Linux - Vmstat (Virtual memory statistics)

About

vmstat (Virtual Memory Stats) reports virtual memory statistics.

It shows:

• how much virtual memory there is,
• how much is free and paging activity.

Most important, you can observe page-ins and page-outs as they happen.

Using this resource monitor, it is possible to get an overview of process, memory, swap, I/O, system, and CPU activity.

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Syntax

The process-related fields are:

• r — The number of runnable processes waiting for access to the CPU
• b — The number of processes in an uninterruptible sleep state
• w — The number of processes swapped out, but runnable

The memory-related fields are:

• swpd — The amount of virtual memory used
• free — The amount of free memory
• buff — The amount of memory used for buffers
• cache — The amount of memory used as page cache

The swap-related fields are:

• si — The amount of memory swapped in from disk
• so — The amount of memory swapped out to disk

The I/O-related fields are:

• bi — Blocks sent to a block device
• bo— Blocks received from a block device

The system-related fields are:

• in — The number of interrupts per second
• cs — The number of context switches per second

The CPU-related fields are:

• us — The percentage of the time the CPU ran user-level code
• sy — The percentage of the time the CPU ran system-level code
• id — The percentage of the time the CPU was idle