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Hello, |
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|
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On Mon, 12 May 2014 14:47:36 +0400 Alexander Tsoy wrote: |
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> В Sun, 11 May 2014 18:26:32 -0500 |
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> Gordon Pettey <petteyg359@×××××.com> пишет: |
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> |
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> > A lot of small files (e.g. AUTHORS, ChangeLog |
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> > |
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> > FWIW: On my system, I have 59M of bz2 files in /usr/share/man and |
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> > /usr/share/doc. A short script to decompress those and recompress with xz |
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> > -6e reduced that to 36M. |
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> |
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> Very strange o_O |
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> |
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> Here is my test results. xz options: "--lzma2=preset=6e,dict=4MiB". |
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> Larger dictionary size does not improve compression ratio, I get |
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> even worse results with just "-6e" or "-9e". man-bz2 is a full copy of |
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> my /usr/share/man, man-xz is a recompressed one. |
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> |
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> Size comparison: |
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> |
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> $ du -s man-bz2/ man-xz/ |
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> 82032 man-bz2/ |
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> 82308 man-xz/ |
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|
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Please consider that by default du shows block size, not byte size. |
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Than means that if file is actually 1234 bytes large, without -b it |
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will be still accounted for 4096 bytes on 4K-block filesystem. |
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|
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Here are my results: |
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|
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1. With bzip2 -9: |
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find -O3 /usr/share/man -type f -name "*.bz2" -print0 | du -bhc --files0-from - |
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63M |
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find -O3 /usr/share/man -type f -name "*.bz2" -print0 | du -hc --files0-from - |
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146M |
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|
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find -O3 /usr/share/doc -type f -name "*.bz2" -print0 | du -bhc --files0-from - |
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151M total |
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find -O3 /usr/share/doc -type f -name "*.bz2" -print0 | du -hc --files0-from - |
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249M total |
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|
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2. With xz -9e: |
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find -O3 /usr/share/man -type f -name "*.xz" -print0 | du -bhc --files0-from - |
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64M |
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find -O3 /usr/share/man -type f -name "*.xz" -print0 | du -bhc --files0-from - |
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146M |
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|
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find -O3 /usr/share/doc -type f -name "*.xz" -print0 | du -bhc --files0-from - |
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147M total |
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find -O3 /usr/share/doc -type f -name "*.xz" -print0 | du -hc --files0-from - |
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245M total |
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|
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As one can see, on man pages xz is slightly worse or apparent file sizes |
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and has no difference on real disk usage. On docs xz is better for both sizes. |
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|
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As for decompression speed, xz is about twice as good as bzip2 for a large man |
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pages (bash, mplayer, cmake, zshall). Though this speed gain needs to be |
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measured directly for bunzip2 and unxz applications. I'll publish statistically |
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meaningful results later. Both scripting and testing requires time. |
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|
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Best regards, |
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Andrew Savchenko |
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