Process Memory Type

Memory type	Memory Type description
VSS (Virtual Set Size)	virtual memory consumption . It is the size of all memory space addresses that a process can access. This size contains some memory that does not reside in RAM, just as Mallocs has been allocated, but not yet written. VSS is seldom used to measure the actual memory of the program .
rss (resident Set Size)	Physical memory is actually used. rss is the amount of memory that a process actually holds in RAM. RSS can be misleading because it contains all the memory that is consumed by the shared library used by the process, and a shared library that is loaded into memory may be used by many processes. RSS is not an accurate representation of the amount of memory that a single process uses.
PSS (proportional Set Size)	actual physical memory used . For example, if there are three processes sharing a shared library of 30-page memory controls, each process will only calculate 10 pages when it calculates PSS. PSS is a very useful value if all of the processes in the system are added together by PSS, and that is the sum of the memory that is consumed by the system. When a process is killed, the shared library memory that it occupies is shared by other processes that still use the shared library. In this way, PSS can also be misleading, because when a process is killed, PSS does not represent the amount of memory the system recycles.
Uss:unique Set Size	the physical memory that the process occupies on its own . This part of the memory is completely exclusive to the process. USS is a very useful value because it indicates the true memory cost required to run a particular process. When a process is killed, the USS is the memory that is reclaimed by all systems. USS is the best option to check for memory leaks in the process.

Process Memory Type