You should’t benchmark in global scope like that https://docs.julialang.org/en/stable/manual/performance-tips/
julia 0.5:
julia> using BenchmarkTools
julia> a = randn(90,90); b = randn(90);
julia> @btime $a \ $ b;
103.155 μs (8 allocations: 65.08 KiB)
julia 0.6:
julia> using BenchmarkTools
julia> a = randn(90,90); b = randn(90);
julia> @btime $a \ $ b;
100.378 μs (8 allocations: 65.08 KiB)