I have am running Windows 11 on a cleanly-installed computer with 32GB RAM. Both Resource Monitor and Task Manager report that 100% of my memory is used, although if you sum the memory committed by the running processes it accounts for only a tiny proportion of my memory.
I've tried rebooting the computer, but the same thing happens.
Update
I rebooted into Safe Mode, and the RAM usage stayed low.
I have two user accounts on the computer. If I sign in with the first one, RAM stays normal. But I've noticed that if I sign in with the second, even if I don't open any applications (and none start automatically) RAM usage then starts linearly and fairly rapidly increasing until it gets to 100%. It takes about 2-3 minutes to reach 100%, during which time the RAM used by no processes increase (according to Task Manager and Resource Monitor) and the computer doesn't appear to be doing anything.
Here are some screenshots of RamMap:
Use CountsProcessesPriority Summary
The lion's share of the Physical Pages appear to be active nonpaged pool:
Update 2
Here are the screenshots from AutoRuns. Working user on the left, broken user on the right.
Everything that the broken user runs is also run by the working user.
I'm very confused! I'm tempted to delete and recreate the broken user, but I'd like to know what the cause is.