[Cake] cake at 60gbit

Pete Heist pete at heistp.net
Fri Jul 6 06:00:55 EDT 2018

> On Jul 6, 2018, at 11:29 AM, Toke Høiland-Jørgensen <toke at toke.dk> wrote:
> Pete Heist <pete at heistp.net <mailto:pete at heistp.net>> writes:
>> - is tin_deficit overflowing at these rates? at 50gbit, 2^31-1 bytes
>> happen in 344 ms (involuntary chuckle)
>> - what’s the value of tin_quantum_band here? but I suspect it’s ok.
> I thought about overflows, but I don't get any "weird" values, and
> everything ends up back at zero when the flows stop. And it's not
> actually tin_backlog that's causing the looping…

Ok, I think tin_deficit is meant here, esp. in light of what follows regarding *_flow_count.

Once we do get past this infinite loop, which it sounds like is not caused by overflow here, I guess it’s still worth reviewing whether tin_backlog or other values _could_ overflow in certain conditions. In your case rtt is probably low, but what if it weren’t? Adding delay with netem might coax something out. In fact, I’ll see if I can add some delay to the 30-40gbit local testing that I _can_ do to see if I notice anything...

>> - I’m assuming sparse_flow_count + bulk_flow_count wouldn’t be 0…
> Yeah, they are; that's why it keeps looping. I've been looking at both
> tin_backlog and the *_flow_count vars as different ways of checking
> whether the tins are actually empty... they are all 0 when this happens.

Aha, ok. It does look physically possible for these to both be 0 since there appear to be cases where one is decremented without the other being incremented. That _all_ *_flow_count vars are 0 seems strange logically. I’ll leave this alone now though as don’t yet understand what the values represent well enough… :)
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