Parallelism Calculator
Estimate optimal number of parallel processes
Input Parameters
Minimum improvement required to justify adding another process
Results
How it works
Determine the optimal number of parallel processes for a workload based on performance scaling characteristics.
Formula
Estimated Mode:
Measured Mode:
Interpolates speedup linearly between measured points, then calculates:
Time(N) = Single Process Time ÷ Speedup(N)
Calculation Modes
- Estimated: Uses a scaling efficiency percentage (how well each additional process improves performance). Ideal with limited data
- Measured: Uses actual measurements at different process counts for piecewise-linear interpolation. Provides accurate predictions based on real-world data
Efficiency-optimal vs Speed-optimal
The efficiency-optimal point is where adding more processes gives less than the threshold improvement, while speed-optimal is the fastest measured or extrapolated completion time.
When to use this calculator
- Determining optimal parallelism for data migration tools (rsync, rclone, etc.)
- Balancing speed vs resource usage for parallel operations
- Evaluating if adding more processes will significantly improve performance
- Comparing efficiency-optimal vs speed-optimal configurations
Important Note
This calculator assumes sufficient system resources (CPU cores, memory, I/O bandwidth) are available for all parallel processes. In practice, resource constraints such as CPU saturation, memory limits, or disk/network bottlenecks may prevent achieving the predicted performance. Use measured mode with real-world tests to account for specific system limitations.