Re: Propose Release Goals (delayed ;) - xz compression
On Wednesday 16 Oct 2013, Marius Gavrilescu wrote:
> David Goodenough <david.goodenough@btconnect.com> writes:
> > The only problem is that on small machines (things like the BeagleBone)
> > xz compression requires enough memory that you have to enable swap to
> > use dpkg. Now on a machine with a sensible disk this is not a problem,
> > but on a machine where the "disk" is an SD-card it is a disaster.
>
> From the xz manpage:
> # 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
>
> At the default preset (-6), the required RAM for decompressing is about
> 9MB. The BeagleBone seems to have 256MB of memory (that's what
> Wikipedia says), so 9MB shouldn't be an issue.
>
> And if 9MB is too much for some random board, xz -0 still compresses
> better than gzip -9 (or so it should) with only 1MB of DecMem.
xy may only use a tiny bit, but the combination of apt-get, dpkg and
xy seems to cause problems. Its not just BeagleBones, there are x86
machines with just 64MB still on sale.
David
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