GNU Mach does not cope well with lots of memory. Newer versions of the Debian
gnumach package will limit themselves to around 1 GiB of memory. If you have
an older version, or still experience problems with vmstat (see above)
reported much less memory than you have, the best is to limit the memory it can
see via GRUB's upppermem feature. Add uppermem 786432 to GRUB's Hurd entry
in menu.lst.
