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Use XZ compression in binary caches

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XZ compresses significantly better than bzip2.  Here are the
compression ratios and execution times (using 4 cores in parallel) on
my /var/run/current-system (3.1 GiB):

  bzip2: total compressed size 849.56 MiB, 30.8% [2m08]
  xz -6: total compressed size 641.84 MiB, 23.4% [6m53]
  xz -7: total compressed size 621.82 MiB, 22.6% [7m19]
  xz -8: total compressed size 599.33 MiB, 21.8% [7m18]
  xz -9: total compressed size 588.18 MiB, 21.4% [7m40]

Note that compression takes much longer.  More importantly, however,
decompression is much faster:

  bzip2: 1m47.274s
  xz -6: 0m55.446s
  xz -7: 0m54.119s
  xz -8: 0m52.388s
  xz -9: 0m51.842s

The only downside to using -9 is that decompression takes a fair
amount (~65 MB) of memory.
This commit is contained in:
Eelco Dolstra 2012-06-29 14:26:31 -04:00
parent 49cd7387ad
commit 4911a10a4e
6 changed files with 24 additions and 19 deletions
Download patch file Download diff file Expand all files Collapse all files

3
perl/lib/Nix/Config.pm.in
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@ -7,7 +7,8 @@ $manifestDir = $ENV{"NIX_MANIFESTS_DIR"} || "@localstatedir@/nix/manifests";
$logDir = $ENV{"NIX_LOG_DIR"} || "@localstatedir@/log/nix";
$confDir = $ENV{"NIX_CONF_DIR"} || "@sysconfdir@/nix";
$bzip2 = $ENV{"NIX_BZIP2"} || "@bzip2@";
$bzip2 = "@bzip2@";
$xz = "@xz@";
$curl = "@curl@";
$useBindings = "@perlbindings@" eq "yes";