Linux Load Average: A Comprehensive Guide

Understanding System Load Averages

On Linux, Mac, and other Unix-like operating systems, "load average" figures are commonly displayed.

These values indicate the current demand placed on the system’s CPU, disk, and other vital resources.

While initially appearing complex, understanding load averages is straightforward with a little familiarization.

Where You'll Find Load Averages

Regardless of whether you are managing a Linux desktop computer or a server environment, you will likely encounter a "load average" metric.

This measurement is also present in Linux-based router firmware, network-attached storage (NAS) systems utilizing Linux or BSD, and even Mac OS X.

Essentially, it’s a ubiquitous indicator of system performance across a wide range of platforms.

What Do Load Averages Represent?

• Load averages provide a snapshot of system activity over specific time intervals.
• Typically, three load averages are shown: the average over the last 1 minute, 5 minutes, and 15 minutes.
• These averages reflect the number of processes waiting to use the CPU.

A higher load average suggests a busier system, while a lower average indicates less demand.

Interpreting these numbers accurately is key to assessing system health and identifying potential bottlenecks.

Load vs. Load Average

Related: What Is Unix, and Why Does It Matter?

In Unix-based operating systems, such as Linux, system load represents the amount of work the system is currently handling. This metric is presented as a numerical value. A system that is completely inactive will exhibit a load average of 0.

Each process actively utilizing or contending for CPU resources contributes 1 to the load average. Consequently, a system load of 5 indicates that five processes are either actively using the CPU or are queued, awaiting access.

Historically, Unix systems primarily tallied processes awaiting CPU time. However, Linux extends this calculation to include processes pending on other resources, like disk I/O operations.

The raw load number, taken in isolation, offers limited insight. A computer’s load can fluctuate rapidly, shifting from 0 to 5 within a fraction of a second as processes demand CPU cycles.

An instantaneous load reading would therefore be largely uninformative. Instead, Unix-like systems present the load average.

The load average is calculated as the average system load over a defined period, providing a more stable and meaningful indication of system workload.