Re: xz (was Re: Mac-only binary, was Re: Modernizing a Macintosh LC III)

[Finn Thain <fthain@telegraphics.com.au>]

On Mon, 18 Nov 2013, Thorsten Glaser wrote:

> Finn Thain dixit:
> 
> >I don't know how much memory is needed by the "xz -0d" algorithm. The 
> >xz
> 
> RTFM ;-)
> 
>                      Preset   DictSize   CompCPU   CompMem   DecMem
>                        -0     256 KiB       0        3 MiB    1 MiB
>                        -1       1 MiB       1        9 MiB    2 MiB
>                        -2       2 MiB       2       17 MiB    3 MiB
>                        -3       4 MiB       3       32 MiB    5 MiB
>                        -4       4 MiB       4       48 MiB    5 MiB
>                        -5       8 MiB       5       94 MiB    9 MiB
>                        -6       8 MiB       6       94 MiB    9 MiB
>                        -7      16 MiB       6      186 MiB   17 MiB
>                        -8      32 MiB       6      370 MiB   33 MiB
>                        -9      64 MiB       6      674 MiB   65 MiB
> 
> It depends on what it was _compressed_ with.

Right.

> 
> Rule of thumb: xz -0 is faster than gzip -6 in compression and has about 
> the same ratio...

For the kernel binary, xz -0 has a better ration than gzip -9. RTFOP ;-)

> With -e, compression ratio increases...

Indeed it does (though the man page warns that it can get worse):

$ gzip -d < vmlinux-3.12.0-mac.gz | xz -0c | wc -c
1325352
$ gzip -d < vmlinux-3.12.0-mac.gz | xz -0ec | wc -c
1196876

Finn