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Nix, the purely functional package manager
20797 commits 177 branches 218 tags 162 MiB
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Sergei Zimmerman e1c9bc0ef6
libstore: Get rid of allocations in printString, allocate 2K bytes on the stack 
Looking at perf:

   0.21 │       push   %rbp
   0.99 │       mov    %rsp,%rbp
        │       push   %r15
   0.25 │       push   %r14
        │       push   %r13
   0.49 │       push   %r12
   0.66 │       push   %rbx
   1.23 │       lea    -0x10000(%rsp),%r11
   0.23 │ 15:   sub    $0x1000,%rsp
   1.01 │       orq    $0x0,(%rsp)
  59.12 │       cmp    %r11,%rsp
   0.27 │     ↑ jne    15

Seems like 64K is too much to have on the stack for each invocation, considering
that only a minuscule number of allocations are actually larger than 4K.

There's actually no good reason this function should use so much stack space. Or
use small_string at all. Everything can be done in small chunks that don't require
any memory allocations and use up 2K bytes on the stack.

This patch also adds a microbenchmark for tracking the unparsing performance. Here
are the results for this change:

(Before)

BM_UnparseRealDerivationFile/hello         7275 ns         7247 ns        96093 bytes_per_second=232.136Mi/s
BM_UnparseRealDerivationFile/firefox      40538 ns        40376 ns        17327 bytes_per_second=378.534Mi/s

(After)

BM_UnparseRealDerivationFile/hello         3228 ns         3218 ns       215671 bytes_per_second=522.775Mi/s
BM_UnparseRealDerivationFile/firefox      39724 ns        39584 ns        17617 bytes_per_second=386.101Mi/s

This translates into nice evaluation performance improvements (compared to 18c3d2348f):

Benchmark 1: GC_INITIAL_HEAP_SIZE=8G old-nix/bin/nix-instantiate ../nixpkgs -A nixosTests.gnome --readonly-mode
  Time (mean ± σ):      3.111 s ±  0.021 s    [User: 2.513 s, System: 0.580 s]
  Range (min … max):    3.083 s …  3.143 s    10 runs

Benchmark 2: GC_INITIAL_HEAP_SIZE=8G result/bin/nix-instantiate ../nixpkgs -A nixosTests.gnome --readonly-mode
  Time (mean ± σ):      3.037 s ±  0.038 s    [User: 2.461 s, System: 0.558 s]
  Range (min … max):    2.960 s …  3.086 s    10 runs
2025-08-31 00:48:37 +03:00
.github prepare merge queues for nix 2025-08-15 08:05:01 +02:00
ci/gha flake: Apply nixfmt 1.0.0 2025-08-18 20:29:45 +03:00
contrib function-trace: always show the trace 2019-09-18 23:23:21 +02:00
doc/manual Merge pull request #13804 from NixOS/release-notes 2025-08-22 17:18:15 +02:00
maintainers Update work meeting time in README 2025-08-26 00:50:12 +02:00
misc add rc.d script for the nix-daemon 2025-08-08 09:09:58 +02:00
nix-meson-build-support treewide: Bump C++ standard version to C++23 2025-08-19 15:33:27 +03:00
packaging flake: Apply nixfmt 1.0.0 2025-08-18 20:29:45 +03:00
scripts add freebsd multi-user installer 2025-08-08 09:10:35 +02:00
src libstore: Get rid of allocations in printString, allocate 2K bytes on the stack 2025-08-31 00:48:37 +03:00
tests Simplify handling of statuses for build errors 2025-08-27 20:05:06 -04:00
.clang-format Update clang-format with fixing namespace coments, and separate definition blocks 2025-07-18 12:46:51 -04:00
.clang-tidy Add .clang-tidy 2024-02-01 01:01:39 +01:00
.dir-locals.el .dir-locals.el: Set c-block-comment-prefix 2020-07-10 11:21:06 +02:00
.editorconfig No global eval settings in libnixexpr 2024-06-24 12:15:16 -04:00
.git-blame-ignore-revs git-blame-ignore-revs: Add nixfmt 1.0.0 reformat 2025-08-18 20:30:54 +03:00
.gitignore Overriding gtest with gmock 2025-05-31 07:41:27 -07:00
.mergify.yml Update mergify.yml 2025-08-25 10:28:47 +02:00
.shellcheckrc housekeeping: shellcheck for tests/functional/ca/build-cache.sh 2024-06-12 17:41:16 -04:00
.version Bump version 2025-08-25 10:27:46 +02:00
CITATION.cff chore: PhD thesis as reference in CITATION.cff 2024-05-18 20:05:22 +02:00
CONTRIBUTING.md Update developer facing links to nix.dev 2025-07-25 10:59:44 +02:00
COPYING * Change this to LGPL to keep the government happy. 2006-04-25 16:41:06 +00:00
default.nix Format .nix files 2025-01-24 17:04:02 +01:00
docker.nix Merge pull request #13524 from gmarti/fix_cacertificate 2025-08-28 23:28:53 +03:00
flake.lock flake: Update nixpkgs 2025-08-27 02:23:05 +03:00
flake.nix flake: nixpkgs: nixos-unstable -> nixos-25.05-small 2025-08-18 20:04:57 +03:00
HACKING.md Rename doc/manual{src -> source} 2024-10-14 11:21:24 -04:00
meson.build meson: Get rid of multiline array formatting hack 2025-08-07 02:57:02 +03:00
meson.format flake: Add meson formatter 2025-06-11 22:08:03 +00:00
meson.options add derivation parser benchmark 2025-07-29 16:51:55 +02:00
README.md fix(docs): update Matrix channel links 2025-05-04 12:17:48 +02:00
shell.nix Remove url literals 2022-01-24 13:28:21 +01:00

README.md

Nix

Open Collective supporters CI

Nix is a powerful package manager for Linux and other Unix systems that makes package management reliable and reproducible. Please refer to the Nix manual for more details.

Installation and first steps

Visit nix.dev for installation instructions and beginner tutorials.

Full reference documentation can be found in the Nix manual.

Building and developing

Follow instructions in the Nix reference manual to set up a development environment and build Nix from source.

Contributing

Check the contributing guide if you want to get involved with developing Nix.

Additional resources

Nix was created by Eelco Dolstra and developed as the subject of his PhD thesis The Purely Functional Software Deployment Model, published 2006. Today, a world-wide developer community contributes to Nix and the ecosystem that has grown around it.

License

Nix is released under the LGPL v2.1.