Hi Stephen! Thanks for trying to help me out!
That's an unfamiliar format to me. Is this a Linux system running systemd? Our mailman + hyperkitty runs on RHEL 8 and yes, all the services are systemd format.
How much swap do you have, and how much is in use? What other daemons are running on the host besides Mailman?
Host has 8GB swap at the moment ,which decreases in small steps if main memory is consumed. But if this happens, then something happens and there is again couple of hundreds free memory.
In addition to the above mentioned services, there is also NGINX and postfix services as well.
Have you modified any web pages associated with Mailman, including any of the Django templates? Are there any pages with unusually long load times? No and usually all pages are very smooth. Only if i open archives, then sometimes it will load like sec or three.
I also noticed that after midnight, if one of the mailman-web cronjob was finished, the free memory jumped from 100mb to 1gb. And then it will start to decrease again. I will try to investigate little bit more and play little bit with the services to be sure, that the issue is related with mailman or gunicorn or with something else.