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pennae 26a8b220eb avoid ostream sentries per json string character 
we don't have to create an ostream sentry object for every character of a JSON
string we write. format a bunch of characters and flush them to the stream all
at once instead.

this doesn't affect small numbers of string characters, but larger numbers of
total JSON string characters written gain a lot. at 1MB of total string written
we gain almost 30%, at 16MB it's almost a factor of 3x. large numbers of JSON
string characters do occur naturally in a nixos system evaluation to generate
documentation (though this is now somewhat mitigated by caching the largest part
of nixos option docs).

benchmarked with

  hyperfine 'nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) {e})"' --warmup 1 -L e 1,4,256,4096,65536

before:

  Benchmark 1: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 1)"
    Time (mean ± σ):      12.5 ms ±   0.2 ms    [User: 9.2 ms, System: 4.0 ms]
    Range (min … max):    11.9 ms …  13.1 ms    223 runs

  Benchmark 2: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 4)"
    Time (mean ± σ):      12.5 ms ±   0.2 ms    [User: 9.3 ms, System: 3.8 ms]
    Range (min … max):    11.9 ms …  13.2 ms    220 runs

  Benchmark 3: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 256)"
    Time (mean ± σ):      13.2 ms ±   0.3 ms    [User: 9.8 ms, System: 4.0 ms]
    Range (min … max):    12.6 ms …  14.3 ms    205 runs

  Benchmark 4: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 4096)"
    Time (mean ± σ):      24.0 ms ±   0.4 ms    [User: 19.4 ms, System: 5.2 ms]
    Range (min … max):    22.7 ms …  25.8 ms    119 runs

  Benchmark 5: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 65536)"
    Time (mean ± σ):     196.0 ms ±   3.7 ms    [User: 171.2 ms, System: 25.8 ms]
    Range (min … max):   190.6 ms … 201.5 ms    14 runs

after:

  Benchmark 1: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 1)"
    Time (mean ± σ):      12.4 ms ±   0.3 ms    [User: 9.1 ms, System: 4.0 ms]
    Range (min … max):    11.7 ms …  13.3 ms    204 runs

  Benchmark 2: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 4)"
    Time (mean ± σ):      12.4 ms ±   0.2 ms    [User: 9.2 ms, System: 3.9 ms]
    Range (min … max):    11.8 ms …  13.0 ms    214 runs

  Benchmark 3: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 256)"
    Time (mean ± σ):      12.6 ms ±   0.2 ms    [User: 9.5 ms, System: 3.8 ms]
    Range (min … max):    12.1 ms …  13.3 ms    209 runs

  Benchmark 4: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 4096)"
    Time (mean ± σ):      15.9 ms ±   0.2 ms    [User: 11.4 ms, System: 5.1 ms]
    Range (min … max):    15.2 ms …  16.4 ms    171 runs

  Benchmark 5: nix eval --raw --expr "let s = __concatStringsSep \"\" (__genList (_: \"c\") 256); in __toJSON (__genList (_: s) 65536)"
    Time (mean ± σ):      69.0 ms ±   0.9 ms    [User: 44.3 ms, System: 25.3 ms]
    Range (min … max):    67.2 ms …  70.9 ms    42 runs
2022-01-07 06:53:47 +01:00
.github add pull_request_template.md 2021-12-09 14:31:34 -05:00
config Run autoupdate 2021-06-01 11:42:38 +02:00
contrib function-trace: always show the trace 2019-09-18 23:23:21 +02:00
doc/manual add zipAttrsWith primop 2022-01-03 21:05:53 +01:00
m4 autoconf: Fix C++17 detection not working on Ubuntu 16.04. 2019-07-03 04:32:25 +02:00
maintainers Update release script 2021-11-02 11:53:25 +01:00
misc Merge pull request #5820 from ncfavier/completion-nospace 2021-12-22 17:55:05 +01:00
mk mk/libraries.mk: fix trace-ld and trace-ar expansions 2021-10-08 22:59:42 +01:00
nix-rust Apply OS checks to host platform, not build 2021-06-23 15:00:36 +00:00
perl Document libsodium, which is now mandatory, as a dependency 2021-11-27 23:11:11 +01:00
scripts Merge pull request #5521 from abathur/clearly_mark_validation_step 2021-12-08 20:04:03 +00:00
src avoid ostream sentries per json string character 2022-01-07 06:53:47 +01:00
tests Merge pull request #5546 from NixOS/allow-paths-in-flake-local-options 2022-01-06 21:55:20 +01:00
.dir-locals.el .dir-locals.el: Set c-block-comment-prefix 2020-07-10 11:21:06 +02:00
.editorconfig Add .editorconfig 2017-06-05 22:57:28 +01:00
.gitignore Remove nix-reduce-build and nix-http-export 2021-11-18 21:17:57 +01:00
.version Bump version 2021-12-14 00:01:42 +01:00
boehmgc-coroutine-sp-fallback.diff Fix leaking pthread_attr_t 2021-11-03 22:54:16 +01:00
bootstrap.sh bootstrap: Simplify & make more robust. 2011-09-06 12:11:05 +00:00
configure.ac Merge pull request #5678 from t184256/document-libsodium 2021-11-29 11:11:10 +01:00
COPYING * Change this to LGPL to keep the government happy. 2006-04-25 16:41:06 +00:00
default.nix Simplify shell.nix and default.nix 2020-06-17 19:21:46 +02:00
docker.nix Add iana-etc for /etc/protocols to default packages 2022-01-04 12:49:02 +01:00
flake.lock Revert "update flake.nix to 21.11" 2021-12-15 13:49:05 +01:00
flake.nix Make bash completion for 'nix' work in a devshell 2021-12-22 13:21:45 +01:00
local.mk Remove 'dist' target 2020-12-03 16:17:58 +01:00
Makefile Install nlohmann_json headers 2021-11-11 11:05:44 +01:00
Makefile.config.in Apply OS checks to host platform, not build 2021-06-23 15:00:36 +00:00
precompiled-headers.h Config: Use nlohmann/json 2020-08-20 11:02:16 +02:00
README.md throw freenode down the memory hole 2021-05-27 21:48:39 +02:00
shell.nix Add back flake-compat shell.nix 2020-07-17 14:58:59 +00:00

README.md

Nix

Open Collective supporters Test

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

On Linux and macOS the easiest way to install Nix is to run the following shell command (as a user other than root):

$ curl -L https://nixos.org/nix/install | sh

Information on additional installation methods is available on the Nix download page.

Building And Developing

See our Hacking guide in our manual for instruction on how to build nix from source with nix-build or how to get a development environment.

Additional Resources

License

Nix is released under the LGPL v2.1.