Smaps is better than not taking shared memory into account but it only differentiates between 'shared' and 'not shared'. If you're only looking at a collection of mostly-identical processes (e.g. all your mod_perls) then this is probably good enough.

exmap does per-page reckoning of how many processes have that page mapped, then maps that to ELF section and symbols for you.

Exmap is a more complex to use and lacks a programmatic interface, but if you have a more heterogenous selection of processes to analyse I'd probably use that. (Actually, I'd probably use it anyway, since I wrote it...)