How to benchmark memory managers?

I am in the process of writing a garbage collector, and would like a
good test-suite for benchmarking it.  I would also like to compare its
performance with other memory managers, such as malloc.

Are there any standard approaches to testing memory managers?  I can't
use it as a malloc-replacement in real applications since it requires
marking and relocation which is not easy on opaque binary data (unless I
go the way of Boehm et al, but that is not the design of this collector).

I've put together a few simple test cases, allocating a few million
objects in some simple data structures, but they just don't seem to be
realistic enough.  I want to be able to say "n% faster/slower than
malloc on xyz" with confidence.

Calum