Stack vs malloc: real-world benchmark shows 2–6x difference

Usually, we assume that malloc is fast—and in most cases it is. However, sometimes "reasonable" code can lead to very unreasonable performance. In a previous post, I looked at using stack-based allocation (VLA / fixed-size) for temporary data, and another on estimating available stack space to use it safely. This time I wanted to measure the actual impact in a realistic workload. Full Article (Medium - no paywall): Stack vs malloc: real-world benchmark shows 2–6x difference I built a benchmark based on a loan portfolio PV calculation, where each loan creates several temporary arrays (thousands of elements each). This is fairly typical code-clean, modular, nothing unusual. I compared: stack allocation (VLA) heap per-loan (malloc/free) heap reuse static (baseline) Results: stack allocation stays very close to optimal heap per-loan can be ~2.5x slower (glibc) and up to ~6x slower (musl) even optimized allocators show pattern-dependent behavior The main takeaway for me: allocation cost is