So I started a "gotadmin cleanup" on an instance of the FreeBSD ports
repository.

$ gotadmin info
repository: /home/naddy/ports.git
hashing algorithm: sha1
default author: Christian Weisgerber <naddy@FreeBSD.org>
remote "origin" (fetch): ssh://anongit@git.freebsd.org/ports.git
remote "origin" (send): ssh://git@gitrepo.freebsd.org/ports.git
pack files: 23
packed objects: 7037127
packed total size: 1.9G
loose objects: 3031
loose total size: 42.4M

After 33 hours it's still running.  Coloring commits at snail's pace.

  PID USERNAME    THR PRI NICE   SIZE    RES STATE    C   TIME    WCPU COMMAND
92384 naddy         1 138    0  1702M  1475M CPU0     0  31.9H  92.87% got-read-pack
92378 naddy         1  13    0  4687M  1344M sbwait   3 223:03  11.13% gotadmin

I stashed away a copy for some tests.  git gc finished in 11 minutes
or so.  Running gotadmin cleanup on that optimized copy then only
took an hour plus.

-- 
Christian "naddy" Weisgerber                          naddy@mips.inka.de