当golang为字符串到字节转换进行分配时

var testString = "ABCDEFGHIJKLMNOPQRstuVWXYZ"
//var testString = "ABCDEFGHIJKLMNOPQRstuVWXYZABCDEFGHIJKLMNOPQRstuVWXYZ"
func BenchmarkHashing900000000(b *tesTing.b){
    var bufByte = bytes.buffer{}
    for i := 0; i < b.N ; i++{
        bufByte.WriteString(testString)
        Sum32(bufByte.bytes())
        bufByte.Reset()
    }
}

func BenchmarkHashingWithNew900000000(b *tesTing.b){
    for i := 0; i < b.N ; i++{
        bytStr := []byte(testString)
        Sum32(bytStr)
    }
}

测试结果：

With  testString = "ABCDEFGHIJKLMNOPQRstuVWXYZ"
BenchmarkHashing900000000-4         50000000            35.2 ns/op         0 B/op          0 allocs/op
BenchmarkHashingWithNew900000000-4  50000000            30.9 ns/op         0 B/op          0 allocs/op

With testString = "ABCDEFGHIJKLMNOPQRstuVWXYZABCDEFGHIJKLMNOPQRstuVWXYZ"
BenchmarkHashing900000000-4         30000000            46.6 ns/op         0 B/op          0 allocs/op
BenchmarkHashingWithNew900000000-4  20000000            73.0 ns/op        64 B/op          1 allocs/op

为什么在Bench’sHashingWithNew900000000的情况下,当字符串很长时有分配,但是当字符串很小时没有分配.
Sum32：@L_419_0@
我正在使用go1.6