Section 6.7. Process Virtual and Resident Set Size

6.7. Process Virtual and Resident Set Size

A process's memory consumption can be categorized into two major groups: virtual size and resident set size. The virtual size is the total amount of virtual memory used by a process, or more specifically, the sum of the virtual size of the individual mappings constituting its address space. Some or all of a process's virtual memory is backed by physical memory; we refer to that amount as a process's resident set size (RSS).

The basic tools such as ps and prstat show both the process's total virtual size and resident set size (RSS). Take the RSS figure with a grain of salt, since a substantial portion of a process's RSS is shared with other processes in the system.

$ ps -eo pid,vsz,rss,args   PID  VSZ  RSS COMMAND 11896 1040  736 ps -eo pid, vsz, rss, args 11892 1032  768 sh  3603 1032  768 sh  2695 1896 1432 telnet donan  2693 1920 1456 telnet donan  2433 1920 1440 telnet firefly  3143 1920 1456 telnet devnull  2429 1920 1440 telnet firefly.eng  2134 1920 1440 telnet devnull