Use ccache in builds

Add ccache support to the OsBase definition, so it's automatically setup for all
machines. Hopefully this can speed up builds and at least prevent the worst case
performance.

Unfortunately, if I modify the stdenv of any upstream targets, the cache is
invalidated and I have to rebuild the whole package. In particular webkitgtk is
a pain to build, and it has crashed my machine a number of times. I was able to
build it once, after enabling zram, which should be enabled anyway like why not?

- https://nixos.wiki/wiki/CCache
- https://github.com/NixOS/nixpkgs/issues/195522#issuecomment-2043999608
- https://github.com/NixOS/nixpkgs/pull/216363#issuecomment-2043998790

4 files changed, 66 insertions, 3 deletions

diff --git a/Biz/Bild.nix b/Biz/Bild.nix
index 077f364..c92f749 100644
--- a/Biz/Bild.nix
+++ b/Biz/Bild.nix
@@ -7,7 +7,8 @@ let
   stable = {
     inherit (nixpkgs.nixos-23_05)
       sources lib makeWrapper ccacheStdenv haskellPackages haskell
-      lispPackages_new python3 nixos mkShell dockerTools stdenv;
+      lispPackages_new python3 nixos mkShell dockerTools;
+    stdenv = nixpkgs.nixos-23_05.ccacheStdenv;
   };
 
   # for exposing packages as bild.pkgs
diff --git a/Biz/Bild/CcacheWrapper.nix b/Biz/Bild/CcacheWrapper.nix
new file mode 100644
index 0000000..78e5a08
--- /dev/null
+++ b/Biz/Bild/CcacheWrapper.nix
@@ -0,0 +1,57 @@
+self: super:
+
+let
+  # this should come from config.programs.ccache.cacheDir but I can't figure out
+  # how to access that from a nixpkgs overlay, so just hardcode the default
+  ccacheDir = "/var/cache/ccache";
+
+  # https://github.com/NixOS/nixpkgs/pull/216363#issuecomment-1430356886
+  fixwebkit = pkg:
+    self.useCcacheStdenv (pkg.overrideAttrs (attrs: rec {
+      preConfigure = attrs.preConfigure + ''
+        # not sure which of these works so just do them both
+        export NUMBER_OF_PROCESSORS=$NIX_BUILD_CORES
+        ninjaFlagsArray+=("-l$NIX_BUILD_CORES")
+      '';
+    }));
+in {
+  ccacheWrapper = super.ccacheWrapper.override {
+    extraConfig = ''
+      export CCACHE_COMPRESS=1
+      export CCACHE_DIR="${ccacheDir}"
+      export CCACHE_UMASK=007
+      if [ ! -d "$CCACHE_DIR" ]
+      then
+        echo "====="
+        echo "Directory '$CCACHE_DIR' does not exist"
+        echo "Please create it with:"
+        echo "  sudo mkdir -m0770 '$CCACHE_DIR'"
+        echo "  sudo chown root:nixbld '$CCACHE_DIR'"
+        echo "====="
+        exit 1
+      fi
+      if [ ! -w "$CCACHE_DIR" ]
+      then
+        echo "====="
+        echo "Directory '$CCACHE_DIR' is not accessible for user $(whoami)"
+        echo "Please verify its access permissions"
+        echo "====="
+        exit 1
+      fi
+    '';
+  };
+
+  useCcacheStdenv = pkg: pkg.override { stdenv = super.ccacheStdenv; };
+
+  cudann = self.useCcacheStdenv super.cudann;
+  llvm = self.useCcacheStdenv super.llvm;
+  magma = self.useCcacheStdenv super.magma;
+  nvcc = self.useCcacheStdenv super.nvcc;
+  onnx = self.useCcacheStdenv super.onnx;
+  onnxruntime = self.useCcacheStdenv super.onnxruntime;
+  webkit = fixwebkit super.webkit;
+  webkitgtk = fixwebkit super.webkitgtk;
+  webkitgtk_4_1 = fixwebkit super.webkitgtk_4_1;
+  webkitgtk_5_0 = fixwebkit super.webkitgtk_5_0;
+  webkitgtk_6_0 = fixwebkit super.webkitgtk_6_0;
+}
diff --git a/Biz/Bild/Nixpkgs.nix b/Biz/Bild/Nixpkgs.nix
index f0e8698..3de56c4 100644
--- a/Biz/Bild/Nixpkgs.nix
+++ b/Biz/Bild/Nixpkgs.nix
@@ -16,7 +16,7 @@ in {
     inherit system config;
     overlays = [
       (_: _: { inherit sources; })
-
+      (import ./CcacheWrapper.nix)
       (import ./Functions.nix)
 
       # override pinned deps with our sources, this must come before other
@@ -33,6 +33,7 @@ in {
     inherit system config;
     overlays = [
       (_: _: { inherit sources; })
+      (import ./CcacheWrapper.nix)
       (import ./Functions.nix)
       (import ./Deps.nix)
     ];
@@ -42,6 +43,7 @@ in {
     inherit system config;
     overlays = [
       (_: _: { inherit sources; })
+      (import ./CcacheWrapper.nix)
       (import ./Functions.nix)
       (import ./Deps.nix)
     ];
diff --git a/Biz/OsBase.nix b/Biz/OsBase.nix
index 50899d2..a9407ab 100644
--- a/Biz/OsBase.nix
+++ b/Biz/OsBase.nix
@@ -1,4 +1,4 @@
-{ pkgs, ... }:
+{ pkgs, config, ... }:
 let ports = import ./Cloud/Ports.nix;
 in {
   boot.tmp.cleanOnBoot = true;
@@ -19,6 +19,8 @@ in {
   nix.gc.dates = "Sunday 02:15";
   nix.optimise.automatic = true;
   nix.optimise.dates = [ "Sunday 02:30" ];
+  nix.settings.extra-sandbox-paths = [ config.programs.ccache.cacheDir ];
+  programs.ccache.enable = true;
   programs.mosh.enable = true;
   programs.mosh.withUtempter = true;
   security.acme.defaults.email = "ben@bsima.me";
@@ -34,4 +36,5 @@ in {
   services.openssh.settings.PasswordAuthentication = false;
   services.openssh.settings.PermitRootLogin = "prohibit-password";
   system.autoUpgrade.enable = false; # 'true' breaks our nixpkgs pin
+  zramSwap.enable = true;
 }