Removing the gc.collect() in media.py does make a huge difference for me.
With nearly 18000 media objects that get included in my report (after excluding over 300 that are marked private), the last time I created a report that included media objects using version 5.2.0, it took over 24 hours and less than an hour without media objects. Tonight I tried version 5.2.1 with gc.collect() removed, and it took about two hours to generate the report.
Since there don’t seem to be any changes to media.py from 5.2.0 to 5.2.1, I think it is safe to assume that gc.collect() has been the culprit in the long report generation times I’ve seen over the last several versions of gramps. I would guess this is what I’ve been looking for.