... Here's a quick test with our latest xulrunner package: $:> mkdir foo $:> tar -C foo -xf xulrunner#1.9.0.11-1.pkg.tar.gz $:> time tar -czf foo.tar.gz foo real 0m4.409s user 0m4.250s sys 0m0.150s $:> time tar -cJf foo.tar.xz foo # -9 compression real 1m11.419s user 1m10.950s sys 0m0.570s $:> echo 'scale=2; (60+11.42)/4.41' | bc 16.19 $:> ls -l *.gz *.xz -rw-r--r-- 1 juergen users 18224116 Jun 15 10:02 foo.tar.gz -rw-r--r-- 1 juergen users 12979240 Jun 15 10:04 foo.tar.xz ... Well, IMHO i don't think that time spent to compress xulrunner would be much longer than time spent to compile it. And there're not that many BIG packages and they are compiled not that often to care about it i suppose.