On Thu, 22 Nov 2018 12:28:36 -0800 Fabian Ruffy <[email protected]> wrote:
> Hello, > > this is a somewhat esoteric question. I am trying to actually force > bufferbloat in an emulation setup I am using. I set up a dumbbell topology > and push traffic through it, causing congestion at the central link. I use > this setup to compare congestion avoidance algorithms such as DCTCP to other > solutions. > This has worked nicely with the 4.18 kernel. However, after upgrading to 4.19 > I cannot reproduce bufferbloat anymore. The traffic (even UDP packets) is > perfectly rate limited and I never see any congestion happening. This is > great, but in practice it prevents me from prototyping algorithms. > > My interface configuration for bottlenecked links is: > > qdisc tbf 5: dev OBcbnsw1-eth2 root refcnt 2 rate 10Mbit burst 15000b lat > 12.0ms > > Sent 6042 bytes 51 pkt (dropped 0, overlimits 0 requeues 0) > > backlog 0b 0p requeues 0 > > qdisc netem 10: dev OBcbnsw1-eth2 parent 5:1 limit 500 > > Sent 6042 bytes 51 pkt (dropped 0, overlimits 0 requeues 0) > > backlog 0b 0p requeues 0 > > > I have the suspicion that it is related to the CAKE changes in the 4.19 > kernel, but I am not exactly sure. I am not using tc cake at all. Do you > maybe know what could cause this behavior? Apologies if this is the wrong > mailing list. More likely it is a combination of TCP small queues and pacing support. To emulate a network you need to have an intermediate box, otherwise the local feedback in TCP will defeat what you are trying to do. _______________________________________________ Cake mailing list [email protected] https://lists.bufferbloat.net/listinfo/cake
