On Thu, 2017-01-26 at 00:04 +0100, 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. >
But is FQ installed at the point TCP sockets are ? You should give us "tc -s qdisc show xxx" so that we can check if pacing (throttling) actually happens. > On 25 January 2017 at 23:48, Neal Cardwell <ncardw...@google.com> > wrote: > On Wed, Jan 25, 2017 at 5:38 PM, Hans-Kristian Bakke > <hkba...@gmail.com> 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 > <ncardw...@google.com> wrote: > On Wed, Jan 25, 2017 at 3:54 PM, Hans-Kristian > Bakke <hkba...@gmail.com> 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 > > > > > > > > > _______________________________________________ > Bloat mailing list > Bloat@lists.bufferbloat.net > https://lists.bufferbloat.net/listinfo/bloat _______________________________________________ Bloat mailing list Bloat@lists.bufferbloat.net https://lists.bufferbloat.net/listinfo/bloat
