How is memory calculated when Solarwinds agent is used for Linux servers

Question

Hi ALl, 
 
 How is memory calculated when Solarwinds agent is used for Linux servers? Do we have any command or formula that is run in back end? 
 
 We are doing an automation for most of the metrics so the team needs to know the forumla in order to compare and then put in prod...

aLTeReGo · Answer

The Linux Agent polls memory statistics from the /proc filesystem (/proc/meminfo) as follows:

Value

Capacity

Used

Physical Memory 
 MemTotal 
 MemTotal-MemFree

Virtual Memory 
 MemTotal+SwapTotal 
 (MemTotal+SwapTotal) - (MemFree+SwapFree)

Swap Space 
 SwapTotal 
 SwapTotal-SwapFree

Shared Memory 
 Shmem 
 Shmem

Cached Memory 
 Cached 
 Cached

aLTeReGo · Answer

Alerting uses the same values displayed within the Orion web interface for that node.

aLTeReGo · Answer

The node' memory usage show in the radial gauge is showing actual Memory Used, excluding cache memory. Because this is a volatile cache that is used dynamically and surrendered when applications need that additional memory to function properly, most people would not consider that to be 'used'. At least not in the sense that undue memory pressure is occurring on the system that needs to be addressed. 
 The 'Physical Memory' volume, shown as a linear gauge in your screenshot above, is showing the actual amount of physical memory consumed, irrespective of what that memory is used for. 
 You can choose to alert on either (or both) of these metrics in Orion depending upon what you are concerned with. Most people simply choose to use Node Memory Utilization, as that is the value most representative of a problem with memory preasure on the system.