[knot-dns-users] benchmarking (was: Re: Knot DNS 1.4.0 released!)

Marek Vavruša wrote: Hi, I wonder if you could publish more technical details about your benchmark setup, especially the hardware CPU/NIC models, etc.? I see you've tested "Intel 10 GbE" and "Intel 1GbE" network adapters, but these are large families of different hardware models. Apologies if I overlooked these details somewhere. I've recently been testing different models of Intel 1GbE adapters and I've found a large variation in the maximum response rate that the same DNS server can deliver depending on the network adapter -- for instance, to take an extreme example, I was able to get over 100% more performance from the latest Intel I350 "server" card against a very ancient Intel 82572EI "desktop" card, in an otherwise identical system. That is an extreme example, but I still found large differences between the Intel I210 and I217 adapters, which can be found together on a lot of current generation single socket Xeon motherboards from Supermicro. And these are all considered "Intel 1GbE" network adapters. I would also be interested to know about the distribution of IP addresses and port numbers in your benchmark DNS query traffic. If I understand things correctly, Intel 1GbE (and probably 10GbE) adapters that support multiple RX queues and "Receive Side Scaling" are usually configured to select from the available RX queues based on a hash of only the IP source and destination addresses, e.g.: # ethtool -n <INTERFACE> rx-flow-hash udp4 UDP over IPV4 flows use these fields for computing Hash flow key: IP SA IP DA That may result in a single RX queue processing the incoming DNS queries in a benchmark if the queries are all sourced from a single IP address, which may be detrimental. It may be advantageous to configure the network adapter to also hash over the source and destination ports, if supported, e.g.: # ethtool -N <INTERFACE> rx-flow-hash udp4 sdfn # ethtool -n <INTERFACE> rx-flow-hash udp4 UDP over IPV4 flows use these fields for computing Hash flow key: IP SA IP DA L4 bytes 0 & 1 [TCP/UDP src port] L4 bytes 2 & 3 [TCP/UDP dst port] There are statistical counters available with the "ethtool -S" command to verify if packets are being evenly balanced among the RX queues on a network adapter with multiple RX queues. It may also be advantageous to configure "Transmit Packet Steering" [0]. If I understand things correctly, network adapters with multiple TX queues will only utilize a single TX queue until XPS is configured. [0] http://www.mjmwired.net/kernel/Documentation/networking/scaling.txt#364 -- Robert Edmonds edmonds(a)debian.org