copy onto cifs-utils samba mount maxes out at 100KiB/s on 100Mib/s eth link

[Zenaan Harkness <zen@freedbms.net>]

Hi, I can't get a normal lan-speed copy from debian wheezy client to
xp "server":

Server is WindowsXP SP3, client is debian testing (updated as at about
a week or two ago).

Fresh boot:
$ sudo mount -t cifs -o
file_mode=0666,dir_mode=0777,setuids,credentials=mycreds
//server.ip.address/git /x
$ rsync -vv --progress libreoffice-calc-guide_CG34-CalcGuideLO.pdf /x/
delta-transmission disabled for local transfer or --whole-file
libreoffice-calc-guide_CG34-CalcGuideLO.pdf
     9729872 100%   71.14MB/s    0:00:00 (xfer#1, to-check=0/1)
total: matches=0  hash_hits=0  false_alarms=0 data=9729872

sent 9731164 bytes  received 31 bytes  93121.48 bytes/sec
total size is 9729872  speedup is 1.00
-----------------

Please note the about 90KiB/second result above. The fastest run I got
was nearly 100KiB/second, but all runs a similar slow speed. The
client is a gigabit eth network, but the server is only 100Mib
ethernet port, so maximum speed should (and used to be) about 6 to 9
MiB/second!
The duration of the above rsync command is also in the order of 2 minutes.

I've been experiencing this slowness over the last 5 months, and know
of no changes to the server at all - other clients (windows XP) do not
have this slowness problem.

I've tried 3 different cables, two different switch ports on one
switch, one port on a second switch (to which the server is also
directly connected to, all produce the same slow file copy result. So
it appears to be a debian configuration problem on my part.

Any help appreciated,
Zenaan