jsdiff runs out of memory when diffing pages with a lot of wikitext lines. Test case:
node roundtrip-test.js --prefix zhwiki '2011年香港區議會選舉結果'
After a cursory inspection it looks as if the algorithm will use memory bounded by O(l^2) with l being the number of lines in the page.
We could either try to optimize (afaik there is no bug) jsdiff, or we could consider switching to another diff library such as https://github.com/paulgb/simplediff.