[tor-relays] Load balancing (with IPVS) multiple Tor daemons

Roman Mamedov rm at romanrm.net
Sat Jul 8 16:10:46 UTC 2017


On Sat, 8 Jul 2017 09:54:20 +1000
teor <teor2345 at gmail.com> wrote:

> Tor uses multithreaded crypto already: depending on the speed of your
> processor, you can get up to 400 Mbps per instance (250 Mbps is
> typical).

In practice I don't remember seeing much more than 120-130% CPU use per
process, and even that, only in brief peaks. Maybe crypto is not actually the
bottleneck, but some other non-parallel operation instead.

Speaking of CPU use, is there any roadmap to phase out TAP mode circuits? IIRC
those are very CPU-expensive compared to NTor. Even though now TAP counts are
only 10-20% compared to NTor, could it be that those are actually responsible
for something like 50%+ of total CPU usage.

> You can also get a second IPv4 address, and run 2 Tor daemons on that
> IP address as well.

This is not always feasible and carries additional expense even if it is.

Another idea that I proposed some time ago is raising the relay-per-IP limit
from 2 to 4. There are almost no 1 or 2-core CPUs anymore, and 4-core CPUs (for
4 Tor processes) are extremely common. Especially considering the ARM
architecture, where it's really common now to see 4-core CPUs, with each core
being relatively weak on its own.

-- 
With respect,
Roman


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