Mastering Embedded Linux Programming - Second Edition

Using smem

In 2009, Matt Mackall began looking at the problem of accounting for shared pages in process memory measurement and added two new metrics called unique set size, or Uss, and proportional set size, or Pss:

• Uss: This is the amount of memory that is committed to physical memory and is unique to a process; it is not shared with any other. It is the amount of memory that would be freed if the process were to terminate.
• Pss: This splits the accounting of shared pages that are committed to physical memory between all the processes that have them mapped. For example, if an area of library code is 12-pages long and is shared by six processes, each will accumulate two pages in Pss. Thus, if you add the Pss numbers for all processes, you ...