node_size.go

package node

const elemSize = 128

type node struct {
	inodes []*inode
}

type inode struct {
	k []byte
	v []byte
}

func createNode(size int) *node {
	n := &node{}
	n.inodes = make([]*inode, 0, size)

	for i := 0; i < size; i++ {
		in := &inode{k: []byte("boo"), v: []byte("bar")}
		n.inodes = append(n.inodes, in)
	}
	return n
}

func (n *node) Size_AddElemSizeInLoop() int {
	sz := 0
	for _, in := range n.inodes {
		sz += elemSize + len(in.k) + len(in.v)
	}
	return sz
}

func (n *node) Size_SumElemSizeFirst() int {
	sz := elemSize * len(n.inodes)
	for _, in := range n.inodes {
		sz += len(in.k) + len(in.v)
	}
	return sz
}

node_size_bench.go

package node

import (
	"testing"
)

func BenchmarkSize_AddElemSizeInLoop(b *testing.B) {
	n := createNode(100)

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		n.Size_AddElemSizeInLoop()
	}
}

func BenchmarkSize_SumElemSizeFirst(b *testing.B) {
	n := createNode(100)

	b.ResetTimer()
	for i := 0; i < b.N; i++ {
		n.Size_SumElemSizeFirst()
	}
}

node_size_benchmark_result

[lorneli@localhost GoTest]$ go test -bench .
BenchmarkSize_AddElemSizeInLoop-4   	10000000	       197 ns/op
BenchmarkSize_SumElemSizeFirst-4    	10000000	       171 ns/op
PASS
ok  	_/mnt/hgfs/vmfolder/workspace/GoTest	4.176s

[lorneli@localhost GoTest]$ go test -bench .
BenchmarkSize_AddElemSizeInLoop-4   	 5000000	       218 ns/op
BenchmarkSize_SumElemSizeFirst-4    	10000000	       173 ns/op
PASS
ok  	_/mnt/hgfs/vmfolder/workspace/GoTest	3.404s

[lorneli@localhost GoTest]$ go test -bench .
BenchmarkSize_AddElemSizeInLoop-4   	10000000	       188 ns/op
BenchmarkSize_SumElemSizeFirst-4    	10000000	       168 ns/op
PASS
ok  	_/mnt/hgfs/vmfolder/workspace/GoTest	4.071s

[lorneli@localhost GoTest]$ go test -bench .
BenchmarkSize_AddElemSizeInLoop-4   	10000000	       190 ns/op
BenchmarkSize_SumElemSizeFirst-4    	10000000	       169 ns/op
PASS
ok  	_/mnt/hgfs/vmfolder/workspace/GoTest	4.043s