Re: [tor-dev] Scaling tor for a global population

[thread reconstructed]

On 09/30/2014 06:28 AM, AFO-Admin wrote:

if we would get multithread support, this would boost the bandwith
that is avaible, there i'm sure.
All my relays run in CPU limit because i don't think wasting even more
ipv4 addresses is great, today you get more and more cpu cores that is
not linier with the IPC increase.

E.g. you have a Server with 2x E5-2683 v3 v3 and a 10 Gbit/s pipe you
would need atleast 14 IP's to use most of the CPU. And every IP's gets
blacklistet, with that much Tor nodes in the same /24 maybe the entire
/24. So most ISP's wouldn't be happy with that and with the IPv4
shortage this days im also not very happy with that.
We really shouldn't waste more IPv4 IP's then needed and the only
solution is to change the max amount of Tor Processes from 2 to a
higher number or move to IPv6 or get multithreading working.

[Moritz quoted]

E.g. you have a Server with 2x E5-2683 v3 v3 and a 10 Gbit/s pipe you
would need atleast 14 IP's to use most of the CPU.

Moritz Bartl transcribed 0.5K bytes:
Raising the limit from 2 relays per IP to x per IP has been discussed in the
past and would be an easy change.

Date: Tue, 30 Sep 2014 20:35:21 +0000

From: isis <isis@xxxxxxxxxxxxxx>

We *still* have that limit? I thought we killed it a long time ago.

Can we kill it now? It's not going to do anything to prevent Sybils, it'll
only prevent good relay operators on larger machines from giving more
bandwidth.

Allowing multiple (>2) tor instances would alleviate AFO's issue in the short term, although in this particular case, they might need 14(!) instances (or AES-NI).

Given the shortage of IPv4s, and the availability of multi-processor, high-bandwidth servers, we could trial raising the Tor instance limit per IP. (As this is an authority parameter, the change could happen much sooner than predominantly-IPv6 tor or multithreaded tor.)

4 would allow 1 tor process per logical processor in many server machines (e.g. 4x1 and 2x2). At ~320Mbps per tor process (the maximum bandwidth in the current network), this could saturate a 1 Gbps link with 1 IP.

8 would allow 1 tor process per logical processor in almost all servers (e.g. 4x2 and 8x1), and could saturate a 2.5 Gbps link with 1 IP. In AFO's 10 Gbps case, they'd need 32 processes, or 4 IPs. (Which doesn't seem as unreasonable as 14 IPs.)

The only drawback I can see is that IPs with slow connections/few CPUs could then launch 4 or 8 instances, and slow down the network. This could exacerbate the "wasted consensus entry" issue, where the consensus bytes used for a router outweigh its contribution. (But this seems unlikely.)

In the short term, can we trial raising the Tor instance limit per IP to 4 or 8?

(In the longer term, I'm happy to help with (network) performance, multithreading, or IPv6 - probably in that order.)

teor
pgp 0xABFED1AC
hkp://pgp.mit.edu/

https://gist.github.com/teor2345/d033b8ce0a99adbc89c5
http://0bin.net/paste/Mu92kPyphK0bqmbA#Zvt3gzMrSCAwDN6GKsUk7Q8G-eG+Y+BLpe7wtmU66Mx