grahamc/hydra2 - Change 7I2VJDS6UO3W36E64RNRJTJ6ZEB5Y6EP3ZWUGZY4TQW25HJORBHAC

Use pixz instead of bzip2 for compressing nars

According to following two benchmarks:

https://www.rootusers.com/gzip-vs-bzip2-vs-xz-performance-comparison/
http://catchchallenger.first-world.info/wiki/Quick_Benchmark:_Gzip_vs_Bzip2_vs_LZMA_vs_XZ_vs_LZ4_vs_LZO

xz has better compression ratio than bzip2 at lowest compression rate.

https://github.com/vasi/pixz has been chosen as it can scale compressing over multiple cores linearly.

We're using this in snabblab for a month now and it has improved CPU wise the main Hydra server.

Created by Domen Kožar on August 12, 2016

7I2VJDS6UO3W36E64RNRJTJ6ZEB5Y6EP3ZWUGZY4TQW25HJORBHAC

Dependencies

In channels

main

Change contents

Insertion in hydra-module.nix at line 228 [7.1]
[6.373]
[3.81]
```
        compress_num_threads 0
```

Replacement in release.nix at line 137 [9.1]

∅:D[5.36] → [8.348:416]

B:BD[8.348] → [8.348:416]

        [ libxslt sqlite subversion openssh nix coreutils findutils

[5.36]

[4.0]

        [ libxslt sqlite subversion openssh nix coreutils findutils pixz

Replacement in src/lib/Hydra/View/NARInfo.pm at line 24 [10.669]
B:BD[10.1135] → [2.0:37]
```
    $info .= "Compression: bzip2\n";
```
[10.1135]
[10.1269]
```
    $info .= "Compression: xz\n";
```

Replacement in src/lib/Hydra/View/NixNAR.pm at line 10 [11.484]

B:BD[11.597] → [11.597:641]

    my $storePath = $c->stash->{storePath};

[11.597]

[12.3112]

    my $storePath  = $c->stash->{storePath};
    my $numThreads = $c->config->{'compress_num_threads'};
    my $pParam     = ($numThreads > 0) ? "-p$numThreads" : "";

Replacement in src/lib/Hydra/View/NixNAR.pm at line 18 [11.484]

B:BD[12.3115] → [2.38:95]

    open $fh, "nix-store --dump '$storePath' | bzip2 |";

[12.3115]

[11.866]

    open $fh, "nix-store --dump '$storePath' | pixz -0 $pParam |";