Hydra and `gc-check-reachability`

It seems as if enabling hydra on my laptop also added the following setting to my nix.conf:

# The default (`true') slows Nix down a lot since the build farm
# has so many GC roots.
gc-check-reachability = false

Since this setting is there any run of nix complains about unknown setting 'gc-check-reachability'. This is annoying.

Also, it feels as if general usage of nix has massively slowed down since then, so the warning ablout slowness above the unknown setting seems to be true.

  • Has this setting removed from nix?
  • What can I do to make nix quick again?