Kubuntu 26.04 LTS - important things to do after an installation

[claydoh]

In my case I have 32 Gb of Ram to avoid swapping as much as possible. You're saying that you've gone to zero swapping if I understand correctly. I think that's what I'm looking for myself. What is the correct command to operate it if you think that it can work in my conditions?

No. Swappiness is a strange thing. Even with large amounts of ram, some systems still want to access swap at times, even just a tiny bit. The swappiness setting is just how much this might be delayed. The tendency to hit swap sooner *seems* to have improved in my usage, from that 8gb laptop (which seldom ever seems to access swap) and even 32Gb systems do.

Basically, if you are not experiencing issues, don't mess with it. I, personally, have not had to mess with it myself, despite the same hardware needing it in the recent past.


if you want zero swapping, then don't have a swap.

[JoshiFresa]

No. Swappiness is a strange thing. Even with large amounts of ram, some systems still want to access swap at times, even just a tiny bit. The swappiness setting is just how much this might be delayed. The tendency to hit swap sooner *seems* to have improved in my usage, from that 8gb laptop (which seldom ever seems to access swap) and even 32Gb systems do.
Basically, if you are not experiencing issues, don't mess with it. I, personally, have not had to mess with it myself, despite the same hardware needing it in the recent past.
if you want zero swapping, then don't have a swap.

Thanks, much appreciated clarification.

[JoshiFresa]

Claydoh hi, look at this page: https://askubuntu.com/questions/1039...ure-swappiness

In his description it says:

Which swappiness should I use?


I highly recommend vm.swappiness=0! It makes my machine run soooo much better. From my anecdote in my answer here:

I have found that setting swappiness to 0 significantly improves the performance of my system which has 32 GB RAM, a 64 GB swap file on a high-speed m.2 SSD, and which is continually running out of RAM.

With swappiness set to the default of 60, I'd regularly get 1 to 2 minute lockup periods while kswapd0 is running (as shown by top) to try to swap memory for some memory hog application like Chrome, Slack, Eclipse, or Google Meet (within Chrome). I'd start to get these lockups at 80% full RAM. The computer would be completely unusable during this time--unable even for me to type into a terminal or click on a menu.

Setting swappiness to 0 significantly helped!. I started not getting really high CPU usage until 90% RAM full, swap space would still get used plenty--but more efficiently, and when my RAM did get almost full my computer would become very sluggish, but still barely usable rather than completely unusable!

See some of my symptoms here, which I originally thought were due to a bug in Google Meet, but now think were due to memory swap making my computer slow: https://github.com/ElectricRCAircraf...sue-1177137900

Is it random or serious allegation?
And if I would choose to try swappiness=0 what is the best command to make it permanent, not just for the current session?

[claydoh]

I have never seen setting it to 0 disable it. That does not mean the top response on the page is wrong.

But if you want to test, then make permanent, just follow the howto from Schwarzer Kater and test changes for a number of days.

[JoshiFresa]

I have never seen setting it to 0 disable it. That does not mean the top response on the page is wrong.
But if you want to test, then make permanent, just follow the howto from Schwarzer Kater and test changes for a number of days.

I opened the 99-sysswappiness.conf to understand what the command of schwarzer kater does. So if I want to try zero-swappiness I guess I just have to transpose to this (?) :

echo -e "# Reduce swappiness for desktop installation (default = 60)\nvm.swappiness=0" | sudo tee /etc/sysctl.d/99-sysswappiness.conf

Then using Reboot.

I've become more careful thanks to you guys so I prefer to ask again to make sure I get it right.

[Schwarzer Kater]

JoshiFresa : yes, this would be the correct command to set swappiness=0.


Concerning step 2.:

I have tried to make the short explanation a bit more technically precise.
Please read e.g. the Arch Wiki for further explanations.

I have come across swappiness values between 0 and 35 for desktop systems, but as "10" is Ubuntu's suggestion for desktop systems (and Ubuntu is the "mother" of Kubuntu - and 10 is a very common value) I will stick to it in this guide.
But feel free to experiment by yourselves.


-> I think if somebody would like to discuss swappiness any further, it would be better to open a separate thread for this…

[claydoh]

as "10" is Ubuntu's suggestion for desktop systems

To be clear, this is a community-created and edited section (when it isn't down ), and not necessarily official with a capital "O." I have edited some things in the wikis in the past, if you dig back far enough. But this page has been in the wiki as long as I can recall. That does lend it some sort of veracity. But it is old and not kept up-to-date enough. I am leaning toward that 10 value being more for HDDs than anything else, but probably good for desktops still in any case, if there are issues seen. And swap as a topic is a more complicated thing; it isn't just "emergency ram " at all. Yes, I went down the rabbit hole on this one.

I know I am digging into the weeds here, but we do suffer in Linux Land from some ideas and thoughts that become the accepted answer but with little or no actual proof or reasoning to explain it. Or have actually changed over time. That wiki page on swap still incorrectly states that you can't have a swap file on btrfs, and I have used one for some time now, as provided by Calamares in Kubuntu, even.