some more patches

[Gavin Carr]

Hi Kostas,

On Tue, Dec 29, 2009 at 09:21:10PM +0200, Kostas Chatzikokolakis wrote:
> http://codereview.appspot.com/183080/show
> 
> Avoids downloading a composite chunk multiple times from the target
> (pretty bad if you have thousands of small files). Fixes issue #1 on
> google code.
> 
> There's a very simple solution for that: brackup currently merges only
> small files, not the tail of large files (a good decision). As a result,
> files containing parts of a composite chunk are all single-chunk files.
> So if the files are restored ordered by the dig of their first chunk,
> and the last seen chunk is kept in memory, all files of the composite
> chunk can be restored without downloading it twice (and without caching
> more than one chunk).
> 
> As a free gift, we get some speedup even for non-composite chunks, in
> case we have many single-chunk identical files (the chunk will be
> downloaded only once).

Great patch, thanks - huge difference with composite chunks and lots of
small files. Committed.

Cheers,
Gavin