JSI Tip 0722. What does Mem Usage and VM Size mean on Task Manager's Processes tab?

Mem Usage - is the working set size. It is the amount of physical memory which is directly (currently) allocated to the process. It can be accessed without causing a page fault. This includes pages shared with other processes.

VM Size - is the total private virtual memory allocated to the process. This is the number you see when you use the Process Private Bytes counter in Performance Monitor.