nrabulinski/lix
0
0
Fork 0
forked from lix-project/lix
Code Pull requests Activity

* `optimise-store.pl' reduces disk space consumption by hard-linking

Browse source 
all identitical files in the Nix store to each other.  (Previously
  it only computed the size that would be saved by doing so.)
This commit is contained in:
Eelco Dolstra 2006-09-19 14:58:35 +00:00
parent 07cec27848
commit 6dbed1bf38
1 changed files with 40 additions and 16 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

52
scripts/optimise-store.pl
View file

@ -1,61 +1,85 @@
#! /usr/bin/perl -w
use strict;
use File::Basename;
#{ my $ofh = select STDOUT;
# $| = 1;
# select $ofh;
#}
#my @paths = ("/nix/store/d49mc94xwwd7wf1xzfh4ch4cypn0ajjr-glibc-2.3.6", "/nix/store/1mgfgy3ga4m9z60747s0yzxl0g6w5kxz-glibc-2.3.6");
my @paths = ("/nix/store");
print "hashing...\n";
my $hashList = "/tmp/nix-optimise-hash-list";
system("find @paths -type f -print0 | xargs -0 md5sum -- > $hashList") == 0
or die "cannot hash store files";
print "sorting by hash...\n";
system("sort $hashList > $hashList.sorted") == 0
or die "cannot sort list";
sub atomicLink {
my $target = shift;
my $new = shift;
my $tmpNew = "${new}_optimise.$$";
# Make the directory writable temporarily.
my $dir = dirname $new;
my @st = stat $dir or die;
chmod ($st[2] | 0200, $dir) or die "cannot make `$dir' writable: $!";
link $target, $tmpNew or die "cannot create hard link `$tmpNew': $!";
rename $tmpNew, $new or die "cannot rename `$tmpNew' to `$new': $!";
chmod ($st[2], $dir) or die "cannot restore permission on `$dir': $!";
}
print "hard-linking...\n";
open LIST, "<$hashList.sorted" or die;
my $prevFile;
my $prevHash;
my $prevInode;
my $totalSpace = 0;
my $savedSpace = 0;
my $files = 0;
while (<LIST>) {
/^([0-9a-f]*)\s+(.*)$/ or die;
my $curFile = $2;
my $curHash = $1;
my $fileSize = (stat $curFile)[7];
my @st = stat $curFile or die;
next if ($st[2] & 0222) != 0; # skip writable files
my $fileSize = $st[7];
$totalSpace += $fileSize;
if (defined $prevHash && $curHash eq $prevHash) {
if ($st[1] != $prevInode) {
print "$curFile = $prevFile\n";
atomicLink $prevFile, $curFile;
$savedSpace += $fileSize;
}
} else {
$prevFile = $curFile;
$prevHash = $curHash;
$prevInode = $st[1];
}
# print "." if ($files++ % 100 == 0);
}
#print "\n";
print "total space = $totalSpace\n";
print "saved space = $savedSpace\n";
my $savings = ($savedSpace / $totalSpace) * 100.0;
print "savings = $savings %\n";
close LIST;