About
Resident memory is the part of the process memory that corresponds to the physical memory actually in operational use by this process.
Over time, the operating system may swap out some of a process's resident memory according to a least-recently-used algorithm to make room for other code or data.
Thus, a process's resident memory size may fluctuate independently of its virtual memory size.
In a properly-sized OS, there is enough physical memory, so that swapping is disabled and should not be observed.