upmap M_UPMAP samples (vmstat -m | grep -w upmap), stock kernel DF-2839 repro:
 sample1 (post earlier 90s runs, pre-v3): 15.4K allocs / 61.4M / 63.6K requests
 sample2 (after v3 45s x4 children):      22.4K allocs / 89.5M / 87.8K requests  (+7.0K / +28.1MB)
 sample3 (after v3 45s x4 children again): 29.2K allocs / 117M  / 112K requests   (+6.8K / +27.6MB)
 live process count constant at 196 across samples -> all growth is orphaned allocation, not live use