[cmucl-imp] Working set

Is there an easy way to determine the working set size (resident size) that is needed to evaluate some form? TIME prints various things but not what I need. The Linux top command shows a column with the resident size; essentially I'd like to see the maximum of the those values sampled while executing the form. Does the GC have this information already? Would it be difficult/expensive to use getrusage in GC hooks to collect the information? Helmut