unruh <un...@wormhole.physics.ubc.ca> wrote: > The dominant rate limiter is the network-- even if you have a 1Gb > network-- switches, interrupts, etc.
Including a 14 byte Ethernet header, an NTP query/response appears to be 80 bytes or 640 bits. The 1GbE interframe gap is allowed to be as low as 64 bit times. So, call that 640+64 or 704 bits. That is a maximum then of a little over 1.42 million queries per second (since 1GbE is full-duplex). Now, I have seen aggregate netperf TCP_RR tests achieve in excess of 1.8M transactions (queries) per second over a 10GbE NIC, but never to a single-threaded process. The 10GbE NIC I was using at the time did have a low-ish PPS limit. The most I've seen a single netperf *single-byte* burst-mode test do is on the order of 350K transactions per second, and that is when netperf is bound to a core other than the one taking interrupts from the NIC to get some additional parallelism. In a netperf TCP_RR test, netperf does virutally nothing but a send()/recv() pair and a couple conditionals and adds. Are there "multi-threaded" NTP server implementations? If not, I suspect it is possible for an NTP server to saturate before the 1GbE network to which it is connected. rick jones -- oxymoron n, Hummer H2 with California Save Our Coasts and Oceans plates these opinions are mine, all mine; HP might not want them anyway... :) feel free to post, OR email to rick.jones2 in hp.com but NOT BOTH... _______________________________________________ questions mailing list questions@lists.ntp.org http://lists.ntp.org/listinfo/questions