Nix 2.6 eval improvement

With the recent Nix 2.6 release, I was curious about how much impact all of @pennae’s work was having on the Nix evaluation.

TL;DR: Nix evaluation is 11-17% faster in Nix 2.6 compared to Nix 2.5.1

Methodology

I have both the nix and nixpkgs repo side by side.

nixpkgs is checked out at ac44b27bab615fd49bc94fe22124deae233b5c94 (latest master)

nix is checked out at 2.6.0

Then run nix-build pkgs/top-level/release.nix -A metrics and collect the output.

For nix 2.5.1 I added a space change to pkgs/top-level/metrics.nix to force the rebuild on my machine.

For nix 2.6 I injected the version from the nix repo:

diff --git a/pkgs/top-level/metrics.nix b/pkgs/top-level/metrics.nix
index d413b881eaa..cf065697923 100644
--- a/pkgs/top-level/metrics.nix
+++ b/pkgs/top-level/metrics.nix
@@ -2,11 +2,17 @@
 
 with pkgs;
 
+let
+  nix = (import ../../../nix).defaultPackage.${pkgs.system};
+in
+

Then I took all the results and painstakingly inserted them in Notion, for your pleasure and mine: