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3a1301cd6d
As it turns out using `std::regex` is actually the bottleneck for root discovery. Just substituting `std::` -> `boost::` makes root discovery twice as fast (3x if counting only userspace time). Some rather ad-hoc measurements to motivate the switch: (On master) ``` nix build github:nixos/nix/1e822bd4149a8bce1da81ee2ad9404986b07914c#nix-cli --out-link result-1e822bd4149a8bce1da81ee2ad9404986b07914c taskset -c 2,3 hyperfine "result-1e822bd4149a8bce1da81ee2ad9404986b07914c/bin/nix store gc --dry-run --max 0" Benchmark 1: result-1e822bd4149a8bce1da81ee2ad9404986b07914c/bin/nix store gc --dry-run --max 0 Time (mean ± σ): 481.6 ms ± 3.9 ms [User: 336.2 ms, System: 142.0 ms] Range (min … max): 474.6 ms … 487.7 ms 10 runs ``` (After this patch) ``` taskset -c 2,3 hyperfine "result/bin/nix store gc --dry-run --max 0" Benchmark 1: result/bin/nix store gc --dry-run --max 0 Time (mean ± σ): 254.7 ms ± 9.7 ms [User: 111.1 ms, System: 141.3 ms] Range (min … max): 246.5 ms … 281.3 ms 10 runs ``` `boost::regex` is a drop-in replacement for `std::regex`, but much faster. Doing a simple before/after comparison doesn't surface any change in behavior: ``` result/bin/nix store gc --dry-run -vvvvv --max 0 |& grep "got additional" | wc -l result-1e822bd4149a8bce1da81ee2ad9404986b07914c/bin/nix store gc --dry-run -vvvvv --max 0 |& grep "got additional" | wc -l ``` |
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| .. | ||
| build-remote | ||
| external-api-docs | ||
| internal-api-docs | ||
| libcmd | ||
| libexpr | ||
| libexpr-c | ||
| libexpr-test-support | ||
| libexpr-tests | ||
| libfetchers | ||
| libfetchers-c | ||
| libfetchers-tests | ||
| libflake | ||
| libflake-c | ||
| libflake-tests | ||
| libmain | ||
| libmain-c | ||
| libstore | ||
| libstore-c | ||
| libstore-test-support | ||
| libstore-tests | ||
| libutil | ||
| libutil-c | ||
| libutil-test-support | ||
| libutil-tests | ||
| nix | ||
| nix-build | ||
| nix-channel | ||
| nix-collect-garbage | ||
| nix-copy-closure | ||
| nix-env | ||
| nix-instantiate | ||
| nix-store | ||
| perl | ||
| nix-functional-tests | ||
| nix-manual | ||