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

Marek Vavruša wrote: Very interesting -- I believe the 82571EB is the dual port "server" version of the single port "desktop" 82572EI controller that I tested. This is a very old chipset (launched in 2005) and may be causing a bottleneck in your tests: http://ark.intel.com/products/20720/Intel-82571EB-Gigabit-Ethernet-Controll… I tested an "Intel(R) Xeon(R) CPU E3-1245 v3 @ 3.40GHz" with the 82572EI chipset and I was not able to get more than about 375K responses/second. I think if you graph *responses* per second rather than queries per second you might find something very interesting in your data. I took a few of your data points for Knot DNS 1.4-dev (Root server, Intel 1 GbE) and multiplied queries/second by response rate (which ought to give responses/second): 359625.5 375177.5 385966.89999999997 388956.60000000003 389368.0 388155.0 That's almost identical to the results/behavior I got, but I'm doing a much different benchmark -- recursive DNS cache with repetitive queries (so, 100% cache hit rate). And the CPU I'm testing is quite a bit faster (quad core 2.4 GHz vs quad core 3.2 GHz + faster memory + microarchitectural improvements). But both configurations (root server vs 100% cache hit recursive server) ought to be able to illuminate bottlenecks that are caused by the platform/hardware. So it is quite suspicious that we both run into response rate bottlenecks that are nearly identical numerically. The interesting thing is that when my setup ran into this response rate bottleneck, CPU usage kept going up as the query load increased, but the response rate stayed the same. So I suspect the bottleneck is not occurring on the input path, but rather on the output path. I started looking into this with the dropwatch utility: https://fedorahosted.org/dropwatch/ And that appeared to confirm my suspicion. It might be interesting to compare the TX packet count as measured by the NIC (ifpps/ethtool) versus the response message count as measured by the DNS server. When I replaced the 82572EI controller with an Intel I350-T2: http://ark.intel.com/products/59062/intel-ethernet-server-adapter-i350-t2 The exact same benchmark run jumped from ~375K responses/second to ~900K responses/second. Everything else was identical except the network card. Of course, it is a very good result to find out that your DNS server is too fast for your hardware :-) -- Robert Edmonds edmonds(a)debian.org