Chapter 3. Tuned
3.1. Tuned Overview
udevto monitor connected devices and statically and dynamically tunes system settings according to a selected profile. Tuned is distributed with a number of predefined profiles for common use cases like high throughput, low latency, or powersave. It is possible to modify the rules defined for each profile and customize how to tune a particular device. To revert all changes made to the system settings by a certain profile, you can either switch to another profile or deactivate the tuned service.
no-daemon mode, which does not require any resident memory. In this mode, tuned applies the settings and exits. The
no-daemon modeis disabled by default because a lot of tuned functionality is missing in this mode, including D-Bus support, hot-plug support, or rollback support for settings. To enable
no-daemon mode, set the following in the
daemon = 0.
sysfssettings and one-shot activation of several configuration tools like ethtool. Tuned also monitors the use of system components and tunes system settings dynamically based on that monitoring information.
/etc/tuned/tuned-main.conffile and changing the
- Gets disk load (number of IO operations) per device and measurement interval.
- Gets network load (number of transferred packets) per network card and measurement interval.
- Gets CPU load per CPU and measurement interval.
- Sets the CPU governor to the value specified by the
governorparameter and dynamically changes the PM QoS CPU DMA latency according to the CPU load. If the CPU load is lower than the value specified by the
load_thresholdparameter, the latency is set to the value specified by the
latency_highparameter, otherwise it is set to value specified by
latency_low. Also the latency can be forced to a specific value without being dynamically changed further. This can be accomplished by setting the
force_latencyparameter to the required latency value.
- Dynamically sets the FSB speed according to the CPU load; this feature can be found on some netbooks and is also known as the Asus Super Hybrid Engine. If the CPU load is lower or equal to the value specified by the
load_threshold_powersaveparameter, the plugin sets the FSB speed to the value specified by the
she_powersaveparameter (for details about the FSB frequencies and corresponding values, see the kernel documentation, the provided defaults should work for most users). If the CPU load is higher or equal to the value specified by the
load_threshold_normalparameter, it sets the FSB speed to the value specified by the
she_normalparameter. Static tuning is not supported and the plugin is transparently disabled if the hardware support for this feature is not detected.
- Configures wake-on-lan to the values specified by the
wake_on_lanparameter (it uses same syntax as the ethtool utility). It also dynamically changes the interface speed according to the interface utilization.
- Sets various
sysctlsettings specified by the plugin parameters. The syntax is
nameis the same as the name provided by the sysctl tool. Use this plugin if you need to change settings that are not covered by other plugins (but prefer specific plugins if the settings are covered by them).
- Sets autosuspend timeout of USB devices to the value specified by the
autosuspendparameter. The value 0 means that autosuspend is disabled.
- Enables or disables transparent huge pages depending on the Boolean value of the
- Sets the autosuspend timeout for audio codecs to the value specified by the
snd_ac97_codecare supported. The value
0means that the autosuspend is disabled. You can also enforce the controller reset by setting the Boolean parameter
- Sets the elevator to the value specified by the
elevatorparameter. It also sets ALPM to the value specified by the
alpmparameter, ASPM to the value specified by the
aspmparameter, scheduler quantum to the value specified by the
scheduler_quantumparameter, disk spindown timeout to the value specified by the
spindownparameter, disk readahead to the value specified by the
readaheadparameter, and can multiply the current disk readahead value by the constant specified by the
readahead_multiplyparameter. In addition, this plugin dynamically changes the advanced power management and spindown timeout setting for the drive according to the current drive utilization. The dynamic tuning can be controlled by the Boolean parameter
dynamicand is enabled by default.
NoteApplying a tuned profile which stipulates a different disk readahead value overrides the disk readahead value settings if they have been configured using a
udevrule. Red Hat recommends using the tuned tool to adjust the disk readahead values.
- Enables or disables barriers for mounts according to the Boolean value of the
- This plugin can be used for the execution of an external script that is run when the profile is loaded or unloaded. The script is called by one argument which can be
stop(it depends on whether the script is called during the profile load or unload). The script file name can be specified by the
scriptparameter. Note that you need to correctly implement the stop action in your script and revert all setting you changed during the start action, otherwise the roll-back will not work. For your convenience, the
functionsBash helper script is installed by default and allows you to import and use various functions defined in it. Note that this functionality is provided mainly for backwards compatibility and it is recommended that you use it as the last resort and prefer other plugins if they cover the required settings.
- Sets various
sysfssettings specified by the plugin parameters. The syntax is
sysfspath to use. Use this plugin in case you need to change some settings that are not covered by other plugins (please prefer specific plugins if they cover the required settings).
- Sets various powersave levels on video cards (currently only the Radeon cards are supported). The powersave level can be specified by using the
radeon_powersaveparameter. Supported values are:
dynpm. For details, refer to http://www.x.org/wiki/RadeonFeature#KMS_Power_Management_Options. Note that this plugin is experimental and the parameter may change in the future releases.
- Adds parameters to the kernel boot command line. This plugin supports the legacy GRUB 1, GRUB 2, and also GRUB with Extensible Firmware Interface (EFI). Customized non-standard location of the grub2 configuration file can be specified by the
grub2_cfg_fileoption. The parameters are added to the current grub configuration and its templates. The machine needs to be rebooted for the kernel parameters to take effect.The parameters can be specified by the following syntax:
cmdline=arg1 arg2 ... argn.
3.1.2. Installation and Usage
yum install tuned
- This is pre-selected on Red Hat Enterprise Linux 7 operating systems which act as compute nodes. The goal on such systems is the best throughput performance.
- This is pre-selected on virtual machines. The goal is best performance. If you are not interested in best performance, you would probably like to change it to the
powersaveprofile (see bellow).
- This is pre-selected in all other cases. The goal is balanced performance and power consumption.
systemctl start tuned
systemctl enable tuned
tuned-adm profile profile
tuned-adm profile powersave
highthroughput by using the
throughput-performanceprofile and concurrently setting the disk spindown to the
lowvalue by the
spindown-diskprofile. The following example optimizes the system for run in a virtual machine for the best performance and concurrently tune it for the low power consumption while the low power consumption is the priority:
tuned-adm profile virtual-guest powersave
3.1.3. Custom Profiles
/usr/lib/tuned/directory. Each profile has its own directory. The profile consists of the main configuration file called
tuned.conf, and optionally other files, for example helper scripts.
/etc/tuned/directory, which is used for custom profiles. If there are two profiles of the same name, the profile included in
/etc/tuned/directory to use a profile included in
/usr/lib/tuned/with only certain parameters adjusted or overridden.
tuned.conffile contains several sections. There is one
[main]section. The other sections are configurations for plugins instances. All sections are optional including the
[main]section. Lines starting with the hash sign (#) are comments.
[main]section has the following option:
- The specified profile will be included, e.g.
include=powersavewill include the
[NAME] type=TYPE devices=DEVICES
devicesline can contain a list, a wildcard (*), and negation (!). You can also combine rules. If there is no
devicesline all devices present or later attached on the system of the
TYPEwill be handled by the plugin instance. This is same as using
devices=*. If no instance of the plugin is specified, the plugin will not be enabled. If the plugin supports more options, they can be also specified in the plugin section. If the option is not specified, the default value will be used (if not previously specified in the included plugin). For the list of plugin options refer to Section 3.1.1, “Plug-ins”).
Example 3.1. Describing Plug-ins Instances
sd, such as
sdb, and does not disable barriers on them:
[data_disk] type=disk devices=sd* disable_barriers=false
[data_disk] type=disk devices=!sda1, !sda2 disable_barriers=false
typeline. The instance will then be referred to with a name, same as the type. The previous example could be then rewritten into:
[disk] devices=sdb* disable_barriers=false
includeoption, then the settings are merged. If they cannot be merged due to a conflict, the last conflicting definition overrides the previous settings in conflict. Sometimes, you do not know what was previously defined. In such cases, you can use the
replaceboolean option and set it to
true. This will cause all the previous definitions with the same name to be overwritten and the merge will not happen.
enabled=falseoption. This has the same effect as if the instance was never defined. Disabling the plugin can be useful if you are redefining the previous definition from the
includeoption and do not want the plugin to be active in your custom profile.
balancedprofile and extends it the way that ALPM for all devices is set to the maximal powersaving.
[main] include=balanced [disk] alpm=min_power
isolcpus=2to the kernel boot command line:
tuned-admutility. You can also create, modify, and delete profiles.
tuned-adm profile profile_name
tuned-adm profile latency-performance
- The default power-saving profile. It is intended to be a compromise between performance and power consumption. It tries to use auto-scaling and auto-tuning whenever possible. It has good results for most loads. The only drawback is the increased latency. In the current tuned release it enables the CPU, disk, audio and video plugins and activates the
radeon_powersaveis set to
- A profile for maximum power saving performance. It can throttle the performance in order to minimize the actual power consumption. In the current tuned release it enables USB autosuspend, WiFi power saving and ALPM power savings for SATA host adapters. It also schedules multi-core power savings for systems with a low wakeup rate and activates the
ondemandgovernor. It enables AC97 audio power saving or, depending on your system, HDA-Intel power savings with a 10 seconds timeout. In case your system contains supported Radeon graphics card with enabled KMS it configures it to automatic power saving. On Asus Eee PCs a dynamic Super Hybrid Engine is enabled.
powersaveprofile may not always be the most efficient. Consider there is a defined amount of work that needs to be done, for example a video file that needs to be transcoded. Your machine can consume less energy if the transcoding is done on the full power, because the task will be finished quickly, the machine will start to idle and can automatically step-down to very efficient power save modes. On the other hand if you transcode the file with a throttled machine, the machine will consume less power during the transcoding, but the process will take longer and the overall consumed energy can be higher. That is why the
balancedprofile can be generally a better option.
- A server profile optimized for high throughput. It disables power savings mechanisms and enables sysctl settings that improve the throughput performance of the disk, network IO and switched to the
deadlinescheduler. CPU governor is set to
- A server profile optimized for low latency. It disables power savings mechanisms and enables sysctl settings that improve the latency. CPU governor is set to
performanceand the CPU is locked to the low C states (by PM QoS).
- A profile for low latency network tuning. It is based on the
latency-performanceprofile. It additionally disables transparent hugepages, NUMA balancing and tunes several other network related sysctl parameters.
- Profile for throughput network tuning. It is based on the
throughput-performanceprofile. It additionally increases kernel network buffers.
- A profile designed for Red Hat Enterprise Linux 7 virtual machines as well as VMware guests based on the enterprise-storage profile that, among other tasks, decreases virtual memory swappiness and increases disk readahead values. It does not disable disk barriers.
- A profile designed for virtual hosts based on the
enterprise-storageprofile that, among other tasks, decreases virtual memory swappiness, increases disk readahead values and enables a more aggressive value of dirty pages.
- A profile optimized for Oracle databases loads based on
throughput-performanceprofile. It additionally disables transparent huge pages and modifies some other performance related kernel parameters. This profile is provided by tuned-profiles-oracle package. It is available in Red Hat Enterprise Linux 6.8 and later.
- A profile optimized for desktops, based on the
balancedprofile. It additionally enables scheduler autogroups for better response of interactive applications.
cpu-partitioningprofile partitions the system CPUs into isolated and housekeeping CPUs. To reduce jitter and interruptions on an isolated CPU, the profile clears the isolated CPU from user-space processes, movable kernel threads, interrupt handlers, and kernel timers.A housekeeping CPU can run all services, shell processes, and kernel threads.You can configure the
cpu-partitioningprofile in the
/etc/tuned/cpu-partitioning-variables.conffile. The configuration options are:
For more information on
- Lists CPUs to isolate. The list of isolated CPUs is comma-separated or the user can specify the range. You can specify a range using a dash, such as
3-5. This option is mandatory. Any CPU missing from this list is automatically considered a housekeeping CPU.
- Lists CPUs which are not considered by the kernel during system wide process load-balancing. This option is optional. This is usually the same list as
cpu-partitioning, see the tuned-profiles-cpu-partitioning(7) man page.
Optionalchannel. These profiles are intended for backward compatibility and are no longer developed. The generalized profiles from the base package will mostly perform the same or better. If you do not have specific reason for using them, please prefer the above mentioned profiles from the base package. The compat profiles are following:
- This has the lowest impact on power saving of the available profiles and only enables CPU and disk plugins of tuned.
- A power-saving profile directed at desktop systems. Enables ALPM power saving for SATA host adapters as well as the CPU, Ethernet, and disk plugins of tuned.
- A medium-impact power-saving profile directed at laptops running on AC. Enables ALPM powersaving for SATA host adapters, Wi-Fi power saving, as well as the CPU, Ethernet, and disk plugins of tuned.
- A high-impact power-saving profile directed at laptops running on battery. In the current tuned implementation it is an alias for the
- A power-saving profile for machines with classic HDDs to maximize spindown time. It disables the tuned power savings mechanism, disables USB autosuspend, disables Bluetooth, enables Wi-Fi power saving, disables logs syncing, increases disk write-back time, and lowers disk swappiness. All partitions are remounted with the
- A server profile directed at enterprise-class storage, maximizing I/O throughput. It activates the same settings as the
throughput-performanceprofile, multiplies readahead settings, and disables barriers on non-root and non-boot partitions.
atomic-hostprofile on physical machines, and the
atomic-guestprofile on virtual machines.
yum install tuned-profiles-atomic
- A profile optimized for Red Hat Enterprise Linux Atomic Host, when used as a host system on a bare-metal server, using the throughput-performance profile. It additionally increases SELinux AVC cache, PID limit, and tunes netfilter connections tracking.
- A profile optimized for Red Hat Enterprise Linux Atomic Host, when used as a guest system based on the virtual-guest profile. It additionally increases SELinux AVC cache, PID limit, and tunes netfilter connections tracking.
realtimeprofile, install the tuned-profiles-realtime package. Run, as root, the following command:
yum install tuned-profiles-realtime
realtime-virtual-guestprofiles, install the tuned-profiles-nfv package. Run, as root, the following command:
yum install tuned-profiles-nfv
yum install tuned-utils
/etc/tuneddirectory and it bases it on the currently selected tuned profile. For safety reasons all PowerTOP tunings are initially disabled in the new profile. To enable them uncomment the tunings of your interest in the
/etc/tuned/profile/tuned.conf. You can use the
-eoption that will generate the new profile with most of the tunings suggested by PowerTOP enabled. Some dangerous tunings like the USB autosuspend will still be disabled. If you really need them you will have to uncomment them manually. By default, the new profile is not activated. To activate it run the following command:
tuned-adm profile new_profile_name