Blair Zajac wrote:
On 5/2/10 8:56 AM, Philipp Marek wrote:
Hello Stefan!
The idea is the following: ra_local (and possibly others)
are "reliable" in that they won't corrupt transmission.
For now, this implies that we don't need to checksum
the data again. There might be more shortcuts that
can be taken in the future.
...
With all other patches applied, this saves 15% runtime
in 'svn export file://'. However, rev'ing svn_delta_editor_t
seems only be feasible in context of 'editor v2'.
I understand your point, and 15% sound very interesting.
But I'd like to note that even for local operations it's a nice
feature to avoid data
corruption via software bugs (off-by-one and similar), and over LAN
it's nice to have,
too (eg. because of bugs in switches and routers, see eg.
http://www.cs.pitt.edu/~kyoungsoo/cs2520/papers/CRC_TCP_Checksum.pdf).
As the WAN (Internet) uses the same protocols as a LAN (TCP, IP)
following that argument
would mean that the checksum is informational only, and doesn't need
to be checked.
So I'd propose that this would be configurable for the paranoid
people (like me, maybe ;-).
Given the size of the patch, reving of the API and that I like the
checksum to always be done, I would just have svn always perform the
checksums.
But you know that today ra_local does NOT checksum
for certain operations, at least for single file gets / exports.
However, I can see the point in making it a client-side option -
maybe on a per-server basis just like everything else in
the 'servers' config file.
-- Stefan^2.
