Re: vdelta performance

Greg Hudson wrote:

> On Wed, 2004-03-17 at 18:10, Florian Weimer wrote:
> > I've compared it to xdelta and rdiff. White it is significantly better
> > than rdiff, it's also worse than xdelta (both compressed and
> > uncompressed).
> >
> > xdelta diffing is also faster, but xdelta doesn't seem to use bounded
> > amounts of memory.
>
> Heh. If you expand the window size to a few hundred megabytes, I'm sure
> you can get some very nice results from svndiff as well.

D'oh.

I would have expected that speed is higher, due to improved locality,
but the window management probably eats up the advantage. xdelta's
linear space nature is thoroughly enshrined in its algorithm, according
the "File System Sypport for Delta Compression" paper.

Anyway, my timing tests suggest that spooling the new file into the DB
is the bottleneck, not the delta operation. (Commit times are much,
much higher than svndiff-test times.)

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