[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] I/O descriptor ring size bottleneck?
Hi everyone, I'm doing some networking experiments over high BDP topologies. Right now the configuration is quite simple -- two Xen boxes connected via a dummynet router. The dummynet router is set to limit bandwidth to 500Mbps and simulate an RTT of 80ms. I'm using the following sysctl values: net.ipv4.tcp_rmem = 4096 87380 4194304 net.ipv4.tcp_wmem = 4096 65536 4194304 net.core.rmem_max = 8388608 net.core.wmem_max = 8388608 net.ipv4.tcp_bic = 0 (tcp westwood and vegas are also turned off for now) Now if I run 50 netperf flows lasting 80 seconds (1000RTTs) from inside a VM on one box talking to the netserver on the VM on the other box, I get a per flow throughput of around ~2.5Mbps (which sucks, but lets ignore the absolute value for the moment). If I run the same test, but this time from inside dom0, I get a per flow throughput of around 6Mbps. I'm trying to understand the difference in performance. It seems to me that the I/O descriptor ring sizes are hard coded to 256 -- could that be a bottleneck here? If not, have people experience similar problems? TIA -- Diwaker Gupta http://resolute.ucsd.edu/diwaker ------------------------------------------------------- SF email is sponsored by - The IT Product Guide Read honest & candid reviews on hundreds of IT Products from real users. Discover which products truly live up to the hype. Start reading now. http://ads.osdn.com/?ad_id=6595&alloc_id=14396&op=click _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxxxx https://lists.sourceforge.net/lists/listinfo/xen-devel
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