Memory check against resident memory is wrong

[Sirtea]

Hi,

According to m202 course, in memory model section, resident memory is not a good metric for memory usage, because is not freed, although it's not used.

db.serverStatus().mem { "bits" : 32, "resident" : 31, "virtual" : 211, "supported" : true, "mapped" : 80 }

Please consider looking at workingSet pages to get a more real approximation

db.serverStatus({workingSet:1}).workingSet { "note" : "thisIsAnEstimate", "pagesInMemory" : 5, "computationTimeMicros" : 15064, "overSeconds" : 417 }

This means that this empty instance is consuming 5 pages of memory (4kb each, for a 20kb total memory usage), but memory check is reporting 31mb. The numbers are more dramatic in our production systems.

Regards