[tor-relays] Bandwidth Authority PID Feedback Experiment #2 Starting

[Mike Perry]

Thus spake Sebastian Urbach (sebastian at urbach.org):

> > Yeah, I agree. I think that it's now clear that both the variance and
> > the mean of the torperf graphs are way above norm, and we don't have
> > much other explaination for it other than the feedback experiment not
> > working. The question is why?
> 
> I don't want to be the guy who posts always the bad news ...
> 
> I can happily report that the load, since your last mail, increased
> rapidly to max values and also the performance from the metrics page
> seems to be increasing very well right now.
> 
> If you want to take a look for yourself:
> 
> https://metrics.torproject.org/routerdetail.html?fingerprint=0aff5440ae93f2ed679b20e543081710312b7333
> 
> Coincidink ;-) ?
> 
> I dont think so ...
> 
> I hope that this will relieve a little bit pressure from you, Mike.

Just to be sure, I decided to shut off the experiment on Sunday at 3pm
US Pacific time anyways. It looks like the performance has in fact
gotten worse since then.

Does this mean the feedback was definitely working? Who the hell
knows. But it does seem clear that the transition between the two
states is definitely a rocky one that requires patience and repeated
trials to sniff out.

I am going to leave it disabled for another week, just to see how it
recovers, then turn it back on again, possibly with the addition of
https://trac.torproject.org/projects/tor/ticket/4730 if I get a hot
minute, but possibly without it, just to watch the transition again.

Robert Ransom is quite insistent on the need for this as well:
https://trac.torproject.org/projects/tor/ticket/4708, but that system
doesn't really need me to build it, as it can be done independent of
the bwauths. I also think #4730 is more likely to capture the problem
we were seeing with fast nodes being fast only sometimes, and it will
be way less work.

Thanks for bearing with me, but we still might have a ways to go
before we really get to the bottom of this one.

I will keep you posted.

-- 
Mike Perry
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