Re: Something like nocompress DEB_BUILD_OPTION
On Fri, Nov 09, 2012 at 07:48:22PM +0100, Guillem Jover wrote:
> There used to be a single global default level (9) for all compressors,
> which got changed in 2010 to be backend specific, but only xz and lzma
> were reduced to 6. I don't have any problem with changing gzip (to its
> upstream default!) if as shown it's a vast improvement speed vs space.
> I can certainly do that for dpkg 1.17.x, some more numbers would be
> nice though, as in different types of data.tar, for example, but I
> would not expect any surprises here, mostly just for reassurance.
Okay. I did some tests with various packages. From binary only to text
only.
Package | gzip -6 | gzip -9 | gzip | xz -1
--------------------------+----------+-----------------+---------
libc6 | 4339010 | 4321933 | 0.5% | 2938132
perl-modules | 3874170 | 3822719 | 1.5% | 3248392
gnome-user-guide | 9217494 | 9172395 | 0.5% | 7589076
linux-image-3.2.0-4-amd64 | 32928159 | 32522228 | | 25945856
"gzip -9" is always much slower then "gzip -6". It is at most 2% better.
"xz -1" is usualy faster then "gzip -9" and much better. However most
packages only needs seconds to compress, so the difference will no
really matter.
So instead of switching to gzip -6, a switch to xz -1 would make more
sense in term of size and also speed.
So my proposal would be:
- Don't do anything for Wheezy.
Any change may break the CD creation.
- Switch to xz per default for Jessie.
xz -3 is often faster in compressing stuff then gzip -9. -6 needs a
lot of memory, especially for compressing the files, so reducing the
default to -3 may make sense and does not cost much.
Bastian
--
Those who hate and fight must stop themselves -- otherwise it is not stopped.
-- Spock, "Day of the Dove", stardate unknown
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