I agree with the previous suggestion to test/measure. Last few weeks I start to use profiling (using Devel::DProf) and benchmarking (see benchmarking your code, this node got me started ) more and more and this helps me trying to understand where my code spends its time and where to begin speeding it up. I've never did this for mod_perl, but google found me that there is a performance tuning guide for mod_perl here, that (from the looks of it) seems to explain this rather well.

If I should have good experience with using Cache::Cache (which I actually have, very nice module), this doesn't mean that it will also speed up your code in it's specific setting (maybe your disk is 10 times as fast as mine is?).