Linux 101 : System load - How to read the output of the "uptime" command -

The "uptime" command gives us an idea about the system load.

The load average of a Linux system is defined by the number of processes - running and uninterruptible -.
  • Runnable state : running or are in the queue waiting to be run.
  • Uninterruptible state : means the processes that are waiting for and input or output.
Example of CPU load average:

A one core CPU system that has a load average of one. is fully loaded.
A CPU load of two on the same system, means that one process is in the waiting queue.

On a four cores CPU, a load average of two, means hat two CPUs are fully loaded.

On the load average output, we have - see above, the output of the uptime command - the one, five, and fifteen minutes load averages.

The one minute load average - 3.33 - tell us about the actual state of the system, the load had declined over the last five minutes to an average of - 2.41 -. 
Throughout the last fifteen minutes the load was an average of - 2.08 -. 
The system was under low load for at least fifteen minutes 2.08 -, the load increased slightly in the past five minutes 2.41 -. 

We run "uptime" again, and this time we have the below output:

The value - 
23.33 - shows a recent spike in activity.
We could run tools like "ps" or "top" to see which processes caused that rise in the CPU load.


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