It seems, that it was the #Friendica daemon which started a lot of defunct #PHP processes, which caused my server to slow down with time. I have changed the setup to run the worker.php script every 10th second.
Thanks to #ChatGPT for writing me a #Python script, which could show me, which application had the most processes running and sort it by showing the one with the most at the top. With this script I could figure out what took up the resources.
I went back to using the daemon. Decreasing the number of parallel workers from 10 to 5 seems to have solved the issue I was having.
The daemon is also faster at delivering updates to other servers than the worker. I think it’s because it has multiple parallel workers.
Correction: it’s not a Cron job that I use. If you do a Cron job every 10th second you might risk that the script will run twice at the same time. What I have is a loop script having a 10s sleep after it’s finished. In this way it won’t run twice.