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8.4.3. KSM Variables and Monitoring
Kernel same-page merging (KSM) stores monitoring data in the
/sys/kernel/mm/ksm/ directory. Files in this directory are updated by the kernel and are an accurate record of KSM usage and statistics.
The variables in the list below are also configurable variables in the
/etc/ksmtuned.conf file, as noted above.
Files in /sys/kernel/mm/ksm/:
- full_scans
- Full scans run.
- merge_across_nodes
- Whether pages from different NUMA nodes can be merged.
- pages_shared
- Total pages shared.
- pages_sharing
- Pages currently shared.
- pages_to_scan
- Pages not scanned.
- pages_unshared
- Pages no longer shared.
- pages_volatile
- Number of volatile pages.
- run
- Whether the KSM process is running.
- sleep_millisecs
- Sleep milliseconds.
These variables can be manually tuned using the
virsh node-memory-tune command. For example, the following specifies the number of pages to scan before the shared memory service goes to sleep:
# virsh node-memory-tune --shm-pages-to-scan number
KSM tuning activity is stored in the
/var/log/ksmtuned log file if the DEBUG=1 line is added to the /etc/ksmtuned.conf file. The log file location can be changed with the LOGFILE parameter. Changing the log file location is not advised and may require special configuration of SELinux settings.
