DF-2309 usrbufs leak loop: nmsgs=100000 iters=20
per-call leak if real: 800000 bytes; total if real: 15.3 MB
start: v_free_count=832270 (3251.1 MB free)
iter 1     faults=1 v_free_count=832350 (delta_from_start=+80 pages = -0.3 MB consumed)
iter 5     faults=5 v_free_count=832853 (delta_from_start=+583 pages = -2.3 MB consumed)
iter 10    faults=10 v_free_count=830824 (delta_from_start=-1446 pages = 5.6 MB consumed)
iter 15    faults=15 v_free_count=830824 (delta_from_start=-1446 pages = 5.6 MB consumed)
iter 20    faults=20 v_free_count=829253 (delta_from_start=-3017 pages = 11.8 MB consumed)

end:   v_free_count=829253  consumed=3017 pages = 11.8 MB
expected if leak real: 15.3 MB; expected if fixed: ~0 MB
faults=20/20