What version are you running? If you refer to this post there was an issue with some versions of 7.6.2 and 7.7.1
The tempfs is just a ram disk, not a hard disk partition. There's also a good chance that a process restart will temporarily clear the issue (or system reboot). I'm not 100% sure but I believe it's used as temporary storage/processing of update files and or AV related data.
You can run an htop from the command line as well and see if any of the processes are using an unusually high amount of Memory or CPU utilization, may identify the problem process.
Hope you are doing well.
Generally /dev/shm is filled with "exprosam-*" files.
The /dev/shm/exprosam-* files are for the SHM based communication between mwg-core and mwg-antimalware.
Generally you can see for mwg-core a huge list of SHM segments dedicated for communication between mwg-core and mwg-antimalware as below:-
00007f6be8329000 4K ---s- /dev/shm/exprosam-1487697121wqFMYLX
00007f6be832a000 1124K rw-s- /dev/shm/exprosam-1487697121wqFMYLX
00007f6be8443000 4K ---s- /dev/shm/exprosam-1487697121wqFMYLX
00007f6be8444000 1124K rw-s- /dev/shm/exprosam-1487697121wqFMYLX
00007f6be855d000 4K ---s- /dev/shm/exprosam-
The above eats up the memory. Using up the memory started using swap space, which finally slow down the system.
The above is an issue which is resolved in >= 18.104.22.168