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I'm not a supernerd, but I know some stuff, and I'm pretty sure my system is not supposed to work like this.

I recently reinstalled Ubuntu 20.04 from the bones up on my home-built desktop because I noticed that my previous installation wasn't using my m.2 SSD drive, and that was probably why it took forever to boot up. After the reinstall, things went swimmingly for a short while, but then some instabilities started creeping up. She'd get increasingly sluggish to the point of freezing up if I left her on for any period of time, and occasionally she'd fail at logging into my domain account.

I started running bytop to monitor her performance and see if anything was eating her RAM or something, and there were a few things that seemed to have a disproportionate impact like snap store (I manually kill it if it gets too demanding), and I switched from using Firefox as well to see if that managed a little better. I gave Brave a try, which was easy on resources, but it isn't supported for my accessibility extension and doesn't like talking to my uni's website. Chromium is a little better, but eh, whatever. Point is, none of that improved performance or mitigated the issue.

The problem as bytop reports is a memory cache problem.

RAM is almost untouched, mem cache is exhausted

The swap space is completely available, the RAM is 91% available, and everything looks ducky except for the mem cache. I've seen various reports that this is "not a big deal," but I can say that it significantly negatively impacts performance. I regularly use sh -c 'sync; echo 3 > /proc/sys/vm/drop_caches' to clear it out, and I do get some performance back for a minute as bytop shows that all the cache is freed back up, but it refills rapidly and I can't seem to locate any app, process, or setting that would affect this at all.

To be clear, this 1% free problem happens before any programs are started. I have everything potentially in my startup applications turned off (lm-launch, Nextcloud, and SSH Key Agent). Just on the absolutely far-weird chance it was hardware related, my DH changed out my RAM yesterday for a more reputable brand, but that did not help.

I've found directions for adjusting or turning on/off swapiness, but the last reference I found to tweaking the mem cache was from Ubuntu 16.x, I think. Before I scrub her down and reinstall yet again, I thought I'd come to you fine folks and see if you had any thoughts. I'm not entirely sure what information would be useful, so ask away, and I will provide.

-- Deges

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    This sounds like something is doing copious amounts of disk access to me. I've seen snapd glitch out weird on 20.04 systems before, and just constantly access the disk without relent. I had to stop snapd in order to fix it. If you're using Snap apps, that might not be an option for you (I can't remember if disabling snapd makes Snaps stop working or not). You might try out Ubuntu 22.04 to see if it works for you, since I've not experienced that problem there.
    – ArrayBolt3
    Jun 12, 2022 at 22:34
  • You are definitely onto something! I used this instruction link to disable snapd, rebooted, and the mem cache was pristine! Of course, that means tracking down everything that runs through snap and installing it with apt, right? (Re-enabling and rebooting, and the mem cache is still stable. Iiiiiinteresting.)
    – Deges
    Jun 13, 2022 at 0:20
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    Maybe. On a 20.04 system, though, I don't believe there will be much to replace. You can use the command "snap list" to see all the Snaps installed on your system.
    – ArrayBolt3
    Jun 13, 2022 at 3:40
  • Yup, I pulled the list and it's... extensive. I'm not sure there are going to be non-snap alternatives for all of my favorite things, never mind these probably unimportant ones like "gnome-something" and "canonical-thingy." "Frameworks" aren't serious, either, right? (COMPLETELY KIDDING!) Doing the disable/enable (with reboots) seems to have mitigated the problem pretty well right now, but I will definitely look at doing the 22.04 update. You're fantastic, ArrayBolt3!
    – Deges
    Jun 13, 2022 at 15:49

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