The 30% is 46%, and it stops dead at 80 bytes
Go 1.27's size-specialised allocation is worth up to 46% on the pointer-containing path, not the 30% announced — and from 96 bytes up it is worth nothing.
−03 · Category
Performance and measurement
Benchmarking method, profiling, allocation, escape analysis and compiler behaviour — the subject where the evidence standard is most visible.
Articles in “Performance and measurement”
3 articlesPerformance and measurement
benchstat reported p=0.000 between a function and itself
Two sub-benchmarks calling the same function with the same argument came back 1.10% apart at p=0.000. What a benchmark measures is not only your code.
Escape analysis is not a rule of thumb
The compiler said "does not escape" and the benchmark reported 104 KiB per operation. Both were right. What -gcflags=-m actually tells you.