[pacman-dev] [PATCH] pkgdelta: use highest compression ratio when creating deltas with xdelta3

Brendan Hide brendan at swiftspirit.co.za
Thu Mar 13 05:41:52 EDT 2014

On 13/03/14 08:11, Allan McRae wrote:
> On 06/03/14 09:25, Matthias Krüger wrote:
>> Side note: it might be even more advantageous to use bsdiff instead of
>> xdelta3
>> 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
> I took a look, and changing from xdelta3 to bsdiff would be very simple.
>   It looks like it is a five minute patch...
> But what I need is for someone to generate deltas (with and without -9
> maybe) for a whole bunch of packages.  Then generate diffs using bsdiff
> and compare the results.  The comparison will need to include:
> 1) size of deltas/diffs
> 2) memory used when reconstructing package
> 3) time taken to reconstruct package.
> Once we have that information, we can make an informed decision.
> Allan
Hi, Allan and Matthias

Related, one of the potentials we saw when originally researching 
performance was that I was using gzip --rsyncable in CentOS to compress 
files for delta'd backups (completely unrelated to repo management of 
course). The --rsyncable flag allows completely avoiding the 
decompress/recompress steps but is not as good at reducing the total 
disk/network usage. The --rsyncable flag is not included in the gzip 
package however. See https://bbs.archlinux.org/viewtopic.php?pid=496539

Unfortunately if I do the testing you've mentioned from our mirror 
server, I'm not sure if the performance results would be relevant as our 
mirror server is now running OpenIndiana. :-/

Brendan Hide

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