The CVS version of ttrace works with openacs 5.2 (at least the parts I was
using - not .LRN though) and for the dev installs reduced the footprint
from about 200mb to 110mb. It broke some of the tcllib packages
which the soap stuff depended on, and when something breaks
because the package breaks because of ttrace it's pretty tricky to
track down.
The overhead for ttrace is pretty low (mostly startup although a few
operations are slower as well) and it's worth using I think but it can
break things in pretty non-intuitive ways.
One reason the memory footprint for aolserver climbs is that over time
it creates a lot of threads for sweepers as there seems to be no way
for those threads to ever expire (so you might end up with 10-15 threads
for handling scheduled procs).