Global Variables vs. Parameter Passing in Go: Does Using Globals Improve Slice Performance?

Performance Analysis: Passing Function Slices as Parameters vs Global Variables

When designing Go functions, it's crucial to optimize performance to ensure efficiency. Parameters are often passed by value, prompting the question: is it beneficial to move parameters to global variables for optimization purposes?

Examine the Impact of Global Variables

First, let's consider the case of excludedPatterns in the given checkFiles function. Since this parameter is never altered, optimizing it by making it global may seem logical. However, it's important to note that the performance gain is negligible because the slice is a minimalistic descriptor, not a substantial data structure.

Understanding Golang's Memory Management

Golang adheres to a copy-on-write principle. When parameters are passed by value, a fresh copy of the original value is created. This ensures data isolation and immutability. However, in the case of slices, they're passed by reference, meaning the original data is not duplicated. Instead, a new descriptor is generated, pointing to the existing backing array.

Performance Implications

Benchmarks prove that passing slices as parameters doesn't introduce a noticeable performance penalty compared to declaring them globally. They both require constant time, regardless of the slice size.

Best Practices

Based on the analysis, it's generally not advisable to move parameters to global variables for performance reasons unless the performance criteria are extremely tight. Passing parameters by value has several advantages:

• Maintains encapsulation and data safety
• Enhances code readability and maintainability
• Allows for optimization by compilers

Conclusion

While global variables might appear as a viable option for performance optimization in certain scenarios, it's generally not recommended unless there's a significant performance bottleneck. In the case of slice parameters, passing them by value is an efficient and preferred approach.

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