eldritch horrors e6cd67591b libexpr: rewrite the parser with pegtl instead of flex/bison ... this gives about 20% performance improvements on pure parsing. obviously it will be less on full eval, but depending on how much parsing is to be done (e.g. including hackage-packages.nix or not) it's more like 4%-10%. this has been tested (with thousands of core hours of fuzzing) to ensure that the ASTs produced by the new parser are exactly the same as the old one would have produced. error messages will change (sometimes by a lot) and are not yet perfect, but we would rather leave this as is for later. test results for running only the parser (excluding the variable binding code) in a tight loop with inputs and parameters as given are promising: - 40% faster on lix's package.nix at 10000 iterations - 1.3% faster on nixpkgs all-packages.nix at 1000 iterations - equivalent on all of nixpkgs concatenated at 100 iterations (excluding invalid files, each file surrounded with parens) more realistic benchmarks are somewhere in between the extremes, parsing once again getting the largest uplift. other realistic workloads improve by a few percentage points as well, notably system builds are 4% faster. Benchmarks summary (from ./bench/summarize.jq bench/bench-*.json) old/bin/nix --extra-experimental-features 'nix-command flakes' eval -f bench/nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix mean: 0.408s ± 0.025s user: 0.355s | system: 0.033s median: 0.389s range: 0.388s ... 0.442s relative: 1 new/bin/nix --extra-experimental-features 'nix-command flakes' eval -f bench/nixpkgs/pkgs/development/haskell-modules/hackage-packages.nix mean: 0.332s ± 0.024s user: 0.279s | system: 0.033s median: 0.314s range: 0.313s ... 0.361s relative: 0.814 --- old/bin/nix --extra-experimental-features 'nix-command flakes' eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system' mean: 6.133s ± 0.022s user: 5.395s | system: 0.437s median: 6.128s range: 6.099s ... 6.183s relative: 1 new/bin/nix --extra-experimental-features 'nix-command flakes' eval --raw --impure --expr 'with import <nixpkgs/nixos> {}; system' mean: 5.925s ± 0.025s user: 5.176s | system: 0.456s median: 5.934s range: 5.861s ... 5.943s relative: 0.966 --- GC_INITIAL_HEAP_SIZE=10g old/bin/nix eval --extra-experimental-features 'nix-command flakes' --raw --impure --expr 'with import <nixpkgs/nixos> {}; system' mean: 4.503s ± 0.027s user: 3.731s | system: 0.547s median: 4.499s range: 4.478s ... 4.541s relative: 1 GC_INITIAL_HEAP_SIZE=10g new/bin/nix eval --extra-experimental-features 'nix-command flakes' --raw --impure --expr 'with import <nixpkgs/nixos> {}; system' mean: 4.285s ± 0.031s user: 3.504s | system: 0.571s median: 4.281s range: 4.221s ... 4.328s relative: 0.951 --- old/bin/nix --extra-experimental-features 'nix-command flakes' search --no-eval-cache github:nixos/nixpkgs/e1fa12d4f6c6fe19ccb59cac54b5b3f25e160870 hello mean: 16.475s ± 0.07s user: 14.088s | system: 1.572s median: 16.495s range: 16.351s ... 16.536s relative: 1 new/bin/nix --extra-experimental-features 'nix-command flakes' search --no-eval-cache github:nixos/nixpkgs/e1fa12d4f6c6fe19ccb59cac54b5b3f25e160870 hello mean: 15.973s ± 0.013s user: 13.558s | system: 1.615s median: 15.973s range: 15.946s ... 15.99s relative: 0.97 --- Change-Id: Ie66ec2d045dec964632c6541e25f8f0797319ee2		2024-06-25 12:24:58 +00:00
..
run-test.py	Add pre-commit checks	2024-03-29 22:57:40 -07:00
setup-functional-tests.py	meson: implement functional tests	2024-03-27 18:37:50 -06:00