8.4.2. The KSM Tuning Service
8.4.2. The KSM Tuning Service The ksmtuned service fine-tunes the kernel same-page merging (KSM) configuration by looping and adjusting ksm . In addition, the ksmtuned service is notified by libvirt when a guest virtual machine is created or destroyed. The ksmtuned service has no options. The ksmtuned service can be tuned with the retune parameter, which instructs ksmtuned to run tuning functions manually. The /etc/ksmtuned.conf file is the configuration file for the ksmtuned service. The file output below is the default ksmtuned.conf file: Within the /etc/ksmtuned.conf file, npages sets how many pages ksm will scan before the ksmd daemon becomes inactive. This value will also be set in the /sys/kernel/mm/ksm/pages_to_scan file. The KSM_THRES_CONST value represents the amount of available memory used as a threshold to activate ksm . ksmd is activated if either of the following occurs: The amount of free memory drops below the threshold, set in KSM_THRES_CONST . The amount of committed memory plus the threshold, KSM_THRES_CONST , exceeds the total amount of memory.
systemctl start ksmtuned Starting ksmtuned: [ OK ] Configuration file for ksmtuned. How long ksmtuned should sleep between tuning adjustments KSM_MONITOR_INTERVAL=60 Millisecond sleep between ksm scans for 16Gb server. Smaller servers sleep more, bigger sleep less. KSM_SLEEP_MSEC=10 KSM_NPAGES_BOOST - is added to the `npages` value, when `free memory` is less than `thres`. KSM_NPAGES_BOOST=300 KSM_NPAGES_DECAY - is the value given is subtracted to the `npages` value, when `free memory` is greater than `thres`. KSM_NPAGES_DECAY=-50 KSM_NPAGES_MIN - is the lower limit for the `npages` value. KSM_NPAGES_MIN=64 KSM_NPAGES_MAX - is the upper limit for the `npages` value. KSM_NPAGES_MAX=1250 KSM_THRES_COEF - is the RAM percentage to be calculated in parameter `thres`. KSM_THRES_COEF=20 KSM_THRES_CONST - If this is a low memory system, and the `thres` value is less than `KSM_THRES_CONST`, then reset `thres` value to `KSM_THRES_CONST` value. KSM_THRES_CONST=2048 uncomment the following to enable ksmtuned debug information LOGFILE=/var/log/ksmtuned DEBUG=1