Re: [kernel.org users] XZ Migration discussion

[Justin P. Mattock]

On 02/14/10 01:23, Jean Delvare wrote:
> On Sat, 13 Feb 2010 23:52:17 +0000, Phillip Lougher wrote:
> > Jean Delvare wrote:
> >
> > > Compared to bz2, gz saves... 2% on the overall time. As a conclusion, I
> > > think we can plain discard the argument "I need .gz because my machine
> > > is slow" from now on. It simply doesn't hold.
> >
> > I agree, but, IMHO the main argument for keeping .gz is cross-platform
> > availability and wide language support, not hardware limitations.  Doing
> > a quick google brings up .gz interfaces for every language you can think
> > of (C, Java, Perl, Python, TCL etc.), not to mention complete separate
> > implementations in Java and Pascal (not just wrappers on top of the zlib
> > library), and probably more.
> >
> > With xz you have just one C/C++ implementation with a single library with
> > an undocumented API for C/C++ programmers.
>
> This can probably be easily explained. gz is very fast decompressing so
> it is a very good choice for transparent decompression of files which
> must be accessible fast but aren't used frequently. Manual pages or
> printer drivers come to mind. bz2 and lzma, OTOH, are meant for longer
> term archiving. Their compression ratio benefit is only worth it for
> larger files that you don't access that frequently.
>
> I am not claiming that gzip is dead. It is very useful and it is there
> to stay for the years to come, no doubt about that. What I'm saying is
> that it isn't the best choice for large files to be downloaded from a
> remote server.
>
> > It may be a slight stretch of the imagination, but with with .gz you can
> > conceive programmers writing programs to download a .gz from kernel.org and
> > decompressing/searching it, in almost any language of choice.  With the JAVA
> > implementation .gz is genuinely cross platform and you don't need glibc/
> > C++ compilers, just a Java VM.  Contrast with xz, where if the xz utility
> > isn't available, or doesn't do what you want, you're stuck with programming
> > in C/C++ with all the baggage that entails.
>
> Honestly, I don't think we care at all when it comes to the kernel.org
> files. Accessing individual files inside a compressed kernel tarball
> without first expanding it entirely would be horribly slow and
> unpractical, no matter which compression format was used. I can't think
> of any case where you won't unpack the tarball first, and for this task
> an external tool will do just fine.
>
> And, once again, there are several public instances of gitweb and LXR
> available if you only want to browse the code.

just out of curiosity what would happen if by say
I take a file and turn it into .gz then turn the .gz
into .xz or vice versa?

so at the end of the day you have a list of .gz's(or whatever),
then expending on the type(.gz,.bz2,etc..) unpackage and voila either a 
tree or some other compressed file(.bz2,xz, or .gz).

just thinking out loud(so don't shoot me please).

Justin P. Mattock
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