RHEL Performance Tuning Options

Table of Contents

Installing the Tuned Package
Running Tuned
- Tuned Options
Automatically Starting Tuned
Disabling All Tuning

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Setting tuning options can be complicated, so RedHat Enterprise Linux (RHEL) has an installable daemon, tuned, that provides some tuning options, defined as profiles, to improve performance. This tuned periodically collects data about hardware subsystems, such as disks, network I/O, and switches. Then, based on the option selected, tuned dynamically adjusts system settings to raise or lower power consumption modes for these devices on your system.

Note

For Azul Zing Builds of OpenJDK (Zing), lower power consumption modes are detrimental to performance because if a core goes to sleep and the Garbage Collector or application has a thread that needs to run, then the cost of 'warming' up the core is expensive in time as the cache gets loaded and the pipeline is filled, etc.

Two tuned profiles that might be useful with your Zing installation:

throughput-performance

This is a server profile for typical throughput performance tuning. It disables tuned and ktune power saving mechanisms, enables sysctl settings that improve the throughput performance of your disk and network I/O, and switches to the deadline scheduler.
latency-performance

This is a server profile for typical low-latency performance tuning that can reduce RHEL jitter caused by the OS. It disables tuned and ktune power saving mechanisms and enables sysctl settings that improve the latency performance of your network I/O.

The latency-performance profile on RHEL can improve the max response time, depending upon the application running on Zing, by several (maybe 10s) of msec compared to the tuned default profile.

You can set and un-set these profiles with tuned-adm. The profiles are implemented with the tuned daemon.

Installing the Tuned Package

Installing the tuned package sets up a sample configuration file at /etc/tuned.conf and activates the default profile. The default power-saving profile has the lowest impact on power saving of the available profiles. It only enables CPU and disk tuned plug-ins.

Installing tuned-utils adds following dependencies on a standard installation:

systemtap-runtime
kernel-devel
systemtap

To install tuned:

Obtain the tuned installable package.

Refer to your RHEL distribution for the tuned package and documentation on using tuned. It is available with several RHEL distributions, including RHEL 6, CentOS 6, and Fedora.
Install the tuned package and its associated systemtap scripts with the command:
```
 # yum install tuned
```

Running Tuned

To use the tuned daemon:

Enable tuned. At the command prompt, type:
```
 # chkconfig tuned on
```
Start tuned. At the command prompt, type:
```
 # service tuned start
```

View the tuned profiles. At the command prompt, type:

 # tuned-adm list

The system response is:

 Available profiles:
- default
- desktop-powersave
- latency-performance
- laptop-ac-powersave
- server-powersave
- laptop-battery-powersave
- throughput-performance
- enterprise-storage
Current active profile: default

The profiles are implemented through the tuned daemon.

Enable the desired profile. At the command prompt, type:

 # tuned-adm profile <profile_name>

For example:

 # tuned-adm profile latency-performance
Calling '/etc/ktune.d/tunedadm.sh stop': [ OK ]
Stopping tuned: [ OK ]
Switching to profile 'latency-performance'
Applying ktune sysctl settings:
/etc/ktune.d/tunedadm.conf: [ OK ]
Calling '/etc/ktune.d/tunedadm.sh start': [ OK ]
Applying sysctl settings from /etc/sysctl.conf

Tuned Options

tuned has additional options that you can use when you run it manually. The available options are:

-d, --daemon

Starts tuned as a daemon instead of in the foreground.
-c, --conffile

Uses a configuration file with the specified name and path, for example:
```
 --conffile=/etc/tuned2.conf
```
The default is /etc/tuned.conf
-D, --debug

Uses the highest level of logging.

Automatically Starting Tuned

To start tuned every time the machine boots, at the command prompt, type:

 # chkconfig tuned on

Disabling All Tuning

You can turn off the tuned profiles, use the tuned-adm command. At the command prompt, type:

 # - tuned-adm off

This disables all tuned profiles.