Some truly bad graphs there, displaying response time on same axis as responses per second? Leaving in a bracket probably to contain outliers and flattening the rest of the graph?
How does the "Render - No IO" case work? Does it take a different code path? (E.g. render "No entries found" instead of iterating over each entry and rendering it?) Or, put differently, what are you measuring in the "Render - No IO" case?
The source is now on github. See the links at the top of the blog post.