What Is Utilization
Let’s start by taking a look at the definition of Utilization.
Utilization or U
Utilization of any system is defined as the Ratio of Busy Time to Total Time of Observation. Utilization is a ratio that generally refers to how busy or free the resources within a given system are. Utilization can also be used to refer to how busy or free are components within a given system instead of the system as a whole.
The following equations are used to describe Utilization:
- U = Bt / T …………………………. [ Bt = Busy Time, T = Total Observed Time Interval ]
The above equation describes utilization as the ratio of Busy Time to Total Observed Time.
Example: Lets assume we are viewing a system for a period of 180 seconds during which it remains busy for 100 seconds.
- The Utilization of the system is calculated as follows:
- We know : U = Bt / T …………………………. [ Bt = Busy Time, T = Total Observed Time Interval ]
- Utilization (U) = 100/180 = 0.55
The Utilization thus for this system is 0.55.
In addition to the equation above Utilization can be described as:
- U = X * St …………………………. [ X = Throughput, St = Service Time ]
The above equation describes Utilization as the product of Throughput and Service Time. As mentioned earlier the above equation can be applied to either the system as a whole or at a resource level within a given system.
Example: Lets assume we are viewing a system for a period of 180 seconds during which it remains busy for 100 seconds. The Service Time for a transaction is 2s. The throughput of the system is calculated as follows:
- U = X * St
- X = U / St = 0.55 / 2 = 0.275 Transactions/Sec
The equation provided below is very similar to the previous equation but with one subtle difference i.e. the addition of Average Number of Servers (of CPU’s in our case).
- Uavg = [ X * St ] / M …………….. [ Uavg = Average Utilization, X = Throughput, St = Service Time, M = Average Number of Servers ]
On a system with multiple servers (CPUs) the average utilization is obtained by dividing the overall system utilization by the total number of servers (CPUs) present.
Additional Resources
- Dr. Rajesh’s papers on Performance Testing and Performance Requirements Gathering
- Microsoft : Load Testing of Web Applications
- Microsoft : Patterns & Practices – Performance Testing Guidance
- The Server Side : Performance Engineering – A Practitioners approach to Performance Testing
- Dr. Connie Smith on Performance Engineering
- Dr. Rajesh Mansharamani on Performance Engineerirng
- Wikipedia on Performance Engineering
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Trevor Warren is passionate about challenging the status-quo and finding reasons to innovate. Over the past 16 years he has been delivering complex systems, has worked with very large clients across the world and constantly is looking for opportunities to bring about change. Trevor constantly strives to combine his passion for delivering outcomes with his ability to build long lasting professional relationships. You can learn more about the work he does at LinkedIn. You can download a copy of his CV at VisualCV. Visit the Github page for details of the projects he’s been hacking with.