Have you read
https://docs.julialang.org/en/v1/manual/performance-tips/
?
It seems that you are running your code in global scope, which is terrible for performance and will lead to excessive allocations. Make sure that your code is wrapped in a function when you run it.
Also I’m not a differential equation expert but the references to “Runge-Kutta coefficients” in your code make me suspect that you are rolling your own rk4 implementation here? If that’s the case I would concur with Oscar’s advice in a thread a few weeks ago: