That was a theory I had: That Unicorn leaks and that Unicorn Killer is not killing any of the workers, since it does so all 160 requests and there are no request happening at the moment.
Then I saw the new installation uses Puma ;)
Then I saw the new installation uses Puma ;)
Both Puma and Unicorn should be killed after they exceed a certain size to avoid this situation from happening. It's possible either this is not working in some situations/configurations, or there is a leak elsewhere although this is the first time I have heard reports of this.
What configuration is being changed from the defaults? Alternatively if you could open an issue with any additional detail we will try to figure out what is happening and fix it: https://gitlab.com/gitlab-org/omnibus-gitlab/-/issues