Re: build.sh sets with xz (was Re: vfs cache timing changes)

[Martin Husemann <martin%duskware.de@localhost>]

On Thu, Sep 12, 2019 at 09:49:53PM -0700, Tom Spindler (moof) wrote:
> Maybe if xz were cranked down to -2 or -3 it'd be better at not
> that much of a compression loss, or it defaulted to the higher
> compression level only when doing a `build.sh release`.

If I remember the original size tests correctly, that would not give us
any (or much) gain (sizewise) from gzip.

There was nearly 30% size difference between the suggested default compression
and -9 (what we use now).

I see two easy options:

 - move back to gzip for all architectures that do not really need
   a CD-ROM sized ISO and gzip does not compress good enough (that
   would make sparc64 the only xz user for now)

 - provide an easy tunable for local builds where you care more about
   packing size than result size

I am not sure whether the xz compiled in tools supports the "-T threads"
option, but if it does, we can add "-T 0" to the default args and see how
much that improves things. Jörg, do you know this?

Martin