3.6. Tuned and ktune
Tuned is a daemon that monitors and collects data on the usage of various system components, and uses that information to dynamically tune system settings as required. It can react to changes in CPU and network use, and adjust settings to improve performance in active devices or reduce power consumption in inactive devices.
The accompanying ktune partners with the tuned-adm tool to provide a number of tuning profiles that are pre-configured to enhance performance and reduce power consumption in a number of specific use cases. Edit these profiles or create new profiles to create performance solutions tailored to your environment.
The profiles provided as part of tuned-adm include:
- The default power-saving profile. This is the most basic power-saving profile. It enables only the disk and CPU plug-ins. Note that this is not the same as turning tuned-adm off, where both tuned and ktune are disabled.
- A server profile for typical latency performance tuning. This profile disables dynamic tuning mechanisms and transparent hugepages. It uses the
performancegoverner for p-states through
cpuspeed, and sets the I/O scheduler to
deadline. Additionally, in Red Hat Enterprise Linux 6.5 and later, the profile requests a
1. In Red Hat Enterprise Linux 6.4 and earlier,
cpu_dma_latencyrequested a value of
- A server profile for typical throughput performance tuning. This profile is recommended if the system does not have enterprise-class storage. throughput-performance disables power saving mechanisms and enables the
deadlineI/O scheduler. The CPU governor is set to
kernel.sched_min_granularity_ns(scheduler minimal preemption granularity) is set to
kernel.sched_wakeup_granularity_ns(scheduler wake-up granularity) is set to
vm.dirty_ratio(virtual memory dirty ratio) is set to 40%, and transparent huge pages are enabled.
- This profile is recommended for enterprise-sized server configurations with enterprise-class storage, including battery-backed controller cache protection and management of on-disk cache. It is the same as the
throughput-performanceprofile, with one addition: file systems are re-mounted with
- This profile is optimized for virtual machines. It is based on the
enterprise-storageprofile, but also decreases the swappiness of virtual memory. This profile is available in Red Hat Enterprise Linux 6.3 and later.
- Based on the
virtual-hostdecreases the swappiness of virtual memory and enables more aggressive writeback of dirty pages. Non-root and non-boot file systems are mounted with
barrier=0. Additionally, as of Red Hat Enterprise Linux 6.5, the
kernel.sched_migration_costparameter is set to
5milliseconds. Prior to Red Hat Enterprise Linux 6.5,
kernel.sched_migration_costused the default value of
0.5milliseconds. This profile is available in Red Hat Enterprise Linux 6.3 and later.
Refer to the Red Hat Enterprise Linux 6 Power Management Guide, available from http://access.redhat.com/site/documentation/Red_Hat_Enterprise_Linux/, for further information about tuned and ktune.