pprof-test

A simple Go project to experiment slice memory allocation strategies using pprof.

How to Run

Run the unoptimized dynamic append version:

go run main.go -type=bad

Run the optimized pre-allocation version:

go run main.go -type=good

Visualize the memory profile in your browser:

go tool pprof -http=:8080 mem.prof

Result

Good

~2MB: Uses a fixed-size slice and reuses memory.

• A Go string header is 16 bytes (pointer + length).
• $16 \text{ bytes} \times 100,000 \text{ elements} \approx 1.6 \text{ MB}$.
• Since the size is constant, memory usage never exceeds this baseline.

Bad

~27.4GB: Uses append, causing the slice to grow indefinitely for 5 seconds.

• $16 \text{ bytes} \times 1.7\text{B elements} \approx 27.2 \text{ GB}$.
• With 100,000 appends per loop running ~17,000 times, the slice reaches 1.7 billion elements.
• The massive consumption comes from the ever-expanding backing array.