[Cake] [Bloat] Fwd: [Galene] Dave on bufferbloat and jitter at 8pm CET Tuesday 23

Toke Høiland-Jørgensen toke at toke.dk
Fri Feb 26 06:47:25 EST 2021

Nils Andreas Svee <me at lochnair.net> writes:

> On 2/25/21 11:30 AM, Toke Høiland-Jørgensen wrote:
>> Ah, wireguard doesn't have XDP support, so that's likely not going to
>> work; and if you run it on the physical interface, even if you didn't
>> get driver errors, the tool would just see the encrypted packets which
>> is not terribly helpful (it parses TCP timestamps to match
>> incoming/outgoing packets and compute the RTT).
> I figured that might be the case. Yes I would've disabled the VPN if I 
> didn't get driver errors.
> I changed the network interface to use an emulated Intel E1000 tonight, 
> and if I bypass the VPN it works as it should.

Right, awesome!

>> I guess we should be more flexible about which hooks we support, so it
>> can also be used on devices with no XDP support. Adding in Simon, who is
>> writing the code; I think he is focused on getting a couple of other
>> features done first, but this could go on the TODO list :)
> It's not like I'm in a hurry, and I'd probably need some time to figure 
> out how to tweak the CAKE parameters correctly with this anyway ;)
> Speaking of, isn't one of the challenges with solutions like these that 
> it's hard to tell when conditions have improved and allow for more 
> throughput? At least that's what I remember being the issue when I 
> tested CAKE's autorate-ingress back in the day.

Yeah, there would have to be some kind of probing to discover when the
bandwidth goes up (maybe something like what BBR does?). Working out the
details of this is still in the future, this is all just loose plans
that I'll try to get back to once we have the measurement tool working
reasonably well. Input and experiments welcome, of course!


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