Instead of explaining it poorly, try this admittedly older article from Brendan Gregg https://www.brendangregg.com/blog/2014-05-11/strace-wow-much-syscall.html

Instead of explaining it poorly, try this admittedly older article from Brendan Gregg https://www.brendangregg.com/blog/2014-05-11/strace-wow-much-syscall.html https://www.brendangregg.com/blog/2014-05-11/strace-wow-much... tldr - syscalls and userland / kernel context switching