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Profiling

Measuring where a program actually spends its time, before deciding what to optimize.

The step most often skipped. Distributing an I/O-bound workload multiplies the waiting, which profiling would have revealed in advance.

Performance & optimization

Related terms

  • I/O-bound: A workload whose runtime is limited by reading and writing data rather than by calculation. Adding workers to an I/O-bound job adds waiting, not throughput.
  • Compute-bound: A workload whose runtime is limited by how fast calculations can be performed. Adding workers to a compute-bound job generally makes it finish sooner.
  • Speedup: How many times faster a distributed run is than the same work on one worker. Ideal speedup equals worker count; real speedup falls short of it.