I'm writing an optimized caching module. I've been using 2.0.50. Here are the "top 50" from oprofile ( http://oprofile.sourceforge.net/ ):
I submitted a patch to rework ap_rgetline/core_input_filter a year or so ago that provided some performance improvements. If you are inclined, it might be interesting to dig that patch out and see how it profiles.
Bill
