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by Kumuda G | Published January 31, 2018
A tuned daemon uses the udev daemon to monitor connected devices and statically and dynamically tunes system settings according to a selected profile. The tuned daemon has predefined profiles such as Throughput-performance, Balanced, and Virtual-guest for common use cases. System administrators can also create custom profiles for their workloads.
In the Red Hat Enterprise Linux (RHEL) version 7 operating system, the default profile is Throughput-performance. The Virtual-guest profile is selected for virtual machines and the Balanced profile is selected for all other cases. The Balanced profile is the default profile in the CentOS 7.x operating system. The tuned daemon has a set of rules that recommend or select one of the profiles as the default profile. These rules use regular expressions to match the computenode|server strings in the /etc/system-release-cpe file and also use the output of the virt-what command. If the first expression is true and the output of the virt-what command is empty, the Throughput-performance profile is recommended. If the output of the virt-what command displays data about the virtual machine, the Virtual-guest profile is recommended. When both these rules are not met, the Balanced profile is selected as the default profile in the Tuned daemon.
Systems with operating systems that act as compute nodes always aim for best throughput performance. The Throughput-performance profile is a server profile that is optimized for high throughput. This profile disables energy savings mechanisms and enables the sysctl settings that improve the throughput performance of the disk, network I/O, and switches to the deadline scheduler. The CPU governor parameter is set to performance.
The goal of this profile is balanced performance and energy consumption. It is intended to be a solution in between performance and energy consumption and uses auto-scaling and auto-tuning whenever possible. It has good results for most loads. Increased latency is a drawback with this profile.
This profile enables the processor, disk, audio, and video plug-ins and activates the on-demand governor policy, which is a CPU frequency governor policy. The radeon_powersave parameter of the Radeon video graphics card is set to auto.
You can change or switch between these profiles by using the tuned-adm command. For example, run the tuned-adm profile <profile> command. You can select the profile that is best suited for your workload. The Throughput-performance and Balanced profiles are the default profiles on non-virtual systems.
tuned-adm profile <profile>
This profile is optimized for virtual machines. The settings of this profile decrease virtual memory swappiness and increase disk read-ahead values.
The following table describes the comparison of a few system parameters that differ between these profiles.
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