tweaking sockets / OS parameters for speed

Bruce Labitt bruce.labitt at myfairpoint.net
Thu Oct 1 20:36:48 EDT 2009


Have a client-server app that is set up to communicate over a local Gbit 
network.  The bottleneck appears in the client to server uplink for 
large payloads.  At this point it isn't clear where the delay is, 
(client or server side) but the sustained rate is not good enough.

Can anyone recommend some tweaks at the OS level?  Google has revealed 
quite a few, such as editing values in sysctl.conf.  What appears to be 
missing for me is a coherent way to figure out decent values. 

The BDP product for the link is ~ 25K since the RTT is 0.2 ms maximum. 

I've also tried using setsockopt to set TCP_NODELAY.  It doesn't seem to 
make much of a difference.  Changing the data from double to float only 
reduced the uplink time by ~10%.  Kind of puzzling to me since the 
payload reduced in size by 50%.

Any suggestions?  Places to look?  Guess it is time for wireshark...  
Anything else?


Thanks,
Bruce






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