Brion Vibber <vibber(a)aludra.usc.edu> posted some nice stats,
showing that the CPU usage is primarily in the Apache daemons.
So, a profiler/hotspot/gprof-like tool for PHP would be useful.
I found "APD" (as well as APC, a PHP compilation caching tool) at:
http://www.omniti.com/~george/php/
I didn't find any other PHP profiling tools, though perhaps they're
out there.
Of course, an alternative could be to run gprof itself against
the Apache daemon (including PHP). Perhaps there's a hotspot
in the underlying Apache/PHP implementation; fixing that would
help Wikipedia and probably many others too.
Anybody have a test platform willing to run the profile?
Again, I don't have such a setup :-(.