Smem

Smem is an open-source memory reporting tool for Linux and other Unix-like operating systems. It analyzes the memory usage of processes and reports a set of metrics designed to give a clearer picture of how memory is consumed, especially when sharing occurs. The tool derives its data from the /proc filesystem, particularly the smaps data for each process, and attributes shared memory proportionally to each process.

A key feature of smem is its use of USS (Unique Set Size), PSS (Proportional Set Size), and RSS (Resident Set Size). USS represents memory that would be freed if the process were terminated, excluding shared pages. PSS weights shared pages by the number of processes sharing them, providing a more accurate per-process accounting when shared libraries or memory mappings are involved. RSS is the total resident memory mapped into the process, including shared pages in full. smem can present per-process data as well as aggregated views by user or by command, helping diagnose memory bloat, compare memory usage across programs, and understand the impact of shared libraries on total consumption.

In typical use, smem is run from the command line and can produce output that includes pid, user, command, USS, PSS, RSS, and swap usage. It is widely available in many Linux distributions and can be installed via standard package managers. As a tool intended for system administrators and developers, smem complements other utilities such as top, ps, and pmap by providing a more nuanced view of memory accounting and sharing.