[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] I/O descriptor ring size bottleneck?
Diwaker Gupta wrote: 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 If you're trying to tune TCP traffic, then you might want to increase the default TCP socket size (87380) above as well, as simply increasing the core size won't help there. 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. Could you get any further information on your test/data? Which netperf test were you running, btw? 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? Someone on this list had posted that they would be getting oprofile working soon - you might want to retry your testing with that patch. thanks, Nivedita ------------------------------------------------------- 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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