwre vendor specific software provided. On many machines, however lm_sensors will not properly recognize the integrated CPU temperature sensors and hence ACPI is mostly useless.

There are 3 ways to disable fully or partially ACPI support.

- One is to disable it straight for BIOS (best way IMHO)
- Disable via GRUB or LILO passing a kernel parameter
- Partial ACPI off-ing - /disabling the software that controls the CPU fan/

1. Disable ACPI in BIOS level

Press DEL, F1, F2, F10 or whatever the enter bios key combination is go through all the different menus (depending on the vios BENDOR) and make sure every occurance of ACPI is set to off / disable whatever it is called.

Below is a screenshot of menus with ACPI stuff on a motherboard equipped with Phoenix AwardBIOS:

BIOS ACPI Disable power Off Phoenix BIOS

This is the in my opinon best and safest way to disable ACPI power saving, Unfortunately some newer PCs lack the functionality to disable ACPI; (probably due to the crazy "green" policy the whole world is nowdays mad of).

If that's the case with you, thanksfully there is a "software way" to disable ACPI via passing kernel options via GRUB and LILO boot loaders.

2. Disabling ACPI support on kernel boot level through GRUB boot loader config

There is a tiny difference in command to pass in order to disable  ACPI depending on the Linux installed  GRUB ver. 1.x or GRUB 2.x.

a) In GRUB 0.99 (GRUB version 1)

Edit file /etc/grub/menu.lst or /etc/grub/grub.conf (location differs across Linux distribution). Therein append:

acpi=off

to the end of kernel command line.

Here is an example of a kernel command line with ACPI not disabled (example taken from CentOS server grub.conf):

[root@centos ~]# grep -i title -A 4 /etc/grub/grub.conf
title Red Hat Enterprise Linux Server (2.6.18-36.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-36.el5 ro root=/dev/VolGroup00/LogVol00 console=ttyS0,115200n8
initrd /initrd-2.6.18-36.el5.img

The edited version of the file with acpi=off included should look like so:

title Red Hat Enterprise Linux Server (2.6.18-36.el5)
root (hd0,0)
kernel /vmlinuz-2.6.18-36.el5 ro root=/dev/VolGroup00/LogVol00 console=ttyS0,115200n8 acpi=off
initrd /initrd-2.6.18-36.el5.img

The kernel option root=/dev/VolGroup00/LogVol00 means the the server is configured to use LVM (Logical Volume Manager).

b) Disabling ACPI on GRUB version 1.99 +

This version is by default installed on newer Ubuntu and Debian Linux-es.

In grub 1.99 on latest Debian Squeeze, the file to edit is located in /boot/grub/grub.cfg. The file is more messy than with its predecessor menu.lst (grub 0.99).
Thanks God there is no need to directly edit the file (though this is possible), but on newer Linuces (as of time of writting the post), there is another simplied grub config file /etc/grub/config

Hence to add the acpi=off to 1.99 open /etc/grub/config find the line reading:

GRUB_CMDLINE_LINUX_DEFAULT="quiet"

and append the "acpi=off" option, e.g. the line has to change to:

GRUB_CMDLINE_LINUX_DEFAULT="quiet acpi=off"

On some servers it might be better to also disable APIC along with ACPI:

Just in case you don't know what is the difference between ACPI and APIC, here is a short explanation:

ACPI = Advanced Configuration and Power Interface

APIC = Advanced Programmable Interrupt Controllers

ACPI is the system that controls your dynamic speed fans, the power button behavior, sleep states, etc.

APIC is the replacement for the old PIC chip that used to come imbedded on motherboards that allowed you to setup interrupts for your soundcard, ide controllers, etc.

Hence on some machines experiencing still problems with even ACPI switched off, it is helpful  to disable the APIC support too, by using:

acpi=off noapic noacpi

Anyways, while doing the changes, be very very cautious or you might end up with un-boot-able server. Don't blame me if this happens :); be sure you have a backup option if server doesn't boot.

To assure faultless kernel boot, GRUB has ability to be configured to automatically load up a second kernel if 1st one fails to boot, if you need that read the grub documentation on that.

To load up the kernel with the new setting, give it a restart:

[root@centos ~]# shutdown -r now
....

3. Disable ACPI support on kernel boot time on Slackware or other Linuxes still booting kernel with LILO

Still, some Linux distros like Slackware, decided to keep the old way and use LILO (LInux LOader) as a default boot loader.

Disabling ACPI support in LILO is done through /etc/lilo.conf

By default in /etc/lilo.conf, there is a line:

append= acpi=on

it should be changed to:

append= acpi=off

Next to load up the new acpi disabled setting, lilo has to be reloaded:

slackware:~# /sbin/lilo -c /etc/lilo.conf
....

Finally a reboot is required:

slackware:~# reboot
....

(If you don't have a physical access or someone near the server you better not 🙂 )

4. Disable ACPI fan control support on a running Linux server without restart

This is the most secure work-around, to disabling the ACPI control over the machine CPU fan, however it has a downside that still the ACPI code will be loaded in the kernel and could cause kernel issues possibly in the long run – lets say the machine has uptime of more than 2 years…

The acpi support on a user level  is controlled by acpid or haldaemon (depending on the Linux distro), hence to disable the fan control on servers this services has to be switched off:

a) disabling ACPI on Debian and deb based Linux-es

As of time of writting on Debian Linux servers acpid (Advanced Configuration and Power Interface event daemon) is there to control how power management will be handled. To disable it stop it as a service (if running):

debian:~# /etc/init.d/acpid stop

To permanently remove acpid from boot up on system boot disable it with update-rc.d:

debian:~# update-rc.d acpid disable 2 3 4 5
update-rc.d: using dependency based boot sequencing
insserv: Script iptables is broken: incomplete LSB comment.
insserv: missing `Required-Start:' entry: please add even if empty.
insserv: warning: current start runlevel(s) (empty) of script `acpid' overwrites defaults (2 3 4 5).
insserv: warning: current stop runlevel(s) (2 3 4 5) of script `acpid' overwrites defaults (empty).
insserv: missing `Required-Start:' entry: please add even if empty.

b) disabling ACPI on RHEL, Fedora and other Redhat-s (also known as RedHacks 🙂 )

I'm not sure if this is safe,as many newer rpm based server system services,  might not work properly with haldaemon disabled.

Anyways you can give it a try if when it is stopped there are issues just bring it up again.

[root@rhel ~]# /etc/init.d/haldaemon stop

If all is fine with the haldaemon switched off (hope so), you can completely disable it to load on start up with:

[root@centos ~]# /sbin/chkconfig --level 2 3 4 5 haldaemon off

Disabling ACPI could increase a bit your server bills, but same time decrease losses from downtimes, so I guess it worths its costs 🙂

 

How to disable ACPI (power saving) support in FreeBSD / Disable acpi on BSD kernel boot time

Tuesday, May 15th, 2012

FreeBSD disable ACPI how ACPI Basic works basic diagram

On FreeBSD the default kernel is compiled to support ACPI. Most of the modern PCs has already embedded support for ACPI power saving instructions.
Therefore a default installed FreeBSD is trying to take advantage of this at cases and is trying to save energy.
This is not too useful on servers, because saving energy could have at times a bad impact on server performance if the server is heavy loaded at times and not so loaded at other times of the day.

Besides that on servers saving energy shouldn't be the main motivator but server stability and productivity is. Therefore in my personal view on FreeBSD used on servers it is better to disable complete the ACPI in order to disable CPU fan control to change rotation speeds all the time from low to high rotation cycles and vice versa at times of low / high server load.

Another benefit of removing the ACPI support on a server is this would probably increase the CPU fan life span and possibly prevent the CPU to be severely heated at times.

Moreover, some piece of hardware might have troubles in properly supporting ACPI specifications and thus ACPI could be a reason for unexpected machine hang ups.

With all said I would recommend to anyone willing to use BSD for a server to disable the ACPI (Advanced Configuration and Power Interface), just like I did.

Here is how;

1. Quick review on how ACPI is handled on FreeBSD

acpi support is being handled on FreeBSD by a number of loadable kernel modules, here is a complete list of all the kernel modules dealins with acpi:

freebsd# cd /boot
freebsd# find . -iname '*acpi*.ko'
./kernel/acpi.ko
./kernel/acpi_aiboost.ko
./kernel/acpi_asus.ko
./kernel/acpi_fujitsu.ko
./kernel/acpi_ibm.ko
./kernel/acpi_panasonic.ko
./kernel/acpi_sony.ko
./kernel/acpi_toshiba.ko
./kernel/acpi_video.ko
./kernel/acpi_dock.ko

By default on FreeBSD, if hardware has some support for ACPI the acpi gets activated by acpi.ko kernel module. The specific type of vendors specific ACPI like IBM, ASUS, Fujitsu are controlled by the respective kernel module from the list …

Hence, to control if ACPI is loaded or not on a FreeBSD system with no need to reboot one can use kldload, kldunload module management BSD cmds.

a) Check if acpi is loaded on a BSD

freebsd# kldstatkldstat | grep -i acpi
9 1 0xc9260000 57000 acpi.ko

b) unload kernel enabled ACPI support

freebsd# kldunload acpi

c) Load acpi support (not the case with me but someone might need it, if for instance BSD is running on laptop)

freebsd# kldload acpi

2. Disabling ACPI to load on bootup on BSD

a) In /boot/loader.conf add the following variables:

hint.acpi.0.disabled="1"
hint.p4tcc.0.disabled=1
hint.acpi_throttle.0.disabled=1


b) in /boot/device.hints add:

hint.acpi.0.disabled="1"

c) in /boot/defaults/loader.conf make sure:

##############################################################
### ACPI settings ##########################################
##############################################################
acpi_dsdt_load="NO" # DSDT Overriding
acpi_dsdt_type="acpi_dsdt" # Don't change this
acpi_dsdt_name="/boot/acpi_dsdt.aml"
# Override DSDT in BIOS by this file
acpi_video_load="NO" # Load the ACPI video extension driver

d) disable ACPI thermal monitoring

It is generally a good idea to disable the ACPI thermal monitoring, as many machines hardware does not support it.

To do so in /boot/loader.conf add

debug.acpi.disabled="thermal"

If you want to learn more on on how ACPI is being handled on BDSs check out:

freebsd# man acpi

Other alternative method to permanently wipe out ACPI support is by not compiling ACPI support in the kernel.
If that's the case in /usr/obj/usr/src/sys/GENERIC make sure device acpi is commented, e.g.:

##device acpi