For complex semisimple Lie algebras, the maximal dimension of an abelian subalgebra was determined by Mal'cev in 1945. For E7$E_7$, for example, it is 27$27$, and is the radical of the E6$E_6$ parabolic.
What about in characteristic p$p$ for p>0$p>0$? I suspect the answer is nearly, but not quite, the same. Maybe you have that it is bounded by 29$29$ or something. Is there any literature on this? All of the papers and references I have found so far are in characteristic 0 $0$.
I don't need the exact bound, just something close will do. (I have a Lie algebra L$L$ with an abelian subalgebra of dimension, say, 43$43$, and I want to know that L$L$ cannot be embedded in E7$E_7$, and in particular is not E7$E_7$. But I'm in characteristic 7$7$, for example, or worse, 2$2$ or 3$3$.)