how is load average calculated

System administrators and software developers may often need to monitor the performance of their operating system or application. One key metric used for this purpose is the load average. Understanding how load average is calculated can help you analyze system utilization and diagnose performance issues. In this article, we will explore how load average is calculated, what it represents, and how it can be used to assess system performance.

What is Load Average?

Load average is a numerical value that represents the average number of processes or threads that are waiting for CPU resources over a certain period of time. It is typically reported as three values: the average load over the past 1 minute, 5 minutes, and 15 minutes. For example, a load average of 0.5 over 1 minute means that on average, there were 0.5 processes or threads waiting for CPU resources during that time period.

How is Load Average Calculated?

Load average is calculated using a formula that takes into account the number of processes or threads that are waiting for CPU resources and the total number of available CPU cores. The formula is as follows:load_avg = (a × 1 b × 5 c × 15) / (1 5 15)where a, b, and c represent the number of processes or threads waiting for CPU resources over the past 1 minute, 5 minutes, and 15 minutes, respectively.The result of this formula is the load average over the time periods considered. The load average value is normalized to the number of available CPU cores, so that a value of 1.0 means that the CPU is fully utilized, while a value below 1.0 means that the CPU is not fully utilized.

What Does Load Average Mean?

Understanding the meaning of the load average values can be helpful in making decisions about system performance and capacity planning. Generally speaking, the following guidelines can be used to interpret the load average values:- Load average below 0.5: the system is lightly loaded, and there are plenty of available CPU resources.- Load average between 0.5 and 1.0: the system is moderately loaded, and some processes or threads are waiting for CPU resources.- Load average above 1.0: the system is heavily loaded, and there are more processes or threads waiting for CPU resources than there are available.It is important to note that the load average is a relative measurement, and what constitutes a high or low load average value depends on the specific system hardware and workload. In general, a high load average value over an extended period of time can indicate a need for additional CPU capacity, while occasional spikes in load average may not necessarily indicate a problem.

How to Monitor Load Average

There are various tools that can be used to monitor load average on a system. The most common tool is the 'top' command line utility, which displays a real-time view of system processes and resource utilization. Other tools include graphical system monitor applications, performance analysis tools, and system log analysis tools.When monitoring load average, it is important to consider the context of the system workload. For example, a lightly loaded web server may have a higher load average than a heavily loaded database server due to differences in the workload nature and resource requirements. It is also important to monitor other system performance metrics, such as CPU usage, memory utilization, and disk I/O, to get a complete picture of system performance.

Conclusion

Load average is a useful metric for assessing system performance and capacity planning. It represents the average number of processes or threads waiting for CPU resources over a certain period of time, and is calculated using a formula that takes into account the past 1 minute, 5 minutes, and 15 minutes. Understanding load average can help you analyze system utilization, diagnose performance issues, and make informed decisions about system capacity planning.