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edolstra
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flake-regression-test
If the mark stack size is too small, it greatly inhibits parallel marking, which is very bad for performance on multi-core systems.
cole-h
reviewed
Aug 5, 2025
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Upstream PR: NixOS#13708 |
grahamc
approved these changes
Aug 7, 2025
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Motivation
Previously marking was done by only one thread, which takes a long time if the heap gets big. Enabling parallel marking speeds up evaluation a lot, for example (on a Ryzen 9 5900X 12-Core):
nix search nixpkgsfrom 24.3s to 18.9s.NixOS/nix/2.21.2flake regression test from 86.1s to 71.2s.Context