@ trimis:-
Computer semi-expert is thinking along the right lines. It's almost certainly accessing the swap partition (think 'page file' in Windows; it performs exactly the same task).
Linux OSs do a lot of stuff in the background - in that respect they're quite similar to Windows - but it's rather different stuff to what Windows does. The prevalent thinking in Linux is that regardless of the amount of RAM you have installed, RAM is there to be used.....so let's use it!
Most of what goes on in the background boils down to disk caching, with the intention of making your system faster, and more responsive. Unlike Windows, which has a horrible tendency to allocate large chunks of your RAM to background processes which then refuse to release it when YOU want it, Linux always puts the system user first. This is a legacy of its UNIX 'roots'.
I
was going to link you to a site called
www.linuxatemyram.com which explains this beautifully, but it's been 'down' for a while, so.....this one here gives a pretty good synopsis of the main site:-
https://calix.force.com/CalixCommunity/s/article/LINUX-ate-my-RAM-1
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If you check the amount of free RAM you have (just open a terminal, and type 'free' followed by Enter) you'll almost certainly find that your RAM is nearly 100% 'used up'.....all the time. However, whenever you want to do anything, run something, carry out a task, whatever, the OS instantly releases that RAM for use by the application. It only ever uses it, productively, when it's not required by anything else.
A corollary to all this is the way the swap partition is accessed. Because of the background usage of your machine's memory, the degree of what's called 'swappiness' tends to be dialled up rather high by default; typically, about the 60% mark. (The higher this percentage, the more likely the OS is to start accessing the swap partition, as opposed to using RAM for tasks.....and we all know that HDD access is a darned sight slower than RAM access, since RAM is by far the fastest component of any machine.)
So; re-setting this 'swappiness' level down to a saner figure (10% is the usual recommendation) is one of the first things most people do after installation. It
can be done during a 'Live' session, but you have to set it up again at every boot, since 'Live' sessions don't normally save (unless you deliberately tell them to save something to a specific location). A 'Live' session is intended for trying an OS out, primarily to see whether the OS and your hardware like each other, and are happy to 'play ball' together.
Sorry to be long-winded, but I wanted to make it clear what this phenomenon stems from. You're by no means the first to notice this over the years....probably 25-30% of new users ask this same question during their first few months of 'ownership' (because with any Linux OS, you essentially DO 'own it'. Unlike M$, who go out of their way to make it crystal-clear in the initial EULA that the whole thing remains their 'property' for the duration......and you, the user, only EVER 'borrow it'.)
Mike.
