Golang基准测试中的alloc / op零是什么？

Question

Here I have a benchmark test:

// bench_test.go

package main

import (
    "testing"
)

func BenchmarkHello(b *testing.B) {
    for i := 0; i < b.N; i++ {
        a := 1
        a++
    }
}

The test result are strange. The metric allocs/op shows zero. I know variable a is a int type and doesn't take too much memory, but it's not zero.

> go test -bench=. -benchmem
goos: darwin
goarch: amd64
pkg: a
BenchmarkHello-4    2000000000           0.26 ns/op        0 B/op          0 allocs/op
PASS
ok      a   0.553s

Questions

This post points that allocs/op means how many distinct memory allocations occurred per op (single iteration).

• But what does memory allocation mean? does that mean set a value for a variable? Is it kind ofmalloc in C` ?

• Why is this metric allocs/ops zero?

Answer 1

Possible Answer

From Dave Cheney, one of the Go contributors:

The benchmark tool only reports heap allocations. Stack allocations via escape analysis are less costly, possibly free, so are not reported.

Reference

Why is this simple benchmark showing zero allocations?