zimbatmandYvan Sraka
363ae292bf
`//` forces its rhs to compute the merged keyset, so the original
`// spliceReal (...)` recursed eagerly on every spliced derivation's
outputs even when no specific output (.dev, .doc) was selected.
genAttrs over the known output names with the splice in the
value-thunk defers it: pkg.dev forces, pkg alone doesn't.
Addresses #338231.
Repro:
EXPR='let pkgs = import ./. { localSystem = "x86_64-linux"; crossSystem = "aarch64-linux"; }; in (pkgs.python3.withPackages (ps: [ ps.requests ])).drvPath'
NIX_SHOW_STATS=1 nix-instantiate --eval -E "$EXPR"
drvPath byte-exact (mb82vdkqafg9i8x0makrgxw8xcc4y8lz both ways).
Before:
cpuTime: 0.649
nrFunctionCalls: 651343
nrOpUpdates: 153257
nrOpUpdateValuesCopied: 7908622
nrThunks: 2018744
values: 5061740
sets (bytes): 205342176
gc totalBytes: 320504688
After:
cpuTime: 0.554
nrFunctionCalls: 586266
nrOpUpdates: 125579
nrOpUpdateValuesCopied: 5482176
nrThunks: 1494021
values: 3498806
sets (bytes): 141905680
gc totalBytes: 229067888
Nixpkgs is a collection of over 120,000 software packages that can be installed with the Nix package manager. It also implements NixOS, a purely-functional Linux distribution.
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