[tor-scaling] Summary of 5/31 meeting; next steps

[David Goulet]

On 31 May (20:39:00), Mike Perry wrote:

Thanks for this summary Mike!

[snip]

> In the meantime, with input from folks on this list and on the wiki
> page, I would like to add the EWMA re-tuning experiment, fill out the
> KIST tuning experiment, and flesh out the metrics section to highlight
> metrics that need new data collection. (I will start separate threads
> for this on-list as I run into questions -- I have several already).

(Maybe this could be on the thread you want to start?)

Just an observation here. The real Tor network is very heterogeneous in terms
of "tor versions". There is probably ~95% Linux and the rest BSDs but the
point I want to make is about the different cell scheduler between relays.  It
creates a big partition of KIST relays, KISTLite relays and non-KIST relays.
(And any new improvements we will release will create more groups like that.)

We currently have ~1000 that are on 0.2.9, one of our LTS until Jan 2020.
These relays are running the Vanilla scheduler versus the rest either the KIST
or KISTLite scheduler.

The former totally buffer bloat the TCP connection where KIST should not. A
circuit of a mix of Vanilla and KIST will end up with I believe different
performance than an only KIST for instance. And on BSD, it is KISTLite so the
limits are set to the limit of the outbuf which is 32KB, not the kernel space
which is actually often lower in my observations per scheduler run (10 msec).

Thus, we get this mixture affecting performance on a circuit so tweaking EWMA
parameters on such a setup (the Tor network ;) could not result in what we do
expect from experimentation that is more likely to only have the same Tor
version.

And I would also like to point out that for optimal performance, whatever
client measuring it should follow the workaround in #29427 (bring down the
KISTSchedRunInterval to 2msec.

Just to keep in mind!

Cheers!
David

-- 
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