On 23.06.2012 00:23, Vincent Lefevre wrote:
> Thanks for the explanations.
>
> On 2012-06-22 00:18:50 +0200, Stefan Fuhrmann wrote:
>> xdelta uses fixed-size 100kByte deltification windows.
>> The Changelog file in question is >400k, i.e. 4+ windows.
>> You insert about 2k at the beginning of the file, moving
>> the older parts by a similar distance. At the beginning
>> of each delta window, those 2+k don't have deltification
>> partner. Expected delta size: > 4 x 2kBytes.
> Wouldn't it be possible to change this size of deltification windows,
> with a command-line option (for svnadmin dump) and/or an option in
> the config file?
>
> The gain would be quite important on some kinds of changes (typically
> ChangeLog update), and a dump of a revision is something that could
> be done once and for all, so that it would be worth to spend time on
> optimizing it.
It's not that simple, unfortunately. Currently both the delta generator
and especially the delta combiner expect the windows to be a known,
constant size. You can't just change them without affecting a /lot/ of code.
Frankly I don't know how to make all the delta code paths gracefully
deal with variable window sizes. I'm sure it can be done, but the ROI at
this point is not good at all.
-- Brane
Received on 2012-06-23 17:15:07 CEST