W dniu 11.05.2014 23:27, Pacho Ramos pisze: > El dom, 11-05-2014 a las 19:46 +0200, Michał Górny escribió: >> Hello, developers. >> >> I'd like to raise the following item for discussion: making .xz >> the default compressor used by portage for documentation, man pages >> and info files. That is, the equivalent of: >> >> PORTAGE_COMPRESS=xz >> >> in make.globals. >> >> Rationale: xz-utils is quite widespread nowadays and it is a part >> of @system set. It can achieve better compression ratio than bzip2, >> and faster decompression at the same time. >> >> I have confirmed that both sys-apps/man and sys-apps/man-db can >> handle .xz compressed man pages, and sys-apps/texinfo can handle .xz >> compressed info pages. Major text editors and pagers support .xz >> alike .bz2 (i.e. usually they support both or neither :)). >> >> The additional question is: what preset to use? To help discussing >> this, I'd like to quote the tables from 'man xz': >> >> 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 >> >> Preset DictSize CompCPU CompMem DecMem >> -0e 256 KiB 8 4 MiB 1 MiB >> -1e 1 MiB 8 13 MiB 2 MiB >> -2e 2 MiB 8 25 MiB 3 MiB >> -3e 4 MiB 7 48 MiB 5 MiB >> -4e 4 MiB 8 48 MiB 5 MiB >> -5e 8 MiB 7 94 MiB 9 MiB >> -6e 8 MiB 8 94 MiB 9 MiB >> -7e 16 MiB 8 186 MiB 17 MiB >> -8e 32 MiB 8 370 MiB 33 MiB >> -9e 64 MiB 8 674 MiB 65 MiB >> >> I'd like to note here that increasing dictionary size over file size >> does not improve compression. However, the options involved in CompCPU >> may. >> >> Depending on the expected amount of complexity, I'd either go for: >> >> 1) -6e (or -6, the default) -- max CompCPU, reasonable use of memory, >> and dictionary larger than most (or all?) documents that are going to >> be compressed, >> >> 2) -Ne with minimal 'N' for CompCPU==8 and DictSize > filesize -- still >> max compression ratio while keeping lowest memory requirements possible. >> >> Your thoughts? >> > > Per: > https://bugs.gentoo.org/show_bug.cgi?id=372653 > > Looks like bzip2 was still better for small files :/
Hi! I did test on medium sized man file (bash): $ man -a -w bash /usr/share/man/man1/bash.1.bz2 $ stat --printf=%s\\n /usr/share/man/man1/bash.1.bz2 62606 $ time man -c -P /bin/cat bash >/dev/null real 0m0.248s user 0m0.316s sys 0m0.012s $ time man -c -P /bin/cat bash >/dev/null real 0m0.252s user 0m0.324s sys 0m0.016s $ time man -c -P /bin/cat bash >/dev/null real 0m0.249s user 0m0.320s sys 0m0.012s Now I recompress using xz -6 and next: $ stat --printf=%s\\n /usr/share/man/man1/bash.1.xz 66628 $ time man -c -P /bin/cat bash >/dev/null real 0m0.234s user 0m0.304s sys 0m0.004s $ time man -c -P /bin/cat bash >/dev/null real 0m0.244s user 0m0.288s sys 0m0.024s $ time man -c -P /bin/cat bash >/dev/null real 0m0.239s user 0m0.308s sys 0m0.012s And with file compressed using '-6e': $ stat --printf=%s\\n /usr/share/man/man1/bash.1.xz 66700 $ time man -c -P /bin/cat bash >/dev/null real 0m0.233s user 0m0.292s sys 0m0.016s $ time man -c -P /bin/cat bash >/dev/null real 0m0.234s user 0m0.300s sys 0m0.008s Imho there is no real advantages to change current compressor for man files. Regards
