Disables the page lock cache flushing when trying to retire a page that might belong to ISM.
When locked or busy (heavy I/O) pages are in the pending page retirement queue, the page retire thread flushes the segp_cache to encourage retirement of pending pages that might be owned by ISM. Periodic or repeated flushes of the segp_cache can be a bottleneck for high memory machines.
Default behavior is to flush the page cache every 30 seconds and if locked pages are observed in queue, then timeout exponentially backs off until 1 hour in multiples of 2.
Enabling pr_segp_disable does not disable the system's ability to retire memory pages, such as those that are faulted as a result of system diagnostic measures.
Boolean
1 (disabled)
0 (enabled) and 1 (disabled)
No
No
When locked or busy (heavy I/O) pages are in the pending page retirement queue, the page retire thread flushes the segp_cache to encourage retirement of pending pages that might be owned by ISM. Periodic or repeated flushes of the segp_cache can be a bottleneck for high memory machines.
If you have a latency sensitive database or a large shared memory application, consider disabling this parameter to completely skip segp cache flushing.
Symptoms of locked kernel pages that can't be retired are as follows:
Brief database latency or momentary database unresponsive events along with brief periodic elevated SYS CPU events upon successful page retirements, However, locked or busy pages that repeatedly fail to retire might continue to trigger page retirement threads at slower rates.
For example, locked memory pages that can't be retired might retry at small intervals and repeat forever at 1 hour intervals. After the system reboots, the scheduled pages might retire, or it might start trying again at 30 seconds, the default rate.
Brief unexpected or elevated smtx lock contention might be seen when monitoring segspt_shmfault, segspt_softunlock, segspt_shmpagelock, segspt_shmfree, segspt_shmunmap, segspt_shmattach, and segspt_dismfault structures.
Unstable