The Memory Usage check polls the selected Memory Performance Indicators every 5 seconds and averages this out over the monitored period (5 or 15 minutes). Where the average for any indicator exceeds the entered threshold figure an Alert is generated.
RAM used is the total memory minus the available memory. Available memory is the sum of the following three internal memory lists.
- Standby list
- Free list
- Zero list
Unused pages of memory and pages of memory returned to the Operating System when a process quits or its working set was reduced to comply with system resource requirements are placed on one of the above three lists.
Consists of memory allocated to processes that either exited abnormally, have not returned the memory allocation to the Operating System for reuse or memory in use by running processes. As such the Operating System cannot swap such memory from physical RAM to the pagefile as it is classed as in use.
The demand for memory and may be thought of as the number of bytes of physical (RAM) and virtual memory allocated to all running programs, applications and the Operating System a RAM page frame or page slot in the pagefile is committed to.
Swap Usage (Page File Usage)
The memory pages used by a process not stored in physical RAM. Paging files can be resized to accommodate the additional memory requirements of the running processes. Problems may occur where the systems paging file is inadequately sized for the paging activity of the system.
Pages per second (hard page faults only):
Hard page faults occur where the system attempts to access a virtual memory page not currently in physical memory working set. This page is instead retrieved from the disk resulting in a delay.
From Dashboard 2020.01.20 we updated the default threshold values for new Checks. Existing Check thresholds are unaffected.
|Indicator||Threshold||Pre-2020.01.2 Threshold||Threshold from 2020.01.2|
|RAM Used||Alert if average available MB <||10MB||500MB|
|Pages per second (hard page faults only)||Alert if average pages per sec >||20 /Sec||1000 /Sec|
|Swap Usage (Page File Usage)||Alert if average page file usage >||70%||80%|
|Non-pageable memory||Alert if non-paged pool >||100MB||500MB|
|Commit Charge||Alert if average committed bytes >||1.5 *Physical RAM||1 *Physical RAM|