<div dir="ltr"><div class="gmail_default" style="font-family:verdana,sans-serif">I listed the qdiscs and put them with the captures, but the setup is:<br><br>KVM VM:</div><div class="gmail_default" style="font-family:verdana,sans-serif">tun1 (qdisc: fq, OpenVPN UDP to dst 443)</div><div class="gmail_default" style="font-family:verdana,sans-serif">eth0 (qdisc: fq, local connection to internet)</div><div class="gmail_default" style="font-family:verdana,sans-serif">BBR always set</div><div class="gmail_default" style="font-family:verdana,sans-serif">Nics are using virtio and is connected to a Open vSwitch</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">Physical host (Newest proxmox VE with kernel 4.4):</div><div class="gmail_default" style="font-family:verdana,sans-serif">fq_codel on all interfaces (default qdisc). 2 x gigabit in OVS bond LACP (with rebalancing every 10 sec) towards the switch</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">Switch is then connected using a 4 x gigabit LACP to a Debian testing linux gateway (fq_codel on all nics). This gateway is using my own traffic shaper script (HTB/FQ_CODEL) based what I could find from your bufferbloat project on the internet and shapes the 500/500 fiber link to just within specs (only upload is touched, no inbound shaping/policing)</div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">The script is actually quite useful for it's simplicity and can be found here: <a href="https://github.com/hkbakke/tc-gen">https://github.com/hkbakke/tc-gen</a></div><div class="gmail_default" style="font-family:verdana,sans-serif"><br></div><div class="gmail_default" style="font-family:verdana,sans-serif">The VPN connection is terminated in netherlands on a gigabit VPN server with around 35 ms RTT. </div></div><div class="gmail_extra"><br><div class="gmail_quote">On 26 January 2017 at 00:33, Eric Dumazet <span dir="ltr"><<a href="mailto:eric.dumazet@gmail.com" target="_blank">eric.dumazet@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><span class=""><br>
On Thu, 2017-01-26 at 00:04 +0100, Hans-Kristian Bakke wrote:<br>
> I can do that. I guess I should do the capture from tun1 as that is<br>
> the place that the tcp-traffic is visible? My non-virtual nic is only<br>
> seeing OpenVPN encapsulated UDP-traffic.<br>
><br>
<br>
</span>But is FQ installed at the point TCP sockets are ?<br>
<br>
You should give us "tc -s qdisc show xxx" so that we can check if<br>
pacing (throttling) actually happens.<br>
<div class="HOEnZb"><div class="h5"><br>
<br>
> On 25 January 2017 at 23:48, Neal Cardwell <<a href="mailto:ncardwell@google.com">ncardwell@google.com</a>><br>
> wrote:<br>
> On Wed, Jan 25, 2017 at 5:38 PM, Hans-Kristian Bakke<br>
> <<a href="mailto:hkbakke@gmail.com">hkbakke@gmail.com</a>> wrote:<br>
> Actually.. the 1-4 mbit/s results with fq sporadically<br>
> appears again as I keep testing but it is most likely<br>
> caused by all the unknowns between me an my<br>
> testserver. But still, changing to pfifo_qdisc seems<br>
> to normalize the throughput again with BBR, could this<br>
> be one of those times where BBR and pacing actually is<br>
> getting hurt for playing nice in some very variable<br>
> bottleneck on the way?<br>
><br>
><br>
> Possibly. Would you be able to take a tcpdump trace of each<br>
> trial (headers only would be ideal), and post on a web site<br>
> somewhere a pcap trace for one of the slow trials?<br>
><br>
><br>
> For example:<br>
><br>
><br>
> tcpdump -n -w /tmp/out.pcap -s 120 -i eth0 -c 1000000 &<br>
><br>
><br>
><br>
> thanks,<br>
> neal<br>
><br>
><br>
><br>
><br>
> On 25 January 2017 at 23:01, Neal Cardwell<br>
> <<a href="mailto:ncardwell@google.com">ncardwell@google.com</a>> wrote:<br>
> On Wed, Jan 25, 2017 at 3:54 PM, Hans-Kristian<br>
> Bakke <<a href="mailto:hkbakke@gmail.com">hkbakke@gmail.com</a>> wrote:<br>
> Hi<br>
><br>
><br>
> Kernel 4.9 finally landed in Debian<br>
> testing so I could finally test BBR in<br>
> a real life environment that I have<br>
> struggled with getting any kind of<br>
> performance out of.<br>
><br>
><br>
> The challenge at hand is UDP based<br>
> OpenVPN through europe at around 35 ms<br>
> rtt to my VPN-provider with plenty of<br>
> available bandwith available in both<br>
> ends and everything completely unknown<br>
> in between. After tuning the<br>
> UDP-buffers up to make room for my 500<br>
> mbit/s symmetrical bandwith at 35 ms<br>
> the download part seemed to work<br>
> nicely at an unreliable 150 to 300<br>
> mbit/s, while the upload was stuck at<br>
> 30 to 60 mbit/s.<br>
><br>
><br>
> Just by activating BBR the bandwith<br>
> instantly shot up to around 150 mbit/s<br>
> using a fat tcp test to a public<br>
> iperf3 server located near my VPN exit<br>
> point in the Netherlands. Replace BBR<br>
> with qubic again and the performance<br>
> is once again all over the place<br>
> ranging from very bad to bad, but<br>
> never better than 1/3 of BBRs "steady<br>
> state". In other words "instant WIN!"<br>
><br>
><br>
> Glad to hear it. Thanks for the test report!<br>
><br>
> However, seeing the requirement of fq<br>
> and pacing for BBR and noticing that I<br>
> am running pfifo_fast within a VM with<br>
> virtio NIC on a Proxmox VE host with<br>
> fq_codel on all physical interfaces, I<br>
> was surprised to see that it worked so<br>
> well.<br>
> I then replaced pfifo_fast with fq and<br>
> the performance went right down to<br>
> only 1-4 mbit/s from around 150<br>
> mbit/s. Removing the fq again regained<br>
> the performance at once.<br>
><br>
><br>
> I have got some questions to you guys<br>
> that know a lot more than me about<br>
> these things:<br>
> 1. Do fq (and fq_codel) even work<br>
> reliably in a VM? What is the best<br>
> choice for default qdisc to use in a<br>
> VM in general?<br>
><br>
><br>
> Eric covered this one. We are not aware of<br>
> specific issues with fq in VM environments.<br>
> And we have tested that fq works sufficiently<br>
> well on Google Cloud VMs.<br>
><br>
> 2. Why do BBR immediately "fix" all my<br>
> issues with upload through that<br>
> "unreliable" big BDP link with<br>
> pfifo_fast when fq pacing is a<br>
> requirement?<br>
><br>
><br>
> For BBR, pacing is part of the design in order<br>
> to make BBR more "gentle" in terms of the rate<br>
> at which it sends, in order to put less<br>
> pressure on buffers and keep packet loss<br>
> lower. This is particularly important when a<br>
> BBR flow is restarting from idle. In this case<br>
> BBR starts with a full cwnd, and it counts on<br>
> pacing to pace out the packets at the<br>
> estimated bandwidth, so that the queue can<br>
> stay relatively short and yet the pipe can be<br>
> filled immediately.<br>
><br>
><br>
> Running BBR without pacing makes BBR more<br>
> aggressive, particularly in restarting from<br>
> idle, but also in the steady state, where BBR<br>
> tries to use pacing to keep the queue short.<br>
><br>
><br>
> For bulk transfer tests with one flow, running<br>
> BBR without pacing will likely cause higher<br>
> queues and loss rates at the bottleneck, which<br>
> may negatively impact other traffic sharing<br>
> that bottleneck.<br>
><br>
> 3. Could fq_codel on the physical host<br>
> be the reason that it still works?<br>
><br>
><br>
> Nope, fq_codel does not implement pacing.<br>
><br>
> 4. Do BBR _only_ work with fq pacing<br>
> or could fq_codel be used as a<br>
> replacement?<br>
><br>
><br>
> Nope, BBR needs pacing to work correctly, and<br>
> currently fq is the only Linux qdisc that<br>
> implements pacing.<br>
><br>
> 5. Is BBR perhaps modified to do the<br>
> right thing without having to change<br>
> the qdisc in the current kernel 4.9?<br>
><br>
><br>
> Nope. Linux 4.9 contains the initial public<br>
> release of BBR from September 2016. And there<br>
> have been no code changes since then (just<br>
> expanded comments).<br>
><br>
><br>
> Thanks for the test report!<br>
><br>
><br>
> neal<br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
><br>
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<br>
</div></div></blockquote></div><br></div>