vmstat — system load summary

💬 "vmstat command"

vmstat summarizes CPU, memory, and I/O in a single line. It quickly identifies where the bottleneck is.

Starting from the second line, the values are actual measurements; specify an interval to observe continuously.

• r / b: number of processes waiting to run / blocked.
• si / so: swap in/out. If not 0, it indicates memory pressure.
• bi / bo: block I/O. This is a disk bottleneck indicator.
• wa: percentage of CPU waiting on I/O. If high, it indicates a disk bottleneck.

Frequently used options

Three essential command combinations

• vmstat 1 5 — system summary at 1-second intervals, 5 times
• vmstat -s | head — memory statistics summary
• vmstat -d | head -5 — per-disk I/O statistics

💬 "Just point out one pattern commonly used on real production servers"

Here are common situations encountered on real production servers, organized step by step.

Step 1 · Summary observation

Measure for a few seconds and observe the trend.

vmstat 1 5

Step 2 · Identify the bottleneck

If si/so is high, it is memory; if wa is high, it is disk.

vmstat 1 5 | awk '{print $1,$2,$7,$8,$16}'

Step 3 · Find the cause

Look at the process using that resource.

ps -eo pid,%cpu,rss,comm --sort=-rss | head

How it is used in practice

1. Identifying I/O bottlenecks

Situation — The server is slow, but the CPU is idle.

vmstat 1 5

Result — If wa (wait) is high and bi/bo is large, it is a disk bottleneck.

Point — Use iostat to narrow down which disk, then identify the process.

2. Detecting swap usage

Situation — Check whether memory is insufficient.

vmstat 1 5 | awk 'NR>2{print $7,$8}'

Result — If si/so is not 0, swap is actually being used.

Point — Heavy swapping causes a sharp drop in performance.

Things to keep in mind

• The first line is an average since boot, so do not use it as a measurement.
• A single run without an interval is a snapshot and misses trends.
• In containers, host-wide values may be displayed.

Actual execution output

This is the result of observing CPU, memory, and I/O status at 1-second intervals.

!vmstat command execution result: system load summary

Production server

Source (HTML): https://games.aidebatehub.com/programs/linux/troubleshooting/vmstat.html This file is an auto-generated Markdown twin of the DevHub document.