On Wed, Sep 12, 2012 at 04:05:02PM +0000, Brandeburg, Jesse wrote: > Hi Dick, we need to know exactly what you are expecting to happen > here.
I'm surprised by the large increase in latency (from <1ms to >100ms). In our production environment we see this phenomenon even on "moderate" load, transmitting 1.5-2Gbit. This effect on 10G infrastructure appears to be much more pronounced compared to 1G. When testing on 1G nics latency also increases, but much less so; from <1ms to ~10ms. A difference is that the 1G nics are saturated but the 10G ones are "only" transmitting ~1.5 Gbit. > When you saturate transmit and put lots of data on all tx queues, > any ping or other traffic that gets put in has to contend with the > large amount of data in front of it. Aha. Thanks for the explanation. > There is a simple test you can do, try to disable TSO using > ethtool. ethtool -K ethx tso off I just tried that. The results are very similar. > If that helps then we know that we need to pursue ways to get > your high priority traffic onto its own queue, which btw is why the > single thread iperf works. Ping goes to a different queue (by luck) > and gets out sooner due to not being behind other traffic Interestingly multi threaded iperf (iperf -P 50) manages to do +/- 7.5Gbit while ping latency is still around 0.1 - 0.3 ms. -- Dick Snippe, internetbeheerder \ fight war beh...@omroep.nl, +31 35 677 3555 \ not wars NPO ICT, Sumatralaan 45, 1217 GP Hilversum, NPO Gebouw A ------------------------------------------------------------------------------ Live Security Virtual Conference Exclusive live event will cover all the ways today's security and threat landscape has changed and how IT managers can respond. Discussions will include endpoint security, mobile security and the latest in malware threats. http://www.accelacomm.com/jaw/sfrnl04242012/114/50122263/ _______________________________________________ E1000-devel mailing list E1000-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/e1000-devel To learn more about Intel® Ethernet, visit http://communities.intel.com/community/wired
