目的

値のサイズが、配置されるメモリ領域（ヒープ or スタック）に影響を及ぼす可能性があることを理解する。

環境

$ go version
go version go1.23.2 linux/amd64

検証

(1) 値のサイズが小さく、スタックに置かれるパターン

package main

const size = 64 * 1024

func main() {
	_ = make([]byte, size)
}

package main

import "testing"

func Benchmark(b *testing.B) {
	for i := 0; i < b.N; i++ {
		main()
	}
}

$ go build -gcflags "-m=2" .
# gopractice
./main.go:5:6: can inline main with cost 4 as: func() { _ = make([]byte, 65536) }
./main.go:6:10: make([]byte, 65536) does not escape

$ go test -bench=. -benchmem
goos: linux
goarch: amd64
pkg: gopractice
cpu: Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz
Benchmark-2     1000000000               0.3695 ns/op          0 B/op          0 allocs/op
PASS
ok      gopractice      0.418s

$ go build -o main_binary main.go
$ objdump -d main_binary > objdump.txt
0000000000466be0 <main.main>:
  466be0:	c3                   	ret
  466be1:	cc                   	int3
  466be2:	cc                   	int3
  466be3:	cc                   	int3
  466be4:	cc                   	int3
  466be5:	cc                   	int3
  466be6:	cc                   	int3
  466be7:	cc                   	int3
  466be8:	cc                   	int3
  466be9:	cc                   	int3
  466bea:	cc                   	int3
  466beb:	cc                   	int3
  466bec:	cc                   	int3
  466bed:	cc                   	int3
  466bee:	cc                   	int3
  466bef:	cc                   	int3
  466bf0:	cc                   	int3
  466bf1:	cc                   	int3
  466bf2:	cc                   	int3
  466bf3:	cc                   	int3
  466bf4:	cc                   	int3
  466bf5:	cc                   	int3
  466bf6:	cc                   	int3
  466bf7:	cc                   	int3
  466bf8:	cc                   	int3
  466bf9:	cc                   	int3
  466bfa:	cc                   	int3
  466bfb:	cc                   	int3
  466bfc:	cc                   	int3
  466bfd:	cc                   	int3
  466bfe:	cc                   	int3
  466bff:	cc                   	int3

(2) 値のサイズが大きく、ヒープに置かれるパターン

package main

const size = 64*1024 + 1

func main() {
	_ = make([]byte, size)
}

package main

import "testing"

func Benchmark(b *testing.B) {
	for i := 0; i < b.N; i++ {
		main()
	}
}

$ go build -gcflags "-m=2" .
# gopractice
./main.go:5:6: can inline main with cost 4 as: func() { _ = make([]byte, 65537) }
./main.go:6:10: make([]byte, 65537) escapes to heap:
./main.go:6:10:   flow: {heap} = &{storage for make([]byte, 65537)}:
./main.go:6:10:     from make([]byte, 65537) (too large for stack) at ./main.go:6:10
./main.go:6:10: make([]byte, 65537) escapes to heap

$ go test -bench=. -benchmem
goos: linux
goarch: amd64
pkg: gopractice
cpu: Intel(R) Xeon(R) CPU E5-2686 v4 @ 2.30GHz
Benchmark-2        79288             15874 ns/op           73728 B/op          1 allocs/op
PASS
ok      gopractice      1.415s

$ go build -o main_binary main.go
$ objdump -d main_binary > objdump.txt
0000000000466be0 <main.main>:
  466be0:	49 3b 66 10          	cmp    0x10(%r14),%rsp
  466be4:	76 25                	jbe    466c0b <main.main+0x2b>
  466be6:	55                   	push   %rbp
  466be7:	48 89 e5             	mov    %rsp,%rbp
  466bea:	48 83 ec 18          	sub    $0x18,%rsp
  466bee:	48 8d 05 4b 56 00 00 	lea    0x564b(%rip),%rax        # 46c240 <type:*+0x5240>
  466bf5:	bb 01 00 01 00       	mov    $0x10001,%ebx
  466bfa:	48 89 d9             	mov    %rbx,%rcx
  466bfd:	0f 1f 00             	nopl   (%rax)
  466c00:	e8 5b 79 ff ff       	call   45e560 <runtime.makeslice>
  466c05:	48 83 c4 18          	add    $0x18,%rsp
  466c09:	5d                   	pop    %rbp
  466c0a:	c3                   	ret
  466c0b:	e8 10 b1 ff ff       	call   461d20 <runtime.morestack_noctxt.abi0>
  466c10:	eb ce                	jmp    466be0 <main.main>
  466c12:	cc                   	int3
  466c13:	cc                   	int3
  466c14:	cc                   	int3
  466c15:	cc                   	int3
  466c16:	cc                   	int3
  466c17:	cc                   	int3
  466c18:	cc                   	int3
  466c19:	cc                   	int3
  466c1a:	cc                   	int3
  466c1b:	cc                   	int3
  466c1c:	cc                   	int3
  466c1d:	cc                   	int3
  466c1e:	cc                   	int3
  466c1f:	cc                   	int3

参考