vmstat
also: virtual memory statistics
A command-line tool that displays virtual memory statistics and system performance metrics including CPU, memory, disk I/O, and process activity.
vmstat (virtual memory statistics) is a diagnostic command that provides a snapshot or continuous monitoring of system performance. It shows CPU usage, memory consumption, swap activity, disk I/O operations, and the number of running and blocked processes.
The command outputs data in columns: procs (running/blocked processes), memory (RAM and swap usage), swap (disk swap I/O), io (block device I/O), system (interrupts/context switches), and cpu (CPU time breakdown).
Example: vmstat 1 5 displays statistics every 1 second for 5 iterations, helping identify bottlenecks like excessive paging, high I/O wait, or CPU contention in real-time.