Okay, here is some captures. It took a while as I of course had to create a script for it as the public iperf3 server is not always free to do tests. I think there are enough context with the folder names to make sense of it. https://owncloud.proikt.com/index.php/s/eY6eZmjDlznar0N On 26 January 2017 at 00:04, Hans-Kristian Bakke wrote: > I can do that. I guess I should do the capture from tun1 as that is the > place that the tcp-traffic is visible? My non-virtual nic is only seeing > OpenVPN encapsulated UDP-traffic. > > On 25 January 2017 at 23:48, Neal Cardwell wrote: > >> On Wed, Jan 25, 2017 at 5:38 PM, Hans-Kristian Bakke >> wrote: >> >>> Actually.. the 1-4 mbit/s results with fq sporadically appears again as >>> I keep testing but it is most likely caused by all the unknowns between me >>> an my testserver. But still, changing to pfifo_qdisc seems to normalize the >>> throughput again with BBR, could this be one of those times where BBR and >>> pacing actually is getting hurt for playing nice in some very variable >>> bottleneck on the way? >>> >> >> Possibly. Would you be able to take a tcpdump trace of each trial >> (headers only would be ideal), and post on a web site somewhere a pcap >> trace for one of the slow trials? >> >> For example: >> >> tcpdump -n -w /tmp/out.pcap -s 120 -i eth0 -c 1000000 & >> >> thanks, >> neal >> >> >> >>> >>> On 25 January 2017 at 23:01, Neal Cardwell wrote: >>> >>>> On Wed, Jan 25, 2017 at 3:54 PM, Hans-Kristian Bakke >>> > wrote: >>>> >>>>> Hi >>>>> >>>>> Kernel 4.9 finally landed in Debian testing so I could finally test >>>>> BBR in a real life environment that I have struggled with getting any kind >>>>> of performance out of. >>>>> >>>>> The challenge at hand is UDP based OpenVPN through europe at around 35 >>>>> ms rtt to my VPN-provider with plenty of available bandwith available in >>>>> both ends and everything completely unknown in between. After tuning the >>>>> UDP-buffers up to make room for my 500 mbit/s symmetrical bandwith at 35 ms >>>>> the download part seemed to work nicely at an unreliable 150 to 300 mbit/s, >>>>> while the upload was stuck at 30 to 60 mbit/s. >>>>> >>>>> Just by activating BBR the bandwith instantly shot up to around 150 >>>>> mbit/s using a fat tcp test to a public iperf3 server located near my VPN >>>>> exit point in the Netherlands. Replace BBR with qubic again and the >>>>> performance is once again all over the place ranging from very bad to bad, >>>>> but never better than 1/3 of BBRs "steady state". In other words "instant >>>>> WIN!" >>>>> >>>> >>>> Glad to hear it. Thanks for the test report! >>>> >>>> >>>>> However, seeing the requirement of fq and pacing for BBR and noticing >>>>> that I am running pfifo_fast within a VM with virtio NIC on a Proxmox VE >>>>> host with fq_codel on all physical interfaces, I was surprised to see that >>>>> it worked so well. >>>>> I then replaced pfifo_fast with fq and the performance went right down >>>>> to only 1-4 mbit/s from around 150 mbit/s. Removing the fq again regained >>>>> the performance at once. >>>>> >>>>> I have got some questions to you guys that know a lot more than me >>>>> about these things: >>>>> >>>> 1. Do fq (and fq_codel) even work reliably in a VM? What is the best >>>>> choice for default qdisc to use in a VM in general? >>>>> >>>> >>>> Eric covered this one. We are not aware of specific issues with fq in >>>> VM environments. And we have tested that fq works sufficiently well on >>>> Google Cloud VMs. >>>> >>>> >>>>> 2. Why do BBR immediately "fix" all my issues with upload through that >>>>> "unreliable" big BDP link with pfifo_fast when fq pacing is a requirement? >>>>> >>>> >>>> For BBR, pacing is part of the design in order to make BBR more >>>> "gentle" in terms of the rate at which it sends, in order to put less >>>> pressure on buffers and keep packet loss lower. This is particularly >>>> important when a BBR flow is restarting from idle. In this case BBR starts >>>> with a full cwnd, and it counts on pacing to pace out the packets at the >>>> estimated bandwidth, so that the queue can stay relatively short and yet >>>> the pipe can be filled immediately. >>>> >>>> Running BBR without pacing makes BBR more aggressive, particularly in >>>> restarting from idle, but also in the steady state, where BBR tries to use >>>> pacing to keep the queue short. >>>> >>>> For bulk transfer tests with one flow, running BBR without pacing will >>>> likely cause higher queues and loss rates at the bottleneck, which may >>>> negatively impact other traffic sharing that bottleneck. >>>> >>>> >>>>> 3. Could fq_codel on the physical host be the reason that it still >>>>> works? >>>>> >>>> >>>> Nope, fq_codel does not implement pacing. >>>> >>>> >>>>> 4. Do BBR _only_ work with fq pacing or could fq_codel be used as a >>>>> replacement? >>>>> >>>> >>>> Nope, BBR needs pacing to work correctly, and currently fq is the only >>>> Linux qdisc that implements pacing. >>>> >>>> >>>>> 5. Is BBR perhaps modified to do the right thing without having to >>>>> change the qdisc in the current kernel 4.9? >>>>> >>>> >>>> Nope. Linux 4.9 contains the initial public release of BBR from >>>> September 2016. And there have been no code changes since then (just >>>> expanded comments). >>>> >>>> Thanks for the test report! >>>> >>>> neal >>>> >>>> >>> >> >