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Chapter 2. Customizing TuneD profiles

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You can create or modify TuneD profiles to optimize system performance for your intended use case.

Prerequisites

2.1. TuneD profiles

A detailed analysis of a system can be very time-consuming. TuneD provides a number of predefined profiles for typical use cases. You can also create, modify, and delete profiles.

The profiles provided with TuneD are divided into the following categories:

  • Power-saving profiles
  • Performance-boosting profiles

The performance-boosting profiles include profiles that focus on the following aspects:

  • Low latency for storage and network
  • High throughput for storage and network
  • Virtual machine performance
  • Virtualization host performance

Syntax of profile configuration

The tuned.conf file can contain one [main] section and other sections for configuring plug-in instances. However, all sections are optional.

Lines starting with the hash sign (#) are comments.

Additional resources

  • tuned.conf(5) man page.

2.2. The default TuneD profile

During the installation, the best profile for your system is selected automatically. Currently, the default profile is selected according to the following customizable rules:

EnvironmentDefault profileGoal

Compute nodes

throughput-performance

The best throughput performance

Virtual machines

virtual-guest

The best performance. If you are not interested in the best performance, you can change it to the balanced or powersave profile.

Other cases

balanced

Balanced performance and power consumption

Additional resources

  • tuned.conf(5) man page.

2.3. Merged TuneD profiles

As an experimental feature, it is possible to select more profiles at once. TuneD will try to merge them during the load.

If there are conflicts, the settings from the last specified profile takes precedence.

Example 2.1. Low power consumption in a virtual guest

The following example optimizes the system to run in a virtual machine for the best performance and concurrently tunes it for low power consumption, while the low power consumption is the priority:

# tuned-adm profile virtual-guest powersave
Warning

Merging is done automatically without checking whether the resulting combination of parameters makes sense. Consequently, the feature might tune some parameters the opposite way, which might be counterproductive: for example, setting the disk for high throughput by using the throughput-performance profile and concurrently setting the disk spindown to the low value by the spindown-disk profile.

Additional resources

*tuned-adm man page. * tuned.conf(5) man page.

2.4. The location of TuneD profiles

TuneD stores profiles in the following directories:

/usr/lib/tuned/
Distribution-specific profiles are stored in the 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/
If you need to customize a profile, copy the profile directory into the directory, which is used for custom profiles. If there are two profiles of the same name, the custom profile located in /etc/tuned/ is used.

Additional resources

  • tuned.conf(5) man page.

2.5. Inheritance between TuneD profiles

TuneD profiles can be based on other profiles and modify only certain aspects of their parent profile.

The [main] section of TuneD profiles recognizes the include option:

[main]
include=parent

All settings from the parent profile are loaded in this child profile. In the following sections, the child profile can override certain settings inherited from the parent profile or add new settings not present in the parent profile.

You can create your own child profile in the /etc/tuned/ directory based on a pre-installed profile in /usr/lib/tuned/ with only some parameters adjusted.

If the parent profile is updated, such as after a TuneD upgrade, the changes are reflected in the child profile.

Example 2.2. A power-saving profile based on balanced

The following is an example of a custom profile that extends the balanced profile and sets Aggressive Link Power Management (ALPM) for all devices to the maximum powersaving.

[main]
include=balanced

[scsi_host]
alpm=min_power

Additional resources

  • tuned.conf(5) man page

2.6. Static and dynamic tuning in TuneD

Understanding the difference between the two categories of system tuning that TuneD applies, static and dynamic, is important when determining which one to use for a given situation or purpose.

Static tuning
Mainly consists of the application of predefined sysctl and sysfs settings and one-shot activation of several configuration tools such as ethtool.
Dynamic tuning

Watches how various system components are used throughout the uptime of your system. TuneD adjusts system settings dynamically based on that monitoring information.

For example, the hard drive is used heavily during startup and login, but is barely used later when the user might mainly work with applications such as web browsers or email clients. Similarly, the CPU and network devices are used differently at different times. TuneD monitors the activity of these components and reacts to the changes in their use.

By default, dynamic tuning is disabled. To enable it, edit the /etc/tuned/tuned-main.conf file and change the dynamic_tuning option to 1. TuneD then periodically analyzes system statistics and uses them to update your system tuning settings. To configure the time interval in seconds between these updates, use the update_interval option.

Currently implemented dynamic tuning algorithms try to balance the performance and powersave, and are therefore disabled in the performance profiles. Dynamic tuning for individual plug-ins can be enabled or disabled in the TuneD profiles.

Example 2.3. Static and dynamic tuning on a workstation

On a typical office workstation, the Ethernet network interface is inactive most of the time. Only a few emails go in and out or some web pages might be loaded.

For those kinds of loads, the network interface does not have to run at full speed all the time, as it does by default. TuneD has a monitoring and tuning plug-in for network devices that can detect this low activity and then automatically lower the speed of that interface, typically resulting in a lower power usage.

If the activity on the interface increases for a longer period of time, for example because a DVD image is being downloaded or an email with a large attachment is opened, TuneD detects this and sets the interface speed to maximum to offer the best performance while the activity level is high.

This principle is used for other plug-ins for CPU and disks as well.

2.7. TuneD plug-ins

Plug-ins are modules in TuneD profiles that TuneD uses to monitor or optimize different devices on the system.

TuneD uses two types of plug-ins:

Monitoring plug-ins

Monitoring plug-ins are used to get information from a running system. The output of the monitoring plug-ins can be used by tuning plug-ins for dynamic tuning.

Monitoring plug-ins are automatically instantiated whenever their metrics are needed by any of the enabled tuning plug-ins. If two tuning plug-ins require the same data, only one instance of the monitoring plug-in is created and the data is shared.

Tuning plug-ins
Each tuning plug-in tunes an individual subsystem and takes several parameters that are populated from the TuneD profiles. Each subsystem can have multiple devices, such as multiple CPUs or network cards, that are handled by individual instances of the tuning plug-ins. Specific settings for individual devices are also supported.

Syntax for plug-ins in TuneD profiles

Sections describing plug-in instances are formatted in the following way:

[NAME]
type=TYPE
devices=DEVICES
NAME
is the name of the plug-in instance as it is used in the logs. It can be an arbitrary string.
TYPE
is the type of the tuning plug-in.
DEVICES

is the list of devices that this plug-in instance handles.

The devices line can contain a list, a wildcard (*), and negation (!). If there is no devices line, all devices present or later attached on the system of the TYPE are handled by the plug-in instance. This is same as using the devices=* option.

Example 2.4. Matching block devices with a plug-in

The following example matches all block devices starting with sd, such as sda or sdb, and does not disable barriers on them:

[data_disk]
type=disk
devices=sd*
disable_barriers=false

The following example matches all block devices except sda1 and sda2:

[data_disk]
type=disk
devices=!sda1, !sda2
disable_barriers=false

If no instance of a plug-in is specified, the plug-in is not enabled.

If the plug-in supports more options, they can be also specified in the plug-in section. If the option is not specified and it was not previously specified in the included plug-in, the default value is used.

Short plug-in syntax

If you do not need custom names for the plug-in instance and there is only one definition of the instance in your configuration file, TuneD supports the following short syntax:

[TYPE]
devices=DEVICES

In this case, it is possible to omit the type line. The instance is then referred to with a name, same as the type. The previous example could be then rewritten into:

Example 2.5. Matching block devices using the short syntax

[disk]
devices=sdb*
disable_barriers=false

Conflicting plug-in definitions in a profile

If the same section is specified more than once using the include option, the settings are merged. If they cannot be merged due to a conflict, the last conflicting definition overrides the previous settings. If you do not know what was previously defined, you can use the replace Boolean option and set it to true. This causes all the previous definitions with the same name to be overwritten and the merge does not happen.

You can also disable the plug-in by specifying the enabled=false option. This has the same effect as if the instance was never defined. Disabling the plug-in is useful if you are redefining the previous definition from the include option and do not want the plug-in to be active in your custom profile.

NOTE

TuneD includes the ability to run any shell command as part of enabling or disabling a tuning profile. This enables you to extend TuneD profiles with functionality that has not been integrated into TuneD yet.

You can specify arbitrary shell commands using the script plug-in.

Additional resources

  • tuned.conf(5) man page

2.8. Available TuneD plug-ins

Monitoring plug-ins

Currently, the following monitoring plug-ins are implemented:

disk
Gets disk load (number of IO operations) per device and measurement interval.
net
Gets network load (number of transferred packets) per network card and measurement interval.
load
Gets CPU load per CPU and measurement interval.

Tuning plug-ins

Currently, the following tuning plug-ins are implemented. Only some of these plug-ins implement dynamic tuning. Options supported by plug-ins are also listed:

cpu

Sets the CPU governor to the value specified by the governor option and dynamically changes the Power Management Quality of Service (PM QoS) CPU Direct Memory Access (DMA) latency according to the CPU load.

If the CPU load is lower than the value specified by the load_threshold option, the latency is set to the value specified by the latency_high option, otherwise it is set to the value specified by latency_low.

You can also force the latency to a specific value and prevent it from dynamically changing further. To do so, set the force_latency option to the required latency value.

eeepc_she

Dynamically sets the front-side bus (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 (SHE).

If the CPU load is lower or equal to the value specified by the load_threshold_powersave option, the plug-in sets the FSB speed to the value specified by the she_powersave option. If the CPU load is higher or equal to the value specified by the load_threshold_normal option, it sets the FSB speed to the value specified by the she_normal option.

Static tuning is not supported and the plug-in is transparently disabled if TuneD does not detect the hardware support for this feature.

net
Configures the Wake-on-LAN functionality to the values specified by the wake_on_lan option. It uses the same syntax as the ethtool utility. It also dynamically changes the interface speed according to the interface utilization.
sysctl

Sets various sysctl settings specified by the plug-in options.

The syntax is name=value, where name is the same as the name provided by the sysctl utility.

Use the sysctl plug-in if you need to change system settings that are not covered by other plug-ins available in TuneD. If the settings are covered by some specific plug-ins, prefer these plug-ins.

usb

Sets autosuspend timeout of USB devices to the value specified by the autosuspend parameter.

The value 0 means that autosuspend is disabled.

vm

Enables or disables transparent huge pages depending on the value of the transparent_hugepages option.

Valid values of the transparent_hugepages option are:

  • "always"
  • "never"
  • "madvise"
audio

Sets the autosuspend timeout for audio codecs to the value specified by the timeout option.

Currently, the snd_hda_intel and snd_ac97_codec codecs are supported. The value 0 means that the autosuspend is disabled. You can also enforce the controller reset by setting the Boolean option reset_controller to true.

disk

Sets the disk elevator to the value specified by the elevator option.

It also sets:

  • APM to the value specified by the apm option
  • Scheduler quantum to the value specified by the scheduler_quantum option
  • Disk spindown timeout to the value specified by the spindown option
  • Disk readahead to the value specified by the readahead parameter
  • The current disk readahead to a value multiplied by the constant specified by the readahead_multiply option

In addition, this plug-in 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 option dynamic and is enabled by default.

scsi_host

Tunes options for SCSI hosts.

It sets Aggressive Link Power Management (ALPM) to the value specified by the alpm option.

mounts
Enables or disables barriers for mounts according to the Boolean value of the disable_barriers option.
script

Executes an external script or binary when the profile is loaded or unloaded. You can choose an arbitrary executable.

Important

The script plug-in is provided mainly for compatibility with earlier releases. Prefer other TuneD plug-ins if they cover the required functionality.

TuneD calls the executable with one of the following arguments:

  • start when loading the profile
  • stop when unloading the profile

You need to correctly implement the stop action in your executable and revert all settings that you changed during the start action. Otherwise, the roll-back step after changing your TuneD profile will not work.

Bash scripts can import the /usr/lib/tuned/functions Bash library and use the functions defined there. Use these functions only for functionality that is not natively provided by TuneD. If a function name starts with an underscore, such as _wifi_set_power_level, consider the function private and do not use it in your scripts, because it might change in the future.

Specify the path to the executable using the script parameter in the plug-in configuration.

Example 2.6. Running a Bash script from a profile

To run a Bash script named script.sh that is located in the profile directory, use:

[script]
script=${i:PROFILE_DIR}/script.sh
sysfs

Sets various sysfs settings specified by the plug-in options.

The syntax is name=value, where name is the sysfs path to use.

Use this plugin in case you need to change some settings that are not covered by other plug-ins. Prefer specific plug-ins if they cover the required settings.

video

Sets various powersave levels on video cards. Currently, only the Radeon cards are supported.

The powersave level can be specified by using the radeon_powersave option. Supported values are:

  • default
  • auto
  • low
  • mid
  • high
  • dynpm
  • dpm-battery
  • dpm-balanced
  • dpm-perfomance

For details, see www.x.org. Note that this plug-in is experimental and the option might change in future releases.

bootloader

Adds options to the kernel command line. This plug-in supports only the GRUB 2 boot loader.

Customized non-standard location of the GRUB 2 configuration file can be specified by the grub2_cfg_file option.

The kernel options are added to the current GRUB configuration and its templates. The system needs to be rebooted for the kernel options to take effect.

Switching to another profile or manually stopping the TuneD service removes the additional options. If you shut down or reboot the system, the kernel options persist in the grub.cfg file.

The kernel options can be specified by the following syntax:

cmdline=arg1 arg2 ... argN

Example 2.7. Modifying the kernel command line

For example, to add the quiet kernel option to a TuneD profile, include the following lines in the tuned.conf file:

[bootloader]
cmdline=quiet

The following is an example of a custom profile that adds the isolcpus=2 option to the kernel command line:

[bootloader]
cmdline=isolcpus=2
service

Handles various sysvinit, sysv-rc, openrc, and systemd services specified by the plug-in options.

The syntax is service.service_name=command[,file:file].

Supported service-handling commands are:

  • start
  • stop
  • enable
  • disable

Separate multiple commands using either a comma (,) or a semicolon (;). If the directives conflict, the service plugin uses the last listed one.

Use the optional file:file directive to install an overlay configuration file, file, for systemd only. Other init systems ignore this directive. The service plugin copies overlay configuration files to /etc/systemd/system/service_name.service.d/ directories. Once profiles are unloaded, the service plugin removes these directories if they are empty.

Note

The service plugin only operates on the current runlevel with non-systemd init systems.

Example 2.8. Starting and enabling the sendmail sendmail service with an overlay file

[service]
service.sendmail=start,enable,file:${i:PROFILE_DIR}/tuned-sendmail.conf

The internal variable ${i:PROFILE_DIR} points to the directory the plugin loads the profile from.

scheduler
Offers a variety of options for the tuning of scheduling priorities, CPU core isolation, and process, thread, and IRQ affinities.

For specifics of the different options available, see Functionalities of the scheduler TuneD plug-in.

2.9. Functionalities of the scheduler TuneD plugin

Use the scheduler TuneD plugin to control and tune scheduling priorities, CPU core isolation, and process, thread, and IRQ afinities.

CPU isolation

To prevent processes, threads, and IRQs from using certain CPUs, use the isolated_cores option. It changes process and thread affinities, IRQ affinities, and sets the default_smp_affinity parameter for IRQs.

The CPU affinity mask is adjusted for all processes and threads matching the ps_whitelist option, subject to success of the sched_setaffinity() system call. The default setting of the ps_whitelist regular expression is .* to match all processes and thread names. To exclude certain processes and threads, use the ps_blacklist option. The value of this option is also interpreted as a regular expression. Process and thread names are matched against that expression. Profile rollback enables all matching processes and threads to run on all CPUs, and restores the IRQ settings prior to the profile application.

Multiple regular expressions separated by ; for the ps_whitelist and ps_blacklist options are supported. Escaped semicolon \; is taken literally.

Example 2.9. Isolate CPUs 2-4

The following configuration isolates CPUs 2-4. Processes and threads that match the ps_blacklist regular expression can use any CPUs regardless of the isolation:

[scheduler]
isolated_cores=2-4
ps_blacklist=.*pmd.*;.*PMD.*;^DPDK;.*qemu-kvm.*

IRQ SMP affinity

The /proc/irq/default_smp_affinity file contains a bitmask representing the default target CPU cores on a system for all inactive interrupt request (IRQ) sources. Once an IRQ is activated or allocated, the value in the /proc/irq/default_smp_affinity file determines the IRQ’s affinity bitmask.

The default_irq_smp_affinity parameter controls what TuneD writes to the /proc/irq/default_smp_affinity file. The default_irq_smp_affinity parameter supports the following values and behaviors:

calc

Calculates the content of the /proc/irq/default_smp_affinity file from the isolated_cores parameter. An inversion of the isolated_cores parameter calculates the non-isolated cores.

The intersection of the non-isolated cores and the previous content of the /proc/irq/default_smp_affinity file is then written to the /proc/irq/default_smp_affinity file.

This is the default behavior if the default_irq_smp_affinity parameter is omitted.

ignore
TuneD does not modify the /proc/irq/default_smp_affinity file.
A CPU list

Takes the form of a single number such as 1, a comma separated list such as 1,3, or a range such as 3-5.

Unpacks the CPU list and writes it directly to the /proc/irq/default_smp_affinity file.

Example 2.10. Setting the default IRQ smp affinity using an explicit CPU list

The following example uses an explicit CPU list to set the default IRQ SMP affinity to CPUs 0 and 2:

[scheduler]
isolated_cores=1,3
default_irq_smp_affinity=0,2

Scheduling policy

To adjust scheduling policy, priority and affinity for a group of processes or threads, use the following syntax:

group.groupname=rule_prio:sched:prio:affinity:regex

where rule_prio defines internal TuneD priority of the rule. Rules are sorted based on priority. This is needed for inheritance to be able to reorder previously defined rules. Equal rule_prio rules should be processed in the order they were defined. However, this is Python interpreter dependent. To disable an inherited rule for groupname, use:

group.groupname=

sched must be one of the following:

f
for first in, first out (FIFO)
b
for batch
r
for round robin
o
for other
*
for do not change

affinity is CPU affinity in hexadecimal. Use * for no change.

prio is scheduling priority (see chrt -m).

regex is Python regular expression. It is matched against the output of the ps -eo cmd command.

Any given process name can match more than one group. In such cases, the last matching regex determines the priority and scheduling policy.

Example 2.11. Setting scheduling policies and priorities

The following example sets the scheduling policy and priorities to kernel threads and watchdog:

[scheduler]
group.kthreads=0:*:1:*:\[.*\]$
group.watchdog=0:f:99:*:\[watchdog.*\]

The scheduler plugin uses a perf event loop to identify newly created processes. By default, it listens to perf.RECORD_COMM and perf.RECORD_EXIT events.

Setting the perf_process_fork parameter to true tells the plug-in to also listen to perf.RECORD_FORK events, meaning that child processes created by the fork() system call are processed.

Note

Processing perf events can pose a significant CPU overhead.

The CPU overhead of the scheduler plugin can be mitigated by using the scheduler runtime option and setting it to 0. This completely disables the dynamic scheduler functionality and the perf events are not monitored and acted upon. The disadvantage of this is that the process and thread tuning will be done only at profile application.

Example 2.12. Disabling the dynamic scheduler functionality

The following example disables the dynamic scheduler functionality while also isolating CPUs 1 and 3:

[scheduler]
runtime=0
isolated_cores=1,3

The mmapped buffer is used for perf events. Under heavy loads, this buffer might overflow and as a result the plugin might start missing events and not processing some newly created processes. In such cases, use the perf_mmap_pages parameter to increase the buffer size. The value of the perf_mmap_pages parameter must be a power of 2. If the perf_mmap_pages parameter is not manually set, a default value of 128 is used.

Confinement using cgroups

The scheduler plugin supports process and thread confinement using cgroups v1.

The cgroup_mount_point option specifies the path to mount the cgroup file system, or, where TuneD expects it to be mounted. If it is unset, /sys/fs/cgroup/cpuset is expected.

If the cgroup_groups_init option is set to 1, TuneD creates and removes all cgroups defined with the cgroup* options. This is the default behavior. If the cgroup_mount_point option is set to 0, the cgroups must be preset by other means.

If the cgroup_mount_point_init option is set to 1, TuneD creates and removes the cgroup mount point. It implies cgroup_groups_init = 1. If the cgroup_mount_point_init option is set to 0, you must preset the cgroups mount point by other means. This is the default behavior.

The cgroup_for_isolated_cores option is the cgroup name for the isolated_cores option functionality. For example, if a system has 4 CPUs, isolated_cores=1 means that Tuned moves all processes and threads to CPUs 0, 2, and 3. The scheduler plug-in isolates the specified core by writing the calculated CPU affinity to the cpuset.cpus control file of the specified cgroup and moves all the matching processes and threads to this group. If this option is unset, classic cpuset affinity using sched_setaffinity() sets the CPU affinity.

The cgroup.cgroup_name option defines affinities for arbitrary cgroups. You can even use hierarchic cgroups, but you must specify the hierarchy in the correct order. TuneD does not do any sanity checks here, with the exception that it forces the cgroup to be in the location specified by the cgroup_mount_point option.

The syntax of the scheduler option starting with group. has been augmented to use cgroup.cgroup_name instead of the hexadecimal affinity. The matching processes are moved to the cgroup cgroup_name. You can also use cgroups not defined by the cgroup. option as described above. For example, cgroups not managed by TuneD.

All cgroup names are sanitized by replacing all periods (.) with slashes (/). This prevents the plugin from writing outside the location specified by the cgroup_mount_point option.

Example 2.13. Using cgroups v1 with the scheduler plug-in

The following example creates 2 cgroups, group1 and group2. It sets the cgroup group1 affinity to CPU 2 and the cgroup group2 to CPUs 0 and 2. Given a 4 CPU setup, the isolated_cores=1 option moves all processes and threads to CPU cores 0, 2, and 3. Processes and threads specified by the ps_blacklist regular expression are not moved.

[scheduler]
cgroup_mount_point=/sys/fs/cgroup/cpuset
cgroup_mount_point_init=1
cgroup_groups_init=1
cgroup_for_isolated_cores=group
cgroup.group1=2
cgroup.group2=0,2

group.ksoftirqd=0:f:2:cgroup.group1:ksoftirqd.*
ps_blacklist=ksoftirqd.*;rcuc.*;rcub.*;ktimersoftd.*
isolated_cores=1

The cgroup_ps_blacklist option excludes processes belonging to the specified cgroups. The regular expression specified by this option is matched against cgroup hierarchies from /proc/PID/cgroups. Commas (,) separate cgroups v1 hierarchies from /proc/PID/cgroups before regular expression matching. The following is an example of content the regular expression is matched against:

10:hugetlb:/,9:perf_event:/,8:blkio:/

Multiple regular expressions can be separated by semicolons (;). The semicolon represents a logical 'or' operator.

Example 2.14. Excluding processes from the scheduler using cgroups

In the following example, the scheduler plug-in moves all processes away from core 1, except for processes which belong to cgroup /daemons. The \b string is a regular expression metacharacter that matches a word boundary.

[scheduler]
isolated_cores=1
cgroup_ps_blacklist=:/daemons\b

In the following example, the scheduler plugin excludes all processes which belong to a cgroup with a hierarchy-ID of 8 and controller-list blkio.

[scheduler]
isolated_cores=1
cgroup_ps_blacklist=\b8:blkio:

Recent kernels moved some sched_ and numa_balancing_ kernel run-time parameters from the /proc/sys/kernel directory managed by the sysctl utility, to debugfs, typically mounted under the /sys/kernel/debug directory. TuneD provides an abstraction mechanism for the following parameters via the scheduler plugin where, based on the kernel used, TuneD writes the specified value to the correct location:

  • sched_min_granularity_ns
  • sched_latency_ns,
  • sched_wakeup_granularity_ns
  • sched_tunable_scaling,
  • sched_migration_cost_ns
  • sched_nr_migrate
  • numa_balancing_scan_delay_ms
  • numa_balancing_scan_period_min_ms
  • numa_balancing_scan_period_max_ms
  • numa_balancing_scan_size_mb

    Example 2.15. Set tasks' "cache hot" value for migration decisions.

    On the old kernels, setting the following parameter meant that sysctl wrote a value of 500000 to the /proc/sys/kernel/sched_migration_cost_ns file:

    [sysctl]
    kernel.sched_migration_cost_ns=500000

    This is, on more recent kernels, equivalent to setting the following parameter via the scheduler plugin:

    [scheduler]
    sched_migration_cost_ns=500000

    Meaning TuneD writes a value of 500000 to the /sys/kernel/debug/sched/migration_cost_ns file.

2.10. Variables in TuneD profiles

Variables expand at run time when a TuneD profile is activated.

Using TuneD variables reduces the amount of necessary typing in TuneD profiles.

There are no predefined variables in TuneD profiles. You can define your own variables by creating the [variables] section in a profile and using the following syntax:

[variables]

variable_name=value

To expand the value of a variable in a profile, use the following syntax:

${variable_name}

Example 2.16. Isolating CPU cores using variables

In the following example, the ${isolated_cores} variable expands to 1,2; hence the kernel boots with the isolcpus=1,2 option:

[variables]
isolated_cores=1,2

[bootloader]
cmdline=isolcpus=${isolated_cores}

The variables can be specified in a separate file. For example, you can add the following lines to tuned.conf:

[variables]
include=/etc/tuned/my-variables.conf

[bootloader]
cmdline=isolcpus=${isolated_cores}

If you add the isolated_cores=1,2 option to the /etc/tuned/my-variables.conf file, the kernel boots with the isolcpus=1,2 option.

Additional resources

  • tuned.conf(5) man page

2.11. Built-in functions in TuneD profiles

Built-in functions expand at run time when a TuneD profile is activated.

You can:

  • Use various built-in functions together with TuneD variables
  • Create custom functions in Python and add them to TuneD in the form of plug-ins

To call a function, use the following syntax:

${f:function_name:argument_1:argument_2}

To expand the directory path where the profile and the tuned.conf file are located, use the PROFILE_DIR function, which requires special syntax:

${i:PROFILE_DIR}

Example 2.17. Isolating CPU cores using variables and built-in functions

In the following example, the ${non_isolated_cores} variable expands to 0,3-5, and the cpulist_invert built-in function is called with the 0,3-5 argument:

[variables]
non_isolated_cores=0,3-5

[bootloader]
cmdline=isolcpus=${f:cpulist_invert:${non_isolated_cores}}

The cpulist_invert function inverts the list of CPUs. For a 6-CPU machine, the inversion is 1,2, and the kernel boots with the isolcpus=1,2 command-line option.

Additional resources

  • tuned.conf(5) man page

2.12. Built-in functions available in TuneD profiles

The following built-in functions are available in all TuneD profiles:

PROFILE_DIR
Returns the directory path where the profile and the tuned.conf file are located.
exec
Executes a process and returns its output.
assertion
Compares two arguments. If they do not match, the function logs text from the first argument and aborts profile loading.
assertion_non_equal
Compares two arguments. If they match, the function logs text from the first argument and aborts profile loading.
kb2s
Converts kilobytes to disk sectors.
s2kb
Converts disk sectors to kilobytes.
strip
Creates a string from all passed arguments and deletes both leading and trailing white space.
virt_check

Checks whether TuneD is running inside a virtual machine (VM) or on bare metal:

  • Inside a VM, the function returns the first argument.
  • On bare metal, the function returns the second argument, even in case of an error.
cpulist_invert
Inverts a list of CPUs to make its complement. For example, on a system with 4 CPUs, numbered from 0 to 3, the inversion of the list 0,2,3 is 1.
cpulist2hex
Converts a CPU list to a hexadecimal CPU mask.
cpulist2hex_invert
Converts a CPU list to a hexadecimal CPU mask and inverts it.
hex2cpulist
Converts a hexadecimal CPU mask to a CPU list.
cpulist_online
Checks whether the CPUs from the list are online. Returns the list containing only online CPUs.
cpulist_present
Checks whether the CPUs from the list are present. Returns the list containing only present CPUs.
cpulist_unpack
Unpacks a CPU list in the form of 1-3,4 to 1,2,3,4.
cpulist_pack
Packs a CPU list in the form of 1,2,3,5 to 1-3,5.

2.13. Creating new TuneD profiles

This procedure creates a new TuneD profile with custom performance rules.

Prerequisites

Procedure

  1. In the /etc/tuned/ directory, create a new directory named the same as the profile that you want to create:

    # mkdir /etc/tuned/my-profile
  2. In the new directory, create a file named tuned.conf. Add a [main] section and plug-in definitions in it, according to your requirements.

    For example, see the configuration of the balanced profile:

    [main]
    summary=General non-specialized TuneD profile
    
    [cpu]
    governor=conservative
    energy_perf_bias=normal
    
    [audio]
    timeout=10
    
    [video]
    radeon_powersave=dpm-balanced, auto
    
    [scsi_host]
    alpm=medium_power
  3. To activate the profile, use:

    # tuned-adm profile my-profile
  4. Verify that the TuneD profile is active and the system settings are applied:

    $ tuned-adm active
    
    Current active profile: my-profile
    $ tuned-adm verify
    
    Verification succeeded, current system settings match the preset profile.
    See tuned log file ('/var/log/tuned/tuned.log') for details.

Additional resources

  • tuned.conf(5) man page

2.14. Modifying existing TuneD profiles

This procedure creates a modified child profile based on an existing TuneD profile.

Prerequisites

Procedure

  1. In the /etc/tuned/ directory, create a new directory named the same as the profile that you want to create:

    # mkdir /etc/tuned/modified-profile
  2. In the new directory, create a file named tuned.conf, and set the [main] section as follows:

    [main]
    include=parent-profile

    Replace parent-profile with the name of the profile you are modifying.

  3. Include your profile modifications.

    Example 2.18. Lowering swappiness in the throughput-performance profile

    To use the settings from the throughput-performance profile and change the value of vm.swappiness to 5, instead of the default 10, use:

    [main]
    include=throughput-performance
    
    [sysctl]
    vm.swappiness=5
  4. To activate the profile, use:

    # tuned-adm profile modified-profile
  5. Verify that the TuneD profile is active and the system settings are applied:

    $ tuned-adm active
    
    Current active profile: my-profile
    $ tuned-adm verify
    
    Verification succeeded, current system settings match the preset profile.
    See tuned log file ('/var/log/tuned/tuned.log') for details.

Additional resources

  • tuned.conf(5) man page

2.15. Setting the disk scheduler using TuneD

This procedure creates and enables a TuneD profile that sets a given disk scheduler for selected block devices. The setting persists across system reboots.

In the following commands and configuration, replace:

  • device with the name of the block device, for example sdf
  • selected-scheduler with the disk scheduler that you want to set for the device, for example bfq

Prerequisites

Procedure

  1. Optional: Select an existing TuneD profile on which your profile will be based. For a list of available profiles, see TuneD profiles distributed with RHEL.

    To see which profile is currently active, use:

    $ tuned-adm active
  2. Create a new directory to hold your TuneD profile:

    # mkdir /etc/tuned/my-profile
  3. Find the system unique identifier of the selected block device:

    $ udevadm info --query=property --name=/dev/device | grep -E '(WWN|SERIAL)'
    
    ID_WWN=0x5002538d00000000_
    ID_SERIAL=Generic-_SD_MMC_20120501030900000-0:0
    ID_SERIAL_SHORT=20120501030900000
    Note

    The command in the this example will return all values identified as a World Wide Name (WWN) or serial number associated with the specified block device. Although it is preferred to use a WWN, the WWN is not always available for a given device and any values returned by the example command are acceptable to use as the device system unique ID.

  4. Create the /etc/tuned/my-profile/tuned.conf configuration file. In the file, set the following options:

    1. Optional: Include an existing profile:

      [main]
      include=existing-profile
    2. Set the selected disk scheduler for the device that matches the WWN identifier:

      [disk]
      devices_udev_regex=IDNAME=device system unique id
      elevator=selected-scheduler

      Here:

      • Replace IDNAME with the name of the identifier being used (for example, ID_WWN).
      • Replace device system unique id with the value of the chosen identifier (for example, 0x5002538d00000000).

        To match multiple devices in the devices_udev_regex option, enclose the identifiers in parentheses and separate them with vertical bars:

        devices_udev_regex=(ID_WWN=0x5002538d00000000)|(ID_WWN=0x1234567800000000)
  5. Enable your profile:

    # tuned-adm profile my-profile

Verification steps

  1. Verify that the TuneD profile is active and applied:

    $ tuned-adm active
    
    Current active profile: my-profile
    $ tuned-adm verify
    
    Verification succeeded, current system settings match the preset profile.
    See TuneD log file ('/var/log/tuned/tuned.log') for details.
  2. Read the contents of the /sys/block/device/queue/scheduler file:

    # cat /sys/block/device/queue/scheduler
    
    [mq-deadline] kyber bfq none

    In the file name, replace device with the block device name, for example sdc.

    The active scheduler is listed in square brackets ([]).

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