Performance Terminology

This page contains definitions for common terminoloy used when discussing the art of systems performance. Some words, in particular, already contain an abundance of meanings, and it's important to distinguish which is being used when discussing performance engineering.

Term	Definition
Architecture	The software configuration and hardware on which an application runs.
Bottleneck	A resource that limits the performance of the system.
Caching	Storing the results from a slower storage tier in a faster storage tier, for reference.
IOPS	Input/output operations per second (read/writes per second for disks).
Latency[^1]	A measure of time an operation spends waiting to be serviced.
Profiling	The building of a picture of a target that can be studied and understood.
Response Time	The time for an operation to complete.
Saturation	The degree to which a resource has queued work it cannot service.
Scalability	The performance of the system under increasing load.
Throughput	The rate of work performed.
Utilization[^2]	How busy a resource is.
Workload	The input to the system or the load applied.

[^1]: This specific term can be ambigious without qualifying information; it's better to quantify it with additional terms (i.e. TCP connection latency) [^2]: Utilization can be time-based or capacity based: the average amount of time a resource is busy vs the utilization of a certain percent of total resource capacity (i.e. disk I/O usage vs disk capacity usage).