[tex4ht] what is the fastest way to convert large document to HTML?

[Karl Berry]

Martin: please see https://tug.org/pipermail/tex4ht/2018q3/001984.html
and thread following about slow operation handling a huge document (not
surprising in my view).

Is it perhaps possible to cache results so that dvisvgm does not have to
recompute every math fragment every time? Any other possibilities come
to mind?

Thanks,
Karl