[arch-general] About Arch pkg compress format

[Aaron Griffin]

On Wed, May 21, 2008 at 12:39 PM, Jan de Groot <jan at jgc.homeip.net> wrote:
> On Wed, 2008-05-21 at 18:47 +0300, Dimitrios Apostolou wrote:
>> Hi,
>>
>> On Tue, 2008-05-20 at 10:14 +0200, Jan de Groot wrote:
>> > Pacman itself is ready for .tar.bz2 package files. The whole issue
>> > with .bz2 files is that compression and decompression times increase a
>> > lot without giving the same amount of size reduction back. We've done
>> > some recent tests with LZMA, which compresses just as good as bzip2 at
>> > the lowest compression rate, but does it at the same speed as gzip.
>>
>> About LZMA I should add that when using higher (actually the default)
>> compression rate, compression is much better than bzip2 but takes more
>> time/memory. Decompression however, which is what really matters in a
>> packaging format, is kept fast and lightweight.
>
> What's the memory usage when unzipping an LZMA file? Is it much higher
> than the needs of gzip? We already have problems supporting low-memory
> systems with our installer, adding a compression algorithm that eats
> more memory will cause even more problems for these systems.

That's actually not entirely true. Dan and I investigated this. The
previous low memory issues were caused by the entire install system
never leaving the initramfs, and remaining entirely in RAM - which
soaked far more than pacman ever will. Additionally, with the dynamic
package patch (dunno if this is in the master branch yet), memory
usage sank by leaps and bounds.