Back in August I submitted a "patch":http://kerneltrap.org/mailarchive/linux-netdev/2010/8/23/6283640 to enable/disable the TCP Quick ACK behavior. Linux default Quick ACK behavior is in many cases counterproductive and increase the packet count. Especially short-lived interactive protocols like HTTP will suffer of TCP Quick ACK. For example a interactive HTTP flow of 16 data packets will send one additional but unnecessary Quick ACK packet - 1/16. Accumulated this is not to underestimated! Not sure why big HTTPD users like facebook or $BIGCOMPANY do not tune their stack - do they not question their @tcpdump@ traces?
At that time where I submitted the patch Davem rejected the @sysctl@ based approach with the suggestion to use a per-route approach to reduce sysctl pollution. The big disadvantage is that it is now a little bit tricky to enable/disable Quick ACK's, because each route must be addressed separately -- I am not happy with the idea to ban nearly all new @sysctl@ extensions. Anyway, I modified the patch, I will tests the patch a couple of days and afterwards it should goes into net-next, hopefully.