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Instruments are a key component of CodSpeed. They are used to measure the performance of your code using different techniques.

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Choosing an Instrument

Not sure which instrument to use? This decision tree will help you find the right one:
  • CPU Simulation: Simulates CPU behavior to measure performance, taking into account instructions executed, cache and memory access patterns. Benchmarks run only once for consistent, hardware-agnostic results.
  • Walltime: Measures real-world execution time on bare-metal runners managed by CodSpeed, with low noise and high precision.
  • Memory: Captures detailed memory usage and heap allocations to help you identify and optimize allocations.
* Simulation is the recommended default, but use Walltime when your benchmark contains I/O (which can introduce variance in simulation) or is too large (simulation adds overhead that slows down long-running benchmarks significantly).

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Executor Instruments

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CPU Simulation

Measure performance by simulating the CPU behavior
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Memory

Track memory usage, allocations, and leaks in your benchmarks

Walltime

Measure performance by measuring the real time taken

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Ad Hoc Instruments

Those ad hoc instruments can be used on top of an executor instrument to measure specific performance metrics.

Database Instrument

Measure the performance of database queries