[pacman-dev] [PATCH] pkgdelta: use highest compression ratio when creating deltas with xdelta3
allan at archlinux.org
Wed Mar 5 18:33:05 EST 2014
On 06/03/14 09:25, Matthias Krüger wrote:
> Looking how pkgdelta works, I found this line
> xdelta3 -q -f -s "$oldfile" "$newfile" "$deltafile" || ret=$?
> which seemed to be responsible for the actual delta generation, however
> man xdelta3
> revealed that there were different compression levels (0-9) (not sure
> which one is default).
> To make it short, we could have had smaller deltas since pkgdelta was
> -9 16660K
> default 17832K blender-12:2.69.c7ac0e-1_to_13:2.69.13290d-1-x86_64.delta
> -9 504K xbmc-12.3-10_to_12.3-11-x86_64.delta
> default 572K xbmc-12.3-10_to_12.3-11-x86_64.delta
How is memory usage changed? Mainly when regenerating the package from
> The attached patch adds the "-9" option to the line above.
> Side note: it might be even more advantageous to use bsdiff instead of
> comparing the /usr/bin/blender binaries of the above versions
> (12:2.69.c7ac0e-1 and 13:2.69.13290d-1) :
> xdelta3 10.4M
> xdelta3 -9 9.9M
> bsdiff 4.7M
> ,however bsdiff is only for direct diff creation, bsdiff foo1.pkg.tar.xz
> foo2.pkg.tar.xz will create a diff between the archives and not their
> contents, so that'd require further coding which I am unable to do
> (maybe someone else volunteers :) ).
What do you mean "create a diff between the archives and not their
contents". That does seem a significant decrease.
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