On Sun, Jul 22, 2012 at 01:58:59AM +0200, Adam Borowski wrote: > > BTW, when we switched to building udebx with xz, Philipp Kern benchmarked > > it using little or no additional CPU to decompress xz produced with > > -Zxz -z1 -Sextreme http://lists.debian.org/debian-boot/2011/10/msg00247.html > Per the above, you'd want a higher setting than -1. With the default (-6), > you need just 10MB memory to decompress. The main point I looked at was memory usage compared to gzip and I wanted to pick something for d-i that does not increase the RAM requirements. That's why I went for 1e. The case for udebs is probably not comparable to plain debs: with udebs wrote more intense compression options do not gain significant space savings. Obviously higher compression ratios require more RAM to decompress for quick lookups and need to touch less input bytes because they are fewer, so I don't find it that surprising that it will be faster to decompress. (If you collapse larger chunks to a few bits on compression, you'll need fewer dictionary lookups.) And going from 30M (-0) to 21M (-9) is significant given the size of the whole file. Kind regards Philipp Kern
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