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Thread: 17.10 systemd-resolve takes 100% CPU since upgrade from Zesty Zapus

  1. #1
    Join Date
    May 2006
    Location
    greenville, south carolin
    Beans
    43
    Distro
    Ubuntu 18.04 Bionic Beaver

    Question 17.10 systemd-resolve takes 100% CPU since upgrade from Zesty Zapus

    Hello

    since upgrade, systemd-resolve takes 100% CPU.

    Code:
    PID USER      PR  NI    VIRT    RES    SHR S  %CPU %MEM     TIME+ COMMAND
    925 systemd+  20   0   67476   7552   5104 R  98,3  0,1  82:48.57 systemd-resolve
    954 dnsmasq   20   0   57440   2840   2420 R  51,2  0,0  38:50.39 dnsmasq
    As you see dnsmasq is using a lot of CPU as well. Maybe due to the same root cause?

    Here is the config /etc/systemd/resolved.conf

    Code:
    [Resolve]
    #DNS=
    #FallbackDNS=
    #Domains=
    #LLMNR=yes
    #MulticastDNS=yes
    #DNSSEC=no
    #Cache=yes
    #DNSStubListener=udp
    and status

    Code:
    guillaume@XPS:~$ sudo service systemd-resolved status
    ● systemd-resolved.service - Network Name Resolution
       Loaded: loaded (/lib/systemd/system/systemd-resolved.service; enabled; vendor preset: enable
       Active: active (running) since Tue 2017-10-24 18:20:02 EDT; 3h 8min ago
         Docs: man:systemd-resolved.service(8)
               https://www.freedesktop.org/wiki/Software/systemd/resolved
               https://www.freedesktop.org/wiki/Software/systemd/writing-network-configuration-mana
               https://www.freedesktop.org/wiki/Software/systemd/writing-resolver-clients
     Main PID: 925 (systemd-resolve)
       Status: "Processing requests..."
        Tasks: 1 (limit: 4915)
       CGroup: /system.slice/systemd-resolved.service
               └─925 /lib/systemd/systemd-resolved
    
    oct. 24 18:20:02 XPS systemd[1]: Starting Network Name Resolution...
    oct. 24 18:20:02 XPS systemd-resolved[925]: Positive Trust Anchors:
    oct. 24 18:20:02 XPS systemd-resolved[925]: . IN DS 19036 8 2 49aac11d7b6f6446702e54a1607371607
    oct. 24 18:20:02 XPS systemd-resolved[925]: . IN DS 20326 8 2 e06d44b80b8f1d39a95c0b0d7c65d0845
    oct. 24 18:20:02 XPS systemd-resolved[925]: Negative trust anchors: 10.in-addr.arpa 16.172.in-a
    oct. 24 18:20:02 XPS systemd-resolved[925]: Using system hostname 'XPS'.
    oct. 24 18:20:02 XPS systemd[1]: Started Network Name Resolution.
    anyone with the same issue or a way to fix it?

  2. #2
    Join Date
    May 2013
    Beans
    3

    Re: 17.10 systemd-resolve takes 100% CPU since upgrade from Zesty Zapus

    I've got a similar issue with it taking up 100% of one CPU. i do a service systemd-resolvconf restart and it goes to zero for a while then after 10 minutes or so its' back up to 100% of a CPU.

    Also when I first log in to 17.10 Ubuntu on X.ORG I get no DNS until I do a service systemd-resolvconf restart followed by a service NetworkManager restart

    I've been trying to understand what is going on since before I upgraded from 17.04 which I did in the hopes it would fix the problems I was having with DNS not working but unfortunately the upgrade has made it even worse. I've seen this issue with systemd-resolveconf taking up high CPU in previous versions of Ubuntu but usually when I restart systemd-resolvconf service it's good for the session and even wouldn't happen for multiple sessions after that. Now with ubuntu 17.10 it's way way worse. I'm at my wits end about to format and reinstall.

    I have a fresh 17.10 install on another machine and even though systemd-resolvconf works there it unfortunately won't use DNS servers from my openconnect cisco vpn network so I've had to hard code my VPN network machines into /etc/HOSTS. I think something changed with Ubuntu resolving mechanism sometime around 16.04 or 16.10. I just found an article which is suggesting to replace systemd-resolved with unbound. It's the second time I've run into the suggestion to ditch systemd-resolvconf for unbound and I'm going to try it now.

    I think systemd-resolved is either garbage and/or it's badly implemented in ubuntu desktop, anyway. I've been with Ubuntu since 7.04 and even donated but this resolver nonsense is really giving me the idea to try another distro. It's super frustrating and I don't understand why it's been made so complicated. I can't understand how all the pieces fit together: Network manager, systemd-resolvconf, dnsmasq, etc.. etc... i read up on all of them but I still don't understand how the eff they all fit and work together and I feel like I'm going in circles chasing my tail trying to fix the issue. I enter DNS servers into all the fields in Network Manager where they're asked for and it doesn't make a lick of difference: it's like those settings are for show or to make us feels good or something because they don't actually do squat. And if my system is configured such that those settings won't take effect if I try using them then IMHO Network Manager should detect that and gray them out, FFS!

    Again, it seems to me like it's WAAAAAYYY more complicated than it needs to be. No wonder it's suxors.

  3. #3
    Join Date
    May 2006
    Location
    greenville, south carolin
    Beans
    43
    Distro
    Ubuntu 18.04 Bionic Beaver

    Re: 17.10 systemd-resolve takes 100% CPU since upgrade from Zesty Zapus

    By adding DNSMASQ_EXCEPT=lo in /etc/default/dnsmasq and restarting services I solved this issue

  4. #4

    Re: 17.10 systemd-resolve takes 100% CPU since upgrade from Zesty Zapus

    Same issue with 17.10, systemd-resolve consumes 1 complete core of my CPU, lucky it's a single threaded process ....
    DNSMASQ_EXCEPT=lo is not working in my case
    regards, Roland

    Fenestras morituri erant, liber origo causidicus te salutant.

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