What would be the fastest way to get the parity of sorting permutations for vectors with very small size?

The obvious way is to use the `sortperm!`

function and the parity function from `Combinatorics.jl`

.

However, `sortperm!`

costs 85ns on my laptop:

```
julia> p = zeros(Int64, 8);
julia> v = rand(Int8, 8);
julia> @btime sortperm!($p, $v);
85.254 ns (1 allocation: 16 bytes)
julia> using Combinatorics
julia> parity(p)
1
```

I need to calculate the parity for billions of times. Given that the vectors have very small size: (<15), is there any optimization I can do to improve the performance?