I did some more testing with fq as a replacement of pfifo_fast and it now behaves just as good. It must have been some strange artifact. My questions are still standing however.
Regards, Hans-Kristian On 25 January 2017 at 21:54, 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!" > > 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? > 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? > 3. Could fq_codel on the physical host be the reason that it still works? > 4. Do BBR _only_ work with fq pacing or could fq_codel be used as a > replacement? > 5. Is BBR perhaps modified to do the right thing without having to change > the qdisc in the current kernel 4.9? > > Sorry for long post, but this is an interesting topic! > > Regards, > Hans-Kristian Bakke >
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