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Set default binary-caches-parallel-connections to 25 

Some benchmarking suggested this as a good value. Running

  $ benchmark -f ... -t 25 -- sh -c 'rm -f /nix/var/nix/binary-cache*; nix-store -r /nix/store/x5z8a2yvz8h6ccmhwrwrp9igg03575jg-nixos-15.09.git.5fd87e1M.drv --dry-run --option binary-caches-parallel-connections <N>'

gave the following mean elapsed times for these values of N:

N=10:  3.3541
N=20:  2.9320
N=25:  2.6690
N=30:  2.9417
N=50:  3.2021
N=100: 3.5718
N=150: 4.2079

Memory usage is also reduced (N=150 used 186 MB, N=25 only 68 MB).

Closes #708.
This commit is contained in:
Eelco Dolstra 2015-11-25 17:13:11 +01:00
parent efd6a8c9f6
commit c0d4173263
2 changed files with 2 additions and 2 deletions
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2
doc/manual/command-ref/conf-file.xml
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@ -426,7 +426,7 @@ flag, e.g. <literal>--option gc-keep-outputs false</literal>.</para>
<listitem><para>The maximum number of parallel HTTP connections
used by the binary cache substituter to get NAR info files. This
number should be high to minimise latency. It defaults to
150.</para></listitem>
25.</para></listitem>
</varlistentry>

2
scripts/download-from-binary-cache.pl.in
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@ -21,7 +21,7 @@ Nix::Config::readConfig;
my @caches;
my $gotCaches = 0;
my $maxParallelRequests = int($Nix::Config::config{"binary-caches-parallel-connections"} // 150);
my $maxParallelRequests = int($Nix::Config::config{"binary-caches-parallel-connections"} // 25);
$maxParallelRequests = 1 if $maxParallelRequests < 1;
my $ttlNegative = 24 * 3600; # when to purge negative lookups from the database