Hello Felix,
How long does it take to uncompress with bunzip or p7zip? I suppose uncompressing with external program beforehand is still faster, or has this switched around now? (until now, for me uncompressing with p7zip the geofabrik extracts and then running mkgmap with no cache on small countries, with cache on larger countries was the fastest way to do..).
I haven't tried benchmarking that before sorry so I don't really know. Any numbers you might have would be appreciated. One thing I want to add is the ability to pipe the osm file in via stdin, which (depending on OS buffering) will allow external decompression at the same time as processing and it might prove to be the fastest approach. It will certainly be more reliable - I've seen the Java bz2 decompression fail with strange errors a few times now due to bugs in the Apache Java decompression code. Chris