This question might be specific to gnome-shell, which is constantly using 60-80% CPU on my system. (4.1GHz CPU frequency, arch linux, up-to-date software)

How can I find out what exactly is the cause of this? I'm suspecting that it's one of the extensions I use but how, other than disabling them all one by one (which would be hard in case multiple ones are just adding up), can I make sure of that and find out which? I found this related question but it's not really helpful and over two years old, so maybe by now there's a better way.

The output of strace (run for approx. 25 seconds), as suggested in the other question:

$ sudo strace -c -p 840
strace: Process 840 attached
^Cstrace: Process 840 detached
% time seconds usecs/call calls errors syscall
------ ----------- ----------- --------- --------- ----------------
 76.08 2.752830 9 299874 clock_gettime
 12.68 0.458897 50988 9 3 clone
 4.34 0.157096 26182 6 rt_sigreturn
 3.51 0.126947 325 390 write
 0.86 0.031007 9 3348 2583 recvmsg
 0.68 0.024611 9 2701 getpid
 0.51 0.018405 10 1839 poll
 0.40 0.014319 13 1026 writev
 0.27 0.009947 46 216 ioctl
 0.17 0.006035 9 656 sched_yield
 0.10 0.003674 10 361 gettimeofday
 0.09 0.003171 13 238 read
 0.05 0.001859 10 176 close
 0.05 0.001845 16 115 1 futex
 0.04 0.001302 16 80 openat
 0.03 0.001210 15 80 munmap
 0.03 0.001116 13 80 mmap
 0.02 0.000793 12 66 mprotect
 0.02 0.000789 9 80 fstat
 0.02 0.000584 12 48 timerfd_create
 0.01 0.000520 10 48 timerfd_settime
 0.01 0.000498 10 48 39 stat
 0.01 0.000291 12 24 pipe2
 0.01 0.000290 58 5 1 recvfrom
 0.01 0.000209 16 13 nanosleep
 0.00 0.000074 12 6 wait4
 0.00 0.000063 10 6 6 lseek
 0.00 0.000036 36 1 restart_syscall
------ ----------- ----------- --------- --------- ----------------
100.00 3.618418 311540 2633 total

However, I don't really know what to do with that or what it says at all either.

Edit:

Just disabled all extensions, CPU usage still constantly 70-80%, no change at all.