Excerpts from Martin T's message of Wed Apr 06 18:43:12 -0500 2011: > Jon, Marc: > > thank you for information! I modified following kernel parameters: > > #UDP socket receive buffer > net.ipv4.udp_rmem_min > #UDP socket send buffer > net.ipv4.udp_wmem_min > #TCP socket receive max buffer size > net.core.rmem_max > #TCP socket send max buffer size > net.core.wmem_max > > ..under Debian like this(all values are in bytes): > > test: ~# sysctl -w net.ipv4.udp_rmem_min=4194304 > net.ipv4.udp_rmem_min = 4194304 > test: ~# sysctl -w net.ipv4.udp_wmem_min=4194304 > net.ipv4.udp_wmem_min = 4194304 > test: ~# sysctl -w net.core.rmem_max=8388608 > net.core.rmem_max = 8388608 > test: ~# sysctl -w net.core.wmem_max=8388608 > net.core.wmem_max = 8388608 > test: ~# > > > Please correct me if those kernel parameters are not the correct > ones(I doubt about "net.ipv4.udp_rmem_min" and "net.ipv4.udp_wmem_min" > because of "_min") or if values are stupid.
The correct values for those settings is a bit depending on how constrained you are for memory on the machine, the round trip time to the most distant host you care about and what your target performance is. The link Marc sent has a lot of good information. In particular the tutorial section explains this in detail: http://www.psc.edu/networking/projects/tcptune/#tutorial There is also a good explaination in the background information section on fasterdata.es.net: http://fasterdata.es.net/fasterdata/host-tuning/ > One more thing- whats with the double values? I mean why are buffer > values provided by kernel always double the size of the requested > buffer values? Linux, in it's infinite wisdom, gives you twice what you ask for. <soapbox> You won't see this behavior on any other platform. You can safely ignore this behavior, since Linux will allocate more memory than it has anyway. Linux believes it knows better than the programmer about how to manage memory. If you've got a strong stomach you can search for "Linux OOM Killer" to learn the gory details. Here's a good summary of the strange machinations Linux goes through in it's "enlightened" memory management: http://thoughts.j-davis.com/2009/11/29/linux-oom-killer/ </soapbox> Jon ------------------------------------------------------------------------------ Xperia(TM) PLAY It's a major breakthrough. An authentic gaming smartphone on the nation's most reliable network. And it wants your games. http://p.sf.net/sfu/verizon-sfdev _______________________________________________ Iperf-users mailing list Iperf-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/iperf-users
