Linux

Let it be. The people designing the OS most likely know better than you or anyone else in this thread. I know the urge to "tweak" things is strong, but some defaults are defaults for a good reason.

You should set it back to whatever it was. It shows 5.6 GB in active use and 19 GB used for cache. You're already using all your RAM, just not actively. You don't sit on 100% of the chairs in your house at once either. 3 GB swap used is very low usage, which is expected when you're not actively using a lot of memory.

Don't mess with things you don't understand, especially when you don't have an actual problem. You're going to end up breaking things. (Which, to be fair, is one way to learn, but at the cost of breakage.)

It is probably normal. Don't decrease your swappiness too much.

I think it happened the following way:

See the "cached" ram is taking 19 gigs. Theese cached ram improves performance by keeping frequently used system files on ram. So the actual occupied amount of ram would be 5+19 ≈ 25gb. Thoose system files might be used more than other app's ram so that they have higher priority to be in ram. So at the time you opened certain other applications, the total ram usage including cached might be a little over the availiable ram and likely got swapped. The once swapped thing won't be cleared immediately or with any much priority. I often see swapped contents remain even after closing a bunch of apps which gave empty space in ram.

So its just normal but is it using swap without once opening enough apps to fill the availiable space with used+cached? If so I would also be concerned

Yes, this is normal and it's a good thing (unless you've come across a bug). I don't know exactly what app the screenshot is showing, but I'm guessing that the caching shown is referring to the filesystem cache. The kernel is keeping a cache of files you are likely to access again so that it doesn't have to read them from storage again. So what you're seeing here is that some memory contents were moved to swap to make room for filesystem cache. This is because the kernel believes you're more likely to access those files again rather than the memory contents. If it's right, then this a performance improvement despite the fear surrounding swap usage.

Setting a low non-zero swappiness value is telling the kernel that memory contents have priority over filesystem cache for remaining in RAM, or conversely that file cache is more likely to be evicted from the RAM. A value of 100 would mean that they have equal priority. So that memory content must have been very stale to be evicted despite having a significantly higher priority to reside in RAM.

So:

• don't worry about swap usage unless you're experiencing actual performance issues
• for ssd's the value should be close to 100
• for hdd's it should be low
• if you're using both on your system, the default value of 60 is probably a decent approximation of the optimal value

Source: https://chrisdown.name/2018/01/02/in-defence-of-swap.html

Strange, I also have 32GB of RAM, my swapiness is 15, and my swap is always at 0 bytes used...

I also have a 32gb RAM (30.5 GiB) and a swappiness value of 10. My entire swap is full and my RAM is only filled up to about 3.8 GiB. However my swap is just 512mb small (its not a typo, it's half a GB). You should not worry too much, even if the swap is in use, because those parts are probably like "parked" ram area that is not in use for a while now and waiting "to be waken up". And the performance penalty is not that big, if the swap is on a fast NVME SSD. In old days on old slow spinning hard drives, the penalty for using swap was huge (plus the Kernel and rest of operating system was not fine tuned as today).

Some related commands to check:

grep -H swappiness /etc/sysctl.d/*.conf

swapon --show

free

cat /proc/meminfo

Here is an interesting article: https://chrisdown.name/2018/01/02/in-defence-of-swap.html

Do you have zram set up?

if you really feel the need to fuss with it then replace with swap on zram

how do you change swappiness?

You probably just had a program(s) use a lot of ram and that pushed some processes to swap. When the system needs it, it will be moved back. I’d +1 on setting up zram. Can be setup easily on most distros.

I've been trying to run a stable system with never overcommit and no swap . It's impossible. this is the thing that may make me a kernel developer once I retire.

I've settled for tons of swap with never overcommit but I still can't do normal things sometimes.

The downside to swap is wearing out your disk and latency when swapping, it's good to have swap usage before ram is gone to let the system have more ram available for random allocations. My goal is to never need the oom killer, but it seems like many apps (chrome and FF mostly) basically require overcommit to function.

Right now my system has 30% ram used and is still keeping 700MB is swap. I would recommend to try benchmarking your settings but I don't do that myself so I don't know what to use 😅.

You can try disabling swap with swapoff, then your system is definitely maximizing your ram use, just be prepared for the oom killer to wreck your session.