CCache
CCache is useful for Packaging large packages with Incremental builds.
With CCache, recompile time can be reduced from many hours to a few minutes.
Add CCache to sandbox
Add to /etc/nixos/configuration.nix
nix.extraOptions = ''
extra-sandbox-paths = /nix/var/cache/ccache
'';
TODO: use nix.sandboxPaths? [1]
Run sudo nixos-rebuild switch
Now /etc/nix/nix.conf should have sandbox-paths = /nix/var/cache/ccache
Ceate the cache folder
sudo mkdir -m0770 -p /nix/var/cache/ccache # Linux sudo chown --reference=/nix/store /nix/var/cache/ccache # macOS workaround for chown --reference nix-shell -p coreutils --run 'sudo chown --reference=/nix/store /nix/var/cache/ccache'
Derivation CCache
To enable CCache only for one derivation, patch the default.nix file
{ stdenv
, ccacheStdenv
# ...
}:
#stdenv.mkDerivation {
ccacheStdenv.mkDerivation {
preConfigure = ''
export CCACHE_DIR=/nix/var/cache/ccache
export CCACHE_UMASK=007
'';
# ...
Add ccacheStdenv to dependencies.
Run nix-build.
System CCache
todo
Monitor CCache status
# watch ccache size sudo watch du -sh /nix/var/cache/ccache # watch ccache stats sudo watch ccache --dir /nix/var/cache/ccache --show-stats --verbose
Uncacheable
TODO: why are some compilations "uncacheable" according to ccache --show-stats