System update spec proposal

[Wayne Davison]

On Wed, Jun 27, 2007 at 11:37:07AM +1000, tridge at samba.org wrote:
> That "100 bytes per file" is very approximate. It also increases quite
> a lot if you use --delete and also increases if you use --hard-links.

The increase for --delete got greatly improved a while back (the delete
scan used to at least double the size of the file list, but now only
requires the memory size of the largest directory in the delete scan).

Rsync doesn't attempt to be a really low-memory application for small
transfers, but it does try to keep the per-file memory use as low as it
can.  One sad thing is that the forking of the second rsync process on
the receiving side no longer shares the file-list memory between the two
processes on 2.6.x versions of Linux (due to a move away from copy-on-
write memory allocation in forks), so that doubles the size of the file-
list on the receiving side.

> Alternatively, talk to Wayne Davison about rsync 3.0. One of the core
> things that brings is lower memory usage (essentially automating the
> breakup into directory trees that I mentioned above).

I wouldn't recommend deploying rsync 3 widely just yet.  I'm going to be
working on finalizing the release in the near future, but there is still
a chance that protocol 30 (which is new for this release) may still need
to be changed a bit before it is released.  The program is stable enough
that I use it for all my own rsync copying, but I also ensure that my
installed versions get updated for new releases.

..wayne..