Why is My CGo Function Slower Than My Pure Go Function?

Performance Considerations of CGo

You have conducted a comparison of execution times for CGo and pure Go functions, and the cgo function exhibits slower performance. While your testing code appears valid, there are underlying factors that can account for this disparity.

CGo functions incur a performance penalty due to the overhead involved in invoking C/C code. Minimizing the frequency of CGo calls is recommended to optimize performance. However, for your example, it might be more efficient to move the loop into the C code rather than repeatedly calling a CGo function.

Several aspects of Goroutine setup and execution in Go can challenge C code expectations:

• Goroutines utilize a limited stack and grow their stacks through segmentation or copying.
• Go-created threads may have compatibility issues with libpthread's thread local storage implementation.
• The Go runtime's signal handler can interfere with C/C code.
• Go employs thread reuse for Goroutine execution. If C code triggers blocking system calls or thread monopolization, it can negatively impact other Goroutines.

To ensure stability, CGo opts to execute C code in a separate thread with a traditional stack.

Unlike languages like Python, where optimizing code with C is common, Go offers a narrower performance gap between equivalent C and Go code.

Therefore, it is generally advisable to employ CGo primarily for interfacing with external libraries, potentially using small C wrapper functions for reduced calls made from Go code.

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