Re: [gentoo-dev] RFC: using .xz for doc/man/info compression

[Alexander Tsoy]

÷ Mon, 12 May 2014 14:17:11 +0200
Tom Wijsman <TomWij@g.o> ÐÉÛÅÔ:

> On Mon, 12 May 2014 14:47:36 +0400
> Alexander Tsoy <alexander@××××.me> wrote:
>
> > Here is my test results. xz options: "--lzma2=preset=6e,dict=4MiB".
> > Larger dictionary size does not improve compression ratio, I get
> > even worse results with just "-6e" or "-9e". man-bz2 is a full copy of
> > my /usr/share/man, man-xz is a recompressed one.
>
> Picking a random post to reply; if you don't already, please consider
> to do these tests in tmpfs to cancel out any fs / storage differences.
>

The same test in tmpfs.

$ time find man-bz2/ -type f -name "*.bz2" -exec bzcat '{}' > /dev/null \;

real	0m35.895s
user	0m14.232s
sys	0m14.121s
$ time find man-xz/ -type f -name "*.xz" -exec xzcat '{}' > /dev/null \;

real	0m44.342s
user	0m16.842s
sys	0m21.459s


And here is additional test. It shows where is actually a bottleneck.
xz is faster in decompression, but looks like it just has a slower
process initialization speed. So it's slower in decompressing of a single
little file.

$ time find man-bz2/ -type f -name "*.bz2" -exec bzcat '{}' > /dev/null \+

real	0m10.096s
user	0m9.000s
sys	0m0.787s
$ time find man-xz/ -type f -name "*.xz" -exec xzcat '{}' > /dev/null \+

real	0m7.846s
user	0m7.108s
sys	0m0.487s

-- 
Alexander Tsoy