browser and everything else on screen froze
 

The problem started when I went to a site and above the top part of browser appeared in yellow asked me to 'wait or stop', I clicked wait, later I clicked stop. Everything froze and I had to power off/on to get back to normal after 40 minutes. I tired Ctrl + Esc, and Alt + space, crtl F2 etc, nothing worked. I wasn't able to get into terminal either using shortcut keys. Was powering off my only option?

What site? Have no way of knowing what you have done. What was the machine waiting for? Downloading, big huge page load, one of those huge images that netflix puts in your browser?

What browser? I have seen Falcon having what I think is memory leaks, filling up the memory all the way, where my computer slows down and I have to close the browser and get back to normal. Not a total computer freeze like you describe.

udacity.com, cause may have been a script perhaps?Firefox browser

I visited that site in Firefox on Mageia v. 8 and was not able to duplicate the issue. In fact, the site seemed to work quite quickly.

I clicked the "Download Report" button and the *.pdf opened in Okular within seconds.

This usually happens when you exhaust your RAM & Swap file. I have had it happen when I accidentally opened too many windows in Firefox (~300) or tried to open multiple pdf and word documents together (>100).

One option you can try is to ssh to the host from another machine, if you are successful then kill the process (in this case Firefox).

I did have quite a few things running at same time. Is there a way to adjust the ram or swap to prevent this from occurring again?

You can see how much memory you use with

You can change swapiness to a lower value so it wont swap as quickly. That's been talked about, the pros and cons of it. As for RAM, put more RAM in if you don't have enough.

I can max out the RAM on an old dual core box with 4GB RAM, without a swap partition, using something like google maps. When I do, the machine doesn't die, it sorta stops and becomes unresponsive for a bit until a bunch of RAM is dumped, and then the browser will crash/close.

You can also clear pages in RAM that are no loner active. Didn't say it was a good or bad thing, just that you can do it.

Systemd or not

Clear PageCache only.
Clear dentries and inodes.
Clear PageCache, dentries and inodes.
I've done that before too. With the web browser open. Cleared pages that the browser is no longer using. That will allow you to continue. If you go back to a web page that you have already opened, you'll have to download it again. But the machine never crashed on me, or the web browser.

For RAM you need would need to add additional RAM chips to your system. I usually try to max out the available RAM. To add swap you would need to resize your partitions to add more space to the swap partition. Else, you can add another disk and create a swap partition on it.

Do we even know what OP's hardware specs are? what point is there in wild speculations about what _might_ help.
Further, what exactly the OS in question is and whether they're running it in a VM or not.

To check current swappiness value should I use this?

Didn't ask because based on their previous threads they seem to be allergic to giving details. (Even in this case, see the response you got for your question (Post#12) :D
However, based on their brief (very brief) description it seemed to match what I had experienced when I exhausted the RAM+Swap on the system, so shared that...

Now unless they share more details can't help them further.

Let me see, some general info:
https://wiki.archlinux.org/title/Swap#Swappiness

Read about that. There are + and - of changing that.
https://bbs.archlinux.org/viewtopic.php?id=271192
https://www.howtogeek.com/449691/wha...-to-change-it/

Thanks, my new swappiness value is 10 after reboot.