The patch I put in cifs-2.6.git recently
http://www.kernel.org/git/?p=linux/kernel/git/sfrench/cifs-2.6.git;a=commitdiff;h=ec637e3ffb6b978143652477c7c5f96c9519b691
improved dbench performance about 10% in my limited testing. I think it
should improve read performance somewhat more.