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.)
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