landscape-client slows down login by 30s on machines with lots of interfaces

[James Troup]

landscape-client on an Ubuntu Focal machine with a lot of interfaces (838) takes 30s to run.

$ /usr/bin/time --verbose sh /etc/update-motd.d/50-landscape-sysinfo

  System information as of Tue 09 Nov 2021 12:16:11 PM UTC

  System load: 10.29 Processes: 3287
  Usage of /: 60.2% of 91.54GB Users logged in: 1
  Memory usage: 19% IPv4 address for br-bondM: 10.216.5.35
  Swap usage: 0% IPv4 address for lxdbr0: 10.0.133.1
  Temperature: 53.0 C
        Command being timed: "sh /etc/update-motd.d/50-landscape-sysinfo"
        User time (seconds): 1.22
        System time (seconds): 28.69
        Percent of CPU this job got: 99%
        Elapsed (wall clock) time (h:mm:ss or m:ss): 0:30.05
        Average shared text size (kbytes): 0
        Average unshared data size (kbytes): 0
        Average stack size (kbytes): 0
        Average total size (kbytes): 0
        Maximum resident set size (kbytes): 33720
        Average resident set size (kbytes): 0
        Major (requiring I/O) page faults: 0
        Minor (reclaiming a frame) page faults: 276965
        Voluntary context switches: 41
        Involuntary context switches: 252
        Swaps: 0
        File system inputs: 16
        File system outputs: 0
        Socket messages sent: 0
        Socket messages received: 0
        Signals delivered: 0
        Page size (bytes): 4096
        Exit status: 0
$

It doesn't get any better with a warm cache. A machine with less interfaces (60) takes ~1s.

[Kevin Nasto (silverdrake11)]

Fix is here https://github.com/CanonicalLtd/landscape-client/pull/98