Wtf are you doing with it? My slack instance (on linux) is resting around 300 MB resident set size and 0% cpu. 300 MB is still a lot for a chat app, but it is definitely not gigabytes.
If you just add up memory usage for subprocesses you are likely to over count due to shared memory. The number you typically want to add up in Linux is ‘proportional set size’ which is, I think, the sum over every page of the process’s memory of page_size / number of processes which can access the page. I don’t know what happens if you mmap some physical memory twice (I think some newish Java GC does this).