[tor-relays] Declining Relay Usage

[Roman Mamedov]

On Mon, 18 Dec 2023 16:57:37 +0000
George Hartley <hartley_george at proton.me> wrote:

> Please read the code, not only Tor's code, but also OpenSSL's code.
> 
> Yes, AES is not displayed as engine itself, however, it still does not seem
> to use aes-ni instructions unless told to initialize engines via the code I
> deducted.
> 
> If this proves anything, I ran an Exit Relay in 2013 before my host forced
> me to switch to a Guard one because of excessive abuse, and even though my
> VM supported aesni instructions, OpenSSL would not actually use them until I
> added the config parameter, the peak CPU usage (single core) dropped from
> 88-95% avg to around 23% avg once I added it.
> 
> Maybe some developer can comment on the deeper workings of OpenSSL and Tor,
> and terminology might get weird between the Tor and OpenSSL (both very big
> code-bases).
> 
>  Also, regarding the e-mail, I post regularly on here and tor-dev, so no
> worries :)
> 
> Let's just end this pointless discussion here, I will do some more research
> the next few days because I actually want to know, but to me everything
> seems pretty clear (from the code I've YET SEEN, not the one I DID NOT YET
> SEE).

My main point though: it would be an insanity and beyond belief, if Tor would
not use the universally-available AES-NI instruction sets on modern CPUs,
unless the user somehow knows to find and set a non-default config option.

Moreover, just recently in my experience leading to the message "[tor-relays]
Worse throughput with 0.4.8.x, on a slow CPU"[1] I tried ALL sorts of the
possible tweaks I could find, which included adding "HardwareAccel 1" to the
config (it was absent before), and it made no difference in CPU use.

[1] https://lists.torproject.org/pipermail/tor-relays/2023-December/021407.html

-- 
With respect,
Roman