Public bug reported:

After having a couple of terminals and and Chrome windows open for most
of the day, everything becomes sluggish. Switching desktops is clearly
very slow and Chrome's windows don't react to all mouse actions.

Looking at htop I can see gnome-shell takes anywhere between 5% and 50%
of CPU, normally between 10% and 20%.

With Chrome and terminal windows open, an strace on the PID of gnome-
shell shows the following:

jpmeijers@jpmeijers-XPS13-9333:~$ sudo strace -c -p 3491
[sudo] password for jpmeijers: 
strace: Process 3491 attached
^Cstrace: Process 3491 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 36.37    0.108651           3     30932     16434 recvmsg
 34.99    0.104531           3     29278           poll
 26.20    0.078272           5     14601           writev
  1.06    0.003158           2      1181           ioctl
  0.35    0.001041           2       430           write
  0.27    0.000812           1       602           getpid
  0.26    0.000773           4       158           read
  0.11    0.000316           3        96           timerfd_create
  0.10    0.000313           3        96           close
  0.10    0.000300           4        73         4 futex
  0.08    0.000241           2        96           timerfd_settime
  0.07    0.000201           0       228           mprotect
  0.04    0.000111          27         4           getrusage
  0.01    0.000038          12         3           sendmsg
  0.00    0.000008           0        11           munmap
  0.00    0.000005           0         6           mmap
  0.00    0.000002           1         2         1 recvfrom
------ ----------- ----------- --------- --------- ----------------
100.00    0.298773                 77797     16439 total


After closing Chrome windows:

jpmeijers@jpmeijers-XPS13-9333:~$ sudo strace -c -p 3491
strace: Process 3491 attached
^Cstrace: Process 3491 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 36.24    0.099458           3     30319     15900 recvmsg
 35.15    0.096450           3     29053           poll
 26.86    0.073711           5     14500           writev
  0.68    0.001858           1       930           ioctl
  0.40    0.001092           3       318           write
  0.14    0.000386           6        64           close
  0.13    0.000344           0       469           getpid
  0.11    0.000295           4        64           timerfd_create
  0.11    0.000292           1       222           mprotect
  0.06    0.000177           2        64           timerfd_settime
  0.06    0.000153           6        25           munmap
  0.04    0.000121           1       121           read
  0.01    0.000038           0        49         4 futex
  0.01    0.000018           6         3           sendmsg
  0.00    0.000013          13         1           restart_syscall
  0.00    0.000000           0         7           mmap
  0.00    0.000000           0         2           getrusage
------ ----------- ----------- --------- --------- ----------------
100.00    0.274406                 76211     15904 total


After closing the terminal windows too, therefore only the terminal running 
strace is open:

jpmeijers@jpmeijers-XPS13-9333:~$ sudo strace -c -p 3491
strace: Process 3491 attached
^Cstrace: Process 3491 detached
% time     seconds  usecs/call     calls    errors syscall
------ ----------- ----------- --------- --------- ----------------
 36.43    0.196569           3     54115     27576 recvmsg
 35.25    0.190224           3     53266           poll
 26.92    0.145275           5     26592           writev
  0.30    0.001631           4       405           write
  0.23    0.001245           5       248           mprotect
  0.23    0.001229           9       136           close
  0.21    0.001120           1       621           ioctl
  0.16    0.000889           6       136           timerfd_create
  0.13    0.000711           5       136           timerfd_settime
  0.06    0.000328           1       300           getpid
  0.03    0.000180           2        68         3 futex
  0.03    0.000159           1        85           read
  0.01    0.000053           8         6           sendmsg
  0.01    0.000027           3         9           mmap
  0.00    0.000002           0         3           munmap
  0.00    0.000002           0         4           getrusage
  0.00    0.000000           0         1           recvfrom
------ ----------- ----------- --------- --------- ----------------
100.00    0.539644                136131     27579 total


I see the calls and errors to recvmsg climbing. What does this mean, and what 
is causing this?

** Affects: gnome-shell (Ubuntu)
     Importance: Undecided
         Status: New

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https://bugs.launchpad.net/bugs/1880723

Title:
  gnome-shell high CPU usage on Ubuntu 20.04

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