[tex-live] (no subject)

Michael Shell list1 at michaelshell.org
Fri Sep 28 05:02:13 CEST 2018

On Thu, 27 Sep 2018 22:34:58 +0200
Johannes Hielscher <jhielscher at posteo.de> wrote:

> 36M xz -6 81.04 user
> 34M xz -7 77.91 user
> 32M xz -8 77.42 user
> 19M xz -9 70.55 user
> texlive_bin_aarch64-linux.tar (uncompressed: 141M)

Another thing to note is in the man page of xz:

   -7 ... -9
   These are like -6 but with higher compressor and decompressor memory
   requirements. These are useful only when compressing files bigger
   than 8 MiB, 16 MiB, and 32 MiB, respectively.

So the -9 gain in your example, which indeed is very significant
(36MB for -6 versus 19MB for -9), can only be obtained with such large
files. This explains Karl's seemingly contradictory result:

On Sun, 23 Sep 2018 23:04:37 GMT
Karl Berry <karl at freefriends.org> wrote:
> For the record, I did indeed experiment with xz -9 (and other values).
> It took tooooooo many hours to create the image for hardly any
> additional compression.

in that, in the TeX Live collection, the number of files over 32MB is
not a high enough percentage of the total to provide much of a
compression advantage for the -9 level. Of course, one could organize
the file collection into a few dozen .tar "parts" compress those and then
decompress/untar each part as needed to the target's filesystem during
install. Tis not pretty and it seems would demand too much of the install
machine in terms of CPU, RAM and drive space, but according to Johannes's
results above, we could potentially get a near halving of the media space
required for the distribution DVD with such an approach.



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