Using valgrind with opencog can be tricky, because many spurious messages are created. These can be suppressed with suppression files, like so:

valgrind --suppressions=../lib/valgrind.guile.suppressions      \
         --suppressions=../lib/valgrind.python.suppressions     \
         --suppressions=../lib/valgrind.boost.suppressions      \
         --suppressions=../lib/valgrind.logger.suppressions   <program_to_debug>

where <program_to_debug> is probably opencog/server/cogserver

Memory leaks: valgrind --leak-check=full

Memory non-leaks: valgrind --leak-check=full --show-leak-kinds=all

Memory profile: valgrind --tool=massif