Created at: 2024-11-12
$ uptime
15:37:23 up 12 min, 2 users, load average: 1.02, 1.01, 0.67
uptime(1): Tell how long the system has been running.
This is a simple tool that returns a one-liner with the following information:
The explanation for load averages is as follows:
System load averages is the average number of processes that are either in a runnable or uninterruptable state. A process in a runnable state is either using the CPU or waiting to use the CPU. A process in uninterruptable state is waiting for some I/O access, eg waiting for disk. The averages are taken over the three time intervals. Load averages are not normalized for the number of CPUs in a system, so a load average of 1 means a single CPU system is loaded all the time while on a 4 CPU system it means it was idle 75% of the time.
Analogously, if the load average is 10 for a system with 2 CPUs, it means that 2 processes are running while 8 are waiting (on average).
Analogy from the Performance book (Gregg):
Imagine a car toll plaza: you could measure the load at various points during the day by counting how many cars were being serviced (utilisation) plus how many cars were queued (saturation).
If the load is increasing over time, it is an indication that a problem affecting CPU performance is scaling.
If it is decreasing, it might mean that you missed the performance bottleneck event!