Linux

Thanks, great input.

I totally agree - ZRAM isn't magic and of course it will fall flat on its face for loads of encrypted, compressed or pure random data. In my limited day to day usage I just never hit that situation, so far.

Again, I fully agree, I wouldn't have expected that the N4120 works so well with ZRAM. For work I am forced to use a recent mac with loads of RAM. When just browsing the web/checking emails I don't feel any noticeable difference between the mac and the Stream for the CPU. (Of course, CPU/IO bound tasks are another story, and the display of the mac is in another league.) Usually I would consider myself to be quite sensitive to speed, I notice a real difference between using Gnome (with impatience etc. extensions) and Xfce, concerning the responsiveness of my desktop.

I'll check the BIOS settings, I expect the same as you. Not sure, if I will lower the reserved RAM for the iGPU, everything works fine at the moment and I want to try some light gaming on this machine.

Programs shouldn't get confused since RAM/swap is transparent for them.

stops having to swap pages to disk, slightly more overhead on the CPU side but for most systems that will be an order of magnitude faster that swapping to disk

Let me give it a try:

Imagine you are having breakfast and sitting on your breakfast table. Everything on your table and reachable w/o getting up is what your CPU holds in its register. When you need something from the fridge in your home, this is your RAM. If you need something that is not in your fridge, you have to get dressed, get out of our home, walk to the groceries store which is half an hour away, find what you are looking for, pay for it, walk home for around half an our, switch back to your relaxed clothing and finally you can continue your breakfast. The groceries store is your hard disk/ssd whatever. With compression, imagine you have a big second fridge in the basement (or the house next to yours, you get the idea). Not as good as having stuff on your table or in your fridge, but usually at least an order of magnitude better than having to visit the groceries store.

Turns out usually a significant amount of RAM is compressible. I was surprised at it too, and actually still am. But of course it also depends on how you use your system. If you run a media player that caches a lot to RAM, its cache wont be compressible, but they say its efficient for example for memory of web browsers.

Rolling out ZRAM to all my boxes right now! 🙃

Do you also tweak other settings for ZRAM? According to ArchWiki PopOS settled for the following settings:

vm.swappiness = 180
vm.watermark_boost_factor = 0
vm.watermark_scale_factor = 125
vm.page-cluster = 0

I am testing this settings right now and cannot say I experience a difference compared to the defaults.

Thank you for your advice. Right now my setup works so I'll try to not waste my entire weekend playing with technology, but if I need further tweaks in the future I'll look into ZSWAP.

One question: Do you know why Fedora and PopOS decided for ZRAM and against ZSWAP? As I wrote already somewhere else: I did choose ZRAM for it being default in Fedora, which gave me some trust that people better informed/experienced choose ZRAM over ZSWAP.

Technically it is a compressed SWAP disk in RAM, but the compression ratio is impressive and it feels like more RAM for me. My pleasure to share, hope it will help you someday! :-)

You don't want to combine zram swap and physical swap. When zram swap is full, you'll get LRU inversion because it won't ever evict from zram swap.

Either zram-only or physical+zswap.

Sorry, just a user myself and because ZRAM is default on Fedora and was easy to setup on Debian, I am just using it.

On the Stream, I have a 4G physical swap partition as a backup, though. AFAIK the physical partition will be utilized by ZRAM when needed. (ZRAM simply has higher priority swap).

I used zram + swap for years. I dedicated 25% of my memory to zram. The problem is that zram would get filled with infrequently used data, and disk swap would get the frequently used data. Once that happens everything slows down.

Zswap tries to fix that be creating a compressed swap buffer in memory. Older/less used data will get written to disk, but fresh/frequently used data will stay in the compressed ram buffer. That's my understanding, at least. I don't remember how to query Zswap usage stats.

I am using Debian 12 and I am pretty sure zswap is not enabled by default.

With zstd the compression ratio is better than 3 in all experiments I saw. (Of course you won't get this numbers for random/encrypted data). Right now I have 12MB compressed to 2MB via ZRAM (fresh reboot) which is a factor of 6.

So, taking 3 as factor learned from others and my experience, with 1.8 GB of ZRAM I can store 5.4 GB of memory, adding the 1.8 GB of usual RAM, I end up with 7.2 GB of RAM which is double my 3.6 GB RAM I started with. (All this is backed by 4 GB of physical SWAP.)

Sorry, I cannot really answer your questions concerning zswap vs ZRAM, I just follow the herd and trust that the Fedora people usually have good reasons for their technical choices and are deploying ZRAM by default for several years now.