[time] resid=4096        pread=1421    kernel-side elapsed=0.000057 s
[time] resid=0x7ffffff0 pread=1615    kernel-side elapsed=2.532421 s

The huge-resid call returned the SAME few KB of map output,
but took orders of magnitude longer: the kernel kmalloc'd and
zero-filled ~2047 MiB up front (procfs_map.c:77 -> subr_sbuf.c:197)
before discarding almost all of it. Caller controls the kmalloc size.
RUN_EXIT=0