Performance Efficiency
Performance efficiency is the degree to which software provides appropriate performance relative to the amount of resources used under specified conditions.
“The degree to which a component or system uses time, resources and capacity when accomplishing its designated functions.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is Performance Efficiency?
It evaluates response time, throughput, resource utilization, and capacity to ensure the system operates efficiently.
Resource usage: CPU, memory, storage, and network utilization are considered.
Performance behavior: Response time and throughput must meet requirements.
Quality characteristic: Defined in ISO/IEC 25010.
Real World Example
A video editing desktop app correctly exports every project without error, but a single 10-minute export pins all 8 CPU cores at 100% and consumes 12GB of RAM, making the computer unusable for anything else during export.
Functional correctness alone — the exported video is right — says nothing about whether the app is a reasonable citizen on the user's machine while producing that result; Performance efficiency is specifically about how much time, CPU, memory, and other resources it consumes to accomplish its function.
The tester measures export duration, CPU utilization, memory consumption, and disk I/O for a fixed, realistic project size, comparing the numbers against a target resource budget rather than only confirming the output file plays back correctly.
Profiling reveals the app isn't using GPU acceleration at all despite the hardware supporting it, explaining the excessive CPU and RAM use — a defect entirely about Performance efficiency, invisible to any test that only checks whether the exported video is correct.
Practice Questions
Question 1
A video editing app always exports a correct file, but a single export pins all CPU cores at 100% and uses 12GB of RAM, making the machine unusable during export. Which quality characteristic does this MOST directly concern?
Question 2
Which measurement is MOST directly aimed at evaluating performance efficiency, as distinct from confirming a feature works correctly?
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