There seems to be a performance problem somewhere on the DairikiDiff engine on some particular diffs
See the history of this page on wikimedia.it: http://wiki.wikimedia.it/index.php?title=Rassegna_stampa&action=history&year=2015&month=10, in particular the huge diff made by @Nemo_bis on 31 oct 2015
Clicking on the diff links gives a broken page with no skin and only a partial diff content:
This is reproducible (comparing the same 2 texts) on current master (1.27alpha (3c15f0d) 02:20 31 oct 2015) and 1.25. I haven't tested other branches.
At first it failed because PHP required more than 150MB. Raising memory limit to 500MB lead to hitting max execution time of 30 seconds. Increasing it to 90 seconds didn't make it finish rendering.
In any case, the output is always the same, which leads to think the diff engine is stuck on some infinite loop that won't make any progress even with higher execution time limits.