CentOS – Fixing Conservative Governor Nice Error

centoscpu-frequency

I changed my CentOS 6 CPU governor from ondemand (the default one) to conservative and got this after restarting the cpufreq service:

/etc/rc5.d/S13cpuspeed: line 88:
/sys/devices/system/cpu/cpufreq/conservative/ignore_nice_load: File or
directory does not exist

So what should I do? Should I create the file and if so, what should I put there?

Best Answer

For 3.x kernels

The interface to CPUFreq has changed in the newer kernels. This would include CentOS 6. You can read about the entire interface here in the Red Hat Enterprise Linux (RHEL) documentation titled: Chapter 3. Core Infrastructure and Mechanics.

Specifically the section on CPUFreq Setup. Here are the steps required to set it up.

CPUFreq drivers

$ ls -1 /lib/modules/`uname -r`/kernel/arch/x86/kernel/cpu/cpufreq/
acpi-cpufreq.ko
mperf.ko
p4-clockmod.ko
pcc-cpufreq.ko
powernow-k8.ko
speedstep-lib.ko

load appropriate driver

$ modprobe acpi-cpufreq

install cpupower tool

$ yum install cpupowerutils

view governors

$ cpupower frequency-info --governors
analyzing CPU 0:
ondemand userspace performance

So we currently only have these 3 governors loaded: ondemand, userspace, and performance.

loading governors that are missing

You can get a list of all governors that are available like so.

$ ls -1 /lib/modules/`uname -r`/kernel/drivers/cpufreq/
cpufreq_conservative.ko
cpufreq_ondemand.ko
cpufreq_powersave.ko
cpufreq_stats.ko
freq_table.ko

$ modprobe cpufreq_powersave

confirm modules thus far:

$ lsmod |grep cpuf
cpufreq_powersave       1196  0 
cpufreq_ondemand       10544  8 
acpi_cpufreq            7763  0 
freq_table              4936  2 cpufreq_ondemand,acpi_cpufreq
mperf                   1557  1 acpi_cpufreq

confirm which governors are loaded

$ cpupower frequency-info --governors
analyzing CPU 0:
powersave ondemand userspace performance

viewing current policy

$ cpupower frequency-info
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3 4 5 6 7
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 1.60 GHz - 3.20 GHz
  available frequency steps: 3.20 GHz, 3.20 GHz, 3.07 GHz, 2.93 GHz, 2.80 GHz, 2.67 GHz, 2.53 GHz, 2.40 GHz, 2.27 GHz, 2.13 GHz, 2.00 GHz, 1.87 GHz, 1.73 GHz, 1.60 GHz
  available cpufreq governors: powersave, ondemand, userspace, performance
  current policy: frequency should be within 1.60 GHz and 3.20 GHz.
                  The governor "ondemand" may decide which speed to use
                  within this range.
  current CPU frequency is 1.60 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    2500 MHz max turbo 4 active cores
    2500 MHz max turbo 3 active cores
    2500 MHz max turbo 2 active cores
    2600 MHz max turbo 1 active cores

In the above output you can see my current policy is ondemand. To tune the policy and speed you use this command to do so:

$ cpupower frequency-set --governor performance
Setting cpu: 0
Setting cpu: 1
Setting cpu: 2
Setting cpu: 3
Setting cpu: 4
Setting cpu: 5
Setting cpu: 6
Setting cpu: 7

confirm new governor

$ cpupower frequency-info
analyzing CPU 0:
  driver: acpi-cpufreq
  CPUs which run at the same hardware frequency: 0 1 2 3 4 5 6 7
  CPUs which need to have their frequency coordinated by software: 0
  maximum transition latency: 10.0 us.
  hardware limits: 1.60 GHz - 3.20 GHz
  available frequency steps: 3.20 GHz, 3.20 GHz, 3.07 GHz, 2.93 GHz, 2.80 GHz, 2.67 GHz, 2.53 GHz, 2.40 GHz, 2.27 GHz, 2.13 GHz, 2.00 GHz, 1.87 GHz, 1.73 GHz, 1.60 GHz
  available cpufreq governors: powersave, ondemand, userspace, performance
  current policy: frequency should be within 1.60 GHz and 3.20 GHz.
                  The governor "performance" may decide which speed to use
                  within this range.
  current CPU frequency is 3.20 GHz (asserted by call to hardware).
  boost state support:
    Supported: yes
    Active: yes
    2500 MHz max turbo 4 active cores
    2500 MHz max turbo 3 active cores
    2500 MHz max turbo 2 active cores
    2600 MHz max turbo 1 active cores

You can also tune the min/max CPU frequencies within a policy using the cpupower frequency-set --min <freq> --max <freq>. See this page for more details on what you can do with cpupower frequency-set.

doing the above without cpupowerutils

So finally, if you don't have the cpupowerutils package installed, you can interact with it similar to how you did in the previous 2.6 kernels. Mainly you echo values into the sysfs filesystem.

for example

$ echo 360000 > /sys/devices/system/cpu/cpu0/cpufreq/scaling_min_freq

For 2.6 kernels

You can read about the various cpufreq features over on this site.

excerpt from CPU frequency scaling in Linux with cpufreq

ignore_nice_load - This parameter takes a value of '0' or '1'. When set to '0' (its default), all processes are counted towards the 'cpu utilization' value. When set to '1', the processes that are run with a 'nice' value will not count (and thus be ignored) in the overall usage calculation. This is useful if you are running a CPU intensive calculation on your laptop that you do not care how long it takes to complete as you can 'nice' it and prevent it from taking part in the deciding process of whether to increase your CPU frequency. To turn this on do the following.

sudo sh -c "echo 1 > /sys/devices/system/cpu/cpu0/cpufreq/ondemand/ignore_nice_load"

I'd put a 0 in this file since this should be the default. If you have any long running niced process, which I highly doubt, you can set it to 1.

Related Solutions

Linux Kernel – Setting CPU Governor to On Demand or Conservative

Assuming your governor is the intel_pstate (default for Intel Sandy Bridge and Ivy Bridge CPUs as of kernel 3.9). This issue is not specific to Arch, but all distros using the new Intel pstate driver for managing CPU frequency/power management. Arch linux CPU frequency scaling.

Theodore Ts'o wrote his explanation on Google+:

intel_pstate can be disabled at boot-time with kernel arg intel_pstate=disable
The problem with the ondemand governor is that it doesn't know the specific capabilities of the CPU
Executing some tasks with higher frequency will consume less power than would a lower frequency taking more time e.g. arithmetic stuff, but not true for all tasks e.g. loading something from memory
The intel_pstate driver knows the details of the how the CPU works and it does a better job than the generic ACPI solution
intel_pstate offers only two governors, powersave and performance. Intel claims that the intel_pstate "powersave" is faster than the generic acpi governor with "performance"

To change back to the ACPI driver, reboot and set the kernel arg intel_pstate=disable
Then execute modprobe acpi-cpufreq and you should have the ondemand governor available.

You can make the changes permanent by editing /etc/default/grub and adding

GRUB_CMDLINE_LINUX_DEFAULT="intel_pstate=disable"

And then updating grub.cfg ala grub-mkconfig -o /boot/grub/grub.cfg

Follow the instructions for Arch kernel module loading and add the acpi-cpufreq module.

Is it possible to set a constant lowest CPU frequency under the modern PSTATE driver

Well, well, turns out that the new pstate Intel driver is awesome, but first one needs to practice a bit of the ancient, lost art of reading the documentation.

I'll leave my question as it is because, judging by all the grief and frustration I see scattered all around the internet, I am not the first to have this issues.

The new CPU driver has lots of options, but I will restrict my explanation to something simple and, for me, more than enough and satisfactory. First of all:

sudo apt-get install linux-cpupower

(or the equivalent in your non-debian based distros)

There are now 2 behaviors (governors) with the names powersave and performance but that is quite an unfortunate naming scheme, because these governors have nothing to do with those that bear the same names in the old driver:

powersave means now variable frequency that depends on the load, i.e. this is essentially the old ondemand governor. You get to set the minimum and maximum frequency, and if that maximum frequency is set to the maximum frequency your CPU is able of (which I believe it's the default) then you don't save a crap. You may even crank up the minimum frequency to the second highest value, and the result will be the CPU nearly at full throttle 24/7 and the governor will still be named powersave. They should have named this governor VARIABLE or something similar, avoiding a lot of confusion among users and sparing the developers a lot of false reports of kernel bugs.
performance means here constant frequency, no matter the load, and this depends on what the user has set as maximum. When this governor is set, the mininum frequency is ignored and the CPU runs at the frequency you set as maximum. If as such you have set a very low frequency, then you will not see any special performance or anything, you just will get a slowed down CPU at constant frequency. So they'd better named this governor CONSTANT or something similar, sparing frustration to many people like me, used to the old scheme.

So, here are some examples that work like a charm, at least with kernel 4.14. I will use as minimum and maximum frequency the values for my CPU: 0.4 and 3.1 GHz. See yours with cpupower frequency-info

CONSTANT, LOWEST FREQUENCY IN ALL CORES

This IS what I wanted! We get that by setting the constant frequency governor and setting the lowest available frequency as the maximum:

sudo cpupower frequency-set -g performance
sudo cpupower frequency-set -u 400MHz

CONSTANT, HIGHEST FREQUENCY IN ALL CORES

(You see this asked very often for desktop computers where it makes sense, although there are also people out there willing to destroy their laptop fan)

sudo cpupower frequency-set -g performance
sudo cpupower frequency-set -u 3100MHz

VARIABLE FREQUENCY BETWEEN THE MINIMUM AND MAXIMUM POSSIBLE FREQUENCIES IN ALL CORES

(this was called ondemand with the old acpi-cpufreq driver)

sudo cpupower frequency-set -g powersave
sudo cpupower frequency-set -d 400MHz
sudo cpupower frequency-set -u 3100MHz

VARIABLE FREQUENCY BETWEEN THE MINIMUM AND A MODERATE FREQUENCY IN ALL CORES

(maybe because you want to get some more speed when required but you don't want to reach the maximum and hear the fan blowing like mad)

sudo cpupower frequency-set -g powersave
sudo cpupower frequency-set -d 400MHz
sudo cpupower frequency-set -u 1200MHz

And so on. It is very easy and works really well. You can set too a constant low frequency in one core where the heavy numerical stuff is running, while you leave a variable frequency in other core where you launch the more usual stuff (email, web browsing...). See taskset for more info.