The problem reported at https://ro.wikipedia.org/wiki/Wikipedia:Cafenea#Eroare might be related (problems saving large pages, the error message is available at http://i.imgur.com/CbVHWu4.jpg )

Has the usage of the template increased since June? If someone went on a major tagging spree, that could have increased the memory usage.

Yes and no. :) Yes, the usage has increased, as it does every September in WLM. But since I noticed the bug on Sept 1st, the increase must have been 1% tops (there were 28.5k files at the beginning of the contest [1] and only 68 photos were loaded in the first day [2], plus say 1-200 before that).

Since I'm asking for 5k pages at a time, I expect the first 5 requests to be the same back in June and now. Is this assumption wrong?

[1] There were 30099 pictures last night and ~1300 uploads during the contest
[2] https://toolserver.org/~superzerocool/wlm/?pais=romania

I've narrowed it down to the inclusion of image metadata, apparently the many small objects involved there use quite a bit of memory. When I locally hack things to just shove in the serialized string (i.e. returning all the same data, just encoded differently) the memory usage is much less.

CCing Bawolff since he's been working with image metadata recently and might have more insights on what may have changed or how to fix it.

As a workaround, you could use a lower geilimit. Gerrit change 83935 (coming with 1.22wmf17, which is scheduled to hit Commons on Monday) will make this happen anyway for people who aren't bots or admins.