[tor-relays] Re: sysctl tweaks for tiny relays

[Toralf Förster via tor-relays <tor-relays@xxxxxxxxxxxxxxxxxxxx>]

On 03/11/2026 03:40, forest via tor-relays wrote:
> > net.ipv4.tcp_keepalive_time = 120
> Why so aggressive? You could get away with 10x that interval.
>
> > net.ipv4.tcp_synack_retries = 2
> Why give up so quickly? This might cause connections to congested relays
> to fail. Is the goal just to reduce the number of open sockets?
Yes.

> > net.ipv6.ip_nonlocal_bind = 1
> This seems like a mistake. Tor does not make use of arbitrary source
> addresses. Unless you're running Unbound with a routed IPv6 netblock and
> want it to randomize source addresses, there's no reason to enable this.

I had reboot (timing?) issues at one of my provider - gone away with that.

> But by far, what helps the most is setting Tor to use a memory allocator
> that is more resistant to memory fragmentation. 1AEO has found mimalloc2
> is the best, but Debian only has mimalloc3 which is actually worse. I
> use jemalloc2 on all of my relays which substantially reduces memory use
> and eliminates thrashing.

Hhm, at my Debian I didn't saw improvements using another memory 
allocator, the number of socket is the biggest problem here.

--
Toralf
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