Re: [tor-relays] Tor relay occasionally maxing out CPU usage

[William Kane <ttallink@xxxxxxxxxxxxxx>]

Not at fixed intervals*, sorry for the typo.

William

2020-05-17 18:20 GMT, William Kane <ttallink@xxxxxxxxxxxxxx>:
> Hi there,
>
> I am the operator of the following relay:
>
> https://metrics.torproject.org/rs.html#details/47E1157F7DA6DF80EC00D745D73ACD7B0A380BCF
>
> The relay is running on my Arch Linux server running kernel version 5.6.11.
>
> This is my tor configuration file:
>
> ORPort 37.157.195.83:38619
> ORPort [2a02:2b88:2:1::3239:0]:38619
> DirPort 37.157.195.83:44776
> Nickname michaelscott
> ContactInfo ttallink@xxxxxxxxxxxxxx
> ControlPort 9051
> SocksPort 0
> CookieAuthentication 1
> ExitPolicy reject *:*
> DataDirectory /var/lib/tor
> Sandbox 1
>
> Linux kernel boot parameters from grub:
>
> quiet mitigations=off
>
> Kernel parameters from /etc/sysctl.d set on boot through systemd:
>
> kernel.dmesg_restrict = 1
> net.ipv6.ip_nonlocal_bind = 1
> kernel.yama.ptrace_scope = 3
> vm.swappiness = 60
>
> Tor systemd unit (shipped by distribution):
>
> [Unit]
> Description=Anonymizing Overlay Network
> After=network.target
>
> [Service]
> User=tor
> Type=simple
> ExecStart=/usr/bin/tor -f /etc/tor/torrc
> ExecReload=/usr/bin/kill -HUP $MAINPID
> KillSignal=SIGINT
> LimitNOFILE=8192
> PrivateDevices=yes
>
> [Install]
> WantedBy=multi-user.target
>
> Tor systemd unit overrides:
>
> [Service]
> ProtectSystem=strict
> ProtectHome=true
> PrivateTmp=true
> ProtectKernelLogs=true
> ProtectKernelModules=true
> ProtectKernelTunables=true
> ProtectControlGroups=true
> NoNewPrivileges=true
> RestrictSUIDSGID=true
> RestrictAddressFamilies=AF_INET AF_INET6
> ReadWritePaths=/var/lib/tor
>
> Occasionally, the CPU usage hit's 100%, and the maximum throughput
> drops down to around 16 Mbps from it's usual 80 Mbps. This happens
> randomly and not a fixed intervals which makes it pretty hard to
> profile.
>
> No abnormal entries in the log files.
>
> I found ticket #24857 in which someone describes a similar behavior,
> but on _Windows_.
>
> https://trac.torproject.org/projects/tor/ticket/24857
>
> Is this also an issue on Linux?
>
> In that case, setting DirCache to 0 should fix the issue, however that
> would mean that, according to the manual, I would no longer be able to
> mirror directory information.
>
> If anyone else encountered the same problem and found a solution,
> please let me know.
>
> Best Regards,
> William
>
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