On Thu, Feb 27, 2014 at 08:25:00AM +0900, Mike Hommey wrote:
> On Wed, Feb 26, 2014 at 08:56:37PM +0100, Andreas Gal wrote:
> >
> > This randomly reminds me that it might be time to review zip as our
> > compression format for omni.ja.
> >
> > ls -l omni.ja
> >
> > 7862939
> >
> > ls -l omni.tar.xz (tar and then xz -z)
> >
> > 4814416
> >
> > LZMA2 is available as a public domain implementation. It uses a bit
> > more memory than zip, but its still within reason (the default level 6
> > is around 1MB to decode I believe). A fairly easy way to use it would
> > be to add support for a custom compression format for our version of
> > libjar.
>
> IIRC, it's also slower both to compress and decompress. Note you're
> comparing oranges with apples, too.
> Jars are per-file compression. tar.xz is per-archive compression.
> This is what i get:
>
> $ stat -c %s ../omni.ja
> 8609399
>
> $ unzip -q ../omni.ja
> $ find -type f -not -name *.xz | while read f; do a=$(stat -c %s $f); xz
> --keep -z $f; b=$(stat -c %s $f.xz); if [ "$a" -lt "$b" ]; then rm $f.xz;
> else rm $f; fi; done
> # The above compresses each file individually, and keeps either the
> # decompressed file of the compressed file depending which is smaller,
> # which is essentially what we do when creating omni.ja
>
> $ find -type f | while read f; do stat -c %s $f; done | awk '{t+=$1}END{print
> t}'
> # Sum all file sizes, excluding directories that du would add.
> 7535827
>
> That is, obviously, without jar headers.
> $ unzip -lv ../omni.ja 2>/dev/null | tail -1
> 27696753 8260243 70% 2068 files
> $ echo $((8609399 - 8260243))
> 349156
Well, the overhead would be different because of different alignments,
but the order of magnitude should be the same.
> Thus, that same omni.ja that is 8609399, with xz compression would be
> 7884983. Not much of a win, and i doubt it's worth it considering the
> runtime implication.
>
> However, there is probably room for improvement on the installer side.
>
> Mike
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